Preparation And Property Investigation On The Biaxially Stretched PLA/PA11 Film

Polylactic acid(PLA)is derived from renewable plant resources,has good plasticity,excellent processing performance,non-toxic and harmless,and can be widely used in the packaging field.The toughness of pure polylactic acid is poor,and further improving the toughness of PLA can expand its scope of use.In this paper,nylon 11(PA11)with high toughness and Joncry 4468 are added to improve the mechanical properties of polylactic acid film such as toughness.The main research contents are as follows:(1)Preparation and properties of PLA/PA11 composite.After uniformly mixing PLA,PA11 and a compatibilizer,a PLA/PA11 composite material is prepared by a melt blending method.The study found that the addition of PA11 improved the toughness and tensile strength of PLA.When the addition amount of PA 11 was 20wt%and the addition amount of Joncry 4468 was 1.6wt%,the impact strength and impact strength of the PLA/PA11 composite Compared with pure PLA,the tensile strength is increased by about 40%and 10.4%,respectively;the addition of PA11 increases the crystallinity of PLA and the thermal decomposition temperature of the composite material;the addition of compatibilizer Joncryl 4468 enhances PLA and PA11 The compatibility of the composite system enables PA11 to achieve good dispersion in the PLA matrix,and at the same time improves the fluidity of the composite material.(2)Preparation and properties of PLA/PA11 biaxially oriented film.The optimal formula of PLA/PA11 composite material was screened out,and PLA/PA11/4468(mass ratio 78.4/20/1.6)cast film was prepared by extrusion casting method,then use the biaxial stretching testing machine to perform unidirectional and bidirectional stretching of the cast film in different directions.The research results show that stretching promotes the reflection and merger of the different crystal planes of the a crystal form of PLA in the stretched film,and the ?' crystal form of PA11 changes to the ? crystal form.As the stretch ratio increases,the degree of crystallinity and orientation in the film increase.Unidirectional stretch in MD(vertical)and TD(horizontal)directions can respectively improve the mechanical properties of the film in the stretching direction,while the mechanical properties of the biaxially stretched film are balanced and homogenized in the MD and TD directions.Among them,the PLA/nylon biaxially stretched film with a stretch ratio of(2x2)has higher strength and the best toughness,and the elongation at break in the MD direction is increased by 22.7%and 29.1%,compared with the unstretched film and the pure PLA film and The elongation at break in the TD direction is increased by 38%and 34.3%,respectively,compared with the unstretched film and the pure PLA film.The Maxwell model is used to fit and analyze the different stress relaxation processes of the film with a stretch ratio of 2×2.The fit results show that the material has the largest elastic modulus and the most obvious viscous flow characteristics when it is stretched three times.