Key Words:Shape-memory polymer;Butadiene - Dynamics - Ethylene - Polymer blends - Polyvinyl acetates - Recovery - Reinforced plastics - Rubber - Shape optimization - Textures - Vulcanization
Abstract:Achieving considerable shape-memory effects is a challenge for typical sea-island structured polymer blends. In this article, we successfully fabricated a novel heat-triggered shape-memory polymer (HSMP) based on ethylene&ndash;vinyl acetate copolymer/nitrile&ndash;butadiene rubber (EVA/NBR) thermoplastic vulcanizates (TPVs) via dynamic vulcanization. The influence of deformation temperature (T<inf>d</inf>), recovery temperature (T<inf>r</inf>), and recovery time on the shape-memory behavior of the EVA/NBR (weight ratio = 80/20) TPV was investigated systematically. The shape-memory result of the EVA/NBR (weight ratio = 80/20) TPV demonstrated that when the T<inf>d</inf> was close to the melting temperature (T<inf>m</inf>) of the EVA phase (76&deg;C), the TPV could obtain a good shape fixity ratio (&gt;95%) and an excellent shape recovery ratio (&gt;95%) at 100% stretch ratio. A shape-memory mechanism was proposed for this HSMP. The dynamic mechanical analysis results under temperature sweep mode showed that with increasing EVA content in TPVs, the tan &delta; decreased, while the storage modulus increased. The morphology observation showed that the cross-linked NBR particles were dispersed evenly in the etched surface of EVA/NBR TPV with an average diameter of approximately 2&ndash;6 &mu;m. The longitudinal stretching surface of the EVA/NBR TPV exhibited the banding-like texture microstructure during the stretching process.<br/> &copy; The Author(s) 2019.
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