聚乳酸的合成与性能研究

以乳酸单体为原料，采用直接缩聚法合成了具有较高粘均分子质量的聚乳酸，用红外光谱、H—NMR等方法初步表征了聚乳酸的结构。研究了聚乳酸的亲水性和降解性。结果表明，聚乳酸的水接触角和吸水率分别为79．30和2．8％，说明聚乳酸具有一定的亲水性。聚乳酸在降解过程中表现为体型降解特点。粘均分子量和降解温度对聚乳酸的降解规律影响不大，但低分子量聚乳酸及聚乳酸在较高降解温度下的降解程度和初期降解速率明显大于高分子量聚乳酸及较低降解温度。本文还研究了聚乳酸粘均分子量在降解过程中的变化情况。

Study on the Synthesis and Properties of Polylactic Acid

In this paper, polylactic acid （PLA） with high viscosity--average relative molecular mass was synthesized by direct melt polyeondensation of lactic acid, and its characterization was studied by FT IR and H--NMIL The hydrophilieity and degradation of PLA were also studied. Results show that the static water contact angle of PLA is 79. 3° and its water absorption ratio is 2. 8%, indicating that PLA has the hydrophilicity to a certain extent. The degradation of PLA is the most serious auto--accelerating degradation. The influence of viscosity--average relative molecular mass and degradation temperature on the degradation of PLA are not clear, but the degradation extent and degradation speed on early days of PLA with lower viscosity-average relative molecular mass and on higher degradation temperature are clearly better than that of higher viscosity-average relative molecular mass and on lower degradation temperature. The Changes of the viscosity average molecular weight with degradation time for PLA were also studied in this paper.