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Gearing up for 2005 !

Quality testing of fabrics: A must for survival & growth

Manjit Singh Saini

As the day of the dawn is approaching near, few facts which were earlier subdued, have started to surface out. It’s been noticed that the bigger and larger exporters, who believe in delivering quality, have started becoming stronger with the passing of each day. The buyers abroad have started showing more confidence in these big players and this attachment can be attributed to the quality mindset of the exporter, usage of advanced technology to enhance productivity, process control and logistics.

Prominent among these being Orient Craft, Shahi Exports, Gokaldas Fashion etc can be truly termed as the real jewels in the crown of Indian garments exports. Paramount is proud to be serving more than 90% of the top exporters of India and is further proud to be the part of this evolution.

On the other hand, the smaller player who actually lacks the quality mindset and the acceptance of the latest technology, are the ones, whose days are now numbered. We need to ask this question sincerely, while introspecting, the real current position of your business. The three core issues remains the same. Do we have competitiveness in regard to Quality, Pricing and On-Time Delivery?

Catering to the Quality aspect, the physical tests, pertaining to the aesthetic performance testing, are covered in this article :

1. To check the drape properties
2. To check the stiffness property
3. To check the crease recovery property.

To check the drape properties of fabrics

Drape is the ability or bending behavior of a fabric under its own weight to assume a graceful appearance in use. Typical examples are how curtains hang; the appearance of a skirt; or the hanging of the cloth over the edge of a table. A fabric is said to possess a good drapability when its configuration is pleasant to the eye. The drapability of a fabric depends on many factors such as weave, cover factor, finish etc.

Drapability of a fabric can be determined using the instrument Drape-meter and is expressed in terms of drape co-efficient.

Equipment

Drape-meter consists of a circular specimen support, an electric lamp and an exposing and developing arrangement using ammonia process paper to determine the area covered by the shadow of test specimen. The circular specimen support made of aluminum is fixed over a clear acrylic sheet. The acrylic sheet is hinged on one side and can be lifted for placing the ammonia process for exposure. The paper is kept below the acrylic sheet on a resilient surface so that it is in close contact with the sheet when it is horizontal. The specimen holding system and paper exposing arrangement is made inside a sheet metal exposing chamber so that light rays coming from it are intercepted by the test specimen. The rays, which are not intercepted fall on the paper and expose it, thus giving a demarcation between exposed and unexposed areas. The chamber has a close fitting door. It has ventilation holes near its bottom and top for keeping it cool.

An ammonia vapour-developing chamber in which the exposed paper is kept for developing is provided below the exposing chamber. This chamber has a close fitting door and an arrangement to keep ammonium hydroxide to create a suitable atmosphere for developing the pint. The test specimen is kept over a welded wire mesh platform to ensure a uniform developing.

Principle of the test

The drape of a fabric is determined by using a circular support over which a specimen of the fabric in the form of a circular piece is placed. The horizontal area covered by the shadow left by the overhanging portion of the fabric is determined and compared against its actual area to obtain the drape co-efficient.

To check the stiffness property of the fabrics

Stiffness is an important characteristic of a fabric. The importance of stiffness depends on the end use of the fabric for e.g. a fabric required for a skirt should have lower stiffness as compared to suiting fabrics. Fabric stiffness indicates the resistance of the fabric to bending and it is a key factor in the study of handle and drape. It is determined by Cantilever method in which the fabric specimen is allowed to bend under its own weight as the length of the overhanging portion of the specimen is gradually increased. Under this method, first we have to measure the bending length of the fabric and from this the flexural rigidity and bending modules can be calculated.

Equipment

Stiffness Tester consists of a metal platform, having a smooth low friction, flat surface. The platform is supported by two side pieces made of acrylic. These side pieces have engraved on them Index lines at an angle of 41.5 degrees. Attached to the instrument is a mirror which enables the operator to view both index lines from a convenient position. A scale is supplied with the instrument to measure the bending length and is graduated in cms. of the bending length.

To carry out the test, the specimen is cut to size with the help of the provided template. Then a special scale (rubber lined scale graduated in cms) and the specimen are transferred to the platform with the fabric underneath. Both are slowly pushed forward. The strip of fabric will commence to droop over the edge of the platform as we move the fabric forward with the scale. The forward push on the fabric is continued until the tip of the specimen, as viewed in the mirror, cuts both the index lines. The bending length can immediately be read off from the scale mark opposite a zero line engraved on the side of the platform.

Principle of the test

The stiffness tester works on the principle of the bending length. In this, the fabric specimen is allowed to bend under its own weight, as the length of the overhanging portion of the specimen, is gradually increased. The free length which bends under its own weight sufficiently to make its leading edge intersect a plane of 41.5 degrees inclination, is taken as the measure of stiffness of the fabric.

To check the crease recovery property of fabrics

One of the major drawbacks of the cotton fabrics compared with synthetics is the poor wrinkle resistance. A wrinkled fabric looks unappealing aesthetically, when it is made into an apparel.

The creasing of textile material is a complex effect involving tensile, flexing, compressive and other stresses. The ability of the fabric to resist creasing is dependent on the type of fibre used in its construction. Some fibre types such as wool and cultivated silk have a good resistance to creasing whereas cellulosic material such a cotton viscose, and linen have a poor resistance to creasing. In many cases different type of resins are applied to the fabric during chemical processing in order to improve its crease resistance.

Equipment

The crease recovery tester determines the property of textile to recover from creases by measurement of the recovery angle. The crease recovery tester consists of two units : The main unit and the loading assemble unit.

The main unit is made of heavy casted base with all other components made of stainless steel. The rotating dial on the main unit is engraved in black colour. This dial moves in the rack with smooth movement. The second unit, the loading assembly, has three stainless steel creasing loads of 10 Newton’s (as per BS Standards), 9.63 Newton’s (as per ISO Standards) and 500 gms (as per American Standards). 20 rectangular specimens are tested each measuring 40mm x 15 mm. The specimens are folded in two, the ends being held by tweezers. The specimens are than placed under a load for 5 minutes. They are than immediately transferred to the holder of the main unit and one leg of the specimen is inserted as far as the back. The scale is adjusted continuously to keep the free limb of the specimen vertical. The crease recovery angle is measured, by reading the scale where the free limp is positioned, 5 min after the removal of the load.

Principle of the test

The basic principle of this test is that a small fabric specimen is first creased under a specified load for a fixed time and is than transferred to the measurement device where one end of the specimen is held in a spring loaded clamp while the free end is allowed to fall free under its own weight. The clamped end is slowly rotated till the free end becomes vertical under its own weight. The deflection of the clamped end from the horizontal is now read on the sale fixed to the moving clamp. This angle gives the measure to the crease recovery angle.

(The author is CEO & executive director, Paramount group. Feedback on this article can be sent to manjitss9@hotmail com)