Textile Testing: Unit Application and Conversion Relationships for Basic Physical Quantities

Textile testing is the testing of the physical and chemical properties of textiles by physical or chemical methods. As there are many textile testing items, the test results are bound to involve various physical quantities. Below I will sort out the textile testing items through the basic physical quantities in the International System of Units to help us understand textile testing in more depth.

International System of Units, also named Système International d’Unités, abbreviated SI.

7 basic units of physical quantities in SI	name	code
Length	meter	m
Mass	kilogram	kg
Time	second	s
Electron Current	ampere	A
Thermodynamic temperature	Kelvins	K
Amount of substance	mole	mol
Luminous intensity	candela	cd

Three of these physical quantities, length, mass and temperature, have multiple names and are related as follows:

Common names and conversions of lengths

name	levels	conversion relationships
meter, m	1km = 1000m = 100000cm = 1000000mm 1mm = 1000um = 1000000nm 1mile = 1760yd = 5280ft = 1.609344km	1yd = 3ft = 0.9144m 1ft = 12in = 30.48cm 1in = 2.54cm
yard, yd
foot, ft

Common names and conversions of mass

name	levels	conversion relationships
gram, g	1t = 1kg = 1000g 1g = 1000mg = 1000000ug	1lbs = 16oz 1oz = 28.350g
pound, lbs
ounce, oz

Note:
1 avoirdupois ounce =1 ounce =28.350 g
1 troy ounce =31.1035 g
1 apothecaries ounce =31.1030 克
1 textile ounce =28.375 g

Common names and conversions of temperature

name	conversion relationships
Thermodynamic temperature, K	°F = 1.8*℃ + 32 K = ℃ + 273.15
Celsius temperature, ℃
Fahrenheit scale, °F

The names and codes of the physical quantities involved in textile testing are listed below

Physical quantities involved in textile testing	name	code
area	square metres	㎡
volume	cubic metres	m³
frequency	Hertz	Hz (1/s)
density	kilogram per cubic metre	kg/m³
velocity	metres per second	m/s
angular velocity	radian per second	rad/s
force	Newton	N
pressure	pascals	Pa (N/㎡)
work, energy, heat	joule	J (N·m)
power	watt	W (J/s)
thermal conductivity	watts per metre kelvin	W/(m·K)
diffusion coefficient	square metres per second	㎡/s
electrical voltage	Coulomb	C (A·s)
voltage, electric potential	Volt	V (W/A)

The properties of textiles include structural properties, strength properties, colour fastness properties, durability, functional properties, etc. I will sort out the units and related testing items of these textile properties.

1 fabric structure

Test Items	Test Method	Unit
fabric grams	weight per unit area of the fabric	1 oz/y2 = 33.936 g/m2
fabric thickness	the vertical distance between the front and back of the fabric	mm
yarn count	weighing method, length method	See below
woven fabric density	Number of yarns per unit length	number/in = 2.54·number/cm

Test indicators of yarn count

Imperial count: At a convention moisture regain, a yarn weighing one pound, how many 840 yards does it have in length? It is the number of imperial counts it has; expressed as S.
Denier: The weight grams of a 9,000 metre length of yarn at a convention moisture regain; expressed as D.
Tex: It is the gram of weight of a 1,000 metre yarn at a convention moisture regain.
Metric count: At a convention moisture regain, How long a 1 gram weight yarn is (multiples of metres), expressed in Nm.
Relational conversion formula.
1 Tex = 10 Dtex
Cotton: S = 583.1/D
Chemical fibre: S = 590.5 /D
1 Tex = 9*D
Tex = 1000/Nm

2 fabric strength

Mechanically, the strength of a material refers to its ability to resist damage under the action of external forces. Common indicators of the fabric strength are: tensile breaking strength, bursting strength, tearing strength, etc.

Test items	Test method	Commonly used units
Fabric Tensile Strength	Textile tensile testing machine	Newton (N) Ten times Newton (DaN) kilogram (Kg) Pound (Lbf, LBS) 1DaN = 10N DaN = deca Newton 1Kg =1000g = 9.8N = 2.2Lbf(s)
Fabric bursting strength (see below)	Diaphragm method Bullet method
Fabric tearing strength	Elemendorf method Tongue tear method single-rip and Double tear Trapezoid method
Single yarn strength	Automatic single yarn strength tester TY400C

Fabric bursting strength: There are two methods of testing for bursting strength, diaphragm method and bullet method.

