Textile Testing & Product Evaluation PDF

UNIT – 2 Textile Testing & Product Evaluation Precision and Accuracy It is common practice to include in both the ASTM and AATCC test methods a statement as to the precision and accuracy of the test methods. Precision is defined as the degree of agreement within a set of observations or test r...

UNIT – 2 Textile Testing & Product Evaluation Precision and Accuracy It is common practice to include in both the ASTM and AATCC test methods a statement as to the precision and accuracy of the test methods. Precision is defined as the degree of agreement within a set of observations or test results obtained by using a test method. Precision can be single-operator (technician), multi-operator within a laboratory, and between laboratories. In other words, precision is a measure of scatter test results when a test is repeated. Precision indicates ability of a test method to give essentially the same results regardless of who, where and when it is done. Accuracy is defined as the degree of agreement between the true value of the property being tested (or an accepted standard value) and the average of many observations made according to the test method, preferably by many observers. When the true value or an accepted standard value of the property being tested is not known, accuracy cannot be established. In many cases, the true value or an accepted standard value of many properties of various textile materials is not known. Atmospheric Conditions for Testing Most textile fibers are hygroscopic, that is, they have the ability to absorb or give up moisture. This moisture is picked up or absorbed by hygroscopic material from the atmosphere if the relative amount of moisture in the air is greater than that in the material. Conversely, the moisture will be given up by the material if the relative amount of moisture in the air is less than that in the material. Under natural conditions, the amount of moisture in the air is continuously changing. This results in varying the amount of moisture contained by a hygroscopic material exposed to the atmosphere, which will lead to a change in the physical properties of this material. For example, cotton absorbs moisture rapidly when exposed to high humidity, as a result, weight and strength of cotton increase while other properties change. Cellulose-base manmade fibers generally show reductions in strength with corresponding increase in elongation as their moisture contents are increased. Wool fibers show a slight decrease in strength with an increase in moisture content. Practically speaking, all textile materials show increased pliability and reduced influence of static electricity with an increase in moisture content. Therefore, in order to make reliable comparisons among different textile materials, products, among different laboratories, it is necessary to standardize the humidity and temperature conditions to which the textile material or product is subjected priority during testing. Such conditions are 65 ± 2% relative humidity [RH) and 21° ± 1°C or 70° ± 2°F. The test samples (fabrics or garments) should be left in a conditioning room with the above atmospheric condition for at least 4 hours to reach equilibrium with the standard relative humidity and temperature. Then, they should be tested under the same atmospheric conditions. If the test is not done at standard atmospheric conditions, then this must be stated clearly in the test report, alongwith the relative humidity and temperature at which the testing had been done. ASTM D 1776 Standard Practice for Conditioning Textiles for Testing, Annual Book of ASTM Standards, Volume 07.01 covers how to condition specimens for testing. Testing Standards for Yarns used for making fabrics Yarn Strength and Elongation The strength of yarn influences the strength of fabrics made from the yarn, although the strength of a fabric also depends on its construction and may be affected by finishing. Since for any fiber type, the breaking load of a yarn is approximately proportional to the linear density of that yarn, yarns of different sizes can be compared by converting the observed breaking load to breaking tenacity in grams/denier or grams/tex. Elongation is an indication of the ability of a yarn or fabric to absorb energy. If the elongation at the break of warp yarns is too low, weaving becomes difficult or even impossible. On the other hand, low elongation yarns and fabrics made from them have greater dimensional stability. Garments made from such yarns are less likely to become "baggy" at the knees, elbows, or other points of stress. Low elongation yarns or cords are also desirable as reinforcement for plastic products, hose, tires, and so on. There are two ASTM test methods for measuring yarn strength and elongation as follows: (a) D 1578 Standard Test Method for Breaking Strength of Yarn in Skein Form, Annual Book of ASTM Standards, Vol. 07.01. (b) D 2256 Standard Test Method for Tensile Properties of Yarns by the Single- Strand Method, Annual Book of ASTM Standards, Vol. 07.01. Yarn Number Yarn number is a measure of the fineness or size of a yarn expressed either as mass per unit length or length per unit mass. Yarn number is also known as yarn count. There are two systems of expressing yarn number or yarn count: a direct system and an indirect system. Under the direct system, yarn number is expressed in terms of mass per unit length. The two most frequently used units of the direct yarn numbering systems are: (a) Denier [de] weight of 9000 meters of yarn in grams (b) Tex [tex] weight of 1000 meters of yarn in grams For example, a 40 de yarn means that 9000 meters of that yarn will weigh 40 grams. A 40 tex yarn means that 1000 meters of that yarn will weigh 40 grams. Therefore, a 40 de yarn is much finer than a 40 tex yarn. In an indirect system, yarn number is expressed in terms of length per unit mass. Three most frequently used units of an indirect yarn numbering systems are: (a) Cotton count [N] the number of 840-yard lengths of yarn in 1 pound, generally used for yarns spun on cotton system. A 120N cotton yarn will have 120 x 840 = 100800 yards of yarn in 1 pound. A 60N cotton yarn will have 60 x 840 = 50400 yards in 1 pound. Therefore, a 120N cotton yarn is much finer than 60N cotton yarn. (b) Worsted count, the number of 560 yard lengths of yarn in 1 pound, generally used for yarns spun on worsted system. (c) Run, the number of 1600-yard lengths of yarn in 1 pound, generally used for yarns spun on woolen system. In a direct system, lower yarn number considered the finer yarn, whereas in indirect system, lower yarn number considered the coarse yarn. For example, 70 de [denier] yarn is finer than 140 de yarn; a 120 cotton count is finer than a 40 cotton count, and so on. Yarn number based on short-length specimens can be determined by an ASTM method D 1059 Standard Test Method for Yarn Number Based on Short Length Specimens, Annual Book of ASTM Standards, Vol. 07.01. In this method, a short length, such as 25 or 50 cm of yarn is taken from a yarn package or fabric, conditioned, and weighed. Then the yarn number is calculated from the weight and the measured length of the yarn. This is a quick method for the determination of the approximate yarn number. Because any error present in the reported length of the yarn specimen is multiplied many times while calculating the theoretical yarn number, it is extremely important that the length must be measured as precisely as possible. For the analysis of fabrics, this method is adequate for estimating the approximate yarn number of the yarn used to weave or knit the fabric. But the results obtained by this method may not agree with the nominal yarn number of the yarns actually used to make the fabric, because of the changes in the yarn number produced by weaving or knitting operations, finishing treatments, etc. Another ASTM method D 1907 Standard Test Method for Linear Density of Yarn [Yarn Number] by Skein Method, Annual Book of ASTM Standards, Vol. 07.01 uses a much longer yarn length than 25 to 50 cm. Under this method, specified lengths of yarn are wound on a reel as skeins and weighed. The yarn number is calculated from the mass and length of the yarn in the skein. There are instruments available, such as the Uster Tester II and msi Denier Monitor, for measuring yarn number on a continuous basis from a yarn package. Such instruments have transducers utilizing the relation- ship between the dielectric constant of a fiber and fiber mass to measure the absolute denier [mass/unit length] of yarn as it moves through the sensing element at high speed. The measuring element itself is a highly sensitive, noncontact, capacitance detection device that uses a unique, patented circuit to translate a continuous dielectric measurement into an electronic signal proportional to the denier or mass of a yarn. Yarn Twist Twist is incorporated in yarns to give them coherence. In a continuous filament yarn without twist, the individual filaments will spread out and separate from one another and the yarn will lack coherent unity. There are a few demand for the same, but, in general, a small amount of twist [e.g., half-turn per inch] is inserted to hold filaments together. For special purposes, higher twists may be used. In staple fiber yarns, twist is even more important, since the frictional forces, which alone hold together the individual fibers in the yarn, are solely due to the transverse pressures that develop when a fiber wrapped in a helical path around other fibers in the yarn is put under tension. Twist has important effects on the physical properties of yarn and fabric. Low- twist yarn is lofty and is usually preferred for knitting because of its softness, covering power, and warmth. Increasing the amount of twist causes an increase in yarn strength by increasing fiber cohesion, but as the twist angle increases beyond an optimum point, strength decreases. Maximum strength is obtained by inserting a medium amount of twist. High twist produces hard or wiry yarns of high density. There are two ASTM methods for determining yarn twist as follows: (a) D 1422 Standard Test Method for Twist in Single Spun Yarn by the Untwist- Retwist Method, Annual Book of ASTM Standards, Vol. 07.01. (b) D 1423 Standard Test Method for Twist in Yarns by Direct Counting, Annual Book of ASTM