Service Testing (Test samples/products in a real life situation; Simple, but takes a long time, because you have to wait a few days/months to see changes)
Laboratory Testing (Reliable, accurate, but indirect; accelerated testing - create a device to simulate what's going on when you wear the garment; separate machines)
GOALS OF TEXTILE TESTING
Conformance to specifications set by standards
Adherence to government regulations
Appearance (color, style, texture, ...)
Comfort (hand: soft vs hard, smooth vs rough, cool vs warm)
Specifications for end use; A precise statement of a set of requirements to satisfied by a material, product, system or service, indicating whenever appropriate, the procedure by means of which it may be determined whether the specified requirements have been met.
Testing methods (Eight sections)
1. Scope: what particular products, exclusion;
2. Referenced Documents: standard testing methods
3. Definitions: ASTM D123
4. Uses and Significance: voluntary; some requirements can be modified.
5. Sampling: at the time to reach the user; number., size and direction of samples,
6. Specification Requirements: characteristics, requirements and testing methods.
7. Testing Methods: details for carrying out the tests.
Yarns of medium twist provide littler or no opportunity for fiber displacement, so these yarns tend to return to their original position
High twisted yarns under heavy wrinkles show poor recovery due to stresses and strains that tend to hold the structure
ability to move in the fabric
Loose structure allows high mobility
Type of weave affecting crease and wrinkle recovery
Woven fabrics of basket, twill or satin-weave constructions recover more easily from wrinkles (due to higher yarn mobility) than plain-weave fabrics
Thread count affecting crease and wrinkle recovery
low thread count fabric structures have higher yarn mobility than high thread count fabric structures thus recover more easily from wrinkles
The way a fabric hangs.
The property which permits a material to orient itself into graceful folds when acted upon by force of gravity.
Fabric stiffness (resistance to bending) is a key factor in study of drape
Affected by yarns, weave structure and finish
Drape coefficient measurement
bending length c to find drape
Relationship between Twist Factor and Fabric Stiffness
Fabric Stiffness is directly proportional to Twist Factor (yarn twist and linear density)
In direct system:
TPM x √Tex
TPM x √Denier
In indirect system:
Twist Factor = TPI / √Cotton count
Drape coefficient relating to fabric stiffness
High Drape Coefficient signifies stiffer fabric
Relationship between overhang length and bending length in Cantilever test
Higher overhand length in Cantilever test translates to stiffer fabric
Relationship between Heart Loop length and fabric
Higher length in Heart Loop test translates to limper fabric
work per unit width which is required to bend a fabric to unit radius of curvature
G = 3.39w1c3 mg - cm
G = w2c3 x 103 mg - cm
w1 = fabric weight in oz per yard2
w2 = fabric weight in grams per cm2
c = bending length
Measure of stiffness and is independent of the dimensions of the strip tested and may be regarded as the "intrinsic stiffness"
Used to compare the stiffness of the material in fabrics of different thicknesses
q (kg/cm2) = 732G / g13
q (kg/cm2) = (12G x 10-6) / g23
g1 = fabric thickness in thousandths of an inch
g2 = fabric thickness in cm
G = flexural rigidity
Pills are bunches or balls of tangled fibers which are held to the surface of a fabric
Fabric surface fault characterized by little fiber balls or pills of entangled fiber clinging to the cloth surface and giving the garment an unsightly appearance
3-stage development of pilling
Development of surface fuzz
Tangling of the fuzz into pills
Breaking away of pills
How fiber can affect Pilling
Length: Short fibers have more loose ends that easily protrude from yarn structure, causing more pilling (ex: staple vs. filament yarns)
Surface characteristics: Smooth fibers show less pilling as compared to fibers with rough surfaces (nylon vs. wool)
Strength: high strength fibers hold pills on fabric surface more firmly, resulting in more visible pilling (Ex: use of special low strength polyester fibers in woolen blends to reduce pilling)
How yarns can affect Pilling
Twist: highly twisted yarn structures hold fibers more firmly, resulting in less pilling
Linear Density (tex, denier): yarn with higher linear density and generally coarse yarns pill more
How fabric structure affects Pilling
Type of weave: plain weave pills less than other basic weave types (ex: twill and satin weave)
Thread count: high thread count structures are more compact and pill less
Factors affecting Pilling
Fiber, yarn, fabric structure
Shrinkage (dimensional stability)
Transverse swelling,longitudinal shrinkage
Test for dimensional stability
Regular washing and drying cycles with the fabric specimen
Types of shrinkages
Relaxation, Consolidation, Felting, Heat or Thermal, Progressive
Increase in fabric dimensions
The Shrinkage Theory
After wetting, filling yarns swell and warp yarns stretch to accommodate them, and warp yarns relax to relieve the stress, bringing the yarns closer together
Transverse swelling (submerged in water), longitudinal shrinkage
Formula to measure shrinkage
S = [(L - L0) / L0] x 100%
'overall' contamination or discoloration of a material.
