Preparation And Properties Of Polylactic Acid-based Composites

In this paper, we studied the preparation of graphene in chloroform, a kind of low boiling point solvent. At the same time, we also prepared the graphene oxide(GO) using modified Hummers method and graphene oxide coated cationic starch. Then polylactic acid(PLA) composite materials were prepared by the solution blending method using chloroform as solvent, and the change of the mechanics and thermal properties of PLA were mainly studied.With chloroform as solvent, we prepared the graphene dispersion which the concentration is about0.5mg/mL adopting the way of the Tip ultrasonic stripping. Transmission electron microscopy (TEM), FT-IR spectrum, Thermogravimetric Analysis(TGA), and Raman tests showed that the graphene that we prepared is in single layer or multilayer, its thermal stability is good, and there is less defect on its edges. The dispersion of graphene in the PLA matrix was examined by SEM, XRD, TEM and metallographic microscope, and found that graphene could be evenly dispersed in the PLA matrix. TGA revealed that the addition of graphene greatly improves the thermal stability of the nanocomposites. The mechanical properties of composite materials was also significantly increased. Dynamic mechanical analysis (DMA) showed that the E’of the resulting PLA/graphene nanocomposites increases by about30times higher at100℃when adding amount is1wt%.GO was prepared by modified Hummers method, and in order to making GO disperse in organic solvent easily, we used the vacuum freeze drying method to dry GO. TEM, XRD, FT-IR, TGA and Raman show that GO is in single layer or multilayer, its thermal stability is worse than graphene, and there are more defects on its edges. SEM, XRD and metallographic microscope showed that GO can be uniformly dispersed in the matrix of PLA. Mechanics performance and TGA test showed that mechanical properties of composite materials increase obviously, and so as to thermal stability.We have prepared cationic starch using3-Chloro-2-hydroxypropyltrimethyl ammonium chloride as etherification agent. Zeta potential and XPS test showed that we have introduced the positive charge on the surface successfully. XPS, FT-IR and SEM tests showed that graphene oxide coated on the cationic starch successfully. SEM and metallographic microscope test indicated that the cationic starch coated with graphene oxide (GO-CS) can be uniformly dispersed in the matrix of PLA. And by the test of TGA and mechanical properties, we found that with the same addition, the enhancement effect of GO-CS is better.