Effect of graphene oxides on thermal degradation and crystallization behavior of poly(l-lactide)

Abstract

Graphene oxides (GO) were introduced into a poly(L-lactide) (PLLA) to prepare the PLLA/GO composites with different concentrations of the GOs. The main attention of the present work was focused on the thermal degradation and crystallization behaviors of a PLLA matrix induced by GOs. The measurements based on gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) clearly proved the thermal degradation of the PLLA matrix during the melt-processing procedure. Consequently, reduced complex viscosity of the composites was achieved. The crystallization behaviors of the PLLA matrix were comparatively investigated under different crystallization conditions including melt-crystallization (nonisothermal or isothermal crystallization occurring from the melt state) and cold-crystallization (crystallization occurring from an amorphous solid state) using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide angle X-ray diffraction (WAXD). Largely enhanced crystallization ability of the PLLA matrix was achieved. The crystallization conditions and the GO content are key factors which influence the crystallization behavior of the PLLA matrix. This work proved that the stabilization of the PLLA matrix during the melt-processing procedure must be considered when designing and preparing the PLLA/GO materials.