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The Distinction of hotmelt-zp Thermoplast


General thermoplast in the polymer molecular weight can reach hundreds of thousands to several million, macromolecule chain length can reach 10-3mm. These macromolecules can be linear, such as LLDPE, HDPE. It can also be branched, such as LDPE. Macromolecules intertwined with each other, was disorderly or relatively orderly arrangement, the formation of "aggregation state structure."

When the macromolecule is completely disordered, we call it amorphous plastic. Such as PVC, PC, PMMA and so on. Its performance characteristics are: good transparency, low mechanical strength, good flexibility. Part of the macromolecules or macromolecules partially arranged in the structure is called crystalline thermoplastics. Such as LLDPE, POM, nylon, etc., its performance characteristics are: poor transparency, high mechanical strength, flexibility is low. As the polymer molecular chain is very long, not as low molecular weight as the whole molecule can be achieved into the "crystallization zone" to achieve complete crystallization. Therefore, the "crystallinity" of crystalline thermoplastics is used to describe the degree of crystallinity (or the size of the crystal region).

The characteristic temperature of the amorphous thermoplastic is the glass transition temperature (Tg). When it is below Tg, the polymer exhibits a "glass" characteristic property, which is called "glassy", and the polymer The use of functional, and no plastic properties; when higher than the Tg, the polymer is a high elasticity and a certain plasticity characteristics, while losing the use of function, professional called "high elastic state." After further warming, its elasticity is lost and completely plastic. Therefore, the maximum operating temperature should be below Tg, and its minimum processing temperature should be above the Tg.

The characteristic temperature of the crystalline thermoplastics is the crystallization temperature (Tc). Below Tc, the polymer showed a hard texture, with the use of functional, non-plastic processing. Higher than the Tc when the polymer is melted plastic, loss of use of the function, and plastic processing. Amorphous thermoplastics and crystalline thermoplastics compared to the former has three physical properties, the latter is not "high elastic state", only two physical properties. This is often seen in the processing of the former often use "gradient screw", while the latter is the use of "mutant screw" typical features.