Bio-based trifunctional diphenolic acid epoxy resin with high Tg and low expansion coefficient: synthesis and properties

Nowadays, the rapid development of industrial technology is putting a great demand for high-performance epoxy resin. Traditional bisphenol A epoxy resin (DGEBA) is facing great challenges from both the perspective of human health and the needs of cost reduction under the background of oil resources shortage. Therefore, it's important to find appropriate substitutes for DGEBA. In this paper, a trifunctional epoxy resin (DPA-E) was prepared using a simple two-step method with diphenolic acid and epichlorohydrin. It was interesting that the DPA-E, cured by 3,3 '-dimethyl-4,4 '-diaminodicyclohexylmethane (DMDC), showed the similar properties as DGEBA except for curing temperature, glass transition temperature, and thermal expansion properties. The gel temperature for DPA-E/DMDC was as low as 29 celcius, which was obtained from curing kinetic study. Even for curing temperature of DPA-E/DMDC was also relatively low (T-p = 83 celcius). Even so, the glass transition temperature of this system was as high as 239 celcius, which was 24% higher than that of DGEBA/DMDC (T-g = 193 celcius). Furthermore, DPA-E/DMDC showed a lower thermal expansion coefficient, especially at elevated temperature (> 150 celcius). Therefore, this kind of new epoxy resin might have a very hopeful future in many important areas including aerospace and microelectronics.