Study On The Structure And Properties Of Reactive Compatibilized PPC/PBAT Blends And Their Films

Poly(propylene carbonate)(PPC)has excellent biodegradability,biocompatibility,and oxygen barrier properties.However,its amorphous structure and low glass transition temperature result in poor thermal properties,mechanical properties,and dimensional stability,which severely limits its wide application.Poly(butylenes adipate-co-terephthalate)(PBAT)presents good thermal,mechanical and processing properties.Nevertheless,its cost is high and the PBAT film has a poor barrier properties.The blending of PPC and PBAT can improve the properties of single polymer and obtain blends with excellent mechanical and barrier properties.PPC/PBAT blends with various composition ratios were prepared via melt mixing using a twin-screw extruder.The effect of melt viscosity on mechanical properties,rheological response,interfacial interaction,thermal properties,and phase morphology was investigated.The relationship between melt viscosity-morphology-performance was established by analyzing the melt viscosity,phase morphology,and properties of the blends.Results of mechanical properties test,dynamic rheological measurement and FTIR showed that PBAT-rich blends exhibited a better mechanical properties,compatibility and intermolecular interaction when compared with PPC-rich blends due to the different melt viscosity of the two polymers.Incorporating of PBAT effectively improved the thermal stability of the blends.The T_c of PPC/PBAT blends markedly increased from 37.5 to 66.8℃with addition of only 10 wt%PPC,indicating an enhanced crystallization ability.The improvement of T_c was helpful for blown film extrusion.SEM microphotographs showed that the size of the dispersed phase was much smaller and the distribution was more uniform for PBAT-rich blends,compared with that for PPC-rich blends.In order to improve the blown film processing stability of the PPC/PBAT blends,ethylene-methyl acrylate-glycidyl methacrylate(EMA-GMA)was added to the blends as a compatibilizer to enhance the compatibility and melt strength.Results showed that EMA-GMA enhanced the compatibility and the interfacial interaction between the two phases,reduced the size of the dispersed phase,improved the uniformity of the dispersed phase distribution,and enhanced the tensile strength.The content of compatibilizer had a great influence on the structure and properties of blends.The melt strength of the blends increased with the increase of the compatibilizer content,which was beneficial to the blown film.When the content of the compatibilizer was 0.5 wt%,the size of the dispersed phase was smallest.With the content of compatibilizer increase,the phase morphology began to change.Results of DSC and mechanical properties test showed that the addition of EMA-GMA improved the crystallization temperature and mechanical properties.When the content of EMA-GMA was 0.5 wt%,the crystallization temperature was the highest and the mechanical properties was optimal.The PBAT/PPC/EMA-GMA films were prepared by extrusion blow molding.SEM,tensile properties test,barrier properties test and light transmittance test were used to characterize the structure and properties of the films.The effect of blends properties on film processing performance and film quality was also studied.Incorporating of PPC improved the surface and cross-sectional morphology of the films,making the surface smoother and more uniform.The addition of EMA-GMA further improved the surface quality and enhanced the tensile strength of the films.The addition of PPC and EMA-GMA lengthened the gas permeation path and reduced the free volume,respectively,enhancing the resistance of the gas through the films and improving the barrier performance.The films had a good ultraviolet blocking property while the light transmittance increased with the increase of PPC content in the visible light range.Therefore,the films have a potential to act as ultraviolet blocking materials and photosensitive products packaging materials without affecting their transparency.