Preparation And Properties Of The Room Temperature Rapid Curing Epoxy Resin Adhesive

Epoxy resins have attractive properties such as low shrinkage during curing, solvent and chemical resistance, good mechanical and electrical properties, and high adhesive strength. For many applications, the need to cure fast at ambient or lower temperature exists. However, with conventional curing agents, the curing process of epoxy resin often showed slow gel time unless curing at high curing temperature. In this work, a unique polymercaptans was synthesized and was applicated to the preparation of the fast curing epoxy adhesive at room temperature. The reaction mechanism and influences on the structure and properties of the polymercaptan were studied. The curing behavior and adhesive properties of the epoxy adhesive using polymercaptan as curing agent were investigated. Several novel multifunctional reactive diluent and toughers were synthesized used to modify the adhesive of E-51/Polymercaptan system.The polymercaptans were synthesized through two steps: polyhydric alcohol was first reacted with epichlorohydrin to produce an intermediate halohydrin, which was then in turn reacted with sodium sulfhydrate to produce polymercaptans. With IR, NMR and chemical analysis, the effects of temperature, ratio of the reactant, catalyst, solvent, reaction time on the structure of the polymercaptan were investigated. Experimental results indicated that in the first step, side reactions could be reduced by correctly selecting the catalyst, reactants ratio. While in the second reaction stage, the solvent, reactants mixture ratio and reaction temperature had significant contribution on the result of the nucleophilic substitution reaction. Under the optimal reaction condition, the -HS of the polymercaptans could be reached to 9.3%. The factors influencing the adhesion properties of the fast curing epoxy adhesive at room temperature were studied. The structure of curing agent and accelerator had great influence on the strength and curing rate of the adhesive. The optimal level of the DMP-30 accelerator was 12 percent of the curing agent. It was found that the curing reaction time and temperature also played an important role on the properties of the adhesive, the higher the curing temperature the faster the curing rate and the higher strength of the adhesive. The rheological behavior of the mixture of epoxy resin and polymercaptans was studied withbrabender experiments. A rheological model based on the dual-Arrhenius equation is established and used to simulate the rheological behavior of the materials. The model predication is in good agreement with experimental data.Two kinds of multi-function aliphatic glycidol ether were synthesized. Orthogonal methods were applied to obtained the optimal reaction conditions. The synthesized aliphatic glycidol ethers were employed to modify the room temperature fast curing adhesive of E-51/Polymercaptan system. It was found that the addition of the aliphatic glycidol ethers decreased the viscosity of the epoxy resin and increased the adhesion strength. When the amount of the aliphatic glycidol ethers in the E-51/Polymercaptan system was 30phr, it was found that the cured product of the epoxy adhesive using four-function aliphatic glycidol ether could reach higher strength and thermal stability than using the tri-function aliphatic glycidol ether. SEM study found that the fracture of all modified epoxy adhesive systems displayed tough fracture feature. DMA analysis also showed that the non-uniform of the cured network configuration leads to the significant increasing in strength.