Standards, Vol. 07.01. Testing Standards for fabrics used for apparel. Strength Properties of Apparel The strength properties of apparel have traditionally been considered the most obvious indicator of the service life of apparel. Knoll and Shiloh  of the Israel Fiber Institute conducted a limited survey to assess the relative importance of laboratory-tested properties in apparel and other textile items. Each participant in the survey was asked to rate the relative importance of strength, wear, comfort, aesthetics, dimensional stability, and colorfastness in terms of percent. The respondents gave strength and wear properties 25% importance for outerwear [coats, pants and jackets, dresses and skirts, shirts and blouses, sweaters and cardigans]; 30% importance for undershirts and hosiery; 45% importance for towels, sheets, pillowcases; and 25% importance for curtains. Therefore, it seems that consumers consider strength properties important, along with other properties of apparel and textile items. Also, the strength of a fabric or garment indicates its ability to resist mechanical damage due to the stresses of normal wear and laundering or dry cleaning. The strength properties of apparel can be divided into the following three areas: (a) Fabric strength (b) Seam strength (c) Resistance to yarn slippage Fabric Strength Fabric strength can be divided into three areas: its resistance to tensile force or breaking strength, its resistance to tearing/shearing force or tear strength, and its resistance to bursting force or bursting strength. Whether the strength of a fabric is measured in all these three areas depends on the type of fabric and its end use. 1. Breaking Strength The breaking strength or tensile strength of a fabric refers to its resistance to tensile force. Breaking strength tests are used for woven fabrics. Breaking strength of a fabric can be tested in either length or width or both. A specimen 15 x 10 cm is placed between two sets of jaws, 7.6 cm apart. These jaws are then pulled away from each other creating a tensile force on the fabric specimen, ultimately result break in the fabric specimen. The force and elongation at this point are noted, which are strength and elongation @ break are expressed in grams and % respectively in the respective direction of the tests. It is customary to take at least three to five specimens in each direction (warp and filling or length and width) to test. The final test result is expressed as an average of the test results of these specimens in the respective direction. Breaking or tensile strength test is not suitable for knitted fabrics because knitted fabrics have a lot of stretch. The complete procedural details of this test can be found in ASTM D 5034 Standard Test Method for Breaking Force and Elongation of Textile Fabrics (Grab Test), Annual Book of ASTM Standards, Volume 07.02. Figure 5-3 shows a tensile strength tester. 2. Tear Strength The tear strength of a fabric refers to its resistance to tearing or shearing force. Resistance to tearing is of importance in clothing fabrics such as those used for shirting, blouses, interlining, and in military fabrics such as those used for parachutes. Tear strength of woven fabric can be tested in both, length and width of the fabric. Tear tests are not suitable for knit fabrics because knit fabrics have lot of stretch. Tear tests are also not suitable for felts or nonwoven fabrics, with the possible exception of machine direction tears in some light-weight nonwoven fabrics. There are two methods for testing tear strength. One is called trapezoid method. In this test method, a small piece of fabric is nicked on one edge with a pair of scissors and then one side of the specimen is held in one jaw that is stationary and the other side is held in a jaw that is allowed to swing, tearing the sample and measuring, the force it took to propagate the tear (nick) that was put in the sample. Trapezoid tear strength tester is shown in Figure 5-4. The other method is called tongue tear test. In this method, the fabric specimen is cut half way in two and then each side is held in jaws and they are pulled apart measuring resistance of fabric to tear. It is customary to take at least three to five specimens in each direction to test and the final test result is expressed as an average of the test results of these specimens in the respective direction, in terms of grams. Testing of tear strength is covered by the following ASTM test methods: 1. D 5587 Standard Test Method for Tearing Strength of Fabrics by Trapezoid Procedure, Annual Book of ASTM Standards, Volume 07.02. 2. D 2261 Standard Test Method for Tearing Strength of Fabrics by the Tongue (Single Rip) Procedure (Constant-Rate-of-Extension Tensile Testing Machine), Annual Book of ASTM Standards, Volume 07.01. 3. Bursting Strength or Burst Strength Since knitted fabrics have far greater elongation (stretch) than woven fabrics, it is not appropriate to measure tensile strength or tear strength of knitted fabrics. Therefore, bursting strength tests are used for knitted fabrics. Bursting strength test are also used for lightweight woven fabrics, and non woven fabrics. Bursting strength is the force, uniformly distributed over a given area, needed to break a fabric when applied at right angles to the fabric. In this test a fabric specimen is held by a clamp and a force is applied against this specimen till the fabric bursts. Although generally used for knitted fabrics, this test does have some application in testing woven fabrics that are stressed equally in every direction when in use, since it picks the weakest yarns, warp, and filling wise and breaks them first, thereby indicating the lowest pressure the cloth will resist. It is customary to take at least three to five specimens to test and the final test result is expressed as an average of the test results of these specimens in terms of grams/square cm. There are two ASTM test methods for measuring bursting strength as follows: 1. ASTM D3786 Standard Test Method for Hydraulic Bursting Strength of Knitted Goods and Nonwoven Fabrics: Diaphragm Bursting Strength Tester Method. Annual Book of ASTM Standards, Volume 07.01. 2. ASTM D3787 Standard Test Method for Bursting Strength of Knitted Goods: Constant Rate of Traverse (CRT), Ball Burst Test. Annual Book of ASTM Standards, Volume 07.01. Figure 5-5 shows diaphragm bursting strength tester and Figure 5-6 shows an attachment used on a Scott tester for testing bursting strength of knitted fabrics by Ball Burst Method. Seam Strength Seam failure in a garment can occur because of either the failure of the sewing thread, leaving the fabric intact, or fabric rupture, leaving the seam intact or both breaking at the same time. The strength of a seam or stitching should be equal that of the material it joins in order to have balanced construction that will withstand the forces encountered in the use of the garment of which the seam is a part. The elements affecting the strength of a seam or stitching are: Thread strength, stitch type, number of stitches per cm, thread tension, seam type and seam efficiency of the material. Generally, a seam made with chain stitch will be stronger than the seam made using lock stitch. Obviously, stronger the sewing thread, the stronger the seam. Higher number of stitches per cm up to a point will give higher seam strength, but too many stitches per cm will weaken the fabric so seam may stay intact but the fabric may rupture resulting in seam failure. Higher thread tension will give higher seam strength but too high a thread tension will result in seam puckering. Lap felled seam will be stronger than lapped seam. Fabric with higher seam efficiency will provide stronger seam than fabric with lower seam efficiency. Seam efficiency is seam strength expressed as % fabric breaking strength. The elasticity of a seam or stitching should be slightly greater than that of the material which it joins, so that the material will support its share of the forces encountered in the end use of the garment. The elasticity of a seam or stitching depends on the stitch type and thread elasticity. Seam strength is tested in almost the same manner as fabric breaking and bursting strength except that, the test specimens include a seam to be tested in the center of those specimens. 1. Seams in Woven Fabrics The following points regarding seams in woven fabrics are worthy to note [Blackwood and Chamberlain, 1970]: When garment seams are subjected to increase transverse stress, a point is reached, when the threads of the fabric which lie parallel to the seam in the "seam allowance" are displaced bodily, then the seam opens slightly which presents an unacceptable appearance. Such a seam has "failed" commercially even though no rupture has occurred. In any examination which the seam opens to an unacceptable extent, and that at which it finally ruptures. The opening load is mainly dependent on: (a) the stitch rate (b) the weave structure of the fabric (c) the width of the seam allowance For a given width of fabric allowance, the seam opening and breaking loads were both found to increase rapidly with stitch rate, the effect being most marked with plain weave structures. Thus a narrow seam allowance can, to some extent, be off set by increasing the stitch rate. It is minimum sewn knot (or loop) strength of the sewing thread that governs seam strength, and not the mean tensile strength measured directly from the cop or bobbin. When stress is applied to a seam at right angles to its length, the load is carried by the intersecting loops of the sewing threads, and when the latter rupture, the break occurs at the opening of the loop. The strength parameter that applies is therefore the loop strength rather than the straight tensile strength of the sewing thread. The seam strength in woven fabric can be tested by cutting a specimen 15 x 10 cm in such a way that the seam is in the middle and parallel to the width of the specimen, which is placed between two sets of jaws, 7.6 cm apart so that the seam is approximately in the center between two jaws. These jaws are then pulled away from each other creating a tensile force on the test specimen, ultimately results a break in either the seam or the fabric, whichever is weaker. The force and at this point is noted, which is the seam strength expressed in grams. It is customary to take at least three to five specimens to test and the final test result is expressed as an average of the test results of these specimens in terms of grams. The complete procedural details of this test can be found in ASTM D 1683 Standard Test Method for Failure in Sewn Seams of Woven Fabrics, Annual Book of ASTM Standards, Volume 07.01. Figure 5-7 shows seam strength testing. 