Optimizing the dielectric and mechanical properties of melamine based‐benzoxazine resin by copolymerizing with epoxy resin

Abstract

AbstractBenzoxazine resins are suffering from high curing temperature, low crosslinking density, and poor toughness, which hampers their broad applications. The introduction of melamine during synthesis has been shown useful in improving these properties, but the dielectric property was deteriorated heavily. Epoxy resins show higher crosslinking density and better toughness but the thermal properties are relatively poor. Herein, the melamine based‐benzoxazine MBF was copolymerized with epoxy resin E51 in this work in order to improve the dielectric properties. The curing reactivity, polymerization mechanism and the comprehensive properties such as thermal, dielectric and mechanical properties were systematically verified. It is found that the abundant active functional groups such as amino and phenolic groups in MBF could catalyze and copolymerize with E51 and form uniform copolymers poly(MBF‐E) at various proportions. With the increasing of epoxy resins, more polar amino groups was consumed, thus the polarity and the water absorption of the copolymers decreased. Additionally, the dielectric constant decreased from 3.67 for poly(MBF) to 2.94 for poly(MBF‐60E). Meanwhile, the highest increasement of tensile strength and elongation at break value reached 130% and 70%, respectively, which may be caused by the higher crosslinking density and more flexible ether bond formed.