Preparation And Characterization Of PBAT/PLA/POSS Composite Films

Plastic film is one of the most commonly used plastic products in every aspect of our lives.Most of its raw materials are petroleum-based polymers such as polyethylene（PE）,polypropylene（PP）and polyvinyl chloride（PVC）,which have a series of white pollution problems due to their non-degradable properties.With the increasing awareness of eco-environmental protection,all biodegradable materials are receiving more and more attention.And it plays an increasingly important role in solving the white pollution problem.Poly（butylene adipate-co-butylene terephthalate）（PBAT）and Poly（lactic acid）（PLA）have been extensively studied in the field of thin films as the most common all-biodegradable resin.The most common method currently used to prepare PBAT/PLA composites is to directly melt blend them.However,the prepared composite material has problems such as poor compatibility,poor mechanical properties,and easy cracking.The addition of reactive nanoparticles is a simple and effective way to improve the above problems.The addition of a reactive solubilizer can enhance the interfacial interaction between the two phases and improve the overall performance.In this thesis,eight-epoxy cage silsesquioxane POSS（epoxy）₈ was melt blended with PBAT and PLA,and PBAT/PLA/POSS composite film was prepared by extrusion blow molding.Initial mixing of raw materials:PBAT,PLA and POSS（epoxy）₈are simply stirred in the sealed pocket.The content of PBAT is 85%,the content of PLA is fixed at 15%,and the amount of POSS（epoxy）₈ is 0%-5%.Preparation of PBAT/PLA/POSS blend masterbatch:The initial blend was poured into a twin-screw extruder,extruded through a twin-screw extruder,and granulated to obtain a blended masterbatch after the reaction.From the feed section to the head section,the temperatures in the seven zones were set at 170oC,180oC,190oC,190oC,190oC,180oC and 180oC.The feed rate was set at 150 g/min and the screw speed was maintained at 60 r/min to achieve stable melt flow and avoid thermal degradation of the PLA.Blowing of PBAT/PLA/POSS composite film:The composite mother film was dried in a drying oven at 80°C for 12 hours,and then a composite film having a thickness of 70μm was blown by a film blowing machine.The four temperature zones of the blown film machine are set to170oC,180oC,190oC,and 190oC.The screw speed is set to 40 r/min,the traction speed is 0.2m/s,and the charging rate is 0.2 m/s.The structure and properties of the prepared PBAT/PLA/POSS composite film were analyzed.It was found by scanning electron microscopy（SEM）that PLA was uniformly dispersed in a PBAT matrix having a long cylindrical shape,while cage silsesquioxanes containing eight epoxy groups were uniformly dispersed in two of PBAT and PLA.At the interface between the phases,this distribution greatly improves the adhesion of the two incompatible interfaces and avoids the cracking of the film material under low stress,thereby improving the mechanical properties.At the same time,the hollow structure of the cage silsesquioxane can store a large amount of stress,which plays a vital role in improving the overall performance of the composite film.X-ray diffraction（XRD）experiments and differential scanning calorimetry（DSC）experiments confirmed that the cage silsesquioxane（POSS）promoted the crystallization of the composite system and played a role as a nucleating agent.In addition,dynamic mechanical thermodynamics（DMA）tests have shown that as the amount of cage silsesquioxane added increases,the difference between the glass transition temperatures（Tg）of the two phases becomes smaller and smaller.It shows that the compatibility of the two-phase system is getting better and better,and the mechanical properties of the film material are greatly improved.Through the testing of the electronic universal testing machine,it was found that the prepared film had a maximum tensile strength increase of 59.6%and a maximum elongation at break of 65.5%,and the two were synchronized.When the addition amount of POSS（epoxy）₈ is 1%,PBAT:PLA（85:15）,blending time is 8 min,screw speed is 70 r/min,and the blending temperature is 190°C,the comprehensive performance of the composite film is optimal.In this paper,the preservative properties of PBAT/PLA/POSS composite films were also studied.The results showed that the freshness preservation performance was better than that of ordinary polyethylene films.