Textile Testing and Standards

• Textile testing applies engineering and science to determine textile material properties.
• The objectives of textile testing include:
  • Checking raw material quality
  • Monitoring production processes
  • Assessing final product quality
  • Investigating faulty materials
  • Setting benchmarks
  • Research and development
  • New product development

Testing Methods

• Tests determine quality, employing diverse methods and instruments, which need standardization.
• Various organizations establish textile testing standards, including:
  • AATCC (American Association of Textile Chemists and Colorists)
  • ASTM (American Society for Testing and Materials)
  • ANSI (American National Standards Institute)
  • ISO (International Organization for Standardization)
  • BSI (British Standards Institute)
  • BS EN (British Standard European Norm)
  • IS (Indian Standards)

Sample Selection

• A sample is a small, representative fraction of a population and should accurately represent the whole.
• Population includes all elements meeting the study's selection criteria.

Need for Sampling

• Textile testing's destructive nature makes testing all material undesirable.
• Textile production volume necessitates representative samples, saving time and costs.
• Sampling methods depend on:
  • Material form
  • Material amount available
  • Test nature
  • Testing instrument type
  • Required information
  • Required accuracy

Types of Samples

• Random sample: Every individual has an equal selection chance, ensuring bias-free representation.
• Numerical (perfect) sample: Proportions of fiber lengths (long, medium, short) mirror the population.
• Biased sample: Selection influenced by factors other than chance, leading to non-representative results.

Fiber Sampling Techniques

• Cotton's non-homogeneity requires multiple random sub-samples from different places.
• When sampling from cotton bales, take fibers one by one at random from bale parts.

Yarn Sampling Techniques

• Yarns come in forms like bobbins, cops, cones, and hanks.
• Random number tables sample yarn bobbins from small bulk sizes.
• Ten packages are selected at random.
• Selection Guidelines:
  • More than five cases: Select at least five cases randomly, then two packages from each.
  • Less than five cases: Select ten packages.

Fabric Sampling

• For woven fabrics, warp and weft samples are separate due to varying properties.
• Identify and mark the warp direction of the fabric.
• Take samples at least 6 inches from the selvedge.
• Avoid wrinkled/damaged areas.
• For knit fabrics, sample from different fabric parts similarly to woven fabrics.

Standard Atmosphere for Textiles Testing

• Lab conditions maintain specific air temperature and humidity levels within tolerances.
• Textile applications dictate temperature and humidity needs.
• Standard testing atmospheres for different materials:
  • Textiles (excluding nonwovens): 20 ± 2°C and 65 ± 2% relative humidity
  • Nonwovens: 23 ± 1°C and 50 ± 2% relative humidity
  • Glass fiber: 21 ± 1°C and 65 ± 5% relative humidity

Humidity

• Absolute humidity: water vapor weight in a unit volume of moist air (gm/m³).

• Relative humidity: the ratio of air's absolute humidity to saturated air's humidity at the same temperature and pressure, in percentage.

  • RH% = (Absolute humidity of air / Humidity air saturated with water vapour) × 100

• Hygrometers/psychrometers measure atmospheric moisture.

• Psychrometer: consists of wet- and dry-bulb thermometers, the wet bulb kept moist with water.

• Wet-bulb shows a temperature than the dry-bulb above freezing point, due to evaporation.

• Conditioning Chamber: To keep samples in a standard Atmosphere.

Fiber Testing

• Textile fiber tests include:
  • Cotton maturity measurement
  • Fiber length measurement
  • Fiber fineness measurement
  • High-volume instrument (HVI)

Cotton Fiber Maturity

• Fiber Maturity term mainly applies to cotton.

• Only cotton fiber is measured for maturity.

• Fiber make-up, Lumen, primary wall, and secondary wall.

• Immature fibers lack strength and longitudinal stiffness, leading to yarn strength loss, neppiness, short fibers, dyeability issues, and processing difficulties.

