Greatly enhanced mechanical properties and heat distortion resistance of poly(l-lactic acid) upon compositing with functionalized reduced graphene oxide

Abstract

Poly(L-lactic acid) (PLLA) is a potential candidate for a new renewable resource, but often suffers from a sharp decrease in the storage modulus and heat distortion resistance when the temperature is higher than 60 °C. In this work, reduced graphene oxide (RGO) was introduced to composite with PLLA, which greatly improved the mechanical properties and heat distortion resistance of PLLA. To assist the blending, RGO was firstly chemically functionalized with N-(aminoethyl)-aminopropyltrimethoxysilane (KH792), to improve its compatibility with PLLA. The storage modulus of the PLLA was enhanced by 1500% (from 20 to 300 MPa) around the glass transition temperature, when only 0.5 wt% KH792–RGO was incorporated. Meanwhile, the heat distortion resistance of the PLLA–KH792–RGO was also greatly improved. An investigation on the rheological behavior of the nanocomposite indicated that a network of RGO had been formed in the nanocomposite, which provided an efficient interface interaction with the PLLA. The enhanced stiffness of the PLLA, by introduction of a functionalized RGO network, was preserved well in the rubber state.