2. Seams in Knitted Fabrics. The following points regarding the strength of seams in knitted fabrics are worthy to note [Blackwood and Chamberlain, 1970): When woven fabrics are seamed, the absolute seam strength is not, in the majority of cases, of paramount importance, providing it is reasonably high, and it is accepted that, with a seam efficiency of say 60-70% (seam efficiency is seam strength expressed as % of the fabric breaking strength), the seam will be commercially acceptable. Knitted fabrics are in general, more extensible than woven fabrics, and in some instances very much more extensible; as a result it often happens that when a seam in a knitted fabric is extended along its length, the extension limit of the sewing threads is reached before that of the fabric itself, and the sewing threads that break at one or more points along the seam, an effect known as "seam cracking." Once a seam has cracked, even at one point, it is no longer useful, as the stitches will run back on either side of the break (in a lock stitch) and this will eventually lead to seam breakdown. Thus the behavior of seams under longitudinal, in contrast to transverse stress, is of much greater importance in knitted structures than in woven ones. Under transverse stress, seams in knitted fabrics show both types of failure, i.e., breaks in which the sewing threads fail but the fabric remains intact, and in which the failure is in the fabric, whilst the sewing threads survive. In a balanced seam an extension of approximately 80% is possible before the seam cracks provided the stitch rate is 20 or over. Reduction of the stitch rate reduces the extensibility, the effect being more pronounced for a cotton thread, than for a polyester thread. Other things being equal, the 2-thread chain stitch seam gives slightly higher extensibility than the lock stitch, though the difference is not so marked as is commonly supposed. Polyester thread gives the best result, with an extension of just over 100% at 20 stitches per inch. Of the four variables, namely, stitch rate, thread composition, thread denier, and seam structure, neither thread composition, nor thread denier is important from seam cracking point of view. The important variables are stitch rate, and seam structure, with the sewing thread extensibility playing a minor part. Seam strength in a knitted fabric can be tested in the same way as testing bursting strength, except that the test specimen should have a seam in the middle. It is customary to take at least three to five specimens to test and the final test result is expressed as an average of the test results of these specimens in terms of grams/square cm. Table 5-1 shows seam strength and stretchability test results for a particular style of ladies' pantsuits using the concept proposed by Blackwood and Chamberlain. Seam stretchability and strength results were obtained by testing seams in a longitudinal direction using a Constant Rate of Extension [CRE] machine such as an Instron tester. The first figure indicates the amount of force [load] in pounds to break the seam or sewing thread and the second figure indicates seam elongation in percent of the original length at the seam break. Yarn Slippage in Woven Fabrics In some garments, enough yarn slippage, that is, filling yarns shifting over warp yarns or vice versa at the seams, develops to render the garment unusable, before seam failure occurs because such mistakes are not readily repairable by seaming. In order to test yarn slippage, the load-elongation curve of the fabric is superimposed over a load-elongation curve of the same fabric with a standard seam sewn parallel to the yarns being tested. The force at which the load- elongation curve of fabric with the seam in a predetermined distance greater than the load-elongation curve of the fabric without a seam, is reported as the kg per cm resistance to yarn slippage. Generally a 0.6 cm separation is used, but for some fabrics, a smaller opening is preferred. See Figure 5-8. It is customary to take at least three to five specimens to test and the final test result is expressed as an average of the test results of these specimens in terms of grams. ASTM had a standard test method for testing resistance to yarn slippage, however, it was withdrawn in July 2004. According to Lyle , seam slippage may occur in a garment or household item because of; 1. A low number of warp or filling yarns to an inch in relation to particular yarn and fabric construction characteristics. 2. Too shallow seam allowances (any strain on the fabric at the seams causes the yarns to shift. 3. Too tight a fit (undue strain during wear may cause yarns to shift at the seam line), and 4. Improper seam construction (not enough stitches per inch). The performance standards for fabric strength, seam strength, and yarn slippage for various fabrics used in various garments are listed in the Chapter 7 on Standards and Specifications. Fabric Stretch Properties There are two categories of stretch fabrics based on degree of stretch- ability [Editors, 1980]: power or action stretch and comfort stretch. Power or action stretch, as the name implies, provides a fabric with a high degree of extensibility and quick recovery. The stretch factor generally ranges from at least 30 to 50% or more with no more than 5 to 6% loss in recovery. Such stretch fabrics are at best adapted to skiwear, swimwear, athletic clothing and professional sportswear. Comfort stretch applies to fabrics with less than 30% stretch factor and no more than 2 to 5% loss in recovery. Such fabrics are used for everyday clothing that needs only a moderate degree of elasticity. This category covers a wide range of end uses in both apparel and home, as well as in transportation upholstery, such as automobile, bus, train, and aircraft seat covers. With stretch fabric, comfort is achieved by reducing garment restraint imposed on the body, through increased fabric "give." This also means that the garments can be cut more neatly and will conform better to the body. No standards exist for the level of stretch required in various garments. However, there are some data available on this subject. Kirk and Ibrahim conducted an experiment to establish the preferred stretch level and direction from a comfort viewpoint and to determine the sensitivity of the consumer to stretch level. The results are given in Table 5-3. They reached the following conclusions: (a) The experiment confirmed the general view that outerwear garments that offer the least resistance to body movements are the most comfortable. (b) Wearers' preferences for stretch were established at a 25 to 45% stretch range, depending on the end use. (c) For women's horizontal stretch slacks, a 35% stretch level effectively satisfies the comfort requirements for this type of garment. The stretch properties of fabrics other than elastic are measured/tested by the following three methods. (a) D 2594 Standard Test Method for Stretch Properties of Knitted Fabrics having Low Power, Annual Book of ASTM Standards, Volume 07.01. The above test method specifies test conditions for measuring growth and stretch of knitted fabrics intended for use in swimwear, anchored slacks and other form- fitting apparel (also commonly known as semi- support apparel) as well as for measuring growth of knitted fabrics intended for use in sportswear and other loose-fitting apparel (also commonly known as comfort stretch apparel). To test fabric growth, a specimen of known length is extended to a stretch of a specified percent and held at this stretch for a prescribed duration of time. The specimen is then allowed to recover under zero load. During the recovery period the length of the specimen is measured at the end of various time intervals. The amount of growth at each time interval during recovery is calculated from the length of the specimen at the end of the time interval and the length of the specimen prior to stretching. Fabric growth is an increase in length or width of fabric due to stretch in repeated use. When a knitted fabric does not come back to its original length or width (recover completely) from its stretched state it is called fabric growth. Ideally, a knitted garment should not grow due to repeated use because, then it would not retain its original shape and won't drape that nicely when worn and ultimately may present an unacceptable appearance. (b) D 3107 Standard Test Method for Stretch Properties of Fabrics Woven from Stretch Yarns, Annual Book of ASTM Standards, Volume 07.01. This test method is used to determine the amount of fabric stretch, fabric growth, and fabric recovery of fabrics woven in whole or in part from stretch yarns after a specified period of tension and extension. Fabric stretch and immediate growth are tested by applying a specified load to a fabric specimen of known length by a prescribed cycling technique and the resulting length is measured; the load is then removed from the specimen and the length is measured again after recovery for a specified time interval. The amount of fabric stretch is calculated from the difference in length of the specimen prior to loading and when under load. The immediate fabric growth after cycling is calculated from the difference in length of the specimen prior to loading and after short-term recovery (30 seconds). For testing fabric growth after stretching to a specified extension, a specimen, paired to the one used in the stretch test, is held at a specified extension for the prescribed period of time; the restraining force is then removed from the specimen and the length measured after the specimen has been allowed to recover for various time periods. The amount of fabric growth at each time interval is calculated from the length of the specimen prior to stretching and the length after each recovery period. This method is intended for use with woven fabrics exhibiting high stretch (12 to 40%) and good recovery properties from low loads, up