Week 1_ Materials and Their Applications PDF

Learning Outcomes By the end of this lesson you should have developed a knowledge and understanding of: Factors that may affect the choice of fabrics for textile products Where fibres come from How fibres are classified according to their source How fabrics are tested for specific propertie...

Learning Outcomes By the end of this lesson you should have developed a knowledge and understanding of: Factors that may affect the choice of fabrics for textile products Where fibres come from How fibres are classified according to their source How fabrics are tested for specific properties in industry How to set up simple workshop tests for specific fabric properties 1.1 Materials and their applications Worksheets As we go through the slides, answer the questions on the worksheet. 1.1 Materials and their applications Materials and their applications Choosing the right textile materials for products is complex because of the interplay between fibre, yarn, construction method and finishing processes. The final choice of fabric will mostly be influenced by product function and the material’s physical and aesthetic properties. Key term Fibre: a fine, hair-like thread. Yarn: a long continuous length of twisted (spun) fibres used in the construction of woven and knitted fabrics. Finishing process: an additional process to improve the appearance and/or performance of a fabric. Aesthetics: the beauty or tastefulness of the look of a product, and how attractive it is to the consumer. 1.1 Materials and their applications Aesthetic properties of textile materials Handle: evaluates how a fabric behaves, performs or feels when touched. Drape: The term used to describe the way a fabric hangs under its own weight. Lustre: refers to a textile material’s ability to reflect light from its surface so it appears glossy. 1.1 Materials and their applications Physical Properties and working characteristics of textile materials Property/ Explanation Characteristic Tensile Strength The ability to resist breaking under tension Abrasion The ability to resist surface resistance wear caused by rubbing contact with another material. Elasticity (crease The ability to be deformed resistance) and then return to the original shape when the force is removed. Absorbency The ability to absorb and retain liquid. Easy-care The ability to maintain optimum appearance with the minimum of effort when laundering. Property/ Explanation Characteristic Colour fastness The ability to retain dye during the manufacturing process and when washed or exposed to sunlight. Electrostatic The ability for static charge electricity to develop in fibres under exceptionally dry conditions. Thermal insulation The ability to trap air, preventing the transfer of heat through the material. Corrosive solvent The ability to withstand resistance attack and decay from substances such as chlorine bleach. Microorganism and The ability to withstand insect resistance attack and decay from organisms such as bacteria and moths. Property/ Explanation Characteristic Flammability The ability to burn or ignite, causing fire or combustion. Thermoplasticity The ability to become pliable and mouldable when heated, enabling textures and creases to be set and retained once heated. Formability The ability to manipulate and deform fabrics without damaging them. It is important to remember that the properties of textile materials vary depending on the fibres used and the way in which the fabric is constructed and finished. Ensure each of these factors is considered in relation to the product and its users when answering product analysis questions. 1.1 Materials and their applications Classification of materials All textile fibres are made from long-chain molecules (polymers). The main sources of fibres are natural cellulose, natural protein, manufactured (regenerated) and synthetic fibres. The combination of atoms in the polymers caries for each type of fibre, resulting in fibres from each classification having different properties. Material classification knowledge is needed so that the most appropriate material is selected for specific applications. Key term Polymer: a long chain of molecules made up of fibre-forming atoms that are linked together. Regenerated fibre: a fibre made from natural cellulose that has been chemically modified. Synthetic fibre: a fibre made entirely from synthetic polymers based on petrochemicals. 1.1 Materials and their applications Classification of natural fibres with examples of specific fibres Key term Natural Fibre: a fibre that comes from a natural cellulose (plant) or protein (animal) source. 1.1 Materials and their applications Classification of manufactured cellulosic regenerated fibres with examples of specific fibres 1.1 Materials and their applications Classification of synthetic fibres with examples of specific fibres 1.1 Materials and their applications Classification of manufactured inorganic fibres with examples of specific fibres 1.1 Materials and their applications Classification of smart materials with examples of specific materials Key term Smart Material: a material that is able to react to external stimuli or changes in its environment without human intervention. 