Preparation Of Stereocomplex PLA And Its Modification Of Biodegradable Polymer Materials

In recent years,a variety of biodegradable polymer materials have attracted wide attention due to the increasing awareness of environmental protection.Among them,polylactic acid(PLA)is completely derived from renewable plant resources,and it captures and seals carbon dioxide in the process of plant growth,which is conducive to reducing carbon dioxide emissions.PLA shows excellent properties,such as mechanical properties,thermal properties,etc.,so it has a good sustainable development prospect.However,due to the defects of slow crystallization rate,poor flexibility,and poor hygroscopicity of PLA,its industrial production and application are limited.According to the performance characteristics and main defects of PLA,this paper poly(L-lactide)/poly(D-lactide)(PLLA/PDLA).The specific research contents and conclusions are as follows:(1)Stereocomplexable polylactide(SC-PLA)with improved thermomechanical performance had been prepared by melt compounding of PLLA/PDLA,and nanosilica.A small amount of nanosilica can be evenly dispersed in the matrix,and agglomeration occurs when the content of nanosilica is high.The introduction of nanosilica facilitated the formation of Stereocomplex.Superior storage modulus was found for SC-PLA/silica nanocomposites compared to neat SC-PLA.The tensile strength and modulus of SC-PLA nanocomposites were greatly improved by the addition of nanosilica.(2)Two kinds of polyvinyl acetate(PVAc)with different molecular weights were selected as the miscible components to prepare the PLLA/PDLA/PVAc ternary blend by melt blending.Low molecular weight PVAc increases the chain fluidity of PLA more efficiently than high molecular weight PVAc,and low molecular weight PVAc promotes crystallization,while high molecular weight PVAc hinders crystallization.The results pave the way for the design and development of high-performance SC-PLA-based blends,and facilitate the practical applications of biodegradable polymers and renewable resource technologies.(3)PBAT/SC-PLA blend system was prepared by mixing equimolar PLLA and PDLA with poly(butylene adipate-co-terephthalate)(PBAT)at appropriate temperature conditions.The SC-PLA particles were evenly dispersed in the PBAT matrix.With the increase of SC-PLA content,the blends displayed increased yield strength and modulus and decreased elongation at break and tensile strength.The SC-PLA particles could reinforce PBAT matrix.Compared with pure PBAT,the heat resistance of PBAT/SC-PLA blends were improved.