Study On The Preparation And Properties Of The Blends Of PLA And PPC

In this paper,the blend of poly(lactic acid)(PLA)/poly(propylene carbonate)(PPC)were obtained by melt blending method,by small molecule assistant(Chain extender,2,4-toluene diisocyanate(TDI),and Transesterification catalyst,tetrabutyl titanate(TBT)and PLA-g-GMA、 PLA-g-MAH were reactive blended with PLA and PPC.The effects of compatibilizer dosage and variety on the thermodynamic properties,crystallization behavior,thermal stability and mechanical properties of PLA/PPC blends were investigated by fourier transform infrared spectrometer(FTIR),differential scanning calorimeter(DSC),small angle X-ray scattering(SAXS),scanning electron microscope(SEM),thermogravimetric analyzer(TGA)and universal electronic material testing machine.(1)The effects of the amount and kinds of small molecular auxiliaries on the thermodynamic properties and crystallization behavior of PLA/PPC blends were investigated.The results show that the compatibilities of PLA and PPC can be improved to some extent by the introduction of two compatibilizers,and with the increase of compatibilizer content,the crystallization ability of the blends increases.When the 2wt% of TBT and TDI were added to PLA/PPC blends,the crystallization rate and crystallinity of the blends were improved.The effect of adding TBT was better,and the crystallinity of the blends increased about 22.10%.The results of synchrotron radiation small angle X-ray scattering showed that the crystal size of PLA in the blends decreased,the distribution of PLA was uneven and the crystal growth was poor after the introduction of TBT.Compared with the transesterification catalyst(TBT),the introduction of chain extender(TDI)made the crystal size of the blends increased,the degree of distribution uniformity improved significantly,and the degree of lamellae stacking was more regular.(2)The effects of the amount and kinds of monomers in PLA graft copolymers on the mechanical properties and thermal stability of PLA/PPC blends were investigated,and the fracture mechanism of the blends was analyzed.The results showed that the compatibilities of PLA and PPC can be improved to some extent by PLA-g-GMA,However the introduction of PLA-g-MAH did not significantly improves the compatibility of the two blends.With the increase of two graft kinds of monomers amount,the impact strength,elongation at break and tensile strength of the blends both show a trend of rising first and then decreasing.The effect of PLA-g-GMA on the mechanical properties of the blends was the best.When the GMA content of the grafted products was 3%,the impact properties of the blends increased nearly twice,and the elongation at break reached 152.88%.SEM results showed that the impact fracture mode of the blends changed from brittle fracture to ductile fracture,and the ductile fracture characteristics of the blends were the most significant after PLA-g-GMA was introduced.The results of TGA showed that the thermal stability of the blends was improved to some extent by adding PLA-g-GMA and PLA-g-MAH,and the effect of adding PLA-g-MAH was the most significant.