Processing, mechanical property development and in vitro hydrolytic degradation studies of a poly(L-lactide-co-ε-caprolactone) monofilament fibre for potential use as an absorbable surgical suture

Abstract

The bulk ring-opening copolymerisation of L-lactide (LL) and e-caprolactone (CL) with an initial comonomer feed ratio of LL:CL = 75:25 mol % was carried out using stannous acetate as the initiator at 120 °C for 48 hrs. The copolymer was characterised by GPC, DSC and TGA. Due to its ability to biodegrade in the human body, this type of copolymer has potential for use as an absorbable surgical suture. The copolymer obtained was melt spun at 153 °C using a small-scale melt-spinning apparatus and extruded into ice-cooled water to produce an as-spun monofilament fibre which was largely if not completely amorphous. Alternate off-line hot-drawing and annealing (3 cycles) was carried out in order to develop the fibre's oriented semi-crystalline morphology. To complete the processing operation, thermal treatment was necessary to stabilize the fibre morphology. It was found that fixed annealing at 60 °C followed by free annealing at 60 °C stabilized the fibre morphology as a result of molecular relaxation. In vitro hydrolytic degradation studied in a phosphate buffer saline (PBS) solution of pH 7.4 at 37.0 ± 0.1 °C indicated that, after 6 weeks immersion in the buffer, the fibre's tensile strength decreased by approximately 50% whereas a commercial 'PDS' suture of similar size lost its strength completely after only 4 weeks. © 2008 Trans Tech Publications, Switzerland.