1.1 Materials and their applications Classification of modern materials with examples of specific materials Key term Modern Material: a material that has been developed through the invention of new or improved processes. Microfibre: an extremely fine synthetic fibre. Microencapsulated fibre: a microfibre that has tiny capsules containing health or cosmetic chemicals embedded into its hollow centre. Nano-fibre: an extremely lightweight strong Modern materials are not smart materials! Don’t confuse the two. You should know the classification of the fibres listed in this chapter and be able to sort fibres into their correct classification. 1.1 Materials and their applications Material Testing Material testing is used to help select the most appropriate fabric for a product. When setting up tests the process and parameters must be consistently fair. Simple Workshop Tests Flammability Use precisely cut fabric samples and paper fuses. Light the fuse and use a stopwatch to time how long it takes for the flame to reach the wire marker. Record the time and other predetermined observations such as what happens when the flame comes into contact with the fabric. Key term Control: a sample that is untreated or unchanged. 1.1 Materials and their applications Crease Resistance The fabric is folded in half and placed between pieces of paper under the weight. After placing the fabric sample on the measuring block as shown, leave it to recover for five minutes then calculate the distance between its two ends on the horizontal scale. Record the result and repeat with other fabrics being tested. Colour Fastness The most important factors affecting colour fastness are washing and exposure to sunlight Workshop tests can replicate industrial tests for wash fastness. Samples are sewn onto white fabric and washed for a predetermined time at an agreed temperature. The dried samples are compared to a control sample and the white fabric is checked for staining. Reliable workshop testing for light fastness in fabrics is impossible. A prolonged period of time is needed and light intensity cannot be controlled in the same way as in a laboratory. 1.1 Materials and their applications Shrink Resistance Sew coloured cross-stitches or use a permanent pen to mark an exact 10cm square. Retain a control sample and wash the remaining samples at different temperatures and levels of washing machine agitation. Dry and iron the samples. Work out the percentage shrinkage, for example: Length between a and b before washing = 10cm Length between a and b after washing = 9.5cm Percentage shrinkage = distance before - distance after ÷ original length x 100 10 - 9.5 x 100 = 5% 10 1.1 Materials and their applications Strength A test for fabric strength is also difficult to replicate in a workshop. It is impossible to achieve the large forces needed to break a fabric using basic tools and equipment. However, some observations can be recorded using a simple test. Prepare same-sized samples. Make a small cut at the warp, weft and bias edges. Tear the samples along the cut to see which tears easily and which fabric requires more force. Pilling Pilling is the formation of little balls of fibres (pills) on the surface of a fabric as a result of wear and friction. It occurs when weak fibres from blended staple yarns are pushed out and held on the surface by stronger fibres. A simple Fabricabrasion testare samples can be done stapled to a onto assess woodenpilling. block. Glass paper is stapled onto a smaller wooden block. The glass paper block is rubbed over the surface of the fabric to simulate wear. The number of passes required for pills to start forming on the surface of the fabric is recorded. 1.1 Materials and their applications Industrial Tests Industrial tests are an important way of ensuring a product complies with the designer’s specifications, and include the manufacturer’s quality control checks and quality assurance standards. For example, a product displaying a BSI Kitemark gives an assurance to consumers that the product is safe and meets agreed product performance codes. Industrial tests are usually carried out in laboratories in controlled conditions using specialist-testing machinery and standardised test pieces of materials. Key term Quality Control (QC): checking the product during the production run to test it against the specification. Quality Assurance (QA): the planning of procedures and policies that ensure good-quality products. Performance codes: the technical requirements 1.1 Materials and their applications Key term Colour fastness: the ability of a fibre or fabric to retain dye fastness during manufacturing processes and when washed or exposed to sunlight. Multi-fibre swatch: a narrow band of woven fabric containing separate segments of acetate, cotton, nylon, polyester, acrylic and wool fibres. It is used to demonstrate the uptake of dye staining when washing different types of fabrics. Grey scale cards: used to show differences in colour intensity when comparing control samples with samples exposed to washing and UV light. Xenon arc lamp: produces a bright white light that closely mimics natural sunlight. Raveled fabric: fabric that has yarn teased or drawn out from its cut edges giving it a frayed appearance. 1.1 Materials and their applications Flammability Industrial test 1: minimum flame application to cause ignition The prepared fabric sample is held vertically in a metal frame. A small flame from a Bunsen burner is applied for two seconds, then three, four, six, eight, and ten seconds until it catches fire. The test is complete if the fabric burns for more than one second. The time and any other predetermined observations are recorded. Industrial test 2: flame spread and flame behaviour This test is used on fabrics that have low flammability. A small flame is applied to a prepared fabric sample and removed after ten seconds. The duration of the flame and afterglow are timed and any debris is recorded. The size of the hole burned into the fabric is measured and recorded. 