Mechanical and hydrolytic properties of thin polylactic acid films by fused filament fabrication

Abstract

Thin polymeric films are widely used as medical applications such as cell culture, stent, drug delivery and mechanical fixation. One of the most commonly used materials is polylactic acid (PLA) - a material, which is non-toxic, biodegradable and biocompatible. Fused filament fabrication (FFF) is a preferable additive manufacturing technique to manufacture polymers, where PLA is one of the most common materials. FFF is a promising technique for customised biomedical applications due to its relatively low cost and geometrical flexibility where biomedical applications are patient tailored. This study is the first to consider FFF monolayered thin films of PLA in terms of mechanical and hydrolytic properties at 37 °C in vitro degradation. Throughout degradation, the reduction in mechanical properties was examined by analysing molecular weight and thermal properties. FFF monolayered PLA underwent autocatalytic bulk degradation with no proof of significant mass loss. Young's modulus, ultimate tensile strength and molecular weight reduced by approximately 60%, 86%, and 80% after 280 days, respectively, while the degree of crystallinity increased by 143% in comparison to benchmark thin films at day 0. It was found that the decrease in mechanical properties was more sensitive to the increase in crystallinity in the early stage of the degradation, while the molecular weight was more dominant in the late stage of the degradation. This study provides practical information in terms of mechanical properties to support medical device designers in a range of potential end-use biomedical applications to achieve safe functional products over the required degradation lifetime.

Keywords: Additive manufacturing; Fused filament fabrication; Hydrolytic degradation; Mechanical properties; Monolayered thin film; Polylactic acid.