'local' contamination or discoloration of a material.
wetting agent. Lower the surface tension of the water, loosen, surround, and suspend the soil. Polar molecules. They have heads that are hydrophilic and tails that are hydrophobic (water-hating).
Wetting (water and surfactant molecules penetration)
Breaking up (small sizes)
Separation (oil-fabric interface formation)
Soiling and Fiber geometry: Fibers with smooth surface, relatively large diameter, made into smooth yarns and firm fabrics...
tend to resist soiling
Soiling and Fabric Geometry: Fabrics with loose structure...
tend to permit penetration of soil into the interstices
Soiling and Fabric Geometry: Fibers with irregular cross-sections...
provide spaces for soil particles to settle in and hinder their removal
Soiling and Fabric Geometry: Loosely twisted yarns that are somewhat coarse...
are readily penetrated by soil
Soil release finishes: Oily stains
Their removal is primarily dependent upon the hydrophobicity of the fibers
Wetting finishes helps water to diffuse between the oil/fiber interface, and thus facilitate removal of oil substances
Soil release finishes: Solid soils
Their deposition does not depend upon the hydrophobicity of the fibers
It depends upon the adhesion of solid particles to the fiber that is caused by Van der Waal's forces and on the contact area between the fiber surface and the particle
The contact area between the fiber surface and the particle is influenced by surface, texture, irregularities, fuzziness, weave
Removal of solids from fiber surface requires breaking the adhesive bound between fiber and solid, followed by separation of two surfaces by wetting
Wetting in the Roll-up process
Surfactant: is wetting agent.
Lower the surface tension of the water, loosen, surround, and suspend the soil.
Surfactants are molecules made up of two parts.
They have heads that are hydrophilic (water-loving) and tails that are hydrophobic (water-hating).
Rolling up step in Roll-up process
As the hydrophobic tail of a surfactant tries to cling to a surface, it forces itself underneath layers of soil, loosening and lifting it from the surface.
Suspension step in Roll-up process
As the cleaning solution rolls up bits of dirt and soil, the surfactant's hydrophobic tails cling to the particles because they're not water.
The soil is held suspended in the cleaning solution by the power of the surfactant, keeping it from settling back on your countertop.
Once the surface is clean, you simply wipe and dry.
These finishes function by coating the fiber surface to increase its surface tension below that of liquids would wet the fiber. This limited wettability would prevent the unwanted liquid from residing on the fiber surface.
These finishes are also effective in preventing or minimizing adhesion of particulate matter to fibers.
fabric coated or impregnated with fats, waxes, rubber to form a continuous wall against the passage of water
Waterproof fabric has low degree of permeability.
Water resistant fabric
Water resistance is the ability of a fabric to resist wetting and penetration of water.
Water repellent fabric
Water repellency is the property of fiber, yarn or fabric characterized by its resistance to wetting by water.
A water repellent fabric is one whose fibers are usually coated with a hydrophobic compound and whose pores are not filled in the course of treatment.
This type of fabric is quite permeable to air and water vapors.
Basic concept of wetting and water repellency
High surface tension beads up liquid.
Water is polar (postively and negatively charged.
When solid surface has polar molecules, water can be attracted and spread--wetting
WR finish improves contact angle to increase surface tension.
a tendency to minimize surface area of liquid on a solid surface.
Angle between the solid surface and the tangent of the water surface as it approaches the solid, the angle being measured in water.
Water Repellency Test
Munsell color system
a color space that specifies colors based on three color dimensions, hue, value (lightness), and chroma (color purity or colorfulness).
actual swatches or chips of colored materials.
Differences among adjacent chips have been made nearly constant visually
Ten hues: R, YR, Y, GY, G, BG, B, PB, P, RP. Four pages are used for shades of each hue (2.5, 5, 7.5, 10)
Value: 1 (black) ~ 10 (white)
Chroma: 0 (gray) ~16 (more colorful)
Notation: 7.5 YR 3/12
Hue (Munsell color system)
Each horizontal circle Munsell divided into five principal hues: Red, Yellow, Green, Blue, and Purple,
along with 5 intermediate hues (YR, GY, BG, PB, RP) halfway between adjacent principal hues.
