Effects of different imidazole accelerators on curing behavior and cross‐linked network of epoxy resin/phenolic resin/benzoxazine ternary system

Abstract

For the molding compounds used in electronic packaging, curing accelerators play a significant effect on the curing behavior of thermosetting resins, thus the cross-linked structure and performance of the cured product. In this study, nine commercially available imidazole compounds, divided into three types, were introduced into a polyfunctional epoxy resin (E 1 )/XYLOK phenolic resin (P 1 )/MDA benzoxazine (B 1 ) ternary system to reduce the curing temperature for molding processing. To understand the cross-linked structure of the cured product, the ternary system was divided into unitary system and binary system, and the curing behavior and chemical structure of each system was monitored by differential scanning calorimetry and Fourier transform-infrared systematically.Due to the nucleophilicity of tertiary amines influenced by the steric hindrance effect, it was discovered that the reaction activity of epoxy resin initiated by nine imidazole compounds, was significantly different. However, the ring opening of benzoxazine occurs at a high temperature, even catalyzed with imidazoles, and its curing behavior was nearly the same owing to the unique ring-opening mechanism initiated by active hydrogen of imidazole. In addition, phenolic resin elevates reaction activity for both epoxy resin and benzoxazine. The cross-linked structure of E 1 P 1 B 1 ternary system was proposed based on the experimental results from each system. It suggested that the formed network of the E 1 P 1 B 1 cured product with Type I and II imidazoles is mainly IPN structure, while the cured products of E 1 P 1 B 1 + Type III is the copolymerization of epoxy, phenolic and benzoxazine. This paper systematically illustrated the ideal chemical structures of epoxy resin/phenolic resin/benzoxazine ternary system with different imidazole compounds, which is valuable for industrial application of resin-based materials.

Bismaleimide/Phenolic/Epoxy Ternary Resin System for Molding Compounds in High-Temperature Electronic Packaging Applications

“…Under the action of 2E4MZ, the phenoxide ion is formed, which reacts preferentially with EP by initiating the ring-opening reaction of epoxy group to generate anionic charged epoxide. Next, the anionic charged epoxide further propagates the epoxy–phenol reactions to form the EP/PF copolymerization structure, which is similar to the cross-linked network in EMC. − Meanwhile, some anionic-charged epoxide may also promote and participate in the polymerization of BMI to form the BMI self-polymerization structure. As a result, the structure of the final cured product of BPE ternary resins is suggested as a cross-linked network including both the network chain structure from EP/PF copolymerization and the network chain structure from BMI self-polymerization (Scheme b).…”

Cure behavior and mechanism of cyanate ester with aromatic amines at room temperature

“…However, cyanate needs a long time to cure at a high temperature, which greatly limits the application of cyanate. 8,9 Therefore, it is of great importance to achieve the rapid polymerization of cyanate esters at low temperatures or even at room temperature.…”