Preparation And Application Of Modified Dicyandiamide In Epoxy Resin

Dicyandiamide is one of the epoxy resin latent curing agents,its application field is very extensive,but its high curing temperature restricts its use value.To decrease the curing temperature of epoxy resin with dicyandiamide,A new kind of modified dicyandiamide curing agent was prepared with diaminodiphenylmethane and dicyandiamideas in the method of chemical modification.This article optimized its synthesis,studied its non-isothermal curing kinetics and investigated the main mechanical properties of the curing system.The main work as follows:(1)The effects of reaction time,reaction temperature and feed ratio on the final yield were investigated by orthogonal experiment method.The results show that the optimal synthesis process for the synthesis of bis-(biguanide-p-phenyl)methane was:the yield of bis-(biguanide-p-phenyl)methan reaches to 85.1%at reaction time of 4 h,reaction temperature of 120?,mole ratio of 1:2.15.The structures of the compounds were analyzed and confirmed by the Infrared spectroscopy and Hydrogen nuclear magnetic spectroscopy.The results confirm that the final product is bis-(biguanide-p-phenyl)methan.(2)By studying the DSC exothermic curves of bis-(biguanide-p-phenyl)methane/epoxy resin,The gel temperature,curing temperature and post-treatment temperature of bis-(biguanide-p-phenyl)methane/epoxy resin were calculated by extrapolation method.The results show that the gel temperature is 83?,the curing temperature is 143.4?,the post-treatment temperature is 184.8?.(3)The non-isothermal kinetics of bis-(biguanide-p-phenyl)methane/epoxy resin was studied by differential scanning calorimetry(DSC).The results show that the activation energy of the bis-(biguanide-p-phenyl)methane/epoxy resin system is 56.4kJ/mol,it is not suitable to use the n-level reaction model to describe the bis-(biguanide-p-phenyl)methane/epoxy resin system,but rather to describe it with self-catalyzed model.(4)The mechanical properties of bis-(biguanide-p-phenyl)methan/epoxy resin were studied by universal testing machine and impact material testing machine,and compared with the mechanical properties of unmodified dicyandiamide/epoxy resin system.The results show that the tensile strength of the bis-(biguanide-p-phenyl)methane/epoxy resin system reached 35.6MPa,the impact strength reached 2.6kJ/m~2and the flexural strength reached 53.8MPa.Compared with the dicyandiamide/epoxy resin,the tensile strength and flexural strength were improved by 81.6%and 47.4%,impact strength reduced by 27.8%.