Melt/Solid State Polycondensation Of PLLA

In this paper, PLA with high molecular weight is synthesized by melt polycondensation and melt-solid state polycondensation, respectively. The structure and properties of condensation and polymerization product were characterized by fourier infrared spectrum (FTIR),1H nuclear magnetic resonance (1H-NMR), viscosity measurements, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC).First, PLLA with high molecular weight was synthesized by direct melt polycondensation which starting from lactic acid as monomer using composite catalyst. Through the design of orthogonal experiment, PLLA molecular weight of each factor influence on the size of the temperature> pressure> Time> catalyst. The optimum reaction condition was obtained by verifying the othogonal experiment. The product has some fibrillary and film-forming ability.Secondly, starting from PLLA synthesized by direct melt polycondensation, PLLA with higher molecular weight was obtained via further solid-state polymerization (SSP) with different temperature controlling. The Mw of PLLA is 426,000, which is 36 times higher than that of PLLA first prepared by melt polycondensation. Using rotary evaporator as the reactor, increasing the feeding amout. Under the experimental condition, PLLA was produced by SSP which Mw is 200,000, Preparation of high molecular weight polylactic acid provides a viable direction for its amplification test and industrial production.Moreover, the influence of nano-particles in solid state polycondenstion was explored for the first time. The results showed that addition of nanoparticles improve the cole crystallization temperature of pre-polymer and promote solid state polycondensation reaction. Under the experimental conditions (SiO2 content of 0.25 wt%, catalyst content of 0.4 wt%, SSP for 20h), the molecular weight (Mw) of PLLA is 179,000, which is higher than that of pure PLLA.