x % Span length is the distance spanned by x %of fibers in the specimen being tested when the fibers are parallelized and randomly distributed and where the initial starting point of the scanning in the test is considered 100%. This length is measured using "Digital Fibrograph‘.
Fiber length
Fibrograph Method
The original idea of the photoelectric scanning or Fibrograph method has been developed by Hertel in 1940 for testing cotton lint. This test method is much faster than the array method and is used widely in fiber laboratories for measuring fiber length and length distribution.
Effective Length of Cotton Fiber
The effective length is the upper quartile of the fiber length distribution obtained by ignoring short fibers whose length is below half the effective length.
Length parameters of cotton fibers
The most frequent length in a fibrous sample is called staple length. Staple length is one of the most important factors of cotton quality because both fiber fineness and fiber tensile strength are associated with staple length. The longer staples are usually finer and stronger than the shorter staples.
Fiber length measurement
The fiber sorter is an instrument which enables the sample to be fractionalized into length groups. The Baer sorter, the Shirley comb sorter, and the Suter-Webb sorter are the most popular method of the fiber sorter. Basically, the operation involves four main steps:
Preparation of a fringe or tuft with all fibers aligned at one end.
The separation or withdrawal of fibers in order of decreasing length.
The preparation of a sorter diagram by laying the fibers on a black velvet pad in decreasing order of length, the fibers parallel and their lower ends aligned along a horizontal base line as shown in Figure.
The analysis of the sorter diagram.
Fiber Length and Length Distribution
After fineness, length is the most important property of a fiber. The length of cotton is directly related to its spinning performance. Knowledge of fiber length is necessary to manufacture a yarn of specific size on ring spinning system and typically longer fibers are used to manufacture fine yarns. Longer fibers are generally more uniform, finer, and stronger than shorter ones.