Flexible bismaleimide resins based on bio‐based diamine: Synthesis and properties

Abstract

The low toughness and high softening temperature of bismaleimide (BMI) resin limit its application in the field of electronic packaging. Herein, a series of flexible BMI resins with maleic anhydride terminated were synthesized via the imide reaction between dianhydrides and bio‐based 8,8′‐(4‐hexyl‐6‐octylcyclohexane‐1,3‐diyl)bis(octane‐1‐amine) (HOBOA). The degree of polymerization of these BMI resins was controlled to 1, 3, and 5 by adjusting the molar ratio of dianhydrides to HOBOA. These BMI resins show a low softening temperature below 100°C. These BMI resins were cured by the thermal procedure as follows: 145°C/2 h, 185°C/2 h, 225°C/2 h, and 275°C/2 h. The thermal decomposition temperature of cured resins is above 395°C. The tensile testing results demonstrated that cured resins exhibit a high elongation at break of around 60%. The dielectric constant of the cured resins is between 2.72 and 3.09 at room temperature. The water absorption rate of cured resins is less than 0.7% after being soaked in water for 30 days. After the cured resins were soaked separately in acid and alkali, the tensile strength retention rate reaches more than 90%. Additionally, the lap shear strength of cured resins coated on 7075 aluminum alloy exceeds 7.0 MPa.