Effect of reinforcing particles on hydrolytic degradation behavior of poly (lactic acid) composites

In this study, degradation behavior of polylactic acid (PLA) composite reinforced with different types of particles (titanium dioxide, multi-walled carbon nanotubes, surface-treated multi-walled carbon nanotubes, and graphene nanoplatelets) were investigated. Samples were prepared by extrusion and injection molding. Hydrolytic degradation was induced by immersing the specimen in a sodium hydroxide solution. Particles can affect the crystallization kinetics of PLA matrix which may affect the degradation behavior. In order to examine the crystallization kinetics and crystallinity of PLA matrix, differential scanning calorimetry and X-ray diffraction measurements were employed. Annealing was done for different durations of time in order to control the crystallinity of the matrix. The results show that the crystallization rate was remarkably increased due to the addition of particles and that there was an optimal concentration of particles. The degradation rate of most of the PLA composites was faster than that of neat PLA, indicating that the interface between the particle and the PLA matrix was not perfect. Meanwhile, the degradation rate of PLA reinforced with multi-walled carbon nanotubes became slower due to increased crystallinity.