TEST METHODS FOR THE DETERMINATION OF VARIOUS

PHYSICAL PROPERTIES OF FIBRES

NATIONAL INSTITUTE OF FASHION TECHNOLOGY,PATNA

By-ASHIF

Tests related to Wool

• Determination of wool fineness.

• Measurement of the crimp.

Determination of wool fineness• Fineness is basically related to the fiber diameter

• Fine wool fibers have low micron value

• Every fleece comprises of a very wide variety of fiber diameter.

A typical merino fleece Fiber diameter variation

OFDA-Optical Fiber Diameter Analyzer

• The diameter(fineness) of wool is measured using OFDA.

Measurement of crimp

• Crimp:- It is natural wave formation found in Huyacaya fleece.

Crimps per inch

Higher amplitude /Deeper crimp Higher frequency/Less-bold crimp

Ci = lo-l * 100 lo

Grades of wool according to the crimp

GRADES CRIMPS PER INCH• Very fine 22-30• Fine 14-22• ½ blood 10-14• 3/8 blood 8-10• ¼ blood 5-8• Low quarter 2-5• Common 0-2• Braid 0-1

Determination of color of wool fiber

Vibrochron tester

Tests related to Silk

• Determination of Tenacity

• Determination of Evenness

Determination of Tenacity

• To determine the tenacity of raw silk, the breaking point(gram/denier) and the degree of elongation(%) is determined

• Ideal environment :- 20 º C temperature and Relative humidity around 65%.

• Apparatus:- Serigraph, Sizing reel & scale

Serigraph

PROCEDURE

• 10 test pieces are taken out of 50 test pieces and 10 sizing samples are prepared from them.

• Each sample is subjected to test for tenacity and elongation.

• The result is tabulated and indicated as average.

Determination of Evenness• Apparatus used:- Seri plane(127*457 mm) ,standard photography & illumination

room.

• The thread are spaced on the inspection panel according to the size under test as follows.

9 denier or finer :- 133 threads per 25.4mm 27-36 denier :- 66 threads per 25.4 mm 198 denier or coarser:- 25 threads per 25.4 mm

• On any one side of the inspection board, each strip on each panel is carefully compared with the standard photographs and accordingly the intensity of variation is determined.

Tests related to Cotton• Determination of fiber strength.

• Determination of length of cotton fibers.

FIBER STRENGTH TESTING• Usually done by Stelo-meter or Pressley fiber strength tester.

Tenacity of fiber = Breaking load(kg)*Sample length(mm) (in g/tex) mass of fiber(mg)

DETERMINATION OF LENGTH OF COTTON FIBERS

• Array Method:numerical sample of fibers is arranged in the form of an array indescending order of length, and from a tracing of this array ,the effective length, mean length, percent short fiber and coefficient of variation of length are calculated

• CUT AND WEIGH METHODTuft of fibers, aligned at one end, is cut into three sections as shownin figure and each section is weighed.

PHOTO-ELECTRIC STAPLER

Working principle behind the Photoelectric stapler

• Fringes of fibers are placed over the velvet pads .

• Photoelectric stapler detects the distance between ,where the density gradient is maximum.

• Depending upon the light intensity the opposite cells pass a current which is proportional to intensity.

• Variation in current is noted by galvanometer.

• As the fringe advances inside the instrument ,there will be two maximum density gradient point and the distance between tem will be the “Staple length”.

Tests related to Nylon

• Measurement of resistance to abrasion.

• Determination of tensile strength.

Measurement of resistance to abrasion

Martindale abrasion tester.

Procedure:-• The test makes the use of a modified specimen holder which stretches the knitted material

thus effectively accelerating the test.

A standard size 38 mm diameter sample is held to size by pinned ring A flattened rubber ball is pushed through the sample as the holder is tightened, thus stretching it.

The holder is then mounted on the Martindale with a 12 kPa weight and the test is carried out as normal.

Determination of tensile strengthThe one end of fiber is tied to a hook which is fixed in a vertical plane.

A weight hanger is tied to the other end and the thread is let to get straight.

A weight is put on the hanger and the stretch in the thread is observed.

The weight is gradually increased on the hanger until the breaking point is reached .The min. weight needed to break the fiber is noted.

Tests related to Jute• Determination of fiber fineness (Air-flow method)

• Determination of moisture content

• Determination of fiber density

• Determination of fiber maturity

Determination of fiber fineness (by Air-flow)• Apparatus used:- Fiber fineness tester.

• Principle:- Fineness of a fiber is related to the rate of airflow through a plug of fiber with fixed weight contained in a container of some definite dimension and subjected to constant pressure.

• Fineness is relative measure of size, diameter ,linear density etc. and plays an important role in determining the commercial value of fiber.

Air-flow method

Determination of fiber maturity

• It is measured to express the development of the fiber.

• 2 methods to determine fiber maturity – Direct & Indirect.

• We mainly use the direct method which includes microscopic analysis by caustic soda swelling and the concept of fiber maturity.

MATURITY COEFFICIENT

Mature(<1) Half-mature(between 1 &2)

Immature(>2)

Maturity coefficient = M + 0.6 H + 0.4 I 100

Determination of moisture content

Empty weighing bottle Hot air oven Analytical balance

• The empty weighing bottle is weighed accurately with the help of precision balance.

• A sample of fiber is placed in the bottle and weighed again.

• Bottle with its contents is dried in the oven at 378 + 3 K with its stopper removed for about 30 seconds.

• The procedure repeated until complete drying takes place.

% regain = Mo – Md *100 Mo

Mo= mass (original sample) ; Md =oven dry mass of dried sample;

Determination of fiber density

Mainly 2 ways of measuring the density of a fiber:-

• By Archimedes principle

• By fluid(liquid/gas) pycnometry

• The gas pycnometry is Based on the principle of gas displacement and volume-pressure relationship.(Boyle’s law).

Gas pycnometry

References:-

• Fabric testing by Jinlian HU.

• Principles of fabric testing

• Fabric Science –JJ Pizutto

• Textiles by Sarah J. Kadolph

Thank you