Enhancement of Mechanical Properties of FDM-PLA Parts via Thermal Annealing

The objective of this study is to investigate the possibility of enhancing mechanical properties of poly(lactic acid) (PLA) samples processed by a rapid manufacturing (RM) technique by increasing PLA crystallinity degree via thermal annealing. The samples are manufactured by fused deposition modeling (FDM) at different temperatures and subsequently evaluated by three-point bending flexural and tensile tests. The polymer processed at 215 degrees C is thermally annealed over its glass transition temperature in order to increase the degree of crystallinity to the maximum attainable level as measured by the differential scanning calorimetry and confirmed by X-ray diffraction. The increase in the degree of crystallinity of FDM-PLA enhances flexural stress of the samples by 11-17%. The study also demonstrates applicability of radiation sterilization for FDM-PLA parts. Therefore, thermal annealing might be introduced into a standard RM technology of PLA, particularly for sterilizable customized implants, to efficiently improve their mechanical properties.