Structure And Property Of Thermosetting/Thermosetting Polymer Systems With Shape Memory Effect

Thermosetting shape memory polymers(SMPs)can recover their original shape quickly from the temporary shape and have excellent performance stability as compared to thermoplastic SMPs,which makes them potential candidate for applications in flexible electronic devices,aerospace,biomedical engineering and so on.However,owing to the high crosslinking density,it is hard for thermosetting polymers to obtain good shape memory effect.Generally,incorporating soft segments or flexible component into thermosetting crosslinking networks can achieve shape memory effect,this certainly can reduce the inherent excellent performance of thermosetting polymers such as strength and thermal stability.Therefore,it is still a great challenge to endow thermosetting SMPs with shape memory effect as well as the improved integrated properties(shape memory,mechanical and thermal properties),which are critical importance for developing applications of thermosetting SMPs.In this work,we designed phase-separated thermosetting polymers for shape memory effect as well as outstanding mechanical properties and thermal stability.The main research contents are as follows.First,in situ self-assembled nanophase structure in thermosetting polymer networks was prepared based on the different reaction kinetics of thermosetting cyanate ester(CE)and epoxy(EP)resins in the presence of zinc(?)acetylacetonate(ZAA)and glutaric anhydride(GA).The polymer systems(CE/EP/GA/ZAA)with three different compositions were prepared.The structure and morphology of the prepared systems were analyzed?and the thermal properties,mechanical properties and shape memory properties of the resulting polymers were investigsted in detail.The research results indicate that in situ self-assembled nanophase separated CE/EP thermosetting polymers can be successfully prepared using heat-curing process because of the different kinetic reactions of CE and EP triggered by ZAA or GA/ZAA and the excellent compatibility between CE and EP.The average diameter of nanophase is about 30 nm.The resulting CE/EP/GA/ZAA systems exhibit good mechanical properties,and their fracture toughness and flexural strength are 1.7-2.0 MPa·m1/2 and 87-135MPa,respectively.CE/EP/GA/ZAA systems have the initial thermal decomposition temperature(7di)of 337-352? and glass transition temperature(Tg)of 167-192?.The CE/EP/GA/ZAA systems show broad glass transition temperature range,which allows the good dual-and triple-shape memory effect of the polymers.CE/EP/GA/ZAA systems have shape fixity rate(Rf)of 83-91%and shape recovery rate(Rr)of 93-95%after five repeated dual-shape memory cycles.Such thermosetting CE/EP/GA/ZAA systems can exhibit triple-shape memory effect between 150-225?.Moreover,CE/EP/GA/ZAA systems exhibit good self-healing behavior resulting from the transesterification and possible reactions between the residual cyanate ester and epoxy groups,and an 81-83%recovery of fracture toughness can be achieved after the first healing schedule of 200oC/2h.Second,considering the interface interaction between EP system containing Iow temperature curing agent polyether amine(D230)and active diluent epoxy propane butyl ether(BGE)(EP/D230/BGE)and EP system containing high temperature curing agent system(GA/ZAA),the microphase separated thermosetting polymers((EP/D230/BGE)/(EP/GA/ZAA))with different crosslinking structure were prepared.Results show that microphase separated structure in(EP/D230/BGE)/(EP/GA/ZAA)can be easily realized,owing to the interface layers formed by the quick reaction of D230 and GA in EP/D230/BGE and EP/GA/ZAA.The existence of phase separation structure can aid the improvement of mechanical properties because of the crack blunting mechanism that can suppress the crack propagation and consume more energy.(EP/D230/BGE)/(EP/GA/ZAA)has fracture toughness of 1.4MPa·ml/2 and flexural strength of 119 MPa,their Tdi and Tg are 370oC and 94?,respectively.The broad glass transition temperature range allows(EP/D230/BGE)/(EP/GA/ZAA)to get good dual-and triple-shape memory effect.The Rr and Rr of(EP/D230/BGE)/(EP/GA/ZAA)system can reach 99%and 94%after four repeated dual-shape memory cycles.(EP/D230/BGE)/(EP/GA/ZAA)system can exhibit good triple-shape memory effect between 55-100?.Furthermore,(EP/D230/BGE)/(EP/GA/ZAA)displays good self-healing behavior owing to the existences of the dynamic reversible ester bond and the residual epoxy groups,and an 84%recovery of fracture toughness can be obtained after the first healing schedule of 200?/2 h.