Shape memory behavior of thermally triggered polymeric materials based on ethylene octene copolymer (EOC) and ethylene propylene diene rubber (EPDM) has been studied in details. Investigation of the shape memory behavior of uncrosslinked EOC-EPDM and electron beam crosslinked EOC-EPDM blends have been pursued thoroughly. Shape memory study has been carried out at 60°C, which shows that with the effect of electron beam radiation shape fixity behavior of the crosslinked blends becomes poor as compared with its uncrosslinked blend system whereas the improvement in shape recovery behavior takes place after the exposure to electron beam radiation. Morphology study by Atomic Force Microscopy (AFM) and crystallinity study by X-ray diffraction analysis also give the clear idea regarding the formation of crosslinked network structure. Improvement in gel content with increasing radiation dose supports the formation of network structure. Even after the crosslinking in presence of electron beam radiation also, it has been found that crosslinked EPDM rich blends is superior in terms of shape memory behavior point of view. Lower decay of stress value coupled with lower relaxation ratio of crosslinked EPDM rich blend support its superior shape memory behavior.
High-performance thermoplastic vulcanizates (TPVs) are the new generation of TPVs that provide superior heat and oil aging behavior. TPVs based on hydrogenated acrylonitrile butadiene rubber and polyamide 12 (PA12) have been first developed by the dynamic vulcanization process, in which selective cross-linking of the elastomer phase during melt mixing with the thermoplastic phase (PA12) was carried out simultaneously. In this present investigation, hydrogenated acrylonitrile butadiene rubber (HNBR)/PA12 and partially hydrogenated carboxylated acrylonitrile butadiene rubber (XHNBR)/PA12 with blend ratio of 50:50, 60:40, and 70:30 wt% were prepared at 185°C at a rotor speed of 80 rpm for 5 min. Di-(2-tert-butyl peroxy isopropyl) benzene was chosen as the suitable cross-linking peroxide to pursue the dynamic vulcanization. TPV based on 50:50 HNBR/PA12 and XHNBR/PA12 show better physico-mechanical properties, rheological behavior, thermal stability, dynamic mechanical analysis, and creep behavior among all the TPVs. Morphology study reveals that dispersed phase morphology has been formed with an average dimension of the rubber particles in the range of 0.8-1.5 μm. For aging test, TPVs were exposed to air and ASTM oil 3, respectively. Air aging tests were carried out in hot air oven for 72 hr at 125°C, while the oil aging tests were carried out after immersion of the samples into the oils in an aging oven. After aging, there is only slight deterioration in the physico-mechanical properties of the TPVs. In case of 50:50 blends of HNBR/PA12 and XHNBR/PA12, the retention of the properties upon after aging was found excellent. These TPVs are designed to find potential application in automotive sector especially for under-hood-application, where high-temperature resistance as well as high oil resistance is of prime importance.
Thermoplastic vulcanizates (TPVs) based on ethylene acrylic elastomer (AEM) and polyamide 12 (PA12) have been developed by the dynamic vulcanization process, in which selective cross-linking of the elastomer phase (AEM) during melt mixing with the thermoplastic phase (PA12) has been carried out simultaneously. TPVs at varied blend ratios (50 : 50, 60 : 40, 70 : 30) of AEM/ PA12 were prepared at 1858C at a rotor speed of 80 rpm up to 5 min of mixing. Di-(2-tert-butyl peroxy isopropyl) benzene (DTBPIB) was chosen as the suitable cross-linking peroxide to carry out the dynamic vulcanization. Morphology study reveals the development of continuous agglomerate of rubber network in case of all the TPVs took place and the average dimension of the rubber particles are in the range of 30-40 nm. TPV based on 50 : 50 AEM/PA12 shows better physicomechanical properties, thermal stability, and dynamic mechanical behavior among all the TPVs. For aging test, TPVs were exposed to air, ASTM oil 2 and 3. Air aging tests were carried out in hot air oven for 72 h at 1258C, while the oil aging tests were carried out after immersion of the samples into the oils in an aging oven. After aging, there are only slight deterioration of physicomechanical properties of the TPVs. Particularly in case of 50 : 50 blend of AEM/PA12, the retention of the properties even after aging was found excellent. The recyclability of these new TPVs is also found to be excellent leading to find potential application in automotives. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym.Sci. 2015, 132, 42655.
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