These 10 steps are then broken into 40 sub-steps, (2.5, 5, 7.5, 10).
Two colors of equal value and chroma, on opposite sides of a hue circle, are complementary colors, and mix additively to the neutral gray of the same value.
The diagram below shows 40 evenly-spaced Munsell hues, with complements vertically aligned.
Value (Munsell color system)
Value, or lightness, varies vertically along the color solid, from black (value 0) at the bottom, to white (value 10) at the top.
Neutral grays lie along the vertical axis between black and white.
Chroma (Munsell color system)
Chroma, measured radially from the center of each slice, represents the 'purity' of a color, with lower chroma being less pure (more washed out, as in pastels).
Note that there is no intrinsic upper limit to chroma.
Different areas of the color space have different maximal chroma coordinates.
For instance light yellow colors have considerably more potential chroma than light purples, due to the nature of the eye and the physics of color stimuli.
This led to a wide range of possible chroma levels--up to the high 30s for some hue-value combinations (though it is difficult or impossible to make physical objects in colors of such high chromas, and they cannot be reproduced on current computer displays).
How is a color fully specified?
by listing the three numbers for hue, value, and chroma.
For instance, a fairly saturated purple of medium lightness would be 5P 6/10 with 5P meaning the color in the middle of the purple hue band, 6/ meaning medium lightness, and a chroma of 10.
CIE L*a*b* system
a*- redness(positive)--greenness (negative)
The property of a dye or a print to retain its hue throughout the wear life of a product.
the degree of color transfer from one colored textile material to another by rubbing.
A standard white cotton fabric is used for all crocking tests
Colorfastness to Perspiration test method
AATCC 15: Fabric attached to multi-fiber fabric is dipped in the perspiration solution (pH 4.3+2) for 20-30 minutes and then heated in the oven for at least 6 hrs maintained at 38+1o C (100+2o F).
Colorfastness to Washing test method
AATCC 61: Multi-fiber fabric is used to see how much color is transferred (staining scale) and then the original specimen is compared to an unwashed specimen to see how much color is lost (gray scale).
Tensile Strength test
subjected to a longitudinal pulling force.
The maximum resistance of material to deformation in a tensile test (carried till the material ruptures).
Units: lbf, kgf, Newton (N)
The amount of pulling a fiber can withstand before it stretches and breaks.
It is a measure of the steady force required to break a yarn i.e. breaking load
'strength per unit cross sectional area'.
Stress = Load / Area.
But the cross sectional area does not remain constant throughout the length of yarns.
It is the 'Linear density' of yarn which remains more or less constant throughout the yarn length.
So we will use the following measure to compare the strength of two different yarns
'Load per unit Linear Density'
Specific Stress = Load / Linear Density
The maximum stress developed in a specimen stretched to rupture is called Tenacity.
Tenacity = Breaking Load / Linear Density
Increase in length of a specimen under some load is called elongation.
ratio of elongation to the original length.
Strain = Increase in Length / Original Length.
Generally, Strain is expressed as the amount of elongation as a percentage of original specimen length.
Strain (%) = (Increase in length x 100) / original length
elongation required to break a yarn
Breaking strain = breaking elongation / original length
To make comparison between the specimens of different original length, use strain over elongation
strain required to break the yarn
Breaking strain = change in length at break / original length = breaking elongation / original length
To make comparison between the specimens of different original length, use strain over elongation
A 20 cm long yarn has breaking elongation of 40 mm. Find out breaking strain.
40 mm = 4 cm
Breaking strain = Breaking elongation / original length
= 4 cm / 20 cm = ****0.2 cm****
A 20 cm long yarn has breaking elongation of 4 cm and 10 cm long yarn has a breaking elongation of 3 cm. Which yarn will give more extensible/stretchable fabric ?
Breaking strain = Breaking elongation / original length
A: BS = 4 / 20 = 0.2 cm
B: BS = 3 / 10 = 0.3 cm
****Second yarn is more stretchable and has higher strain****
Work of rupture (toughness)
the energy required to break a yarn and is also known as Toughness.
The work of rupture is given by the total area under the load-elongation curve. The units are Joules (S.I.).
Work = force x displacement (load x elongation)
Stress strain curve for a relatively stiff and brittle fiber (A) and a relatively soft and tough fiber (B) having the same breaking stress
Rupture of work=?
Which fiber is tougher?
Breaking strength relationship?
Breaking elongation relationship?
Which is stiffer?
