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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
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: cm/ 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

……

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.

 

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