Study On Toughening Of Polylactide-based Blends Through Crystalline Nylon 11 Particles And Elastomer

In recent years,environmental problems caused by petroleum-based polymers have forced us to search for some materials that can replace petroleum-based polymers.As a renewable biological material,polylactic acid(PLA)can be obtained from renewable resources such as sugarcane or corn.PLA has attracted much attention due to its biodegradability,biocompatibility,environmental friendliness,excellent mechanical properties and good processing properties.At present,PLA has been widely used in food and beverage packaging,clothing,agriculture,electronics and medical devices.However,pure polylactic acid is very brittle,and its impact strength value is very low.As a semi-crystalline polymer,polylactic acid has a low crystallinity and a slow crystallization rate.When subjected to external forces,polylactic acid can easily occur Brittle fracture,this disadvantage limits the use of polylactic acid to a large extent.At present,the main methods to improve the toughness of PLA include polymer blending,copolymerization,crosslinking and annealing.In this paper,a super tough ternary blend was prepared by means of polymer melting blending and annealing.The effect of PA11 content on the toughening effect of the system was studied,and the toughening mechanism was explored.At the same time,the mixture was annealed at 80? for 4 h,and the influence of annealing on the properties of samples was studied.The main research contents and results are as follows:PLA and ethylene-acrylate-glycidyl methacrylate(EGMA)were fused and blended in a twin-screw extruder according to the proportion of 80/20,and a small amount of nylon 11(PA11)was added in the later mixing stage to produce a super tough PLA/EGMA/PA11 ternary blend.The properties of ternary blends were studied by differential scanning calorimeter(DSC),dynamic thermo-mechanical analysis(DMA),contact Angle measurement,transmission electron microscope(TEM)and scanning electron microscope(SEM).The test results showed that even with a small amount of PA11,the notch impact strength of the sample increased significantly.The notch cantilever impact strength of PLA/EGMA/PA11 80/20/1 ternary mixture was about 31 kJ/m2,three times that of PLA/EGMA 80/20 binary mixture.The notch cantilever beam impact strength of the ternary mixture with a PA11 ratio of 5/100 was 61 kJ/m2,six times that of the PLA/EGMA 80/20 binary mixture.The tensile test results indicated that the tensile properties of the ternary blend showed slight attenuation due to the addition of a small amount of PA 11 to the blend.The results of DSC test showed that the crystallization of PL A and PA11 had nothing to do with the increase of toughness.By DSC and DMA measurements,it can be detected that the glass transition temperatures of both EGMA and PLA components are increased,indicating that the glass transition in this blend system has no influence on the change of toughness.The interfacial tension and expansion coefficient were calculated using contact Angle measurements,and the existence of the PA 11-EGMA core-shell composite phase domain was revealed by transmission electron microscopy and scanning electron microscopy.PA 11-EGMA core-shell structure was formed in the PLA matrix at the late mixing stage when the PA11 components were coated with the EGMA components.As the crystallinity of PL A matrix was improved,the mechanical properties of the blend system could be changed.Therefore,the obtained ternary blend material was annealed in a vacuum oven at 80? for 4 hours to study the effect of annealing on the properties of PLA/EGMA/PA11 ternary blend.The experimental results show that the notched impact strength and tensile properties of the blends are improved after annealing.In this paper,a super-tough PLA-based material is prepared by simple melt blending,which has potential significance for broadening the application field of PLA.