Component Analysis Of The Products In The Process Of PLA Synthesis

Poly-Lactic Acid (short for PLA) is one kind of polymer materials that have good biological compatibility and degradability. There are two ways to synthesize PLA, one is the direct condensation polymerization by lactic acid monomer; and the other is ring-opening polymerization by lactide, which is synthesized by lactic acid first. The latter is more widely used at present. Different products in the whole procese, such as lactide, hydrolysate and PLA were analyzed in this paper. It helps to optimize PLA producing techniques. The main works and conclusions are as follows:①The synthesizing process of PLA was introduced in the chapter one. Theory of each Analyzing method for the different products was recommended in the chapter two, which emphasized on determination of molar mass and its distribution of PLA. The main purpose and significance of this paper was presented at last.②Non-aqueous titration and Karl·Fischer titration were used respectively to determine the contents of lactic acid and water in the crude lactide and the hydrolysate which was produced in the synthesis period of lactide. It was studied that effects of the solvent and the indicator on the results, and the accuracy and precision of these methods. It shows these methods are accurate and convenient to be used for the products determination.③Lactide of high purity is very important to prepare PLA of high molar mass. Capillary column gas chromatography was used to quantitative determination of crude lactide. Effects of the carry gas and the injector on the results were studied in this paper. It shows this method is accurate and fast to measure purity of the crude lactide.④A multi-angle laser light scattering instrument coupled with size exclusion chromatography and refractive index detector were used to determine molar mass and distribution of PLA. It studied effects of the factors as injecting bulk, sample concentration, temperature, flow rate and purity of solvent on the determination. Compared with standard polystyrene, configuration of PLA was studied. It shows that the method is accurate and convenient to measure molar mass and distribution of PLA.