Isoprene/propylene copolymerisation

A scheme for the alternating copolymerisation of conjugated dienes and a-olefins has been proposed in the case of isoprene/propylene copolymerisation with V-based Ziegler-Natta catalysts [209] ... 

The preparation and introduction of catalytic complex components to the polymeriser, using a tubular turbulent prereactor, enables the synthesis of copolymers (styrene-propylene (SSP) and styrene-ethylene-propylene (SSEPT)) which demonstrate high stability and durability. According to the laboratory results, obtained from the commercial production of ethylene and propylene copolymerisation, during separation of the active site formation and initiation of isoprene polymerisation on a Ti-Al catalytic system, an increase in copolymer yield and its molecular weight, as well as a decrease in catalyst rate were observed. 

The chains must be crosslinked to form a network (cf. Fig 7.16). In most elastomers containing double bonds, covalent bonds are introduced between chains. This can be done either with sulfur or polysulfide bonds (the well known sulfur vulcanisation of natural rubber is an example), or else by direct reactions between double bonds, initiated via decomposition of a peroxide additive into radicals. Double bonds already exist in the chemical structure of polyisoprene, polybutadiene and its copolymers. When this is not the case, as for silicones, ethylene-propylene copolymers and polyisobutylene, units are introduced by copolymerisation which have the property of conserving a double bond after incorporation into the chain. These double bonds can then be used for crosslinking. This is how Butyl rubber is made from polyisobutylene, by adding 2% isoprene. Butyl is a rubber with the remarkable property of being impermeable to air. It is used to line the interior of tyres with no inner tube. 

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