to 179 g/cm (1 lb/in.) of fabric width. Also, this method is used to determine the stretch and growth properties that a garment may be expected to exhibit during use. (c) D 6614 Standard Test Method for Stretch Properties of Textile Fabrics CRE Method, Annual Book of ASTM Standards, Volume 07.02. In this test method, a specified load is applied to a fabric specimen, using a constant rate of extension tensile tester at a prescribed rate of extension. After holding at the specified load for a predetermined time, the length is measured. The load is removed from the specimen and allowed to relax for a specified time. A small amount of force, enough to remove any wrinkles or folds, is applied and the specimen length measured. The amount of fabric stretch is calculated from the difference in length prior to load and under load. Dimensional Changes in Apparel due to Laundering, Dry Cleaning, Steaming, and Pressing Consumers consider the dimensional change in a garment to be a critical performance characteristic. The excessive shrinkage or expansion of a garment can make that item unwearable. Color loss or change may make a garment unacceptable but it does not necessarily make it unusable. Holes and tears might be repaired and frequently can be anticipated by judging the quality of a fabric. Dimensional change is hidden from the consumer until it is too late. In a survey of apparel manufacturers, fabric shrinkage was rated one of the ten leading quality problems, regardless of the size of the company interviewed [Hudson, 1982). Garment shrinkage due to laundering, dry cleaning, steaming, or pressing occurs at three levels: fabric, yarn, and fiber. The total observed shrinkage is the resultant shrinkage at these three levels. The contribution of each to the total depends on both the fabric and yarn structure. as well as the nature of the fiber. For example, cotton fabric may shrink as much as 10% under conditions that cause only 2% shrinkage in the component fibers and yarns. In cotton fabrics, in general, shrinkage occurs principally at the fabric level. It is for this reason that cotton fabrics are successfully preshrunk by a mechanical process known as "sanforizing" Rayon fabrics, on the other hand, exhibit most of their shrinkage at the fiber and yarn levels. For this reason, sanforizing is not effective on rayon fabrics. Fiber and yarn shrinkage is minimized by the same process that is used to obtain better crease resistance, i.e., resin treatment It has been well established that fabric shrinkage may be ascribed to one or more of the following four distinct factors. (a) Relaxation: When yarns are woven into a fabric, they are subjected to considerable tension, particularly in the warp direction, although the filling (weft) yarns are also stretched. In the subsequent tentering and calendering operations, this "stretch" may be further increased and temporarily "set" in the fabric. The fabric is then in a state of dimensional instability, and when it is wetted thoroughly, yarns counteract and try to regain pre-stretch level. The counteraction in the filling direction is normally considerably less than in the warp direction, although in some fabrics it can be high enough to cause complaint unless steps are taken to counteract it. This is called relaxation shrinkage. (b) Swelling: Shrinkage that results from the swelling and deswelling of fibers because of the absorption and desorption of water is called swelling shrinkage. In a loosely woven fabric, the effect of this swelling of the fibers is greater than in a tightly woven fabric because there is greater freedom of movement in a loosely woven fabric. (c) Felting: Shrinkage that result primarily from the frictional properties of the component fibers which cause them to migrate within the fabric/yarn structure is called felting shrinkage. This is normally considered to be significant only for fibers having scales on their surface, such as wool. (d) Contraction: This is the decrease in length that takes place in synthetic yarns/fabrics when they are exposed to temperatures higher than 21°C or 70°F. The tendency of synthetic fabrics toward contraction shrinkage can almost be eliminated by heat-setting the yarns. Synthetic yarns that are not heat-set before or after they are converted into a fabric will shrink due to steaming and/or pressing during apparel manufacturing. Shrinkage of a garment can occur when it goes through one or more of the following processes: There are six test methods (five AATCC test methods and an ASTM method) for evaluating the dimensional change in fabrics and garment as follows: 1. AATCC Test Method 96, Dimensional Changes in Commercial Laundering of Woven and Knitted Fabrics except Wool. 2. AATCC Test Method 99, Dimensional Changes of Woven or Knitted Wool Textiles. 3. AATCC Test Method 135, Dimensional Changes in Automatic Home Laundering of Woven or Knit Fabrics. 4. AATCC Test Method 150, Dimensional Changes in Automatic Home Laundering of Garments. 5. AATCC Test Method 158, Dimensional Changes on Dry cleaning in Perchloroethylene: Machine Method. 6. D 2724, Standard Method of Testing Bonded and Laminated Apparel Fabrics. Annual Book of ASTM Standards, Vol. 07.01. The principle in all these six test methods is that fabric or garment specimens are marked 25 cm x 25 cm or the maximum distance that can be marked in both, length and width with indelible ink, washing or dry cleaning these specimens once, drying them, conditioning them, then measuring the distance between those marks and calculating shrinkage in terms of %. Sometimes these specimens are washed and dried (laundered) or dry cleaned two more times then shrinkage is measured after 3 laundering or dry cleaning cycles. Shrinkage is sometimes measured after 5 laundering or dry cleaning cycles. While most of the garment or fabric shrinkage will occur in the first laundering or dry cleaning, shrinkage may occur in several subsequent launderings or dry cleanings, which is called "progressive shrinkage." That is why some companies make it a practice to measure shrinkage after 3 to 5 launderings or dry cleanings. Some garment manufacturers, knowing that the fabric will shrink excessively in laundering, will make the garment oversized, particularly in length, i.e. will make an allowance for fabric shrinkage. Therefore, considerable judgment must be exercised before deciding that shrinkage test results for a particular garment are unacceptable. Should garments be made oversized to allow for excessive fabric shrinkage, then the manufacturer would be wise to advise consumers to wash that garment first before wearing. Such information/advice can be conveyed on the hang tag. Shrinkage Restorability of Knit Garments Since many commonly used knit fabrics (particularly weft knit fabrics) are stretchable, there is a school of thought that the shrinkage measurement on knit fabrics should be done after restoring, i.e. stretching the shrunk knit fabric. However, it does not make sense from the consumers' point of view because a knit garment is stretchable and its original length/ width is restored only when the garment is constantly held at two points. Except for bodysuits, this is hardly the case. Therefore, for example, when a men's knit undershirt shrinks 20% in length during laundering, it is useless because there is no way that this undershirt will come back to its original length no matter what kind of restoration procedure is used. It may be possible to restore some of the shrinkage by ironing the knit shirt. But how many consumers would want to iron an undershirt or for that matter, any shirt or garment? On the contrary, when this under- shirt is worn, it will be stretched in width, resulting in further shortening of the already shorter length. Similarly, a ladies' knit dress may shrink 8% in length in laundering, resulting in a higher hemline that may not be acceptable to consumers. With the exception of certain garments such as bodysuits, the stress applied to the length of a garment during wear is little or none. However, the stress applied to width during wear is significant. Even if the shrinkage of a knit garment may be restorable to a certain extent, no care instructions that this author has ever seen indicate any reference to restoration procedure. And the consumer nowadays is so demanding that as far as she is concerned, she would want to wear a garment straight out of the dryer without having to worry about touch-up ironing or any other restoration procedure. Therefore, restoring shrinkage of knit garments before measuring shrinkage is not practical from consumers' point of view. Needle Cutting/Yarn Severance Needle cutting or yarn severance is a condition in a fabric where needle has cut yarns rather than displacing them during sewing operations. This can be due to blunt needle or improperly sized needle. Needle cutting or yarn severance in a fabric is objectionable because it may result in reduced seam strength or poor appearance or both due to frayed yarns. For needle cutting or yarn severance testing, sewn seams are prepared, unless seams are taken from previously sewn garments. The sewing threads are removed from the test specimens. The count of the number of fabric yarns and the count of the number of severed and fused fabric yarns in the direction most nearly perpendicular to the direction of sewing are used to calculate the needle cutting index. Needle cutting index (%) = number of yarns cut/cm ×100 number of yarns in fabric/cm It is customary to take at least three to five specimens to test and the final test result is expressed as an average of the test results of these specimens in terms of the needle cutting index. ASTM had a test method for needle cutting and yarn severance, ASTM D1908 Test Method for Needle-Related Damage Due to Sewing in Woven Fabrics, however it was withdrawn in 1998. Sewability of Fabrics Sewability is that characteristic of a fabric that allows it to be seamed at the full limit of high-speed sewing machinery, without the fabric suffering mechanical degradation. Experience has demonstrated that the strength of many woven fabrics is considerably reduced by the seaming operation. The result of such reduction is the shortening of the overall life of a garment. This loss in fabric strength and poor seam appearance, are usually due to the cutting, scorching, or