Diaphragm method of bursting strength
Common units: KPa, mmHg, mBar
Relational conversion formula
1 KPa = 7.5 mmHg =10 mBar
1 KPa = 1000 Pa

Bullet method of bursting strength
Common units: N, kg, Lbf, LBS, DaN
Relational conversion formula
1DaN = 10 N ,  DaN = deca Newton
1Kg =1000 g = 9.8 N = 2.2 Lbf(s)

3 General items of colour fastness

Colour fastness ratings are mainly carried out using the gray scale cards. The gray scale cards are: American (AATCC) gray scale, International (ISO) grey scale, Japanese (JIS) gray scale, and Chinese (GB) gray cards.

The grey card has a total of 5 levels and 9 grades, 1, 2, 3, 4 and 5 respectively, of which 5 is the highest and 1 is the lowest, and can be assessed as the middle half grade. In addition to the AATCC 3.0, 3.5 decimal point representation; ISO, JIS, GB are 3, 3-4 level representation.

Colour fastness to light

ISO, GB, JIS standards:

The rating is compared to the grade of the blue standard wool fabric that is exposed to the light as a test result.The blue standard wool fabric is graded from 1 to 8 and the test sample is exposed to sunlight with its corresponding grade of blue standard together. For example, a grade 4 would give a result of >4, =4 or <4.

AATCC standard: the rating is still done by comparing the gray scale and the results are expressed in the same way as the conventional method of AATCC colour fastness.

4 Durability testing

Test items	Test indicators
Abrasion resistance test	Number of revolutions
Stretch recovery	Ration, %
Pilling	Graded against a standard sample card, grade 5 being the best and grade 1 being the worst.
Anti-snag test	Graded against a standard sample card, grade 5 being the best and grade 1 being the worst.。

5 Functional testing

Test items	Test indicators
Fire Resistance Test	Complex test, generally measuring burn time in various states
Water resistance test	Grading against standard sample cards, grade 5 is best, grade 1 is worst and can be graded in the middle half. ISO, GB, JIS methods: 1, 2, 3, 4, 5 AATCC method: 50, 70, 80, 90, 100 points
Air permeability test	Assessed in two ways: the flow rate of air through the sample per unit time, or the amount of air through the sample per unit time, per unit area. Common units: cm3 / s / cm2 or cm3 / cm2·s, ft3 / min / ft2 Relational conversion formula: 1 cm3 / s / cm2 = 10 mm/s 1 cm3 / s / cm2 = 1.967 ft3 / min / ft2
Water Absorption	Water drops to the surface of the sample until the mirror effect of the water drops disappears. To assess the time it takes.
Moisture Permeability	The weight of water absorbed or evaporated from a sample per unit area and per unit time. Common unit: g/m2·24h Conversion relations: 1g/m2·24h = 24g/m2·h ,  1g/m2·24h = 1g/m2·d
Thermal resistance, Rct	The heat flow rate of a sample through a defined area under stable conditions. Common unit: m2·K/W
Wet resistance, Ret	The evaporative heat flow of a sample through a certain area under stable conditions. Common unit: m2·Pa/W
UV Resistance test	The sample is irradiated with monochromatic or multicolour UV rays (290-415nm). Test the total spectral transmission ratio to calculate the UV protection factor UPF. Common unit: UPF It is expressed as >40 or 40+ when UPF > 40, and UVA < 5%. It is expressed as >50 or 50+ when UPF > 50, and UVA < 5%.
Anti-static test	See below

Anti-static test

Test method	Test principle
Half-life method	The sample is connected to a high voltage current for a defined period of time. Record the time taken between the instant of disconnection and when the voltage decays to 1/2 (i.e. the half-life). Unit: s
Charge surface density method	Rub the surface of the sample a certain number of times and measure the amount of electricity carried per unit area of the sample. Unit: C/m2
Voltage method	The specimen is rubbed against a standard cloth under certain conditions of tension. Evaluate the charged condition of the specimen use the highest voltage generated for a specified period of time. Unit: V
Resistance method	Applying a specified DC voltage, test the resistance between the two electrodes on the surface of the sample. The lower the resistance, the better the electrical conductivity of the sample. Unit: Ω

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These are the commonly used test units and the conversion equations in textile testing. Due to the wide variety of fabric test items, there are many items that are not included and will be updated from time to time when they are found.