What is crystallinity of plastics?

Unlike thermosets and elastomers, thermoplastics can also form crystals. In reality, however, most plastics are only partially crystalline (partial crystallinity). This is due to the fact that pure thermoplastics are not cross-linked and the polymer chains can be highly ordered next to each other. A high degree of order or symmetry in one or all three spatial directions is the most important indication of crystallinity in materials science. Crystalline areas are started by so-called crystallization nuclei and the type of crystallization is determined by the nucleation and crystal formation in a physico-chemical manner. Crystal formation depends on the material, additives and the condition temperatures. In general, it can be said that a higher crystallinity improves the density, melting temperature, strength, dimensional stability and resistance to wear. The opposite of a crystal is an amorphous material. Due to the lack of crystallization nuclei, amorphous materials are non-crystalline and disordered structures. Glass is prevented from forming crystals by very rapid undercooling of the material and is therefore a prime example of an amorphous material. Amorphous materials are characterized by their transparency (see glass). In the case of partial crystallinity, these highly ordered areas are interrupted by disordered amorphous areas.