• Caustic soda method: Fibers are spread on a glass slide, separated with a needle, held in a clamp, irrigated with 18% caustic soda, covered, and examined under a microscope.

• Fiber categories based on the effect of caustic soda.

Fiber Length Measurement

• Cotton fiber length is a key characteristic.
• Longer fibers are generally preferred.
• Benefits of longer Fibers:
  • Easier to process
  • More even yarns
  • Higher Yarn strength at same twist level

Comb Sorter Method

• Comb sorter assesses cotton, wool, viscose, or polyester fiber length to determine length distribution, effective length, mean length, short fibre percentage, and dispersion.
• Steps to create a comb sorter diagram.
• All fibers aligned at the bottom.
• Fibers in the density, with gaps.
• Fibers must not overlap.
• A curve links all tip points.

Fiber Fineness

• Fiber fineness is the diameter or cross-sectional area of the fiber.
• Fineness affects yarn properties
  • strength
  • smoothness
  • uniformity
  • luster
  • handle
  • stiffness
  • drape
  • moisture management
• Air-flow principle (Sheffield Micronaire) measures cotton fineness.
• Resistance to airflow indicates fineness/ Specific surface area.
• Airflow is measured through compression.
• Classification based on fineness:
  • Very fine: Less than 3.0 microgram/inch
  • Fine: 3.0 to 3.9
  • Average: 4.0 to 4.9
  • Coarse: 5.0 to 5.9
  • Very coarse: More than 6.0

High Volume Instrument (HVI)

• Conventional fiber property tests carried out are complex manual operations and consuming.
• The HVI Instrument helps to measure several fiber properties quickly.
• The USTER Technologies hold a patent for HVI.

Measurements

• Micronaire measurement
• Maturity index
• UHML - upper-half mean length
• UI - uniformity index
• SFI short fiber index
• Fiber strength in g/tex
• Elongation
• Moisture content
• Color (reflectance = Rd, yellowness = +b) and color grade (USDA Upland, Pima or regional-customized color chart)
• Trash (% area, trash count) and trash grade (USDA)

Yarn Testing

• Yarn testing is vital for determining yarn quality and suitability for specific fabric types.
• Yarn linear density: influences physical, mechanical, transmission, and aesthetic fabric properties.
• If the yarn count is Known, then length is known by just winding the package, important for both manufacturer and production.

Yarn Numbering System

• Count is a numerical indication of yarn fineness, correlating length and weight.
• Direct yarn count: fixed length system.
• Indirect yarn Count: Fixed weight system.
• Tests are required to measure yarn length and weight.
• Equipment: wrap reel and analytical balance.

Types of Yarn

• Yarn available is in continuous length form.
• Yarn available in a yarn package form like ring bobbin, cone, cheese
• Yarn available in a discontinuous form.
• Tests are required to measure yarn length and weight, Equipment: wrap reel and analytical balance

Discontinuous Yarn Count

• Fabric is the second source of yarn.
• Keeping fabric's material and structural parameters is important for recreating fabric and testing linear density.
• Textile testing integrates engineering and science to evaluate material properties, ensuring quality and adherence to standards set by various organizations. Representative samples are vital, especially for non-homogeneous cotton.
• Yarn crimp is considered.
• Samples weighed.
• Count calculated using length and mass data.

Yarn Twist Test

• Yarn twist: spiral turns to hold fibers together, providing strength.
• Increased Twist strengthens lateral force holding fibers, increases overall strength.
• Twist direction include:
  • S-twist: Spirals align with the letter S when the yarn is vertical.
  • Z-twist: Spirals align with the letter Z when the yarn is vertical.

Twist Level

• Twist level: the turns number per unit yarn length.
• Often expressed in twists per meter (TPM) or twists per inch (TPI).
• Twist factor Formula: t.p.m XV N (direct system).
• Twist factor Formula: t.p.i / √N (indirect system).

Untwist

• Twist is a twist contraction process.
• This assumed method: During twist, Yarn reduces.
• Remove twist and yarn length becomes normal.
• Re-twistting yields initial contracted length.