Preparation Of Polylactic Acid Grafted With Epoxidized Soybean Oil And Properties Of Its Composites

Polylactic acid(PLA)is a compostable,biodegradable,highly biocompatible and non-toxic thermoplastic,but polylactic acid is a linear thermoplastic crystalline polymer,which is hard and brittle,and has poor impact resistance.These shortcomings make the use of PLA severely restricted,so improving the toughness and comprehensive performance of PLA is a practical and effective way to expand its scope of application.Epoxidized soybean oil(ESO)is the largest variety of epoxidized vegetable oil.It can be used as a plasticizer of polylactic acid to improve its brittleness.However,blending ESO directly with polylactic acid not only does not significantly improve the overall performance of the product,but also will greatly destroy the mechanical strength of the product,and the migration of ESO is prone to reduce the overall performance of the product.Therefore,it is necessary to find corresponding countermeasures.In this thesis,in order to improve the comprehensive performance of ESO toughened PLA composites,without excessively damaging the mechanical properties of the material,and at the same time reducing the migration of ESO,the reactive compatibilizer ECP was prepared by chemically grafting ESO and PLA by organic synthesis.First,the maleic anhydride(MAH)was grafted to PLA by melt blending to prepare MPLA masterbatch,and then ESO was chemically grafted to MPLA to prepare ECP products,and then ECP and ESO were melt blended with PLA to prepare PLA/ECP and PLA/ESO composite materials respectively,and finally use ECP and acetyl tributyl citrate(ATBC)as a compound plasticizer to toughen and modify PLA to prepare PLA/ECP/ATBC ternary blend composite materials.The conclusions can be drawn as follows:(1)The best way to prepare ECP is to add part of ESO first in the MPLA stage.In the following chemical grafting stage,all the catalyst and the remaining ESO are added,and the ESO and MAH groups are kept in an equimolar ratio.The grafting rate can reach 4.1514%.And the grafting efficiency of the production of chemical grafted PLA with ESO is better than that of melt blending grafting production.(2)Both ESO and ECP can significantly improve the mechanical properties of PLA,but the overall performance of PLA/ECP composites is better than that of PLA/ESO.The addition of ESO makes the PLA-based composite material change from hydrophobic to hydrophilic,while the addition of ECP can further enhance the hydrophobic performance of the PLA-based composite material.If PLA is melt blend with ESO directly,ESO may disperse unevenly and form agglomerates,while the PLA/ECP system presents a compact and continuous homogeneous dispersion state.(3)The maximum crystallinity of the PLA/ECP/ATBC ternary blend composite is 14.07%,which is 8.96 times that of pure PLA;the maximum notched impact strength is 4.59 k J/m2,which is 99.57% higher than pure PLA;elongation at break The maximum is 167.2%,which is50.21 folds that of pure PLA;changing the content of ECP and ATBC can adjust the hydrophilicity and hydrophobicity and haze of the PLA composite material,which maybe can broad the thinking of the compatibility modification of PLA matrix and other hydrophilic and lipophilic materials,the change of haze makes PLA-based composite materials can be used as a light diffuser,which helps to expand the application range of PLA materials.