聚乳酸/聚丁二酸丁二酯扩链改性材料研究

Study on Polylactic Acid/Polybutylene Succinate Extended Chain Modification Materials

以左旋乳酸(L–LA)为原料合成聚左旋乳酸(PLLA),再与及聚丁二酸丁二酯(PBS)共混,通过使用高效的反应型扩链剂2,2'–(1,3–亚苯基)–二恶唑啉(PBO)和4,4'–二苯基甲烷二异氰酸酯(MDI)合成新的嵌段聚合物。第一步利用PBO易与羧基反应而对脂肪醇呈惰性的特点,生成端基多为羟基的共混体系,并用酸值滴定法验证了PBO对羧基的反应选择性;第二步再加入易与羟基反应的MDI,使得分子链进一步增长,并且提高两相相容性。对产物分别进行了核磁共振谱、傅里叶变换红外光谱、扫描电子显微镜、差示扫描量热、热重分析、熔体流动速率及力学性能测试。结果表明,反应生成了酰胺基团,并验证了PBO对羧基的反应选择性,通过增容扩链,改善了PLLA/PBS的相容性、加工流动性和热稳定性。随着PBO和MDI加入量的增加,材料的拉伸强度和断裂伸长率呈先增大后减小的趋势,且冲击强度显著提高,改变了材料的脆性特征。

Poly-L-lactic acid(PLLA)was synthesized using L-lactic acid(L–LA)as raw materials.Then new block polymers were synthesized by adding highly efficient reactive chain extenders 2,2'–(1,3-phenylene)-dioxazoline(PBO)and 4,4'-diphenylmethane diisocyanate(MDI)into PLLA/polybutylene succinate(PBS)blend.In the first step,the blend system in which the terminal group was mostly hydroxyl was produced by using PBO's characteristics that it was easy to react with carboxyl groups and inert to fatty alcohols,and the selectivity of PBO to carboxyl groups was verified by acid titration.The second step was to add MDI that was easy to react with hydroxyl groups,which caused the molecular chain growing further and improving the compatibility of the two phases.The products were subjected to nuclear magnetic resonance spectroscopy,Fourier transform infrared spectroscopy,scanning electron microscopy,differential scanning calorimetry,thermogravimetric analysis,melt index test and mechanical testing.The experimental data showed that the reaction formed an amide group and verified the selectivity of PBO to the carboxyl group.The compatibilization,processing fluidity and thermal stability of PLLA/PBS were improved by compatibilization and chain extension.With the increase of PBO and MDI content,the tensile strength and elongation at break of the material increased first and then decreased,and the impact strength was significantly improved,which changes the brittleness characteristics of the material.