Development trend of high-performance epoxy resin
In recent years, with the continuous development of the high-tech industry, higher requirements have been placed on the performance and use of epoxy resins, especially with the continuous development of the high-tech fields represented by aviation and aerospace, various industrial countries are vigorously developing performance The development of a perfect new epoxy resin and high-performance epoxy resin can be attributed to three aspects: heat resistance, toughness, and moisture resistance. These three properties are mutually restrictive. For example, increasing the cross-linking density of the cross-linked polymer can effectively improve the heat resistance, but it often causes a decrease in toughness. Many studies have shown that for the same system, the higher the degree of curing (ie, the greater the cross-link density), the higher the water absorption rate, and the better the heat and moisture resistance.
Thermal epoxy resin
Increasing the crosslink density and introducing heat-resistant groups (including rigid structures) are the most important means to improve heat resistance, such as phenolic epoxy resins, p-aminophenol triglycidyl compounds, diaminodiphenylmethane tetraglycidyl Ester (TDDM), pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride and other components. Due to the significantly increased cross-linking density (compared to the common formula of bisphenol A epoxy resin), the temperature resistance of the epoxy system is effectively improved. Using diaminodiphenyl sulfone (DDs) and diaminodiphenylmethane DDM) to cure the same epoxy resin, the Tg obtained by the former is much higher. The system using NN-methylenebis-p-phenylenebismaleimide as a curing agent also has good heat resistance, which is due to the introduction of heat-resistant sulfone groups and imide groups. VG3103 is a trifunctional epoxy resin with an epoxy value of 0.48, a softening point of 59C, a total chlorine content of 0.23% (mass), and a hydrolyzable chlorine content of 0.010% (mass). The resin uses methyltetrahydrophthalic anhydride as the curing agent and 2-ethyl 4-methylimidazole as the accelerator, and is cured at 10C/3h and 230℃/2h. The glass transition temperature (Tg) of the cured product is 250℃, and it is thermally deformed. The temperature (HDT) is 235℃ and the bending strength is 1146MPa. Compared with o-cresol novolac epoxy resin (EOCN), the Tg is increased by 10C and the bending modulus is reduced by 20%. It is an ideal packaging material.
The introduction of heat-resistant heterocycles such as isocyanate ester rings into the epoxy resin structure can also improve heat resistance. The reaction of isocyanate groups and epoxy groups to produce polymers containing isocyanurate and oxazoline rings has a Tg higher than 300°C. Sun Yishi et al. The structure and performance were studied. The heat resistance of epoxy resin can also be improved by introducing special bifunctional resins. Yan-based epoxy resins based on Ⅰ and Ⅱ are not only heat-resistant, but also have low melt viscosity, low hygroscopicity, and excellent adhesion. Now they are being developed into difunctional, trifunctional, and tetrafunctional phenolic novolac resin types Epoxy resin encapsulation material. The heat resistance of the epoxy resin can also be improved by introducing siloxane into a certain main chain or side chain. In order to improve the compatibility of polysiloxane and epoxy resin, poly(methylsiloxane) containing hydroxyl group (or alkoxy group) can be used as the modifier port, and the resulting modified epoxy resin (PMPS, 40 %〔Quality〕) The integrated program decomposition temperature can be increased by 100℃, and the water absorption rate is decreased, and the corrosion resistance of the coating film is significantly improved.