Polyethylene polymerisation rate

Commercial interest in PVC also commenced at about this time. The Russian, I. Ostromislensky, had patented the polymerisation of vinyl chloride and related substances in 1912, but the high decomposition rate at processing temperatures proved an insurmountable problem for over 15 years. Today PVC is one of the two largest tonnage plastics materials, the other being polyethylene. 

Ethylene has a symmetrical monomer, so the concept of tacticity does not apply. Consequently, the crystallinity of polyethylene is controlled either by chain branching or by copolymerisation. Copolymers are classified into random and block copolymers (Fig. 2.7) depending on whether the monomer locations are random, or whether long blocks of each monomer exist. Polyethylene copolymers are random. The figure suggests that the local composition of a random copolymer is the same as that of the monomer mixture. However, in a batch copolymerisation, monomers tend to add to the end of a growing chain at different rates. The monomer ratio drifts as the polymerisation proceeds, so polymer formed at the end of the polymer-... 

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