Vinyl acetate content and electron beam irradiation directed alteration of structure, morphology, and associated properties of EVA/EPDM blends

Abstract

A series of ethylene vinyl acetate/ethylene-propylene diene elastomer (EVA/EPDM) blends with four types of EVAs with various vinyl acetate (VA) content, are prepared without and with crosslinker, trimethylol propane triacrylate (TMPTA). These are irradiated by electron beam (EB). As the VA content increases, the gel content, i.e., degree of crosslinking of EVA/EPDM blends, is increased. With increase in VA content, the modulus and tensile strength are decreased but elongation at break is increased due to increase in amorphousness. On EB irradiation, modulus and tensile strengths are increased but at the cost of elongation at break. Crystallinities of all blends are decreased with increase in VA and EB crosslinking. The thermal stability of EVA/EPDM blend is decreased with increase in VA content but increased after EB irradiation. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) show that with increase in VA content the miscibility of two polymers keeps on increasing, which even become more after EB irradiation.

Effect of vinyl acetate content on the photovoltaic‐encapsulation performance of ethylene vinyl acetate under accelerated ultra‐violet aging

“…For unaged specimens, it is observed that the elongation improves with an increase in VA content but the tensile strength and Young's modulus deteriorate. The amorphousness (softness) is increased with an increment in VA content, which is the cause of the above observations [Figure 4(a)] . An increase in crystallinity as well as cross‐linking density will enhance the modulus as well as the strength.…”

“…The characteristic two‐step degradation curves have been observed for all the EVAs. The degradation temperature ( Td 1 ) corresponding to the first step can be assigned to the evolution of acetic acid from VA segment in the temperature range of 300 to 350 °C . The degradation temperature ( Td 2 ) corresponding to the second step for degradation of the polyethylene segments in the temperature range of 400 to 450 °C.…”

“…It is observed that both Td 1 and Td 2 for EVA tends to decrease with an increase in VA content. This may be due to a decrease in crystallinity (Table ) …”

“…Δ H m 0 for 100% crystalline EVA has been considered as 239 J/g, which is the Δ H m 0 of crystalline low density polyethylene (LDPE) . The crystallinity of EVA originates mainly from long chain hydrocarbon (ethylene segment) of polyethylene unit …”

Effect of electron beam irradiation on the properties of EVA/EPDM blends

“…It is found that EVA/EPDM blends are suitable for making materials in wire and cable insulation. At the same time, Chowdhury et al 32 and Sharma et al 33 found that the content of vinyl acetate (VA) in EVA will affect the compatibility and mechanical properties of the EVA/EPDM blend (different contents of EVA). However, according to our knowledge, the properties of EVA/EPDM blend before or after being irradiated have not been reported in these studies.…”