Rubber types fragmentation

The results obtained for unvulcanised EPDM and NR filled with carbon black provide convincing evidence that the physical network has a bimodal structure [62, 79]. Two types of EPDM chains and/or chain fragments with widely differing densities of EPDM-carbon black adsorption junctions are present in the rubbery matrix outside the EPDM-carbon black interface (tightly bound rubber) (Figure 10.11) [62],... 

If the rubber closure or component is intended to be pierced by a hypodermic needle, then the physical test regime of the European Pharmacopoeia applies. This includes test method limits for penetrability, fragmentation and self-sealing categorisation (type I or type II closures), and methods for the determination of penetration force and fragmentation. 

Another method of preparing saturated rubbers was developed (Harwood et al., 1973) using the diimide reduction. This method can be used to produce a high degree of saturation dependent on the type of reagent used however, side reactions can occur in this method. Generation of the diimide from p-toluenesulfonyl hydrides leaves an acidic fragment that may cause cyclization in some unsaturated elastomers. 

It is essential to note that elastomers do not always behave in the manner known from stretching a rubber band at room temperature. Some of us might have seen an experiment when such a rubber band was put into liquid nitrogen, became brittle, and when stretching was attempted the band broke into little fragments. Thus, in general the type of behavior of an elastomer depends on the temperature. This is shown in Fig. 24.25 the elastic modulus E (for a certain fixed time after the imposition of a force) as a function of temperature T. At low temperatures we have the brittle behavior—as the rubber band in liquid nitrogen ... 

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