Unique Role of Graphite Nanoplatelets in Upgrading Biodegradable Polymer Systems

Application of high-aspect-ratio nanofillers in polymer blends is an important tool to upgrade polymeric materials. This work deals with complex effect of graphite nanoplatelets (GNP) on performance of biodegradable biocompatible poly (e-caprolactone) (PCL)/ poly (lactic acid) (PLA) blend, related microfibrillar composite (MFC) with GNP-aided in-situ PLA microfibril reinforcement, and unique melt spun fibers. In dependence on blend ratio, both synergistic and antagonistic effects of GNP on properties may occur. The former effect consists in structure refinement and formation of effective rigid/soft morphology, whereas the latter originates in strong effect of GNP on continuity of polymeric components with quite dissimilar properties. As a result, GNP-increased continuity of mechanically weak PCL at the expense of rigid strong PLA may eliminate reinforcing effect of GNP. GNP only allow preparation MFC with fair properties due to enhanced stability of extrusion and improved melt-drawing. The strong effect of GNP on elongational viscosity aids melt spinning of biocompatible fibers with wide range of properties and diameters. Complex effect of GNP allows preparation of biocompatible materials with enhanced balanced properties including melt-drawing based MFC and fibers, which is impossible in unmodified system.