The influence of low shear microbore extrusion on the properties of high molecular weight poly(l-lactic acid) for medical tubing applications.

Abstract

Biodegradable polymers play a crucial role in the medical device field, with a broad range of applications such as suturing, drug delivery, tissue engineering, sca olding, 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 (Mn = 7–18%) during processing, with a further loss (Mn 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 di erences in molecular weight between both batches had no e ect on the materials thermal or morphological properties. However, it did a ect its mechanical properties, with a significant impact on tensile strength and modulus. Interestingly there was no e ect on the elongational proprieties of the tubing. There was also an observed temperature-dependence of mechanical properties below the glass transition temperature.