Elastomers radiation effects

In the field of solid polymers, reviews by Schaefer and Stejskal and Lyerla of recently developed techniques for obtaining high-resolution spectra of solids are particularly welcome. High-resolution techniques are included in a wide-ranging article that also covers the use of more traditional broadline n.m.r. in studying molecular motion, spin-diffusion, self-diffusion, and phase structure in both synthetic and biological polymers. Useful specialized reviews have been published on phase structure in polyethylene, elastomers, interfacial effects, and radiation effects. ... 

Physical properties of carbon black-filled EPR and EPDM elastomers have been found to be comparable with the suUur-cured analogues [372]. Aromatic oils increase the optimum dose requirement for these compounds due to the reaction of the transient intermediates formed during radiolysis of the polymer with the oil as well as energy transfer which is particularly effective when the oil contains aromatic groups. The performance and oxidative stability of unfilled EPDM as well as its blend with PE [373], and the thermal stabdity and radiation-initiated oxidation of EPR compounds are reported by a number of workers [374,375]. 

The effect of propylene content on the EB radiation grafting of AA onto EPR to obtain hydrophilic elastomers has been investigated. Degree of grafting has been found to increase with the addition of alcohol (methanol and 1-propanol) into water as solvent for grafting which occurs easily in EPR of lower propylene content of 22% [376]. 

The effect of °Co y-ray irradiation on the mechanical properties, surface morphology, and fractography of blends of plasticized PVC and thermoplastic copolyester elastomer, Hytrel (E.I. Du Pont de Nemours Company, Inc., Wilmington, Delaware), have been studied by Thomas et al. [445]. Radiation has two major effects on the blend cross-linking of the Hytrel phase and degradation of PVC phase. Both effects are found more prominent at higher radiation dose. 

Figure 24. Effect of radiation fluence on thermal expansion of elastomer-toughened specimens during cool down from room temperature. (Reproduced from reference 19.)...

Identical to chemically cross-linked (vulcanized) elastomers, the modulus of radiation cured gum elastomers depends on the concentration of elastically effective network strands and temperature. ... 

Physical Properties of Radiation Cross-linked Elastomers Effects of Radiation on Individual Elastomers... 

IR spectroscopy can be used to characterise not only different rubbers, but also to understand the structural changes due to the chemical modification of the rubbers. The chemical methods normally used to modify rubbers include hydrogenation, halogenation, hydrosilylation, phosphonylation and sulfonation. The effects of oxidation, weathering and radiation on the polymer structure can be studied with the help of infrared spectroscopy. Formation of ionic polymers and ionomeric polyblends behaving as thermoplastic elastomers can be followed by this method. Infrared spectroscopy in conjunction with other techniques is an important tool to characterise polymeric materials. 

Meier, J. F., and Petrie, E. M., The Effect of Ultraviolet Radiation on Sodium Etched Polytetrafluoroethylene Bonded to Polyurethane Elastomer, Journal of Applied Polymer Science, vol. 17,1973, pp. 1007-1017. 

In general, there is a paucity of information on the relationship between polymer structure and degradation kinetics. This becomes especially critical in multiphase polymers like heterophasic copolymers, thermoplastic elastomers and blends. This review should stimulate research in this important area, which could ultimately lead to polymers with better photo-thermal and radiation resistance as well as more effective stabilizers. 

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