Research Of The Effect Of Polyester Grafted Vinyl Copolymer On The Toughening Of Polylactic Acid

Poly(L-lactic acid)(PLLA)is one of the most investigated sustainable polymers,but the inherent brittleness severely restricts its further application.In order to promote the wider application of PLLA,it is necessary to improve its flexibility.The main chains of the vinyl copolymer area flexible carbon chains,which can bring a good toughening effect to the PLLA after blending.Therefore,a variety of copolymerized flexible chain of vinyl monomers was synthesized in this study and polycaprolactone(PCL)was grafted on its side chains to promote the compatibility when blending with polylactic acid.In the interest of the best toughening effect,a large number of different products were synthesized by controlling the structure and the molecular weight of the main chain.In addition,the films of different uses,including solution casting film and electrospun film,were prepared.The effect of different influence factors on the toughening effect of polylactic acid were finally explored particular.A model poly(butyl methacrylate-co-hydroxyethyl methylacrylate)(BMA-co-HEMA)attaching poly(ε-caprolactone)branch(PCL-PBH)was synthesized by combining radical and ring-opening polymerization.With the same route,poly(ε-caprolactone)-branched poly(methyl methacrylate-co-hydroxyethylmethacrylate)(PCL-PMH)is also synthesized.FTIR and ~1HNMR prove successful synthesis of PCL-PMH and PCL-PBH.Plastic films were prepared by blending PCL-PBH with different main chain structures and PLLA.The results shows that miscibility of PCL-PBH and PLLA is subjected to PCL branch density and their blending ratio.PCL-PBH changes from heterogeneous nuclei of PLLA to introducing its crystallization when the molar ratio of[BMA]/[HEMA]is above7.66/1,or the blending ratio exceeds to 5wt%.PCL-PBH and PLLA form good interfacial adhesion at the molar ratio of 1.28/1 and the blending ratio of 10wt%,and the elongation at break and tensile strength are 110.30%and 38.75MPa,respectively.The degradation experiment under different conditions also proves that the blend exhibits the better environmental stability comparable to the original PLLA.Then this work opens another window for modifying PLLA.After comparing the different effect of the two products in the plastic film,the PCL-PMH was chosen to electrospun prepare fiber membrane after blending with PLLA.In this process,the influence of structure and the molecular weight of the main chain were investigated.The fibrous diameter little vary with blending PCL-PMH.The aggregation state of two macromolecules is closely correlated with blend ratio,molecular structure and molecular weight of PCL-PMH.And only when PCL-PMH and PLLA form good interfacial adhesion,can PMH gives full play to its potential of reinforcing the fiber membrane.The tensile strength and elongation at a break of the blend are 6.20MPa and 63.40%under the optimal conditions,respectively,and it also exhibits the representative feature of toughness materials.The blending fiber membrane is as no cytotoxic as original PLLA.This work will provide a new way for reinforcement of electropsun fiber membrane in practice.4.In order to enrich the application range of toughened polylactic acid,some functional vinyl monomers were introduced,and the expected copolymerization structures were successfully obtained by adjusting the synthetic route.