A study of the thermal, dielectric, and flame-retarding characteristics of various bismaleimide blended with halogen-free epoxy resin

This work investigates various blends of a halogen-free epoxy resin (phenolic epoxy resin (703-H) and melamine phenol formaldehyde novolac (MPN) combined with different quantities of bismaleimide (BMI). The goal of this work was to optimize the thermal, flame-retarding, and dielectric properties by modifying the matrix with BMI. The polymerization of the matrices was studied with ¹³C nuclear magnetic resonance spectroscopy (¹³C-NMR) and fourier transform infrared spectroscopy (FTIR). The reaction kinetics and thermal stability were studied using dynamic mechanical analyzer (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The total reaction heat (ΔH) of 703-H/MPN was greater than that of 703-H/MPN/BMI blends. The total activation energy and the dielectric constant were both found to decrease with an increasing BMI content. The Ozawa model can be used to describe the 703-H/MPN/BMI reaction kinetics. The most excellent characteristics, such as the highest T_g of 205 °C, the highest limiting oxygen index (LOI) value of 41, and the lowest dielectric constant of 2.3, were obtained when the EEW ratio of 703-H/MPN was 1.0/0.5, with 0.5 EEW (epoxy equivalent weight) of BMI cured at 145 °C for 2 h.