Compatibility Modification And Characterization Of PBAT-based Biodegradable Composites

In recent years,the development of environment-friendly biodegradable polymers for production has attracted much attention,motivated by the need to reduce the amount of plastic wastes accumulating in the environment.Poly-adipate/butylene terephthalate（PBAT）is considered to be the most suitable substitute for non-degradable polymers such as polyethylenepolyethylene（PE）due to its good molecular flexibility and biodegradability among biodegradable polymers.However,due to the poor processability and high viscosity,PBAT is often blended with PLA,cellulose,etc.to prepare composite materials.Improving the compatibility of the components in the composites has always been a research hotspot.Therefore,this paper selected biodegradable polylactic acid（PLA）and sulfonated lignin as blending components to prepare composites with PBAT respectively.Ionic liquids（ILs）and polyhedral oligomeric silsesquioxane(POSS_（epoxy）8)were used as compatibilizers to enhance the compatibilization of composites,respectively.1.Two novel ionic liquids（IL1 and IL2）which were composed of phosphorus-containing cation（PR₄⁺）with different alkyl chain lengths and asymmetric phosphorus-containing anion(RPO₃^2-),were synthesized.Then,the amount of ILs added into the PBAT/PLA was adjusted to obtain master batch by blending,and the PBAT/ILs/PLA biodegradable composites was obtained by injection molding.The properties of the composites were characterized by X-ray diffraction（XRD）etc.SEM showed PLA was more evenly dispersed in PBAT by adding ILs.The mechanical properties test showed that the elongation at break of composites containing 0.4 wt.%IL1 or IL2increased by 329.9%and 168.5%,respectively,compared to pristine PBAT/PLA composites.At the same time,PBAT/ILs/PLA composites possessed excellent flame retardancy（a limiting oxygen index of 28.1 and 27.3,respectively）when ILs content was 0.7 wt.%.Furthermore,the melt fluidity of the PBAT/ILs/PLA composites increased with increasing ILs content,which indicated that ILs played a good plasticizing effect in the composites.2.PBAT/POSS_（epoxy）8/Lignin biodegradable composite films with a thickness of 90±5μm were prepared by melt blending and blowing using POSS_（epoxy）8 as reactive compatibilizers.The content of POSS_（epoxy）8 was 0 wt.%,0.1 wt.%,0.5 wt.%,1 wt.%,3 wt.%in the composite films.SEM showed that the fracture surface of the composite films with POSS_（epoxy）8 became rough and appeared a state of drawing,especially when the POSS_（epoxy）8 content was 1wt.%.It indicated that POSS_（epoxy）8 improved the interface adhesion between PBAT and lignin,and enhanced the compatibility of PBAT and lignin.The crosslinking test showed that the degree of crosslinking of the films reached the highest when the content of POSS_（epoxy）8 was 1wt.%.Mechanical properties test showed that tensile strength of the composite films increased by 15.9%and 48.2%respectively,and the elongation at break increased by 8.8%and 21.4%respectively of the longitudinal and transverse after the addition of POSS_（epoxy）8.At the same time,the transverse mechanical properties of the films were significantly improved,indicating that the isotropy of the composite films was significantly improved after compatibilization and modification.In conclusion,the novel ionic liquids and POSS_（epoxy）8 were selected as the compatibilizer for the biodegradable composites in this paper,which significantly improved the properties and provided an effective way for the further development of biodegradable materials.