Rupture of work: B > A
Fiber B is tougher than fiber A
Breaking strength: B = A
Breaking elongation: B > A
Fiber A is stiffer than fiber B
Initial (Young's) Modulus
the slope of the tensile stress-strain curve at origin.
Initial Modulus = Stress / Strain
~ Degree of elasticity or Stiffness
The initial part of the curve is fairly straight, and its slope (ratio of stress to strain) usually remains constant.
The modulus is measured in units of specific stress
Modulus gives a measure of the force required to produce a small extension.
An easily extensible/stretchable yarn will have low modulus.
The reciprocal of modulus is called compliance.
Modulus does not tell us any thing about the stiffness of yarn
The property of a body by virtue of which it tends to recover its original length/size/shape after deformation when the external load is removed
Elastic recovery (%) = (elastic elongation / total elongation) x 100
Tensile testing machines
We can increase the load attached to the specimen at constant rate and measure the corresponding elongation.
We can extend the specimen at constant rate and measure the corresponding increase in the in building stress/tension.
Depending upon these two principles we have namely three types of machines:
CRL (constant rate of loading) and CRE (constant rate of elongation)
Constant rate of loading (tensile testing machine)
Specimen is attached between two jaws (grippers) J1, J2. consider J1 is fixed. In CRL the force applied to J2 jaw is increased at constant rate and corresponding elongation is measured.
Constant rate of elongation (tensile testing machine)
In this case the jaw J2 is moved downward/upward at a constant rate or speed and corresponding increase in stress or tension is measured.
The machine in the lab is CRE (Instron) the velocity of moving jaw is set to 10 inch/min
The effect of specimen length in CRE machine (tensile testing)
Gauge length: distance between the edges of two jaws at the start of the test.
If the specimen length in a CRE machine is increased, the rate of loading will decrease i.e. it will take longer to break.
Factors affecting tensile strength
Raw material characteristics
Yarn structure: irregularity, twist factor, etc.
Fabric structure: setting, weave
Grab test (tensile test)
Specimen=6" long and 4" wide
Gage length=as 3 inch (75 cm).
"Fabric assistance" (strip test-tensile test)
Consider the ratio: strip strength per thread / single thread strength
The result is usually higher than unity.
This indicates that the traverse threads have some form of binding effect on the longitudinal threads, so increasing their strength.
Strip test (tensile test)
Unravel yarns from sample to make clamp 1/2" wider than the fabric
Is it correct to compare the results of A (strip test) and B (grab test) directly? (Tensile test)
If we calculate the ratio: grab strength / (strip strength / inch)
The result is usually in the range of 1.0 to 2.0
This indicates that the stressed zone of fabric between the jaws will be reinforced a little by the fabric on either side
The ability to retain physical integrity when subjected to a distending or swelling force, a force applied perpendicular to the fabric surface.
Hydraulic bursting strength tester
The fabric is clamped over a rubbery diaphragm that is expanded by fluid pressure.
The ability to resist rupture when a lateral (sideways) pulling force is applied.
The force required either to start or to propagate a tear in a fabric under specified conditions.
a progressive rupture along a line
Tear strength is high in a fabric if yarns...
can group together under tearing force
Grouping of yarns is made easier if the yarns are smooth and can slip over each other (yarn mobility)
The ability of yarns in a fabric to shift, slide or move under a load.
Yarn mobility increases when number of interlacing points (plain weave>twill), thread count, and yarn size all decrease
Low yarn mobility -> one yarn breaks at a time, and the tearing strength approaches the single yarn strength.
Factors affecting tear strength
Fabric structure (plain < twill < satin)
Tear strength tests
Elmendorf Tear Strength test (Elmendorf tear strength tester)
Tongue Tear Strength test (universal testing machine)
Trapezoid Tear Strength test
Load-Elongation curve (tear strength)
Elongation is given at constant rate (CRE) as the moving jaw moves at constant rate (10" per min)
Corresponding change in the tension in the specimen is measured.
wearing away of any part of a material by rubbing against another surface.
Causes of abrasion in textiles
Friction between Fabric and Fabric surfaces.
Friction between Fabric and external surfaces.
Friction between Fibers and dust or grit in a fabric that results in cutting of fibers.
Types of abrasion
Assessment of abrasion damage
Appearance against an un-abraded specimen
The # of cycles required to produce a hole, broken threads, or broken strip.
Loss in weight, often plotted against the # of cycles.
Change in thickness (pile height, carpets).
Loss in strength, e.g. tensile, bursting, tearing. Often expressed as a percentage of un-abraded strength.
Change in other properties, e.g. air permeability, luster, color.
Microscopic examination of damage to yarns and fibers.