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Therefore, the polypropylene product generally did not require additional purification steps to remove the atactic or low crystalline fraction. This meant that the APP supply from polypropylene plants using standard first- and early second-generation Z-N catalysts decreased as commercial plants adopted the new catalysts.
Atactic polypropylene has lower density, melting point and softening temperature than the crystalline types and is tacky and rubber-like at room temperature. It is a colorless, cloudy material and can be used between −15 and +120 °C. Atactic polypropylene is used as a sealant, as an insulating material for automobiles and as an additive to ...
Atactic polymers such as polystyrene (PS) are technologically very important. [ citation needed ] If a special catalyst [ clarification needed ] is used in its synthesis, it is possible to obtain the syndiotactic version of this polymer, but most industrial polystyrene produced is atactic.
For example, atactic polypropylene is usually amorphous and transparent while syndiotactic polypropylene, which has crystallinity ~50%, is opaque. [30] Crystallinity also affects dyeing of polymers: crystalline polymers are more difficult to stain than amorphous ones because the dye molecules penetrate through amorphous regions with greater ease.
A polymer that lacks any regular arrangement in the position of its alkyl substituents (R) is called atactic. Both isotactic and syndiotactic polypropylene are crystalline, whereas atactic polypropylene, which can also be prepared with special Ziegler–Natta catalysts, is amorphous.
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If PP and PE are the dominant component of a TPO blend then the rubber fraction will be dispersed into a continuous matrix of "crystalline" polypropylene. If the fraction of rubber is greater than 40% phase inversion may be possible when the blend cools, resulting in an amorphous continuous phase, and a crystalline dispersed phase.