Preparation And Properties Of Thermally Responsive Shape Memory Silicone Rubber Based Blends

The research and application of shape memory polymer materials mainly focus on semi-crystalline polymers such as thermoplastic elastomers and thermoplastics.However,The exploration of silicone rubber-based shape memory materials is not systematic enough,and only limited to double shape memory.Silicone rubber has excellent resistance to high and low temperatures,electrical insulation and biocompatibility,and is expected to be used in high voltage cables and biomedical devices.In this paper,methyl vinyl silicon rubber(VMQ),polyolefin elastomer(POE)and olefin block copolymer(OBC)were blended by low-cost physical blending method to prepare dual and triple shape memory blends for researching crosslinking,crystallization and shape memory.Firstly,low temperature controllable VMQ/POE blends were prepared by melt blending method.The effects of different blending ratios,cross-linking agent di-tert-butylperoxydiisopropylbenzene(BIPB)content and POE grades on crosslinking,crystallization and shape memory properties were studied.It was noted from the characterization of vulcanization properties,gel content and thermal properties that crystallization behavior was restricted by the crosslinked structure.POE mainly provided crystalline structures,which restricted to be cross-linked.When the POE content in VMQ/POE blends was 50%,the dual shape memory performance showed the best,and meanwhile the cyclic shape memory performance had excellent stability.The addition of cross-linking agent BIPB provides the polymer with the chemical cross-linking point.At the same time,with the BIPB content increasing,the shape memory fixed rate was reduced,while the recovery rate was increased and the recovery rate accelerated.When the BIPB content was 1 phr,the shape memory performance was the most predominant.According to the three POE grades,the crystallinity increased in the order of 8150,8003,and 8402.Similarly,the crystallinity of the VMQ/POE blends increased,and the degree of crosslinking decreasing successively.The fixed performance was better while the recovery property was worse.The cycle stability of 8150 was excellent.Next,based on the study of low temperature controllable shape memory,it was prepared that high temperature controllable VMQ/OBC shape memory blends.The effects of blending ratios of VMQ and OBC and the amount of BIPB on structures including cross-linking and crystallinity and shape memory properties were studied.The crystallization property of OBC made the VMQ/OBC blends had crystalline structures.The increase of OBC content led to a consequence that the increase of crystallinity as reversible phase,while the chemical cross-linking degree as fixed phase decreases.The shape memory performance was characterized by the two methods of stretching and bending.It was found that the shape memory property of VMQ/OBC blends with 60%OBC content was considered to be the best among all blends.Cyclic shape memory performance reflected that strain showed creep phenomenon as the number of cycle increased.If no crosslinking agent was added,there was no crosslinked structure in polymer blends,of course,no shape memory property accuered.As BIPB added,the degree of crosslinking increased,which limited the formation of crystal structure.The increase of BIPB content led to the fixing rate reducing,the recovery rate increasing,and the recovery time shortening.As a whole,when the BIPB content was 1 phr,the shape memory performance was the best.Finally,three kinds of polymer materials(VMQ,POE and OBC)were blended to prepare triple-shaped memory materials.The effects of different blending ratios on comprehensive properties of VMQ/POE/OBC blends were researched.The addition of VMQ promotes the cross-linking performance of the blend system.However,the increase of the VMQ content hindered the crystallization formation of POE and OBC.The results of brittle section morphology showed that POE and OBC havd great compatibility and when the VMQ content was 40%and 50%,the phase morphology showed co-continuous structures.It can be known from thermo mechanical properties that when the temperature was higher than 117?,the material with high content of VMQ got a larger modulus.The shape memory test results showed that POE/OBC had a triple shape memory effect.As the increase of VMQ content,the two fixaed rate showed a sharp decreasing trend,Rf(A-B)decreased from 81.0%to 25.5%,and Rf(B-C)from 88.8%to 49.2%.Both recovery rate was high,Rr(C-B)was greater than 87.4%,and Rr(B-A)more than 84.3%.The resultes measured by the bending method manifested that the triple shape memory performance was the best when the VMQ content was 40%.