Enhancing mechanical and electrical properties of phthalic anhydride‐based unsaturated polyester resin by structural modification using methylhexahydrophthalic anhydride

This work investigates the influence of methylhexahydrophthalic anhydride (MHHPA) on the properties of phthalic anhydride‐based unsaturated polyester resin (PA‐based UPR) when PA is replaced by MHHPA with different PA/MHHPA mole ratios, ranging from 100/0 to 0/100. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) are used to study the chemical structure, curing process and mechanical properties of the resins, showing the successful incorporation of MHHPA into the structure of UPRs with superior properties, compare to PA‐based UPRs. In particular, the addition of MHHPA significantly lowers the acidity by up to 28% and promotes the curing reaction, reducing the enthalpy of the reaction by 2.5 times, and shortens the curing time by up to 40%. This incorporation also increases the gel content up to 99.9%, thereby increasing the crosslinking between the polyester chains and improving the rigidity of UPRs. In addition, the glass‐transition temperature of the polymer increases approximately 78%, which can improve the working temperature of the MHHPA‐modified UPRs. The electrical properties of the resins containing MHHPA reveal better insulating performance in comparison with the PA‐based UPR. These findings demonstrate great potentials of the MHHPA‐modified UPRs for various applications, especially in outdoor environments. Enhancing mechanical and electrical properties of unsaturated polyester resin (UPR) with replacement of phthalic anhydride (PA) monomer by methylhexahydrophthalic anhydride (MHHPA).