Effects of the Manufacturing Methods on the Mechanical Properties of a Medical-Grade Copolymer Poly(L-lactide-co-D,L-lactide) and Poly(L-lactide-co-ε-caprolactone) Blend.

Biocompatible and biodegradable polymers represent the future in the manufacturing of medical implantable solutions. As of today, these are generally manufactured with metallic components which cannot be naturally absorbed within the human body. This requires performing an additional surgical procedure to remove the remnants after complete rehabilitation or to leave the devices in situ indefinitely. Nevertheless, the biomaterials used for this purpose must satisfy well-defined mechanical requirements. These are difficult to ascertain at the design phase since they depend not only on their physicochemical properties but also on the specific manufacturing methods used for the target application. Therefore, this research was focused on establishing the effects of the manufacturing methods on both the mechanical properties and the thermal behavior of a medical-grade copolymer blend. Specifically, Injection and Compression Molding were considered. A Poly(L-lactide-co-D,L-lactide)/Poly(L-lactide-co-ε-caprolactone) blend was considered for this investigation, with a ratio of 50/50 (w/w), aimed at the manufacturing of implantable devices for tendon repair. Interesting results were obtained.

PLA/PHB Blends: Biocompatibilizer Effects.

The purpose of this work was to formulate a fully bio-based blend with superior properties, based on two immiscible polymers: polylactic acid (PLA) and poly-hydroxy butyrate (PHB). To improve the miscibility between the polymeric phases, two different kinds of compatibilizers with a different chemical structure were used, namely, an ethylene oxide/propylene oxide block copolymer in the form of flakes and a mixture of two liquid surfactants with a variable lipophilic-hydrophilic index. The morphology of the blends and their thermal, mechanical, and rheological behavior were evaluated, aiming at assessing the influence of the selected compatibilizers on the microstructure and final properties of the systems. Morphological analyses of the compatibilized blends indicated that the liquid surfactant is more effective than the solid copolymer in inducing morphology refinement, as also suggested by results coming from rheological measurements. Furthermore, thermal analyses demonstrated that the presence of both kinds of compatibilizers induced an enhancement of the crystallinity content of blends. Finally, a remarkable increase of the elastic modulus values was obtained for the compatibilized blends as compared to the pure counterparts, with a consequent significant enhancement of the HDT values.