Textile Quality Evaluation | Quality Evaluation for Textile


QUALITY EVALUATION OF TEXTILES

Ramandeep Singh
B.Tech, Dept. of Textile Engineering
Giani Zail Singh Punjab Technical University Campus,
Bathinda, Punjab, India
Email: rmnsandhu3335@gmail.com




WHY TESTING : 
Testing of textiles is necessary to achieve one or more of the following objectives :
  1. Assessment of performance during actual use .
  2. Comparison between norms & actual .
  3. Fitness for purpose or end use suitability .
  4. Minimization of trade disputes .
  5. Facilitation of exports & imports .
FIBER TESTING :
Testing of fibers is required for determining their quality and to control the quality of the finished product .

We can broadly divide the fiber testing in two categories-
  1. Cotton fiber testing
  2. Man-made fiber testing
COTTON FIBER TESTING :
Following are the main properties of cotton fiber :
  • Fiber Length
  • Fiber Fineness
  • Fiber Strength
  • Maturity & Colour of cotton
  • Trash %
Fiber Length : It is determined by Digital Fibro graph and is expressed as ‘span length’ .

Fiber Fineness : It is measured by Air Flow method with the help of ‘Fineness Meter’. It is expressed in microgram/inch (micronaire) .

Fiber Strength : It is measured by testing a bundle of fibers with the help of ‘Stealometer’. It is expressed as gm/tex .

In modern textile mills these properties are tested with the help of HVI (High Volume Instrument ) which is an automatic version of the above facilities .
High Volume Instrument
Maturity & Colour of cotton : The HVI instrument can also have a module for measuring ‘Maturity Ratio’ & the ‘Colour Index’ of cotton .

Trash % : It is not a fiber property . However its determination is necessary from commercial as well as quality point of view. Trash % is measured by an instrument called ‘Trash Analyzer’ which works on the principle of ‘separation’. Normally 100-200 gms of cotton is tested for determining the trash% .

MAN-MADE FIBER TESTING :
Following are the main properties of Man-made fiber :
  • Mean Length
  • Denier
  • Tenacity & Elongation
  • Crimp
Mean Length : It is determined by measurement of single fiber on a ruler or measuring tape .

Denier : It can be measured by cutting & weighing method or by using resonance principle on ‘Vibroskop’ instrument.

Tenacity & Elongation : Tenacity and elongation is measured by breaking single fiber on a tensile testing machine . This is expressed as gm/denier and % respectively .

Crimp : Crimp properties of the fibers are important for converting them into yarn. It is expresses the extent of crimpiness in the fiber denoted as crimp% .

HUMIDITY : 
Humidity is the amount of moisture present in the atmosphere .

ABSOLUTE HUMIDITY : It is the weight of water present in a unit volume of moist air . The unit is grams/ cubic meter .

RELATIVE HUMIDITY : It is the ratio of actual vapour pressure to the saturated vapour pressure at the same temperature expressed as percentage .

                       Actual vapour pressure
R.H % = ---------------------------------------------- x 100
                      Saturated vapour pressure

MOISTURE REGAIN : It is an important parameter which effects the behavior of fibers . Moisture regain is determined by difference in weight of fibers at standard condition & after oven drying .

                     Weight of sample at 65% R.H - Oven dry weight
M.R % = --------------------------------------------------------------------------- x 100
                                              Oven dry weight

Standard Atmospheric Conditions :

  • R. H - 65 %
  • Temp - 27 C
YARN TESTING :
Testing of yarns is required for determining their quality and to control the quality of the finished product .

The main yarn quality parameters are given below :
YARN COUNT & LEA STRENGTH : The term count or yarn number is commonly used to define fineness of yarn .

The yarn count is determined by measuring yarn length accurately & weighing it on electronic balance .

Lea yarn strength is determined by testing lea of 120 yards on pendulum type ‘Lea strength tester’. Strength is expressed in lb or kg depending upon the requirement .Yarn strength is important from processing and fabric strength point of view .

SINGLE YARN STRENGTH : Single yarn strength is a better indicator of yarn performance in knitting & weaving .This is tested on Single yarn strength tester working at constant rate of traverse (CRT) or constant rate of extension (CRE). Values are expressed as gm/tex or RKM .

TWIST : Twist is an important property of yarns as it gives strength to yarn & feel in fabric . Depending upon the direction of twist(S or Z type), twist is measured by untwisting the yarn in case of plied yarn & by twist - re twist method in case of single yarn . It is expressed as TPI (Twist per Inch ) or TPM ( Twist per Meter ) .

CLASSIMAT FAULTS: The yarns also have seldom occurring faults, besides Uster imperfections which are known as Objectionable faults.These faults are classified as A,B,C,D,E,F,G,H,I by Uster Classimat system and are generally expressed in terms of no. of faults/lacs meters .

ADVANTAGE OF CLASSIMATE :
Origin of yarn faults can be identified:
  • Optimization of clearer gauge settings .
  • Customer requirement could be fulfilled .
Classimat faults
HAIRINESS : All the fibers are not bound in core of yarn and lots of them protrude from the surface . These are termed as ‘hairs’ . Hairs are varying in length ranging from 0.5 mm to 10 mm.These hairs are measured by optical scanning or by CCD camera technique by Uster hairiness tester

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