fusing of fabric yarns by a sewing needle. In a survey of apparel manufacturers, fabric sewability was mentioned as one of the top ten quality problems by small, medium, and large manufacturer alike [Hudson, 1982). The sewability of a fabric, or the degree of its resistance to needle damage, can be determined in two ways. One measure of this property is the proportion of fabric yarns cut by the needle. This method was discussed under "Needle Cutting/Yarn Severance." Another measure of this property is the loss in fabric strength caused by needle damage. The measurement of the loss in fabric strength due to needle damage consists of sewing a seam in the fabric, breaking the fabric at the line of stitching, and establishing a ratio between the original and the seamed fabric strength. It is generally considered that if this seam efficiency falls below 80%, the fabric has been excessively damaged by the sewing operation. Seam efficiency = Seamed fabric strength ×100 Original fabric strength It is customary to take at least three to five specimens to test and the final test result is expressed as an average of the test results of these specimens in terms of % seam efficiency. Needle cutting or yarn severance occurs due to the stiffness of the fabric yarns and a lack of mobility of the yarns. Instead of moving and/ or deforming when the needle penetrates the fabric structure, the yarns remain taut and are ruptured or burned. Some damage may result from the excessive heat generated due to the friction of the sewing needle and the fabric. Also, using the wrong size needle will result in sewing damage. Bow and Skewness (Bias) in Woven and Knitted Fabrics Filling yarns in woven fabrics and courses in knitted fabrics usually appear as straight lines perpendicular to the selvedge of the fabrics. When there is a deviation from this perpendicularity, the fabric is said to have a bias or bowed condition. The ASTM [D 123] defines bow and skewness as follows: Bow-"A fabric condition results, when filling yarns or knitted, courses are displaced from a line perpendicular to the selvedge and form one or more arcs across the width of the fabric." See Figure 5-10. Skewness-"A fabric condition results, when filling yarns or knitted courses are angularly displaced from a line perpendicular to the edge or side of the fabric. Skewness is also called bias." See Figure 5-11. Bow or skewness can be induced during cloth manufacturing, dyeing, tentering, finishing, or other operations where a potential exists for the uneven distribution of tensions across the fabric width. Bow and skewness are more visually displeasing in colored patterned fabrics than in solid colors because the contrast makes the distortion more prominent. Also, such conditions may cause sewability and drapability problems. Such a condition may be more noticeable in the small parts of garments such as collars, pockets, etc, rather than in the big parts. Bow or skewness in a fabric will sometimes cause a garment to twist in laundering, such as a twisted leg on a pair of jeans or a twisted sleeve on a long-sleeve knit shirt. In a survey of apparel manufacturers, bow was mentioned as one of the top ten quality problems [Hudson, 1982]. Bow and skewness are illustrated in Figures 5-10 and 5-11, respectively, and it is also explained how to calculate the value of each. What degree of bow and skewness are acceptable, depends on the type and price line of the garment being produced, and is a matter of an agreement between the buyer of the fabric and the seller of the fabric. There are no standard values of bow and skewness that may be considered unacceptable. Method for determining bow and skewness of filling yarns in woven fabrics and courses in knitted fabrics is covered in ASTM D 3882 Standard Test Method for Bow and Skewness in Woven and Knitted Fabrics, Annual Book of ASTM Standards, Volume 07.01. Soil/Stain Release testing Much of the dirt on textile material is held by a film of oily or greasy matter. With clothing worn next to the skin, the grease comes from the skin. The air is filled with millions of minute particles of mineral and organic matter, dust, soot, smoke particles, and so on. These particles come into contact with clothing and are held there by grease films. The greasy film that holds dirt to the surface may be of two types: mineral oil, such as machine oil or automobile grease, or grease of the glyceride type, such as fat [Hartsuch, 1950]. With the advent of durable press and 100% synthetic fibers, the removal of certain types of soil has become a problem. Oil-type stains, often found on men's shirt collars, or grease stains, especially on work trousers, are more difficult to remove from the durable press and 100% synthetic fabrics than from untreated cotton. To solve this problem, a number of finishes have been developed for use on durable press and 100% synthetic fiber fabrics. These are called soil-release or SR finishes. AATCC Test Method 130, Soil Release: Oily Stain Release method is designed to measure the ability of fabrics to release oily stains during home laundering. In this test a stain on a test specimen is produced by applying a stain to the specimen and forcing it into the specimen (fabric) using a specified weight. The stained fabric is then laundered in a prescribed manner and the residual stain is visually compared to AATCC's stain release replica and rated on a scale from 5 [complete stain release] to 1 [no stain release]. The standard staining substance used is a refined mineral oil, the "Nujol" brand, a trademark of Plough Inc. It is available in most drug stores. Other nonstandard staining substances of interest to the user such as coffee, ketchup, mustard, salad dressing, lipstick, nail polish, etc., may be applied to the test specimens using the same technique. In such cases, the nonstandard stain should be identified in the report. The laundering conditions used are according to the care instructions or intended care instructions on the garment. Then, three individuals rate the residual stain on the test specimen compared with the stains in the stain-release replica, shown in the Figure 5-29, available from the AATCC. The final rating is the average of the three individual ratings. The rating of class 5 indicates an excellent stain- release property and the rating of class 1 indicates a poor stain-release property. Generally speaking, an item with a stain- release rating of class 3 or less is considered not acceptable from the consumers' point of view. Fabric Thickness Measuring fabric thickness is not a routine quality control procedure in the apparel industry; however, various properties such as warmth and bulk are dependent on fabric thickness. Thicker fabrics generally entrap more air within the fabric structure, creating a thicker shield between the skin and the environment, thereby providing more warmth. Measuring fabric thickness is also used for evaluating the abrasion resistance of a fabric or textile material. Also, sometimes, the garment manufacturers rely on a fabric thickness measurement in calculating the number of fabric lays in cutting garments and determining settings to use for stitching on sewing machines [Lyle, 1977]. Fabric thickness is measured by a thickness gauge, such as the one shown in Figure 5-9. The thickness value of most textile materials will vary considerably, depending on the pressure applied to the specimen at the time of thickness measurement is taken. In all cases, the apparent thickness varies considerably with the pressure applied. For this reason, it is essential that the pressure has to be specified when discussing or listing any thickness values. Also, since the textile material is resilient, the thickness reading will not be stable for the first few seconds after putting the specimen under the thickness measurement gauge. Therefore, it is essential to specify after what time interval the thickness measurement should be taken so that it would be stable. For many materials, 5 seconds after the full load has been applied will represent a stable and suitable time interval. It is customary to take at least three to five specimens to test and the final test result is expressed as an average of the test results of these specimens in terms of mm. ASTM has a standard test method for measuring fabric thickness, D 1777 Standard Method for Measuring Thickness of Textile Materials, Annual Book of ASTM Standards, Volume 07.01. Abrasion Resistance Abrasion or wear is the wearing away of any part of a material by rubbing against another surface. The importance of the adequate abrasion resistance of textile materials should not be underestimated. It is essential for consumer acceptance and satisfaction. A garment is worthy only if it is durable. If becomes useless when it loses its grace. Textile material are discarded for several reasons because of fraying cuffs and collars, worn seats and elbows. Sheets become unserviceable as they threadbare. Carpets are often discarded because of extensive wear. All of these are the results of some form of abrasive action. Abrasive wear is caused by one or more of the following conditions: 1. Friction between cloth and cloth, such as the rubbing of a jacket or coat lining on a shirt, pants pockets against pants fabric, etc. Friction between the cloth and external objects, such as that on the seat of trousers. 3. Friction between the fibers and dust, or grit, in a fabric that results in the cutting of the fibers. This is an extremely slow results and may take years before it is noticeable; it may be observed on drapery, flags, or outdoor fabrics. The measurement of the resistance to abrasion of textile materials is very complex. The resistance to abrasion is affected by many factors, such as the inherent mechanical properties of the fibers, the dimensions of the fibers; structure of the yarns; construction of the fabric, and the type, kind, and amount of finishing material added to the fibers, yarns, or fabric. The resistance to abrasion is also greatly affected by the conditions of the tests, such as the nature of abradant; variable action of the abradant over the area of the specimen, the pressure between the specimen and the abradant; and the dimensional changes in the specimen. ASTM has five test methods for testing abrasion resistance of fabrics and one guide for evaluating abrasion resistance of fabrics as follows: 1. D 3884, Standard Test Method for Abrasion Resistance of Textile Fabrics [Rotary Platform, Double Head Method). Annual Book of ASTM Standards, Vol. 07.01. 