Dear all,
In view of polymer morphology i am bit of confusion. If you see some area amorphous polymers mentioned as a transparent/translucent and crystalline polymers mentioned as a opaque.
Amorphous - PC, GPPS, PMMA, PVC, ABS.
Crystalline/ semi crystalline - PE,PP, PA, PET, POM etc...
But what my confusion is how ABS & PVC will come amorphous?
second PET is transparent but it is mentioned as crystalline?
Third what about HIPS?
Thanks a lot
Hi,
Polymer morphology is quit interesting and no simple rule based on transparency can not explain crystalline or amorphous structure. For example- Transparent PET can be both Crystalline or amorphous, where structural domain configuration determined its morphology.
One should remember that crystalline domain or long order chain domain must have birefringence under polarized light which can be a quick test for crystallinity ( some amorphous polymer might show this behavior). For example- most of polystyrene are amorphous but they have some sort of birefriengence but that is due to stress birefringence not for crystallinity.
Concerning ABS and HIPS… They are so called rubber toughened plastics. In this case, rubber particles, PB mostly, of micron or nanometer (several hundreds) in size are dispersed in SAN (styrene-acrylonitrile copolymer) or PS matrix. The particles scatter the light and cause in opaqueness of the materials, although both matrix polymers (SAN and PS) are transparent (or translucent) and amorphous.
In addition to the previous answers, I suggest you to read some basic literature on polymer morphology. There is no "linear" correlation (as you probably expect) between the transparency and polymer morphology.
My RG colleagues have given good answers. My "humble" addition is to explain why ABS and HIPS are amorphous.
As you know, homopolymerization of ethylene "alone" or propylene "alone" leads to formation of PE & PP plastics with high crystallinity. However, when ethylene & propylene are copolymerized the product is an elastomer (EPR) with significant drop of crystallinity.
Copolymerization does not necessarily improve properties in a single direction but it may be "antagonistic". This applies to ABS "which is a copolymer of acrylonitrile, butadiene, and styrene" with the 3 monomers imparting variety of structures that do not end up with order "which is condition for crystallization".
As for HIPS, it is a graft copolymer with polybutadiene grafted on polystyrene. Both polymers are disordered enough to cause an amorphous product.
ABS is tough copolymer "used for e.g. in calculators". The calculators may drop many times from table to floor without breaking. HIPS has high impact as the name states. Here are 2 cases in which disorder in structure has resulted in useful properties.
ABS is an opaque thermoplastic and is amorphous polymer. Similarly PVC has amorphous structure
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