Dillon Brian, Doran Patrick, Fuenmayor Evert, Healy Andrew V, Gately Noel M, Major Ian, Lyons John G
Materials Research Institute, Athlone Institute of Technology, Dublin Road, Bunnavally, Athlone and Co. Westmeath, Ireland.
Faculty of Engineering and Informatics, Athlone Institute of Technology, Dublin Road, Bunnavally, Athlone, Co. Westmeath, Ireland.
Polymers (Basel). 2019 Apr 18;11(4):710. doi: 10.3390/polym11040710.
Biodegradable polymers play a crucial role in the medical device field, with a broad range of applications such as suturing, drug delivery, tissue engineering, scaffolding, orthopaedics, and fixation devices. Poly-l-lactic acid (PLLA) is one of the most commonly used and investigated biodegradable polymers. The objective of this study was to determine the influence low shear microbore extrusion exerts on the properties of high molecular weight PLLA for medical tubing applications. Results showed that even at low shear rates there was a considerable reduction in molecular weight (M = 7-18%) during processing, with a further loss (M 11%) associated with resin drying. An increase in melt residence time from ~4 mins to ~6 mins, translated into a 12% greater reduction in molecular weight. The degradation mechanism was determined to be thermal and resulted in a ~22-fold increase in residual monomer. The differences in molecular weight between both batches had no effect on the materials thermal or morphological properties. However, it did affect its mechanical properties, with a significant impact on tensile strength and modulus. Interestingly there was no effect on the elongational proprieties of the tubing. There was also an observed temperature-dependence of mechanical properties below the glass transition temperature.
可生物降解聚合物在医疗器械领域发挥着至关重要的作用，具有广泛的应用，如缝合、药物递送、组织工程、支架、骨科和固定装置。聚左旋乳酸（PLLA）是最常用和研究最多的可生物降解聚合物之一。本研究的目的是确定低剪切微孔挤出对用于医用管材的高分子量PLLA性能的影响。结果表明，即使在低剪切速率下，加工过程中分子量也有相当大的降低（M = 7 - 18%），树脂干燥还会导致进一步的损失（M 11%）。熔体停留时间从约4分钟增加到约6分钟，分子量降低幅度增加了12%。降解机制确定为热降解，导致残留单体增加约22倍。两批材料之间的分子量差异对材料的热性能或形态性能没有影响。然而，它确实影响了其机械性能，对拉伸强度和模量有显著影响。有趣的是，对管材的拉伸性能没有影响。在玻璃化转变温度以下还观察到机械性能的温度依赖性。
