Design and synthesis of epoxy prepolymer containing aromatic imide structures for thermoset with excellent thermal, mechanical and dielectric properties

Abstract

Recently, the development of epoxy thermosets with imide rings has received extensive attention due to their superior integrated properties, especially for thermal, mechanical and dielectric properties, compared to those of commercialized bisphenol A epoxy thermosets, yet remains substantial challenges, such as the high epoxy equivalent weight (EEW) of the epoxy prepolymers and the poor processibility of the epoxy systems. In this work, an imide-containing epoxy prepolymer (BAPT-EP) was facilely synthesized. It had a relatively low EEW of 340 g/equiv. and could be dissolved in hardener methylhexahydrophthalic anhydride (MHHPA) to give a homogeneous BAPT-EP/MHHPA system with good processibility. Thanks to the aromatic imide structures, the cured BAPT-EP/MHHPA showed improved overall properties. In particular, it had a 47.9 °C, 24.7 °C, 29.4%, 77.3% and 10.0% increase in the glass transition temperature, temperature at 5% mass loss, tensile strength, Young’s modulus and tensile toughness, respectively, compared to those of bisphenol A epoxy prepolymer (DGEBA)/MHHPA thermoset. Meanwhile, BAPT-EP/MHHPA thermoset featured good charring ability with a high char yield of 26.4% (800 °C/N2), remarkable dimensional stability with a low coefficient of thermal expansion of 52.5 ppm/°C and good dielectric properties with a low dielectric constant of 3.24 at 100 MHz. This work provides an elegant strategy to prepare high-performance epoxy thermosets with imide structures, which have promising applications in electronics.