Relation of Specific Strength of Cotton Fibers to Fiber Length and Testing Method

Four cottons in commercial production, covering a range of such physical properties as strength, length, and fineness, were studied in a comparison of two methods of determining fiber strength—the individual fiber test and the Pressley flat-bundle test.

Because of the combing action in bundle preparation, cotton fibers broken in the flat-bundle test represent the longer fibers found in a sample of cotton. These remaining fibers are not representative of the length of the original sample; and since fiber specific strength increases with fiber length, neither are they representative of the strength of the original sample. This increase in specific strength with increase in length is evident whether fibers are broken indi vidually or in aggregates.

The relationship between the logarithm of individual fiber tensile strength and the logarithm of the specimen length used is inversely linear. The flat-bundle test represents the strength of fibers whose specimen lengths were deduced to be between 1/16 and 3/32 inch.