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In recent years, shape memory smart materials have developed rapidly, and more and more novel shape memory polymers have been developed and applied. In sharp contrast to the rapid development of shape memory smart materials, its theoretical research is obviously lagging behind. Therefore, it is necessary to clearly understand and master the thermodynamic dynamic response mechanism of shape memory polymers. In view of the fact that the influence of thermodynamic properties of hybrid shape memory polymer under the coupling effect of multiple factors is still very vague, a novel hybrid shape memory polymer composites (SMPC) thermodynamic viscoelastic constitutive model is proposed for the first time by combining the macroscopic phenomenological viscoelastic theory with the microscopic phenomenological phase transition model, and a microstructure composed of two parts of reversible phase and stationary phase in parallel is constructed. At the same time, a three-dimensional parameter equation with temperature effect and capable of describing the coordinated changes of various parameters in the phase transition process is established. Through the validation of the model, it can be found that the variation trend of the simulation curve is in good agreement with the experimental curve during the whole static loading process, and the error of the fracture stress is less than 2%. Through the dynamic evolution of multi-content and wide-temperature range, the consistency between the simulation results and the experimental results is successfully proved, and the microscopic mechanism of the macroscopic static mechanical behavior of the hybrid SMPC is revealed. The model established in this paper can accurately describe the internal phase change of the mixed matrix, and realize the effective prediction of the stress-strain response under the coupling effect of the matrix composition and the external environment. The proposal of this model provides a new idea for the exploration of hybrid SMPC thermodynamic viscoelastic theory, and also provides an important theoretical reference for the development and application of novel hybrid shape memory materials in the future.

In order to overcome the shortcomings of high cost of traditional high-performance reinforced fillers, low-cost high-density polyethylene (HDPE) was introduced into TPI matrix as reinforcement phase in this study, and the TPI/HDPE hybrid shape memory polymer composites (SMPCs) was vulcanized by dynamic vulcanization technology. Due to the different vulcanization degree of TPI components the properties of TPI SMPCs are different, so it is particularly important to choose the appropriate content of vulcanizing agent. In order to realize the complementary advantages of the rubber-plastic thermoplastic elastomers, the vulcanization degree of TPI component was controlled by changing the amount of sulfur in the dynamic vulcanization system. The strengthened cross-linked structure made the excellent characteristics of plastics and rubber fully demonstrated. Through a series experiments, the effect of dynamic vulcanization system on the thermodynamics and shape memory properties of TPI/HDPE hybrid SMPCs was revealed. The results show that the TPI/HDPE SMPCs with the sulfur content of 2% has the best thermodynamics and shape memory properties.

The traditional processing technology of shape memory polymer composites is complex and the cost of high performance filler is high. Therefore, low-cost high density polyethylene (HDPE) was introduced into trans-1,4-polyisoprene (TPI) matrix as reinforcing phase, and a novel shape memory polymer was prepared by mechanical melt blending, which fully exerted the excellent properties of plastic and rubber. Because of the difference in molecular chain distribution between different blend ratios of TPI/HDPE hybrid SMPCs specimens, the change of the blend ratio of the two components affects the thermodynamic and shape memory properties of the SMPCs. A series experimental results show that the TPI/HDPE hybrid SMPCs with the blend ratio of 80/20 has excellent thermodynamic and shape memory properties. And we believe that the relevant conclusions of this study can provide valuable design reference for the development of high-performance TPI SMPCs.