2. D 3885, Standard Test Method for Abrasion Resistance of Textile Fabrics [Flexing and Abrasion Method). Annual Book of ASTM Standards, Vol. 07.01. 3. D 3886, Standard Test Method for Abrasion Resistance of Textile Fabrics [Inflated Diaphragm Method). Annual Book of ASTM Standards, Vol. 07.01. 4. D 4157, Standard Test Method for Abrasion Resistance of Textile Fabrics [Oscillatory Cylinder Method). Annual Book of ASTM Standards, Vol. 07.01. 5. D 4158, Standard Guide for Abrasion Resistance of Textile Fabrics [Uniform Abrasion). Annual Book of ASTM Standards, Vol. 07.01. 6. D 4966, Standard Test Method for Abrasion Resistance of Textile Fabrics [Martindale Abrasion Tester Method). Annual Book of ASTM Standards, Vol. 07.02. Rotary platform method is used for testing abrasion resistance of heavy fabrics such as those used for jeans, corduroy, overcoats, pile fabrics, carpets, etc. In this test method, a specimen is abraded using rotary rubbing action under controlled conditions of pressure and abrasive action. The test specimen mounted on a platform turns on a vertical axis against the sliding rotation of two abrading wheels. The resulting abrasion marks form a pattern of crossed arcs over an area of approximately 30 square cm. Resistance to abrasion is evaluated as explained later in this section. Rotary platform tester is shown in Figure 5-37. It is also known as Taber Abraser. Flexing and abrasion method is mainly used for evaluating the abrasion resistance of corduroy, velour, and pile fabrics. In this test method, a specimen is subjected to unidirectional reciprocal folding and rubbing over a metal bar having specified characteristics, under known conditions of pressure and tension. The machine used is called Stoll Quartermaster Abrasion Tester or CSI Stoll Abrasion Tester. This is shown in the Figure 5-38. Inflated diaphragm method is used for light-to-medium weight fabric such as those used for shirting, sheets, blouses, skirts, and slacks/trouser In this test method, a specimen is abraded by rubbing it against an abradant having specified surface characteristics. The specimen is held in a fixed position and supported by an inflated rubber diaphragm [that's why the name of the test method] which is held under a constant pressure. Resistance to abrasion is evaluated as explained later in this section. The same machine, i.e. CSI Stoll Abrasion tester is used in inflated diaphragm method, but with different attachment than the one used in flex abrasion. Oscillatory cylinder method is used widely for upholstery fabrics. In this test method, a specimen is subjected to unidirectional rubbing under known conditions of pressure, tension and abrasive action. The instrument used in this test is known as Wyzenbeek abrasion tester. Resistance to abrasion is evaluated as explained later in this section. Uniform abrasion test method is used for a wide range of textiles. A specimen is mounted in a holder and abraded uniformly in all directions in the plane and about every point on the surface of the specimen. The instrument used in this testing is known as Schiefer abrasion tester. In the Martindale test method, abrasion resistance is measured by subjecting the specimen to rubbing motion in the form of a geometric figure, that is a straight line, which becomes gradually widening eclipse, until it forms another straight line in the opposite direction and traces the same figure again under known conditions of pressure and abrasive actions. This tester is shown in the Figure 5-39. This test method is used for apparel fabrics. Edge and fold abrasion testing-Fabrics frequently wear out on edges and folds such as cuffs and vertical creases of trousers, sleeve cuffs, collars, and so on. The resistance to such wear/abrasion can be determined by this test method. In this test method, the test specimen is folded over a tiny glass rod and then abraded multi-directionally for a number of predeter- mined rubs, using the CSI Stoll abrasion tester. Evaluation of the resistance to abrasion may be based on any of the following criteria: 1. Number of rubs or revolutions required to wear a hole in the specimen. 2. The specimen is subjected to a certain number of rubs or revolutions, and then one of the following is evaluated: (a) Overall appearance, loss in color or shade, signs of damaged yarns, fibers (b) Loss in the breaking strength of the specimen (c) Loss in the weight of the specimen (d) Decrease in the thickness of the specimen (e) Change in the air permeability of the specimen There are no voluntary or mandatory standard minimum require- ments for the abrasion resistance of various fabrics. In general, abrasion tests are not relied on for a prediction of the actual wear life in specific end item uses unless adequate data are available showing a positive relationship between laboratory abrasion tests and actual wear of the item in its intended end use. Usually, the results obtained on an abrasion tester are considered to be comparative only Abrasion tests are meaningful when considered along with other physical properties tests. Together they are very helpful in predicting a fabric's performance. If a garment has a history of satisfactory service for some time and the fabric continues to give its accustomed value in laboratory tests (abrasion along with the other tests), the garment should continue to be satisfactory in use. An end-use product with a satisfactory service history supported by laboratory tests of abrasion, breaking strength, tear strength, and so on can be relied on for continued satis- factory service in end use so long as the test results maintain accustomed levels. Any drastic change in the levels of any of the test properties will predict changes in service life, although not necessarily in strict arithmetical proportion. New and fresh products with laboratory test results, an end use similar to those of a tried and true product can be expected to be satisfactory in service. Wear Testing Factors such as stress and strain in daily wear, abrasive actions, effect of environmental elements, or effects of repeated laundering and dry cleaning that influence the behavior and performance of garments are variable that their cumulative or aggregate effect on an item cannot b predicted with certainty by any of the test methods available today Therefore, actual use through wear testing of the item under by several people will yield much more useful data than all other testit ASTM combined. That is why even though wear testing is expensive and time consuming, some companies "wear test" their fabrics and garments befor make them ready for the market. Wear testing may serve one or more the following purposes: evaluation (a) It can help to evaluate the performance of new or existing produe compared to the performance of known products. (b) It would be an excellent tool to gauge consumer acceptance and product development. (c) It can help to evaluate the suitability of existing products in differen end uses. (d) It can help to evaluate the interaction of wear, laundering and dry cleaning, daily stress-strain, environmental elements, etc. on given fabric, dye, finish, and such. (e) A very real advantage arising from wear testing is the ability to determine what care instructions should be furnished for the consumer, thereby generating greater consumer satisfaction. It is very important to decide the following points prior to initiate wear testing program: (a) The objective of the wear testing, is, to compare a new product design, construction, fabric, etc. with an existing product of satisfactory performance; to compare two or more products with certain differences such as fabric blend composition, construction details, and so on; to determine the proper care label; to judge consumer acceptance of a new product; or to arrive at realistic performance standards for a product. (b) Properties to be evaluated; surely will depend on the objective. (c) How the product of wear test will be evaluated? For example, by visual ratings, by testing certain properties after a certain number of wears, etc. (d) Length of test. (e) Method of refurbishing (laundering or dry cleaning) and who will complete this refurbishing (whether the participants would do it individually, or they should bring the product to the lab after each wear, where refurbishing would be done by the lab, etc.) The ASTM provides excellent guidelines for designing and conducting wear testing trials in D 3181 Standard Guide for Conducting Wear Tests on Textiles. Colorfastness Cotton, Inc.'s research found a wide range of colorfastness at retail. Out of 16 different brands of casual trousers tested for colorfastness, only 5 retained at least 90% of their color after 10 washings. This wide variability in product performance makes it hard for consumers to know what to expect from any given garment. In the same research, it was reported that consumers expect a pair of black pants to be washed at an average of 11 times before fading and sheets to launder 13 times before fading. Colorfastness is the property of a dye or print that enables it to retain its depth and shade throughout the wear period of a product. Dyes are generally considered fast when they resist the deteriorating influences such as laundering or dry cleaning to which they will be subjected in the use for which the fabric is intended. Consumer demand for fabrics with excellent fastness properties is of great concern to apparel manufacturers. Therefore, if apparel manufacturers can test fabrics for various color- fastness properties, then they will be able to prevent customer complaints to poor colorfastness, and they will be able to discuss their test results with the fabric suppliers, if any fabric needs an improvement in colorfastness. The AATCC (American Association of Textile Chemists and Colorists) has established test procedures that indicate the fastness of colors and predict their performance in use. In the colorfastness evaluation of fabrics or apparel, a change in the original color (shade) and/or staining or color transfer on the standard test fabric is evaluated by visually comparing the test specimen to the AATCC gray scale for