| Plastic film materials are closely related to people’s life.However,traditional nondegradable plastic has caused serious pollution to the environment.Compared with sheet and other products,the recycling of plastic film materials after discarding is costly and difficult,which will cause irreversible damage to the environment.Therefore,biodegradable films came into being.As a kind of bio-based thermoplastic aliphatic polyester,polylactic acid(PLA)has the characteristics of good biocompatibility,biorenewable,high strength,high modulus,easy processing,biodegradable and so on.As a substitute for petroleum-based polymers,it has extremely important application value.PLA has the characteristics of brittleness,low melt strength,and easy decomposition during processing,which makes PLA itself unsuitable for film processing and must be modified to meet its application requirements.The main idea of this paper is to modify PLA by melting and blending,use high-strength PLA to play the role of skeleton support in the blending system,and add materials with good toughness to play the role of buffering and absorbing energy.By selecting appropriate compatibilizers to improve the compatibility of the blending system,and construct blend materials with both strength and toughness.Preparing the film products with excellent performance.The main innovations and conclusions of this paper are as follows:(1)PLA,P(3HB-co-4HB),PBAT ternary blend blown film were prepared,that can meet packaging applications.Under the appropriate ratio,the film has good mechanical properties and can well meet the application requirements.P(3HB-co-4HB)and PBAT can effectively increase the elongation at break of PLA and ameliorate the brittleness of PLA without significantly reducing the tensile strength of PLA.The blend films exhibit different mechanical properties in TD and MD.The tensile strength of PLA/P(3HB-co-4HB)/PBAT(55/10/35)ternary blend films can reach 33.0 MPa(MD)and 23.5 MPa(TD),and the elongation at break exceeds 137%/147%(MD/TD),tear strength over 113 kN/m/120 kN/m(MD/TD).The blend films have good biodegradability,and the bio-enzymatic degradation ability of PLA/P(3HB-co4HB)/PBAT(65/0/35)and(60/5/35)can even exceed neat PLA.However,when the content of P(3HB-co-4HB)exceeds 15 wt%,the compatibility of the blended film system deteriorates and the mechanical properties decrease significantly in TD.(2)PLA,PBAT,PPC ternary agricultural mulch film were prepared.Most studies have ignored the effect of processing parameters on the mechanical properties of the film in blown film processing,and explored the effect of different blow-up ratios(BUR)on the mechanical properties of the film.It can be found through experiments that increasing BUR has a better effect on the mechanical properties of the film in TD.Good help can better make up for the disadvantage of poor mechanical properties in TD of the film.The PBAT/PPC/PLA(64/20/16)mulch film has a tensile strength of up to 43.0 MPa/37.6 MPa(MD/TD)and an elongation at break of 160%/450%(MD/TD),the tear strength can reach 140 kN/m and the WVP is 3.09×10-14 g·cm/(cm2·s·Pa).The effect of light stabilizer on the mulch film was studied.After adding high-efficiency hindered amine light stabilizer UV-770,the mulch film obtained good light stability,and after 100 hours of the ultraviolet aging test,its elongation at break could still exceed 100%.(3)The PLA and PBST blended blown films were prepared,and the chain extender ADR was used for in-situ reaction compatibilization to improve the compatibility of the system.Whether the system is compatible with the blending modification is a very critical issue.It is not feasible to simply directly blend PBST and PLA,and the advantages of high strength and high modulus of PLA cannot be exerted.After adding the chain extender ADR,the PBST/PLA/ADR(80/20/0.3)film has good mechanical properties.The tensile strength is 20.1 MPa/17.9 MPa(MD/TD),the elongation at break reaches 350.4%/487.8%(MD/TD),and the tear strength reaches 109.8 kN/m/97.5 kN/m(MD/TD).At the same time,the film also has good barrier properties,and the WVP is as low as 3.09×10-14 g·cm/(cm2·s·Pa).The compatibilization mechanism of the chain extender ADR was explored.The formation of the block copolymer PBST-g-PLA was the most important factor to improve the compatibility of the system and the mechanical properties of the film,which effectively increased the interfacial bonding ability and the two-phase compatibility.(4)PBAT/PLA cast films were prepared,and the reaction compatibilization was carried out by adding the cross-linking agent PAPI.After the reaction compatibilization of PAPI,the PBAT/PLA/PAPI(80/20/0.7)film with the most excellent mechanical properties,the tensile strength is increased to 24.2 MPa,and the elongation at break is increased to 860%.The tear strength exceeds 110 kN/m,and the barrier performance is also improved,and the WVP can reach 12.5×10-14 g·cm/(cm2·s·Pa).GPC,FTIR,and other experiments have proved that the cross-linking agent PAPI can react in the system and has a certain compatibilizing effect on the system.The crystallinity of the cast film is low,and the addition of PAPI will reduce the crystallinity of the film. |
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