Abrasion is one aspect of wear and is the rubbing away of the component fibers and yarns of the fabric.
Abrasion may be classified as follows-
Plane or flat abrasion-A flat area of material is abraded.
Edge abrasion-This kind of abrasion occurs at collars and folds.
Flex abrasion-In this case, rubbing is accompanied by flexing and bending.
Factors affecting abrasion resistance:
Nylon is generally considered to have the best abrasion resistance. Polyester and polypropylene also have good abrasion resistance. Blending either nylon or polyester with wool and cotton is found to increase their abrasion resistance. Viscose and acetates have the lowest abrasion resistance.
A fabric made up with longer fibres gives better abrasion resistance than short fibres because they are harder to remove from the yarn. For the same reason filament yarns are more abrasion resistant than staple yarns made from the same fibre. Increasing fibre diameter up to a limit improves abrasion resistance.
An optimum amount of twist in a yarn gives the best abrasion resistance. At low-twist factors, fibres can easily be removed from the yarn so that it is gradually reduced in diameter. At high twist levels, the fibres are held more tightly but the yarn is stiffer so it is hard abrade under pressure
Fabrics with the crimp evenly distributed between warp and weft give the best wear because the damage is spread evenly between them.
Martindale Abrasion Tester:
1、Four specimens, each of 38mm in diameter are cut by using the appropriate cutter.
2、Then they are mounted in the specimen holders with a circle of standard foam backing behind the fabric. The specimens must be placed flat against the mounting block.
3、The test specimen holders with the specimens are placed on the abradant.
4、A spindle is inserted through the top plate and the correct weight (usually of a size to give a pressure of 12kPa but a lower pressure of 9kPa may be used if specified) is placed on top of this.
5、The standard abradant should be replaced at the start of each test and also replaced after each 50,000 cycles if the test is continued beyond this number.
6、While the abradant is replaced it is held flat by a weight and the retaining ring is tightened.
7、Behind the abradant, there is a standard backing felt which is replaced at longer intervals.
8、After appropriate clamping of specimen on the holders, required numbers of cycles of abrasion is applied.
Assessment of abrasion damage:
1、Several methods are used to judge the amount of damage. Some are mentioned below:
2、The difference in appearance between an abraded and unabraded specimen.
3、The number of cycles required to produce a hole, broken threads or broken strip.
4、Loss in weight often plotted against the number of cycle. Change in thickness e.g. loss of pile height.
5、Loss in strength,g. tensile, bursting or tearing strength, expressed in percentage of unabraded strength.
6、Change in some other properties like lustre, air permeability etc.
7、Microscopic examination of damage of yarns and fibres.
8、The specimen is examined at suitable intervals without removing it from its holder. In the Table, the time intervals between examinations are shown.
8、All four specimens should be judged individually. The individual values of cycles to breakdown of all four specimens are reported and also the average of these.