Preparation And Properties Study Of Shape Memory Epoxy And Its Composites

As a new intelligent material, shape memory polymer has a great application prospect in Aerospace, biomedical, home dress, etc. In this paper, latent curing agent was added into shape memory epoxy (SMEP) to realize secondary curing technology, which to improve the heat resistance and mechanical properties of SMEP. The curing kinetics of various resin systems were studied by non-isothermal DSC method. In addition, the PPGDGE was added to enhance the poor toughness of SMEP, and the carbon fiber to improve mechanical properties. The purpose of this research was preparing shape memory epoxy with high mechanical properties and excellent shape memory properties.The different curing degree SMEP were prepared. Variation of storage modulus and loss factor along with temperature for the resin systems were determined by dynamic mechanics analysis (DMA). The cross-linking degree of resin systems were calculated and the condition of shape memory properties existing was analyzed. The cross-linking degree and deformation recovery temperature, which influence on shape memory properties and deformation recovery time were studied, respectively. The influence of shape deform cycle-index on the shape memory properties and mechanical properties were discussed. The results showed that when the curing degree of SMEP was 70%, the SMEP could recovery to its original shape in 101s, its shape fixed ratio and shape recovery ratio were above 95%, the number of valid folding of the SMEP was 20.The secondary curing was realized by adding high temperature latent curing agent into SMEP. The curing peak temperature of shape memory epoxy resin systems were tested by DSC, results showed that a new exothermic peak was found in epoxy resin system with latent curing agent, the two peaks deviate was more than 105℃, which showed that the secondary curing technology had feasibility. DMA results showed that shape memory performance fell slightly after adding high temperature latent curing agent, but still showed good shape memory properties. The cross-linking density, tensile strength, impact strength, Tg of SMEP were improved after secondary high temperature curing.The curing kinetic parameters of various systems were calculated by Kissinger equation, Ozawa equation, Crane equation, which educed the kinetic equations and curing process. The reaction rate constant of various systems was calculated by Arrhenius equation, and the curing process of various systems were optimized. FT-IR infrared analysis showed that epoxy group conversion rate was improved to almost 100% after high temperature curing by adding high temperature curing agent into SMEP system, verified the rationality of the curing process.Low molecular weight aliphatic series epoxies PPGDGE was added into SMEP to improve the toughness of SMEP. The results showed that the SMEP had good mechanical properties and excellent shape memory properties with 9 phr PPGDGE. The SEM showed that toughened specimen section had obvious phenomenon of silver grain and stress white, changing from brittle fracture to ductile fracture after toughening.The composites of carbon fiber reinforced SMEP was prepared. The results showed that chopped carbon fiber not only impaired the mechanical strength of the SMEP, but also weaken the properties of shape memory; fiber cloth could improve the mechanical properties, shape recovery ratio and shape recovery rate, but the shape fixed ratio declined.