What Is Degree Of Crystallinity?


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Crystallization adds a lot of important properties in a material which are not present in the amorphous polymers. Thus it is important to have crystalline polymers for different applications. The fraction of crystalline material in the polymer is called the degree of crystallinity. However, since the boundary between "crystalline" and "amorphous" is not well defined, the degree of crystallinity is also a somewhat uncertain quantity. The degree of crystallinity also depends on the method of measurement and it can be expressed as a weight fraction Kw or a volume fraction Kv. Each of the two quantities can be calculated from the other by a relation using the density of the total polymers, and the density of the ideal crystalline state of the polymer, pk Kw = Kw-pk/p
Normally, degrees of crystallinity are given in terms of the weight fraction24'.

Most calculations involving the degree of crystallinity of semi-crystalline thermoplastics are based on a two-phase model consisting of perfectly crystalline and perfectly amorphous regions. This is a simplifying assumption because the various lattice and other defects and the amorphous-crystalline transition areas must account for several! percent of total volume.
Because of the dependence on structure and crystal form, semi-crystalline thermoplastics exhibit different but typical degrees of crystallization

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