Research On Reactive Compatibilization Of Sisal Fiber Reinforced Polylactide Composites By Tris (p-isocyanatophenyl) Thiophosphate

The synthesis of biodegradable composites from renewable raw materials has become a hot topic in scientific research and industrial practice.Sisal fiber(SF)has the advantages of high specific strength,light weight and low cost,green degradable,abundant resources and renewable.Polylactic acid(PLA)is one of the most biodegradable materials that have the potential to replace traditional petroleum-based polymers,but its disadvantages such as high cost and poor toughness limit its application in industrial production.The use of both materials to prepare biomass degradable composites can play a synergistic role in the performance advantages and achieve the results of light weight reduction,cost reduction and reducing dependence on petroleum resources,and it is an effective way of protecting the environment and achieving sustainable energy development.The interfacial compatibility between the hydrophilic sisal fiber and the non-polar polylactic acid matrix is poor,which affects the reinforcing effect of the fiber on the matrix.On this issue,this paper adopted the technical method of reaction processing and introduced a multifunctional monomer tris(p-isocyanatophenyl)thiophosphate(TPTI),which has high reactivity with the hydroxyl group at the surface of the sisal fiber and at the end of the polylactic acid molecular chain.Chemical bonding of polylactic acid and sisal fiber was achieved during melt blending to enhance interfacial adhesion properties.In this paper,a series of PLA/TPTI/SF composites with different TPTI content and different sisal content were prepared to study the effects of reaction processing on the surface group,microstructure and thermal stability of sisal,as well as on the mechanical properties,microstructure,thermal stability and crystallization behaviorof the composites.At the same time,we also introduced Polycaprolactone(PCL)as toughening phase on the basis of compatibilization,in order to further improve the impact toughness of composites.The PLA/PCL/TPTI/SF composites with different PCL contents were prepared and the effects of PCL on the thermal stability,crystallization,morphology and mechanical properties of the composites were investigated.Results show that:After the reaction processing,the surface roughness of the sisal fiber was increased.The fibrillation degree of the fiber was increased,and the thermal stability was slightly decreased.During the reaction processing,TPTI acted as a ?bridge? between the two phases,realizing the chemical linkage of sisal fiber on the PLA matrix.After the reaction processing,the interfacial adhesion between the sisal fiber and the matrix in the composite was significantly improved,which made the mechanical properties of the PLA/TPTI/SF composites significantly higher than that of the PLA/SF.When the content of sisal fiber was 20% and the content of TPTI was 0.6%,the mechanical properties of PLA/TPTI/SF composites were the most improved compared with the mechanical properties of PLA/SF composites,with the same fiber content.When the sisal fiber content was 30% and the TPTI content was 0.8%,the mechanical properties of PLA/TPTI/SF composites had the best mechanical properties,with the tensile strength was 69.36 MPa,the bending strength was 112.39 MPa,and the impact strength was 4.90 MPa.The addition of sisal reduces the thermal stability of the composite.Under the same fiber content,the thermal stability of PLA/TPTI/SF composites increased first and then decreased with the increase of TPTI content.The addition of sisal fiber could induce the composite to crystallize at a lower temperature and promote the crystallization.TPTI enhanced the interaction between fibers and PLA molecules,affecting the crystallization properties of the composite.As the TPTI content increases,the cold crystallization peak temperature of the PLA/TPTI/SF composite first rised and then decreased.The introduction of PCL promoted the crystallization of PLA/PCL/TPTI/SF composites and plasticized and softened the matrix resins;The impact toughness and elongation at break of the PLA/PCL/TPTI/SF composites were thus increased,but the strength and stiffness of the material were sacrificed at the same time.Therefore,the composite material matching the mechanical properties can be selected according to the mechanical performance requirements of the application field.