1.1 Materials and their applications Flammability Industrial test 3: rate of flame spread A large sample of fabric is placed in a metal frame. The test is complete if the fabric burns for more than one second. A small flame is applied and then removed after ten seconds. As each cotton trip thread is burnt through, its timer will stop, showing the burn distance and allowing the burning rate to be calculated. Crease resistance Standard test pieces are cut from wrinkle-free fabric. Samples are kept in standard room conditions to ensure the fabric temperature and humidity is identical. A sample is folded in half and compressed under a load for a specified time. The load is removed and one end of the creased sample is clamped onto the instrument. The other end is allowed to fall free. The dial of the instrument is rotated to keep the free edge of the sample in line with the knife edge. At the end of the time allowed for recovery, the recovery angle is recorded from the engraved scale. The larger the angle of recovery the better the crease resistance. 1.1 Materials and their applications Shrink Resistance The fabric sample is overlocked to prevent fraying. Permanent ink is used to mark precise reference on the fabrics. The prepared fabric samples are washed with pieces of polyester fabric to replicate a normal wash load. The samples are dried using all available options. If the results of re-measuring between the reference points show a change has occurred, the formula used in the workshop test is applied to calculate the percentage change. Fabric shrinkage is shown as a negative percentage. Fabric stretch, as a result of the test, is shown as a positive percentage. Pilling A Martindale machine tests for abrasion and pilling. Circular samples of the test fabrics are clamped onto one of the machine’s four discs and a weight is put onto each disc. The test samples are rubbed against an abrasive fabric. The machine controls and records the number of rubbing cycles. The test samples are examined at regular intervals for the presence of wear leading to pilling. On completion, the samples are compared, in a light box, with the control sample. 1.1 Materials and their applications Strength Striptest: tensile strength test for woven fabrics Rectangular fabric samples are cut in a direction parallel to the warp and weft. To ensure all yarns in the sample run along its entire length, the width of each sample is reduced to 5cm by raveling (removing) yarn from both edges. The sample is stretched, and the distance travelled is plotted, giving information on extensibility, yield point, maximum load and final breaking point. The test is repeated with samples cut in the warp and west directions. Non-woven fabrics are tested for strength in the same way using a strip of fabric that can be cut in any direction as non-woven fabrics have no straight grain. Burstin test: strength test for knitted fabrics A circle of knitted fabric is clamped over a rubber diaphragm. Air or water is pumped under pressure into a chamber below the sample fabric and rubber diaphragm. The pressure is applied radially and is increased until the knitted fabric ruptures (bursts). 1.1 Materials and their applications Colour Fastness Industrial test 1: wash fastness Samples are cut to an agreed size. Each sample is secured in a white fabric ‘envelope’ and washed for a set time at an agreed temperature. The dried samples are compared to the control sample. Changes in colour and the staining of the ‘envelope’ fabric are assessed using grey scales. The best grade is 5 and the worst grade is 1. Industrial test 2: wash fastness Samples are cut to an agreed size. A multi-fibre swatch is sewn to the sample. Accelerated washing (replicates five or more home washes) is performed in canisters placed in a machine called a launderometer. Grey scale cards and the control samples are used to evaluate changes in shade, and the extent of the staining on different fibres is recorded. 1.1 Materials and their applications Colour Fastness Industrial test 3: lightfastness Samples are cut to an agreed size. Two-thirds of each sample is enclosed in an opaque cover. The uncovered area of the sample is exposed to intense artificial light generated by a xenon arc lamp. The light is filtered to replicate the accelerated intensity of natural daylight through glass. The area of the exposed sample is compared with the covered part using grey scale cards. Don’t describe an industrial testing method when a workshop testing method is asked for and remember to explain how the test results are interpreted. Be able to state the purpose of named fabric tests and describe how each test is carried out fairly. List the differences between workshop and industrial tests.  1. Place each of the fibres listed below in the correct box of the table. Use each fibre only once. acrylic lyocell tactel cotton polyamide linen polyester wool lycra silk viscose 2. What is meant by the term ‘manufactured fibres’? 3. What are reactive materials? 4. How do micro-encapsulated fabrics help people to live more comfortable daily lives? 5. What is meant by the term ‘colour fastness’? Home Learning: 1. Read through the Industrial Tests pages. Now create revision notes to go with these - could you research some of the equipment mentioned, or find video links showing some of these tests taking place. 2. Answer the exam questions.