Methylene rubber, measurement

Table VI yields the methylene sequence distribution of these two EPDM rubbers. A measure of the fraction of long methylene runs is important to the understanding of physical properties of these and similar materials. Polyethylene blends with EPDM rubbers, having appropriate long runs of ethylene, have been shown ( 1 ,1 ) to have unusually high tensile strengths.

Figure 11.19 Splittings of the C-l methylene carbon signal of (a) rubber from L. volemus, (b) three-trans Ficaprenol-11, (c) two-trans Betulaprenol-18, (d) rubber from Sunflower, (e) rubber from Goldenrod, (f) thr ee-trans Ficaprenol-12 and (g) two-trans Betulapreno-16. (13C-NMR measurements at 100 MHz for (a) to (c) at room temperature for (d) to (f) at 50 °C)...

Although the dynamic mechanical properties and the stress-strain behavior iV of block copolymers have been studied extensively, very little creep data are available on these materials (1-17). A number of block copolymers are now commercially available as thermoplastic elastomers to replace crosslinked rubber formulations and other plastics (16). For applications in which the finished object must bear loads for extended periods of time, it is important to know how these new materials compare with conventional crosslinked rubbers and more rigid plastics in dimensional stability or creep behavior. The creep of five commercial block polymers was measured as a function of temperature and molding conditions. Four of the polymers had crystalline hard blocks, and one had a glassy polystyrene hard block. The soft blocks were various kinds of elastomeric materials. The creep of the block polymers was also compared with that of a normal, crosslinked natural rubber and crystalline poly(tetra-methylene terephthalate) (PTMT). 

---