Study On The Structure And Properties Of PLA/PBS Blend Modified By Small Molecule Reactive Compatibilization

Polylactic acid(PLA)is a kind of biodegradable thermoplastic polyester with high modulus and high strength.It has good biocompatibility and is one of the most promising environmental protection materials at present.However,its brittle nature and slow crystallization rate limit its application in various fields.Polybutylene succinate(PBS)has excellent mechanical properties and good biodegradability.Blending with PLA can improve the mechanical properties of materials while ensuring biodegradability.However,the poor compatibility between PLA and PBS limited the application of the material.In this paper,by adding small molecules as reactive compatibilizers into the PLA/PBS blend system,multi-functional polymer is formed in the original position during the blending process,so as to achieve the compatibilization of the PLA/PBS blend system,which is a simple,efficient and easy way to realize industrialization.In this paper,glycidyl methacrylate(GMA)is added as a small molecule reactive compatibilizer to the PLA/PBS blending system.In the process of mixing at 180 ?,GMA firstly generates polyfunctional polymer glycidyl methacrylate(PGMA)through thermal polymerization.The epoxy group on PGMA reacts with the end-group functional group of PLA or PBS to generate the PLA–PGMA–PBS crosslinking or branching structure,which improves the tensile strength of blends.However,GMA thermal polymerization products are complicated.With the increase of GMA,a large amount of by-products are formed during the mixing process,which act as "plasticizers".They not only reduce the strength of the material,but also compatibilize the PLA/PBS blending system.By adding 10% GMA,the elongation at break of PLA/PBS(70/30)blend was up to 465% and the tensile strength was reduced to 32 MPa.Morphological studies show that the size of PBS particles in PLA matrix is reduced,and the adhesion between the two phases is enhanced.At the same time,the addition of GMA also reduces the glass transition temperature(Tg)of PLA and PBS in the blend,and promotes the crystallization of PLA and PBS.The initiator diisopropyl peroxide(DCP)was added to the PLA/PBS/GMA blend system to produce more PGMA multi-functional polymer and improve the capacityenhancement efficiency.DCP decomposes into free radicals at high temperature.Since GMA contains double bonds and the small molecule has strong mobility,it preferentially undergoes addition polymerization to generate PGMA free radicals of a certain length.At the same time,free radicals decomposed by DCP degrade from PLA or PBS ?-hydrogen atoms are extracted from carbon atoms to generate new free radicals.The three free radicals undergo homogeneous or heterogeneous coupling reaction,and the terminal functional groups of PLA and PBS react with epoxy groups of PGMA to form more complex and large PLA–PGMA–PBS crosslinking or graft copolymer in the system,which eventually increased the strength and modulus of the blend and further improved the compatibility of the two phases.When DCP content is 0.3%,the system has the best viscoelasticity,the best interface adhesion and the best comprehensive mechanical properties.Through XRD and DSC,it was found that the cross-linked or branched structure in the system can be used as a nucleation point to promote PLA nucleation,but it greatly reduces the mobility of PLA molecular chains,which is not conducive to molecular chain rearrangement and inhibits crystal growth.In addition,the excessive crosslinking or branching structure in the system mainly inhibited PLA crystallization.