Study On The Blending Modification Of Poly(propylene Carbonate)/Thermoplastic Starch

Plastic products are widely used in various fields.However,The raw material for producing traditional plastics is petroleum,which is difficult to degrade after being abandoned,and causes a lot of environmental pollution problems.Additionally,oil is a limited resource,consumption can lead to energy crisis.The exploitation of green and environmental protection materials in nature and developing biodegradable materials is an effective way to solve pollution and waste.Starch comes from nature,it's very cheap and renewable.Add plasticizer in starch,thermoplastic starch(TPS)can be obtained by the thermoplastic processing.But the mechanical property of TPS is poor,it's sensitive to environment humidity.So,the application of TPS is limited.Blending TPS with other biodegradable materials can overcome deficiencies,broaden the application fields.Poly(propylene carbonate)(PPC)is biodegradable,but it's expensive and the glass-transition temperature is low,which limits its application.Materials with desired properties could be obtained by blending PPC and TPS.PPC/TPS is degradable.PPC is hydrophobic and starch is hydrophilic,they are incompatible.Compatibilizers for preparing the composites need to be added.In the paper,PPC/TPS suing maleic acid as compatibilizer and glycerol as plasticizer(MPPC/TPS)was prepared by extrusion.PPC/TPS using maleic anhydride(MAPPC/TPS)as compatibilizer and PPC/TPS without compatibilizer are prepared for comparison.Scanning electron microscopy(SEM)was used to observe the interfacial compatibility between PPC and starch,and the glass transition temperature was characterized by differential scanning calorimetry(DSC).The mechanical properties was tested by,a materials testing machine.The mechanical properties of MPPC/TPS are better than those of MAPPC/TPS,The mechanical properties of MAPPC/TPS are better than those of PPC/TPS without compatibilizer.The compatibilization effect of maleic acid is better than that of maleic anhydride.The composites are extracted by methanol firstly,then extracted by acetone.FTIR demonstrates that in the presence of maleic acid or maleic anhydride,transesterification of PPC and starch is the main reaction,which produces the starch-g-PPC graft copolymer.The production of starch-g-PPC copolymer improves the compatibilization of PPC and TPS.Compatibilization mechanism of PPC and TPS during the extrusion process is discussed.The effects of plasticizer on PPC/TPS were analyzed.PPC/TPS using formamide as plasticizer and succinic acid or succinic anhydride as compatibilizer were prepared.As a contrast,the PPC/TPS composites were prepared by using glycerol as plasticizer and succinic acid or succinic anhydride as compatibilizer.SEM,DSC were Used to characterize materials and the mechanical properties and water vapor barrier properties of composites were examined.The elongation at break of composites with formamide as the plasticizer is higher than that of the composites with glycerol as the plasticizer,meanwhile,the water vapor barrier property of the composites with formamide as plasticizer is better than that of glycerol as the plasticizer.