color change and staining and chromatic transference scale. The difference in the color change and the amount of color transfer are given a numerical value ranging from Class 5 to Class 1. Class 5 indicates no change in the original color (shade) and/ or no color transfer. Class 1 indicates a noticeable change in color (shade) and/or heavy color transfer. These classes may be described in qualitative terms as follows: Class 5, excellent Class 4, very good Class 3, good (average) Class 2, fair Class 1, poor Generally those items exhibiting colorfastness equivalent to class 2 or 1 are considered unacceptable from the consumers' point of view. Testing for staining or color transfer is as important as testing for change in the original color. Garments are often in contact with other items while worn or cleaned. The merging of color from one item to another such as from coat lining to shirt, from pants to upholstery, from nightclothes to bed sheets, etc. can result in the latter article becoming unwearable or unusable. It is possible for a fabric to change color in the colorfastness test and not exhibit any staining. It is also possible for the fabric to stain and not seem to change color. Some fabrics will both change and exhibit staining in the test. AATCC has developed three scales that help visual comparison between the original color and color change and/or staining of the test specimen These scales are gray scales for color change, staining, and chromatic transference scale. Gray scale for color change-This scale consists of nine pairs of standard gray chips, each pair representing a difference in color or contrast [shade and strength) corresponding to a numerical fastness rating. The results of colorfastness tests are rated by visually comparing the difference in color represented by the scale. Part of the original fabric and a tested specimen of it are placed side by side in the same plane oriented in the same direction. The gray scale is placed nearby in the same plane. The visual difference between the original and tested fabric is compared with the differences represented by the gray scale. The fastness rating of the specimen is that number of the gray scale which corresponds to the contrast between the original and tested fabric. A rating of 5 is given when there is no difference in the color [shade and strength) between the original fabric and the tested specimen. Gray scale for staining-This scale consists of pairs of nominally white and gray color chips, each representing a difference in color or contrast [shade and strength] corresponding to a numerical rating for staining. The staining of cloth in colorfastness tests is rated by visually comparing the differences in color of the stained and unstained cloth with the difference in color represented by the scale. A swatch of the unstained fabric and the tested piece of it are placed side by side in the same plane and oriented in the same manner. The gray scale for staining is placed nearby in the same plane. The visual difference between the original unstained and tested stained piece is compared with the difference represented by the gray scale. The fastness rating of the specimen is that number of the gray scale which corresponds to the contrast between the original and tested pieces. A rating of 5 is given only when there is no difference in color between the original material and the tested piece of it. Testing Standards for related accessories used in apparel. Testing of Fusible Interlinings The purpose of fusible interlinings is to give shape or form to a garment and improve its aesthetics. There is no better way to test fusible interlining other than to actually fuse the interlining with the end-item fabric and evaluate such specimens before starting mass production. Therefore, at least three 30 x 30 cm pieces of the end-item fabric are cut and fused to 23 x 23 cm pieces of fusible interlining at the time, temperature, and pressure recommended by the fusible interlining supplier/manufacturer. Then these three specimens are checked for compatibility, shrinkage, and bond strength. Compatibility means that the fusible interlining material should provide good drapability, bulk, and support without altering the natural hand of the end-item [shell] fabric. Shrinkage can be measured by placing gauge marks on the interlining and shell fabric before fusing and measuring the distance between these gauge marks after fusing. Any significant shrinkage of the interlining fabric would result in a noticeable bubbled appearance on the right side of the shell/ interlining assembly. Bond strength can be determined by using ASTM D-2724 Standard Test Methods for Bonded, Fused, and Laminated Apparel Fabrics. These specimens may also be used to evaluate fusing performance in laundering and dry cleaning according to the intended care instructions of the end item for defects such as bubbling, cracking, delamination, etc. The three controllable variables in the fusing process are time, temperature, and pressure. If pressure is not sufficient, the bonds will not sustain themselves in washing and/or dry cleaning; if too much pressure is applied, a strike through on lightweight fabrics is possible, but in most circumstances, a change in hand [increased boardiness] will result. In many cases with the new high-performance resins that are used today, the introduction of too little or too much heat [temperature] may affect the hand or drapability of a garment, although it might not drastically alter bond strength. Testing of Zippers There are following ASTM test methods for testing zippers: D 2051 - Standard Test Method for Durability of Finish of Zippers to Laundering D 2052 - Standard Test Method for Colorfastness of Zippers to Dry cleaning D 2053 - Standard Test Method for Colorfastness of Zippers to Light D 2054 - Standard Test Method for Colorfastness of Zipper Tapes to Crocking D2057 - Standard Test Method for Colorfastness of Zippers to Laundering D 2058 - Standard Test Method for Durability of Finish of Zippers to Dry Cleaning D 2059 - Standard Test Method for Resistance of Zippers to Salt Spray [Fog] D 2060 - Standard Test Method for Measuring Zipper Dimensions D 2061 Standard Test Methods for Strength Tests of Zippers D 2062 - Standard Test Methods for Operability of Zippers The durability of the finish of zippers to laundering is evaluated by laundering the test specimen in a LaunderOmeter [AATCC test method 61, paragraph 5, procedure using test condition 3-A]. The effect of laundering on the zipper coating or finish is evaluated by noting the loss of coating on the zipper chain or components or both. The colorfastness of a zipper to dry cleaning is tested by subjecting the zipper stringer [tape) to commercial dry cleaning with a multi-fiber fabric. The dry cleaned specimen is compared with the original specimen and any change in the color of the specimen or staining of the multifiber fabric is then assessed a rate using the AATCC gray scale for color change or the chromatic transference scale. The colorfastness of zippers to light and crocking is tested in the same way as the colorfastness of fabrics. The colorfastness of zippers to laundering is tested by subjecting the zipper with a multifiber test fabric to home laundering according to the intended care instructions for the garments on which this particular zipper would be used. The alteration in shade of the zipper stringer [tape] and the degree of staining of the multifiber test fabric are evaluated by the AATCC gray scale for staining and color change or the chromatic color transference scale. The durability of the finish of zippers to dry cleaning is tested by subjecting the zipper to dry cleaning, as in AATCC test method 86, but the zipper is air-dried rather than hot-pressed. The specimen is then evaluated visually for any exposed base metal compared to a new zipper or compared to a sample illustrating an acceptable degree of coating loss. Sometimes due to corrosion, a zipper will not operate smoothly and its crosswise strength may be reduced. Such deterioration in a zipper can be evaluated by subjecting the zipper to a salt spray test. Of course, plastic/nylon zippers do not corrode, and therefore, this test applies only to metal zippers. In this test method, specimens are subjected to salt spray 5% salt solution at 33° to 36°C or 92° to 97°F for 24 hours continuously as directed in ASTM method B 117. Standard Practice for Operating Salt Spray [Fog) Apparatus, Annual Book of ASTM Standards Vol. 03.02. The exposed specimens are visually evaluated for any sign of corrosion and tested for ease of operation and crosswise strength. Then the results are compared with the ease of operation and crosswise strength of the original specimens. The usefulness of a zipper in service can be evaluated by the following strength tests. No one test determines the suitability of a zipper for a specific end use. Since the tests are interrelated, more than one type of strength tests may be needed for a complete evaluation. Zipper strength is usually tested in the following areas: (a) Crosswise strength. The ability of a zipper chain to withstand lateral stress is measured by loading to destruction a l-in. section of the specimen in a tensile testing machine. (b) Scoop pull-off. The gripping strength of a scoop around the bead is determined by pulling a single scoop from the bead at right angles to the stringer using a tensile testing machine with a specially designed fixture. (c) Holding strength of stops. The ability of stops to perform their intended purpose is determined through the use of five different methods that simulate the important stresses encountered in the end use of zippers. These five different methods are top stop holding; bottom stop holding, slider, bottom stop holding crosswise; bottom stop holding, stringer separation; and bridge top stop, stringer separation. (d) Scoop slippage. The ability of a scoop to resist longitudinal movement along the bead of the tape is determined with a tensile testing machine fitted with a specially designed fixture. (e) Resistance to cushioned compression of sliders. The lower plateau of a compression tester is cushioned with a neoprene pad. The specimen is laid on the pad and a load is applied. Then, the operability of the zipper is tested and compared to the operability of the original