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neerajsinghvns : crystalline   2

Crystalline vs. Amorphous PET;;;
All PET materials are hygroscopic, so exposure to a humid environment will cause them to absorb moisture. This moisture causes a cleavage in the polymer chain during melt and results in a degradation of the physical properties of the product produced.

Virgin PET
Virgin PET is usually in a crystalline state (indicated by its white color) when it is purchased from a supplier.
Reground PET
Regrind PET material is usually not crystalline, but amorphous and clear in color.
Agitating the material while heating it to a temperature of about 180˚ F will convert the material from its amorphous state to a crystallized state, ready for drying. We call this process crystallizing but technically, it is a re-crystallization of the material.
states  state  properties  plastics  plastic  crystalline  amorphous  PET 
april 2013 by neerajsinghvns
What's the difference between Crystalline and Amorphous States?;;;;;;

What's the difference between Crystalline and Amorphous States?;;;

The nature of crystalline and amorphous polymer states is often misconstrued and misused. The term amorphous means to have no defined shape, or an easily altered shape, like a liquid or a rubber. Crystalline, on the other hand, insinuates that there is a regular, defined pattern to the molecular aggregates --- crystallized carbon forms a substance we call “diamond”. These terms are used to define two separate “solid” states that exist particularly in polymers. The confusing part is that they coexist in many polymers --- the so-called semi-crystalline polymers.

The amorphous nature of polymers is analogous to a plateful of spaghetti --- loose and randomly coiled. While the crystalline state is more like the uncooked spaghetti in the box --- the chains are all tightly bundled and ordered in the same direction.

In a polymer, these two states coexist,
plastics  difference  between  crystalline  and  amorphous  states  plastic 
april 2013 by neerajsinghvns

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