Preparation And Properties Of PBAT/PPC Nanocomposite

Poly（butylene adipate-co-terephthalate）（PBAT）is a 100%biodegradable material with the advantages of high flexibility,excellent impact strength and melt processability,but the disadvantages of poor gas barrier properties and high cost limit its use in packaging films.Poly propylene carbonate（PPC）is also biodegradable and has excellent barrier properties,but is difficult to use alone because of its close glass transition temperature and ambient temperature.Blending PBAT and PPC can compensate for the deficiencies in the performance of a single polymer and obtain a composite material with excellent performance.In this thesis,PBAT/PPC biodegradable composites were studied as the main object,and the effects of different ratios of PBAT and PPC components on the properties of the composites were investigated;to address the problem of poor interfacial compatibility between PBAT and PPC,triglycidyl isocyanurate（TGIC）was used as a compatibility modifier to improve the interfacial compatibility between PBAT and PPC.Finally,the performance of nanocomposites prepared by using low-cost nano-Ca CO₃as filler material was investigated to address the problem of high cost of biodegradable materials for large-scale application.PBAT/PPC blends with different component ratios were prepared by twin-screw extruder,and the effects of component ratios on the mechanical properties,thermal properties,microstructure,melt viscosity and barrier properties of the blends were investigated.The mechanical properties of the specimens were also compared for both hot press molding and blow molding.Tensile tests showed that the machine direction（MD）and transverse direction（TD）tensile strengths of PBAT/PPC films were 28.1 MPa/27.8 MPa and elongation at break was 865%/697%when the PPC content was 50 wt%.The test results of oxygen transmission rate and water vapor transmission rate showed that the water vapor transmission coefficient（WVP）of PBAT/PPC（50/50）composite was 1.55 g·mm·m^-2·d^-1,which only 37.4%of that of PBAT,and the oxygen transmission coefficient（OP）was 52.2%of that of PBAT.PBAT/PPC（50/50）composites and the related films were prepared by melt blending followed by film blowing process using TGIC as the reactive compatibilizer.Herein,the structure,thermal properties,mechanical properties,and gas barrier properties of the composites and the related films were systematically characterized via various techniques.The corresponding results indicated that the incorporation of TGIC effectively improved the interfacial compatibility between PBAT and PPC,and enhanced the thermal stability of the composites,especially for PPC.Meanwhile,DSC results exhibited that the glass transition temperature of PBAT and PPC tended to be closer with the increase of TGIC.The morphology results indicated that the PPC phase was uniformly dispersed in the continuous phase of PBAT with a finer spherical shape.In addition,the mechanical properties and water vapor barrier properties of the PBAT/PPC composites and films were significantly improved with the existence of TGIC.The mechanical study revealed that the tensile strength of the composite film increased by 35%as the TGIC content of 1%,and the water vapor permeability of the composite film decreased by 40%as the TGIC content of 2%,respectively.PBAT/PPC/nano-Ca CO₃composite films were prepared by extrusion blown film.The effects of nano-Ca CO₃incorporation and filling amount on the structure,thermal properties,mechanical properties and barrier properties of the composites and composite films were systematically investigated.The results show that nano-Ca CO₃preferentially selectively distributes in the PBAT phase and increases the crystallization temperature of PBAT.nano-Ca CO₃could increase the initial degradation temperature of the composite;with the increase of nano-Ca CO₃filling,the tensile strength and elongation at break of the composite films first increased and then decreased,and when the nano-Ca CO₃content of 15%,the mechanical properties of the composite films were the best,with the machine direction/transverse direction tensile strength of 20.4/17.3 MPa and the machine direction/transverse direction elongation at break of 579/519%,respectively.The water vapor and oxygen barrier properties of the composite films were improved with the existence of nano-Ca CO₃.