Mechanical and shape memory behavior of chemically cross-linked SBS/LDPE blends

A series of polymeric shape memory system of chemically cross-linked poly(styrene-b-butadiene-b-styrene) triblock copolymer(SBS) and linear low density polyethylene(LDPE) blends were developed and characterized. The chemically cross-linked SBS/LDPE blends were prepared by varying the amount of initiator (DCP) between 0 and 1.5 wt.% and the ratio of SBS/LDPE ranges from 90/10 to 60/40. The cross-linked SBS/LDPE blends were fully characterized by gel content, tensile test, dynamic mechanical analysis (DMA), differential scanning calorimeter (DSC) and shape memory behavior. Results demonstrate that the cross-linking degree increases with the increment of the DCP content, leading to reductions in tensile strength and elongation at break. The transition temperature of cross-linked SBS/LDPE blends is tunable through changing SBS/LDPE ratio and DCP content. DMA test shows that the melt strength of the blends is influenced by the DCP and LDPE content. The chemically cross-linked SBS/LDPE blends have excellent shape memory effect when the cross-linking degree between 46 and 77 %. The shape recovery time decreases as the test temperature increases and the shape recovery rate decreases with cycle times increasing.