Wear testing of carpets

The NBS and Shawmut machines for testing the wear resistance of carpets, a gage for measuring the thickness of carpets, and an instrument for measuring the length of a tuft of pile from a carpet are described. The effects of the height of the vacuum-cleaner nozzle above the pile, the amount of suction at the nozzle, and the relative humidity and temperature of the air in which the test is made, on the results obtained wi th the NBS m~hine were studied. The effect of systematic changes in carpet construction on the wear resistance was investigated with each machine and under se vere service conditions. T ests on 24 carpets ofAxminster , velvet , and Wilton weaves were made on the two types of machines in several laboratories, and the results obtained in t he different laboratories wcre corrclated with each other and also with t he results of 3 years of service tests on the same carpets. The correlations were highly significant, but large systematic differences between the weaves and between the laboratories were obtained. The latter difference is attributed primarily to a lack of uniformity in the testing procedures. Three types of vacuum-cleaning systems were used during the service tests, and their effect on t he wear of the carpets and t he effectiveness of cleaning were observed. The S index, which is the time required to wear the pile of a carpet down to one-fourth of t he matted pile thickness, corresponds closely with the t ime at which a carpet in a service test would be discarded on account of visible wear. The deviation of the S index of a single test from the average is less t han 10 percent in 9 trials out of 10. The nature of t he wear produced by t he two machines on the pile fibers was found to be similar to that produced during the service tests. The analyses of carpets do not yield sufficient data to determine t he probable durability of carpets in general. The relative wear of carpets for a given use can be evaluated by means of laboratory wear tests. For general interlaborat ory comparison of the relative wea r resistance of carpets, t he testing machines and the testing procedures must be rigidly standardized and controlled.