Atactic and isotactic structures of polypropylene

The copolymers have better behaviour at low temperature and are more impact resistant but less rigid than the homopolymers. The copolymer blocks present a good balance between rigidity and impact strength that depends on the importance of the blocks and their distribution  

Despite the apparent similarity in the chemical structure, please note that the tertiary carbons attached to the polypropylene backbone induce a slightly different behaviour from that of polyethylene. 

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