zipper. (f) Slide deflection and recovery. There are two procedures for determining the resistance of slider planes of zippers to an opening or spreading force. In one procedure, the force is applied to the mouth of the slider. In an alternative method, the force is applied through the slider pull and back plane of the slider. (g) Resistance to twist of pull and slider. In this method, the twist resistance of a pull and slider assembly against a torsional force applied to the pull of the zipper is evaluated. A fixture is used with a torque wrench to apply a specified twisting force to a slider pull. The amount of permanent twist imparted to the slider pull or other permanent damage or deformation are noted. The specimen is also examined for any other effects such as breaking of deformation of the lug or any other part of the assembly. (h) Resistance to pull-off of slider pull. In this test, with a special fixture, tensile load is applied to the slider pull to determine how much force is required to pull off the slider pull. The operability of zippers is tested by pulling the slider with a force indicator (such as a pull gauge) along the zipper chain alternately in the opening and closing directions then the force required to maintain each movement is recorded. The force required to move the slider on the chain is a measure of the ease with which the zipper will operate in end-use applications. Elastic Waistbands testing There are two properties of elastic waistbands that should be tested: Fit for the labeled size Resistance to degradation (becoming loose, losing elasticity) due to laundering 1. Fit for the Labeled Size This property can be tested by stretching the waistband about 5 cm more than the hip dimension of the labeled size to simulate the condition that exists while which putting on the garment and bringing back the waistband to the waist dimension for the labeled size and measuring the force it takes to keep the waistband stretched at that particular dimension. Then similar garments should be wear tested and the numerical value of the force required must be correlated with actual comfort during wear. This testing  can be done on a tensile testing machine. Waist and hip dimensions may be obtained from various publications containing body measurements for various sizes. Please see the Chapter 9 on Apparel Sizing. 2. Degradation of Elastic Waistband due to Repeated Laundering Elastic waistband may deteriorate in repeated laundering due to the effects of hot water, bleach, agitation in laundering, etc. If the waistband looses its elasticity and becomes "loose" due to repeated laundering, then it will not be serviceable rendering the garment useless. Such effects can be tested by two methods as follows: (a) Take three specimens of the elastic that would be used for a waistband. Mark them in such a way that the distance between the marks is 25 cm. Then subject them to accelerated aging, i.e.. expose them to 149°C or 300°F for 2 hours in a circulated air oven. After aging, let the specimens cool down to room temperature. (b) Then, stretch the specimen 50% and keep them in that stretched condition for 24 hours. Allow them to relax for 10 min. Then, measure the distance between the gauge marks and express that as a percentage of the original distance between the gauge marks, i.e., 25 cm. Use a minus [-] sign to indicate shrinkage and a plus [+] sign to indicate growth in the distance between the gauge marks. The final results are expressed as the average of the growth and/or shrinkage of three specimens. (c) Usually any growth over 7 or 8% is not acceptable because it will result in loose fit. Any shrinkage is unacceptable because it will result in a tight fit. This method accelerates the effects of launderings on a waistband [Federal Specification, 1972]. Another method of measuring resistance to degradation is to measure the loss in strength of the elastic waistband due to laundering. For example, (a) Take three specimens of the elastic that would be used in a waistband. Stretch them to 50% and measure the force it takes to do so. (b) Then, launder these specimens three times as if they were sewn into the garment, i.e., according to intended care instructions. Again measure the force required to stretch them to 50%. (c) The specimens are considered acceptable if the loss in the force required to stretch them 50% after three launderings is up to 10% of the  original force. More than a 10% loss in the force required to stretch the waistband 50% after three launderings indicates that such an elastic waistband will not fit snugly. The final result is expressed as an average of the force required to stretch three specimens. A variation of the above method is to subject a waistband to accelerated aging instead of laundering and then calculate the loss in the force required to stretch it 50% after accelerated aging. More than a 10% loss in the force required to stretch the waistband 50% after accelerated aging indicates that such a waistband will not fit snugly. Sewing Threads For the reasons explained earlier in the Chapter 4, Section 4-2-2, quality of sewing thread has marked effect on sewing producting city, quality of sewing thread is very important There is an ASTM test method for sewing threads, D 204 Standard Test Methods for Testing Sewing Threads, Annual Book of ASTM Standards, Vol. 07.01. This test method outlines the procedure for testing following properties of sewing threads: (a) Colorfastness to dry cleaning, laundering and water migration (b) Diameter (c) Length per thread holder (d) Strength and elongation, single strand conditioned and single strand wet (e) Loop strength (0) Shrinkage, single strand in dry heat and boiling water (g) Twist and twist balance (h) Yarn number A. Colorfastness Colorfastness of sewing threads to dry cleaning, laundering and water migration is tested in similar way as testing colorfastness of fabrics discussed earlier. B. Diameter Knowledge of thread diameter is important because diameter can affect sewing performance and seam appearance. Sewing performance can be influenced because thread is required to pass through restrictions, such as a needle's eye and tension disks. Seam appearance can be adversely affected when the diameter of a thread is large enough to displace fabric yarn and results in a puckered seam. Sewing-thread diameter is also a consideration when selecting sewing threads for embroidery, contrast stitching, or other decorative applications. The diameter of a thread is determined either with a thickness gauge [preferred method] or optically [alternative method). The procedure for measuring sewing-thread diameter by a thickness gauge is as follows: Draw the thread from the side of the sewing-thread holder, taking cars not to disturb the twists. Place four strands of the thread side by side on the anvil and approximately midway between the sides of the pressure foxs under 240 gm/cm² at 10 points along the thread and calculate the averag as the diameter of the sewing thread. The optical method for measuring sewing thread diameter is not recommended because it has difficulty in determining the exact boundaries of threads having hairy fibers on the surface. C. Length per Thread Holder The length of sewing thread on a thread holder is measured in meters or yards while being removed from the thread holder. ASTM D 3693 Standard Specification for Labeled Length per Holder of Sewing Thread, Annual Book of ASTM Standards, Vol. 07.01 addresses length per thread holder. D. Strength and Elongation Strength and elongation of sewing threads are determined in the same way as the strength and elongation of yarn, by a single-strand method ASTM D-2256, Annual Book of ASTM Standards, Vol. 07.01. E. Loop Strength The loop length and elongation of a sewing thread are a measure of the thread's ability to contribute to seam performance. The loop strength of a thread bears a direct relationship to stitch strength and hence to seam strength. Loop elongation is an indication of the degree to which a seam, under stress, can be stretched without a thread breaking. Besides loop elongation, the ultimate elongation of a seam is dependent on the material stitched, the stitch and seam type, and number of stitches per cm. In a loop strength and elongation test, each specimen consists of two pieces of yarn taken from one package or end. Both ends of one piece are secured in one clamp of the testing machine so that the length of the loop is about one-half of the gauge length. One end of the second loop is passed through the loop formed by the first piece of the sewing thread and both ends of the second piece are clamped in the other clamp of the testing machine, When machine starts, we deserve and note, load and elongation at the point of loop breaks. F. Shrinkage, Single End Shrinkage of sewing thread is important because shrinkage can cause puckering of a seam, thus adversely affecting seam appearance. A conditioned single end of thread is measured under a prescribed tensioning force before and after exposure to boiling water for ½ hour or dry heat (152° ±3°C or 350°+ 5°F) for 1 hour. The change in length is expressed as a percentage of the length before exposure. G. Twist and Twist Balance The determination of twist balance in sewing threads is important to predict the snarling tendency of thread during actual sewing operations. Balanced twist is a term used to describe a ply yarn, when the forces due to twist of the ply are equal and opposite to those of the component single yarns [Grover and Hamby, 1969]. In this method, about a meter of conditioned thread from a holder is withdrawn in the same manner as that in which it is delivered to the sewing machine and formed into a  loop, positioning the ends of the thread so that they are 10 cm apart at the top of the loop. The twist balance is reported in terms of the complete rotations that loop makes. See Figure 5-42 for an example of sewing thread with balanced and unbalanced twists. Sewing thread with unbalanced twist will have snarling and kinking tendency. H. Sewing Thread Size/Yarn Number Sewing thread size [yarn size] is generally expressed in terms of a ticket number. ASTM D 3823 Standard Practice for Determining Ticket Numbers for Sewing Threads, Annual Book of ASTM Standards, Vol. 07.01. covers how to determine ticket number of a sewing thread.