Dependence of the air-drying exothermic effect on the double bond in alkyd resins

Authors：Wang, Yong^*; Zhang, Jinxiang; Zhao, Bo; Lu, Ying; Wang, Jie; Jiang, Xuepeng

Source：Journal of Thermal Analysis and Calorimetry, 2022, 147(14): 7785-7791.

DOI：10.1007/s10973-021-11084-8

• Alkyd resin
• Air-drying
• Exothermic effect
• Double bond
• Autoignition

The widely used alkyd resin suffers not only the flammability but also the autoignition of resin waste. Its autoignition should result from the air-drying exothermic effect due to autoxidation and conversion of double bond. However, the air-drying exothermic effect is seldom studied. In this study, five soybean oil-based alkyd resins were synthesized. The content of double bond measured by the titration method increased linearly with increasing the molar fraction of maleic anhydride. After air-drying, the infrared spectroscopy absorption peak for the double bond disappeared. Considering that the curing originated from the conversion of chemical bonds, the exothermic effect was theoretically analyzed to be 1163-1455 kJ mol(-1) double bond based on the air-drying mechanisms and the differences among chemical bond energies. According to thermodynamics principles, the air-drying exothermic effect was also derived from the measured heat of combustion. When the content of double bond increased from 2.19 mol kg(-1) resin to 2.56 mol kg(-1) resin, the exothermic effect linearly increased from 1352 kJ mol(-1) double bond or 2.96 kJ g(-1) resin to 2508 kJ mol(-1) double bond or 6.42 kJ g(-1) resin. The steady and unsteady autoignition theoretical analyses implied that due to the air-drying exothermic effect the alkyd resin waste with a certain thickness would catch fire within one working day.

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