Study On Properties Of PLA/PBAT Blends Prepared Through Tri-Screw Extruder

Plastic products are ubiquitous in our lives.However,most of the raw materials producing polymer plastics come from petroleum resources.With the reduction of petroleum resources and the huge ecological damage caused by petroleum-based plastics,producing polymer materials from renewable resources and developing degradable polymer materials have become an urgent and significant task.As a new environmentally friendly polymer material,polylactic acid(PLA)has good biocompatibility,degradability and easy processing properties,and has the advantages of high strength and high modulus,and PLA is relatively less expensive compared to other degradable materials.PLA has the potential to replace traditional petroleumbased polymer materials such as polyethylene(PE),polystyrene(PS),polypropylene(PP)and polyvinyl chloride(PVC),so that PLA is currently considered to be one of the most promising renewable,green and environmentally friendly materials.PLA has the merit of high strength and modulus,but PLA still has many disadvantages,such as poor toughness,slow degradation rate,strong hydrophobicity and lacking of active side chain groups.Considering these shortcomings of PLA,copolymerization,synthesis,and polymer blending were used to conquer the disadvantages of PLA.Owing to the operation feasibility and high economic benefits,polymer blending has received great attention from industry and academia.Poly(butylene adipate-co-terephthalate)(PBAT)is a fully degradable aliphatic aromatic copolyester.Considering PBAT has good toughness and fast biodegradation rate,PBAT could be used as an excellent choice for toughening PLA.Based on the co-rotating parallel tri-screw extruder developed by our own research group,this paper explored the extrusion process of melt conveying zone of tri-extruder extruder through three-dimensional numerical simulation with Polyflow.The velocity,shear rate,viscosity,mixing index,concentration and particle trajectory of PLA were fully studied,and the processing mechanism of the tri-screw extruder was expounded according to the simulation results,which provided theoretical guidance for the preparation of PLA/PBAT blend.Using the best screw combination,this paper prepared a high-performance PLA/PBAT blend based on the co-rotating parallel tri-screw extruder developed,and the performance of PLA/PBAT blends with different matrix ratios was thoroughly studied.The results showed that addition of PBAT could greatly improve the crystallinity of PLA,and the elongation at break and impact strength of PLA/PBAT blends inclined with the increase of PBAT content.In addition,this paper explored the effects of compatibilizer ethylene-methyl acrylate-glycidyl methacrylate random terpolymer(EMA-GMA),initiator benzoyl peroxide(BPO),diisopropyl peroxide(DCP)and organically modified montmorillonite(MMT)on the chemical structure,micromorphology,crystallization properties,thermal stability and physical and mechanical properties of PLA/PBAT system.The compatibility between PLA and PBAT was significantly improved with the addition of EGMA and the toughness of the PLA/PBAT blend was greatly improved.The elongation at break of the PLA/PBAT blend reached 267% with addition of 6 percent of EGMA.PLA-g-PBAT copolymer,formed by in-situ reaction of the initiator DCP or BPO with PLA/PBAT blends,existed in the phase interface of PLA and PBAT,which is beneficial to enhance the interfacial adhesion and improve the compatibility of PLA and PBAT.The impact strength of the blends increased from 3.76 MPa to 9.38 MPa when adding 0.1 percents of DCP.Blending modification of inorganic fillers with polymers is an important way to achieve high performance of polymer materials.Addition of MMT enhanced the tensile strength and modulus of PLA/PBAT blends,and slightly enhanced impact strength of PLA/PBAT blends.