Effect of Epoxy Chain Extender on the Properties of Polylactic Acid

Abstract

Zhi-yang Liu, Yun-xuan Weng, Zhi-gang Huang, Lei wang, Dan Qiu and Shuang-xi Shao

Modification of polylactic acid (PLA) by chain extension is a method used to improve its melt strength and heat resistance. In this study, the chemical structure, viscosity average molecular weight, thermal properties, melt viscosity, mechanical properties and Vicat softening temperature of PLA before and after the modification were measured by Fourier-transform infrared spectroscopy (FTIR), a viscometer (Mv), differential scanning calorimetry (DSC), a melt index instrument (MI), a rotary rheometer, a universal material testing machine, and a Vicat softening temperature tester, respectively, to characterize the effect of chemically modifying PLA with KL-E4370. The experimental results showed that the epoxy group contained in KL-E4370 reacted with the carboxyl group of PLA. In addition, the modified PLA showed increased molecular weight, enhanced melt strength, decreased melt fluidity, a significantly decreased melt index, significantly increased complex viscosity and modulus, enhanced impact and tensile strengths, and an increased Vicat softening temperature. When the content of KL-E4370 was 0.1%, the viscosity average molar mass increased from 2.88×103 g/mol (that of neat PLA) to 4.02×103 g/mol, the crystallinity increased from 17.0% (that of neat PLA) to 32.5%, the melt index decreased from 6.0 g/10 min (that of neat PLA) to 2.2 g/10 min, the Vicat softening temperature increased from 67.9 °C (that of neat PLA) to 160.1 °C, and the heat resistance of PLA was improved significantly

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