The chemical fiber without curling has a smooth surface and poor cohesion between the fibers, which makes the spinning process difficult. The chemical fiber is crimped to meet the requirements of textile processing, improve the spinnability of the fiber and improve the takeability of the fabric. Whether the chemical fiber has curl or not has a certain influence on the wrinkle resistance, body bone and style of the fabric.

According to the physical properties, chemical properties and appearance defects, the quality of chemical short fibers such as polyester staple fiber, nylon staple fiber and polypropylene staple fiber can be evaluated. Generally divided into excellent, one, two, three and so on. The classification items and specific indicators of various chemical fibers are different and are specified in the inspection standards.

The physical and chemical properties of chemical short fibers such as polyester staple fiber, nylon staple fiber and polypropylene staple fiber generally include breaking strength and coefficient of variation, elongation at break, linear density deviation, length deviation, ultra-long fiber ratio, and long fiber. Content, number of crimps, oil content, and the like. According to the characteristics of different varieties of chemical fiber, other indicators should be tested.

For example, viscose fiber should be tested for wet breaking strength, residual sulfur content, whiteness and oily yellow fiber; synthetic fibers often need to be tested for crimp ratio, specific resistance, dry heat or boiling water shrinkage; polyester should be tested for 10% elongation strength. Acrylic fiber needs to be tested for coloring rate, sodium sulphate content, hooking strength, etc.; Vinylon needs to be tested into package moisture regain, which is required to be within the specified range.

The quality inspection of chemical staple fibers was randomly sampled in batches. The same batch of fiber has the same raw materials, the same process conditions, and the same product specifications. The number of samples is based on the batch size as specified by the standard.

In order to know the crimping properties of polypropylene staple fibers, it is necessary to test and evaluate according to the above method.