聚乳酸与碳酸钙复合物的制备及碳酸钙的降解抑制作用

Preparation of the PLA/CaCO3 Composites and the Retardation Effect of the CaCO3 on the Hydrolytic Degradation of the PLA in the Composites

摘要: 采用熔融共混法，将聚乳酸(PLA)与碳酸钙(CaCO3)(2%、5%和7%)复合制备聚乳酸/碳酸钙复合物。通过复合物和纯PLA在磷酸盐缓冲溶液中浸泡后，不同碳酸钙含量的复合物复合前后PLA发生粘度变化，研究CaCO3对PLA/CaCO3复合物中PLA降解的抑制作用，并提出抑制机理。PLA/CaCO3复合物的力学性能和耐水性能的结果表明，添加一定量CaCO3的复合材料的拉伸强度、断裂伸长率、弹性模量和最大负荷明显增强。通过吸水率的测定，表明吸水率值随着CaCO3含量(2%和5%)的不同变化不大，而当含量增加到7%时，吸水率增大较多。随着吸水实验介质的不同，在磷酸盐缓冲溶液中浸泡的吸水率略高于在蒸馏水中浸泡的吸水率。

Abstract: The poly (lactic acid) (PLA)/CaCO3 composites were prepared via melt blending in an intensive mixer of the torque rheometer. Hydrolytic degradation of the composites obtained was investigated comparatively with the pure PLA matrix. The hydrolytic degradation was carried out by immersing the film samples in phosphate buffer saline (pH = 7.4) at 37˚C, and the viscosity of the PLA in the degraded films was measured. The results indicated that the hydrolytic degradation of the PLA matrix in the composites was retarded as a result of the incorporation of the basic CaCO3 which would react with the partial end-carboxyl groups of the PLA matrix. It was showed that the tensile strength, elastic modulus, elongation at break and maximum load of the composites were enhanced significantly. Also it was found that the water absorption of the PLA/CaCO3 composites at low CaCO3 loading (2% and 5%) slightly increased compared with the pure PLA upon immersion for 4 weeks, while the PLA/CaCO3-7 composite had a much higher water absorption (5.5% - 6.0%) than the pure PLA in two immersion mediums. All composites exhibited slightly higher water resistance in the distilled water than in the phosphate buffer solution at pH = 7.4.