Compatibilization Modification Of Polylactic Acid/bamboo Fiber Composites And The Study Of Its Compatibilization Mechanism

Polylactic acid(PLA),a fully biodegradable polymer with a wide range of raw materials.However,it has some shortcomings such as high brittleness,low softening point,and high cost,which greatly limits its promotion.Bamboo fiber,one of the materials,which has a wide range of sources with renewable property.The advantages of using it as a filler to fill PLA is that it can act as heterogeneous nucleation agent to improve the mechanical properties and thermal stability of PLA;Unluckily,the compatibility of PLA and bamboo fiber is poor,it must be modified to obtain composites with good compatibility.In this study,we solved this problem in three directions: pretreating bamboo fiber,adding compatibilizer and plasticizer,introducing compatibilizer and toughener.A series of PLA/bamboo fiber composites were prepared by using a twin-screw extruder.FTIR,DSC,SEM,mechanical testing and other methods were used to characterize the composite,we discussed the influence of different methods on the compatibility of PLA and bamboo fiber,and achieved toughness on the basis of compatibilization.(1)The bamboo fibers were treated with alkali treatment,maleic anhydride(MAH)grafting and titanate coupling agent grafting treatments,which improved the compatibility between PLA and bamboo fibers;The results showed that: the crystallinity of PLA was improved due to better compatibility.The appropriate amount of coupling agent could improve the brittleness of the composites.When the amount of coupling agent was 0.5%,the mechanical properties of the composites were the best,however,excessive coupling agent would reduce the mechanical properties and melt strength.MAH treatment of bamboo fiber would inhibit PLA crystallization,and the rigidity of the composite would increase due to the introduction of MAH.The ideal amount of MAH was 2.5%.Excessive MAH would cause the composite to degrade;the tensile properties and the two-phase bonding ability of the composite increased with the increased of the concentration of lye.(2)In the second part,Polyethylene oxide(PEO)was added,the characteristics of good compatibility and plasticization of PEO with PLA and BF were used to improve compatibility,after determining the amount of PEO,glycerin was introduced for synergistic compatibilization.The results showed that: the compatibilization mechanism of PEO and glycerin was physical compatibilization.When the amount of PEO was 10%,the mechanical properties,crystallization properties and the fluidity of the composites were the best.The rigidity of the composites would become worse with the excessive PEO;The crystal grains of PLA would be destroyed by the addition of glycerin,but the crystallinity of PLA increased with the increased of the amount of glycerol,the introduction of glycerol reduced the tensile strength of the composites,while the elongation at break of the composites increased.When the amount of PEO was 10% with the amount of glycerin was5%,the overall performance of the composites was the best.The rigidity of the composites decreased with the increased of the amount of PEO and glycerin,but the fluidity and hydrophilicity would increase.(3)We introduced the compatibilizer ADR4368 to improve the compatibility between PLA and bamboo fiber,octadecyl dimethyl tertiary amine was used as the catalyst to improve the reactivity of ADR,after determining the amount of ADR,we introduced the polybutylene succinate(PBS)to achieve compatibilization and toughness.The results showed that: ADR achieved compatibilization through chemical reactions with PLA,PBS and BF;The fluidity,crystallinity and hydrophilicity of the composites decreased with the increased of ADR,when the amount of ADR and catalyst were 0.5% and 0.1% respectively,the mechanical properties,thermal stability,and interface compatibility of the composites were the best,at the same time,the tensile strength and elongation at break of the composite were 55.90 MPa and 9.01% respectively;SEM showed that: the gradually increased of PBS would cause the deterioration of the interface compatibility of the composites.When the amount of PBS exceeded 30%,the pores of the composites increased significantly;the fluidity and water absorption of the composites decreased with the increased of PBS,but the toughness of the composites increased with the increased of PBS.The tensile strength was not greatly affected by the amount of PBS,while the composites showed good mechanical properties.