Synthesis And Properties Of Novel Diphenyl-containing Epoxy Resin

With the development of the electronics and Pb-absent solder, the conventional epoxy resins are unable to satisfy some applications which require higher thermal and moisture resistance. Thus, it is necessary to design and develop high thermal resistant and low moisture absorption epoxy resin systems for these applications. Incorporating multi-phenyl group into the backbone of the epoxy resin is a effective method to improve the thermal stability and reduce the moisture absorption. Diphenyl group is a kind of high rigid group, the incorporation of diphenyl group would improve the properties of epoxy resin in aspects of thermal stability, toughness and moisture absorption.In this paper, the diphenyl-containing epoxy resin(DER) was synthesized through two steps. Firstly, diphenyl-containing phenolic resin(DPR) was synthesized through 4,4'-Bis(methoxy-methyl biphenyl) and phenol. Secondly, DER was prepared via epoxidation of DPR with epichlorohydrin(ECH). This type of epoxy resin is similar to the phenolic epoxy resin. The structure of DER was determined by several methologies such as FTIR spectroscopy, 1H-NMR spectroscopy and epoxide equivalent.Through the selection of the synthesis condition, including the quantity of the phenol, reaction temperature, reaction time, the choice of catalyst and the quantity of the catalyst,the charging sequence, the removal of the catalyst with water and the quantity of the ECH, DER with epoxy value between 0.35 and 0.37, viscosity between 50 mPa.s and 150 mPa.s and organic-chloric content lower than 700 ppm were synthesized.Furthermore, the effect of the molecular weight distribution to the thermal properties of the cured epoxy systems was investigated by Thermal Gravimetric Analysis (TGA). It was found that the thermal properties would be better with narrow molecular weight distribution. The cured products of DER with different curing agent, such as DDS, HPM, DPR and PA were also examined. The cured products with DDS, HPM, DPR had a high initial decomposition temperature which was more than 370℃, and their char yield under 700℃were 32%, 38% and 40% respectively. Through the examination of their gelation time, it was found that the suitable curing temperature of the four curing agent with DER were 190℃～210℃,170℃～190℃,200℃～220℃and 50℃～60℃respectively. And then the thermal stability and moisture resistance of DER with other normal epoxy resins were compared, the results showed that the resultant epoxy resins containing diphenyl group were expected to be applied in the field of super packaging materials due to their excellent thermal stability and moisture resistance.