Study On Structures And Properties Of Polycarbonate/Poly Lactic Acid (PC/PLA) Blending Materials

In this paper, using twin-screw extruder, to prepare the PC(polycarbonate)/PLA (polylactic acid) blend, through cutting, drying, injection molding process, standard samples were made.Then testing the mechanical properties, differential scanning calorimeter (DSC) and scanning electron microscope (SEM) and other means of testing, the effect of different kinds and contents of compatilizers to the mechanical properties and microstructure of PC/PLA blend were studied, to explore the most appropriate compatilizer.in addition,own synthesize the compatilizer MA-GMA, The structure of MA-GMA were characterized by the GPC, Fourier infrared spectroscopy (FTIR) and 1H NMR and other testing methods.Finally after extrusion and injection molding the standard samples were made, through the mechanical properties and microstructure analysis,the compatibility effect of MA-GMA were tested.The results of the study show that:The compatibility of the PC/PLA blend were not good,the mechanical properties were obviously reduced after blending. The compatilizers were needed to added, in order to improve the mechanical properties of the blend.The compatibilizer EMG were added to the PC/PLA (85/15) blends, and had an obvious effect.The mechanical properties such as elongation at break and the notched impact strength, were obviously increased, SEM showed that, only one phase was lefeed, and it was an ideal compatilizer. The maleic anhydride series compatibilizers, such as SMA, EMA, LMA,have some capacity of compatybility, elongation at break was increased, but the notched impact strength was insufficient, and SEM showed that, the blend still had two obviously phases, so further research was not considered for this the material as compatibilizers. Tetrabutyl tianate(TBT) which played the role of the catalyzer of transesterification, when TBT was added to the blend, all of the mechanical properties was improved, but improvment was not obvious, and the color of the blend turned into deep yellow, so TBT was not included in the scope of the excellent compatibility agent. Cerium(Ⅲ) acetate hydrate (Ce(Ac)3), also played as an catalyzer of transesterification, caused the degradation of PLA or PC, which was greater than the transesterification effect, so it was not the appropriate compatibilizers to the PC/PLA blend. Finally, this paper selected EMG as a good compatibilizer. Added the compatibilizer EMG to the PC/PLA(70/30) blend, the glass-transition temperature(Tg) of PC was decreased, the Tg of PLA was increased, this could prove that the compatibility of the blend was improved; and SEM showed that, the interfacial bonding force between the two phases was increased, resulted in improving the compatibility of PC/PLA blend. The addition of E-MA-GMA improved the impact strength of the blend. When the content of E-MA-GMA was 9 phr, the tensile strength, elongation at break and impact strength was the maximum.EMG was usefull for all ratios of PC/PLA blends, it could increase the interfacial bonding force between the two phases, and improve the mechanical properties. To different proportions of PC/P LA blending systems, the proportion of the best compatibility effect was different, such as the PC/PLA(70/30) blend, the proportion of the best compatibility effect was 9%(mass fraction). The ratio of PLA in tne blend could be not more than 40%, if more than the ratio, the mechanical properties of the blend dropped substantially, no practical value.Synthetizing compatibilizer MA-GMA, by the radical polymerization,the relative molecular mass,Mn= 87105 g/mol, dispersion D= 1.91, the product yield 72%, the content of GMA 25%.Adding MA-GMA to the PC/PLA (70/30) blend, its mechanical properties had a dramatic increase, compared with the blend without compatibilizer, SEM showed that, only one phase was lefeed, and it was an ideal compatilizer. But compared with pure PC and PC/PLA blend with the best proportion of EMG, its mechanical properties still had a large gap. So in order to get the PC/PLA blend with excellent mechanical performance,we could add the toughening agents, such as PE.