Structure and Properties of Diene Rubbers

As shown in earlier sections of this chapter, a range of diene polymers may be obtained by the variation of the polymerization system. This range includes several stereoregular forms capable of crystallization and which have the properties indicated in Table 5.3. 

MELTING POINT (Tm), GLASS TRANSITION (Tg) AND IDENTITY PERIOD OF STEREOREGULAR DIENE HOMOPOLYMERS 

Of the stereoregular polymers only the ci5-polybutadiene and poly-isoprene are of interest as technically useful rubbers but in addition a number of polymers of mixed microstructure are of importance. 

The structure of typical polybutadienes of interest as rubbers and made by various polymerization systems are summarized in Table 5.4 (Bahary et a/., 1%7). Data on typical polyisoprenes are given in Table 5.5 (Bruzzone et ai, 1%9). 

It should be stressed that changing the processing conditions may affect both micro- and macrostructure. Nevertheless the data may be considered as characteristic. The data on the Alfin poly butadiene is based on a polymer with a Mw of 0-9 x 10 but the wide molecular weight range is quoted in order to cover the very high molecular weight of early Alfin polymers as well as the low molecular weight materials that can now be prepared. 

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