Insights into the curing and thermal behavior of orthophtalic unsaturated polyester resin with organically modified montmorillonite nanoclay

Abstract

This study investigated the reinforcement of unsaturated polyester resin (UPR) with montmorillonite (MMT) nanoclay, delving into the effects of organic modification using cationic benzododecinium chloride (DDBAC) in contrast to anionic octadecanoic acid (SOD), aiming to discern their contributions. The investigation delves into the curing kinetics of UPR incorporating organically modified clay, initiated by methyl ethyl ketone peroxide (MEKP), and accelerated by cobalt octoate (CoO). Exploiting dynamic differential scanning calorimetry (DSC), the study employs advanced isoconversional methods, namely Trache-Abdelaziz-Siwani (TAS) and Vyazovkin's method coupled with the compensation effect (Vya/CE), to assess the kinetic parameters of the cure reactions. The incorporation of modified nanoclays into the UPR resulted in a significant reduction in the activation energy barrier for the redox reaction. Specifically, the activation energy decreased from 118 kJ/mol for the pristine UPR to 94 kJ/mol for the UPR/MMT-SOD system and 82 kJ/mol for the UPR/MMT-DDBAC system. Furthermore, the thermal decomposition reaction of the two modified UPR systems also exhibited a decrease in activation energy. The pristine UPR had an activation energy of 126 kJ/mol, which is reduced to 88 kJ/mol for the modified UPR systems. Consistently, a decline in the pre-exponential factor is noted, indicating a lowered frequency of collisions between reacting entities, transitioning from 1.39 × 10¹⁵ and 3.09 × 10¹⁶ s⁻¹ in the pristine unsaturated polyester resin to 4.61 × 10⁹ and 4.96 × 10¹⁰ s⁻¹ in the UPR/MMT-SOD system for the redox and thermal decomposition reactions. Thermogravimetric analysis elucidates heightened stability in the formulated UPR systems following the incorporation of modified nanoclay.