Textile testing and Quality control

What is Testing?

Testing is the way of control or the process to check or verify the nature, kind or character of fiber, yarn, fabric or any material, hence control the degree of excellence.

Now, testing may be different type

Fiber-  length, strength, fineness, maturity.
Yarn- strength, count, twist
Fabric- EPI, PPI, GSM 

Objects of textile testing

-selection of raw materials
-process control
-product control
-process development
-product development
-specification test
-research

Importance of textile testing:

-To determine the properties & characteristics of fiber, yarn , fabric & end products.
-To compare the qualities of textile raw materials, intermediate products or finished products.
-To maintain the standard established by different organization or countries.(e.g., ISO, AATCC, ASTM etc)
-To meet market /consumer demand/standard.
-To improve quality & cost ratio.
-To control & improve processing technique.
-For research & developments.

Factors affecting test results:

-The sampling
-Atmospheric condition during testing
-Methods of testing
-Instruments used
-Efficiency of the technician

  

Quality control:

Quality control is defined as the checking, verification & regulation of the degree/grade of excellence of an attribute or property of something. It is concerned with the evaluation of test data & its application to control of the textile process, raw materials, intermediate product& final product with maximum economy & customer satisfaction.
 

Quality control is governed by three M’s

1) Men
2) Machine
3) Materials

1) Men:

-Top management ( 80% responsibilities are carried out) Co-ordination of the activities of the complete labour force
- administrative, technical, operative supervising.
- Men must be well trained up to fulfill their work perfectly.

2)Machines:

Machines should be selected on the basis of skillness of technicians or operators. May select more refined and complex machines for highly trained technicians or simpler and more easily maintainable machines for poor skilled technicians.
( book, J.E. Booth, page- 558)

3) Materials:

The selection of raw materials is a key factor in success or failure of the production.

Yarn→ Fiber
Fabric→ Yarn
Garments→ Fabric

Some important testing standards:

AATCC: American Association of Textile Chemists & Colorists
ASTM: American Society for Testing & Materials
ISO: International Organization for Standardization
BSTI: Bangladesh Standards & Testing Institution
WIRA: The Wool Industries Research Association
AS: Australian Standard
BSI: British Standards Institution

Process Control

Process control is an integral stage of textile manufacture; it involves controlling and predicting process variables such as time, temperature, pH, streaks and broken filaments. Using process control therefore reduces any defects and thereby reduces waste, minimizes costs and reduces the environmental impact.

Product control

Quality systems that focus on sorting and isolating defective product are generally called product controls. Because the process generates defective product, efforts are made to identify, sort, and segregate the defective product.
The end product of a process should be fulfill the desired quality, Thai is
count, TPI, GSM, fastness property etc.

Moisture in case of testing

Most textile fibers are hygroscopic, i.e. they have the ability to absorb or give up moisture. This moisture is picked up or absorbed by the hygroscopic material from the atmosphere if the relative amount of moisture in the air is greater than that in the material. Conversely, the moisture will be given up by the material if the relative amount of moisture in the air is less than that in the material.

Many physical properties of a fiber are affected by the amount of water absorbed, such as dimensions, tensile strength, elastic recovery, electrical resistance and so on.

The mechanism of water absorption

In an orderly array of molecules the side chains will be linked, but in a random arrangement a number of free links “hooks” will be available and if they are of a polar character ( i.e. possessing an attraction for polar chemical groups such as hydroxyl OH, carboxyl COOH, carbonyl CO etc) then water molecules can attach themselves. Orderly arrays of molecules occur in the crystalline regions of the fiber structure and random arrays in the amorphous region. Absorption of water takes place in amorphous region.

Under ideal humidity condition, the following advantages are realized in processing.

1) Reduction in- generation of static electricity.
2) Materials are more easily workable due to increased pliability.
3) Reduction in amount of dust and fly.
4) Allows for the retention of moisture already within the material.
5) Permits greater bodily comfort for personnel in cold weather.