Shape Memory Properties of Melt-Blended Ethylene Vinyl Acetate (Eva)/Metallocene Polyethylene Eco-Blends

摘要

EVA(ethylene vinyl acetate) was melt-blended with mPE(metallocene polyethylene elastomer) to form shapememory, eco-based blends with and without vinyl triethoxysilane (VTEOS) modification. The silane crosslinking modification slightly suppressed the crystallization temperatures of the mPE component due to the increased gel content. The crystallinity of mPE also decreased slightly, from 4.1% to 1.8%, due to the silane crosslinking effect, and further, to 1.3%, due to the interference effect of EVA. Despite this negative contribution to thermal crystallization behaviors, the highest tensile strength and Young's modulus were still observed for the EVA/mPE-g-VTEOS blend, attributed to the higher interaction between the silane groups on mPE and the vinyl acetate groups on EVA. In addition, the silane grafting modification on mPE improved the thermal stability and shape fixity of the EVA/mPE-g-VTEOS blend further with respect to their corresponding EVA/mPE blend. The recovery ratio of the EVA/mPE-g-VTEOS system was still high, up to 92.8 +/- 0.3%, for the recovery from a temporary deformed shape. In considering both the shape fixity and recovery ratios together, the SMI (shape memory index) of the EVA/mPE-g-VTEOS blend was about 81%, which was higher than that of the EVA/mPE, at about 75%. In particular, the EVA/mPE-g-VTEOS could still be melt processed, in comparison with conventional crosslinked shape memory polymer blends which are hard to be recycled. Herein we justify the merit of the silane modification in the preparation of the EVA/mPE-g-VTEOS shape memory eco-blend to expand its applications, especially in terms of environmental concerns.