Microstructural characterization and mechanical properties of functionally graded PA12/HDPE parts by selective laser sintering

The use of selective laser sintering in the production of functional gradient materials offers advantages, as freeform construction and localized control of the composition and process parameters, compared to other rapid manufacturing processes. In this work, selective laser sintering was used for manufacturing three-dimensional parts in functionally graded polymer blends based on polyamide 12 and high-density polyethylene with gradient composition in two directions (Y and Z). Test specimens were prepared in PA12/HDPE ratios of 0/100, 20/80, 50/50, 80/20 and 100/0 (w/w). These specimens were assessed in terms of density, microstructure by scanning electron microscopy and polarized light microscopy and mechanical performance by DMA. The sintered binary blend systems with composition gradient showed microstructure and properties variation as function of the blend compositions. The results demonstrated the potential of selective laser sintering to manufacture advanced polymeric functional gradient material parts.Covenant Brazil‐Portugal supported by CAPES (Brazil) and FCT (Portugal). FAPESC, CNPq and FINEP (Brazil

Thermomechanical and in vitro biological characterization of injection-molded PLGA craniofacial plates

Purpose: To evaluate the thermomechanical and in vitro biological response of poly(lactic-co-glycolic acid) (PLGA) plates for craniofacial reconstructive surgery. Methods: PLGA 85/15 craniofacial plates were produced by injection molding by testing two different temperatures (i.e., 240°C, PLGA_lowT, and 280°C, PLGA_highT). The mechanical properties of the produced plates were characterized by three-point bending tests, dynamic mechanical analysis, and residual stress. Crystallinity and thermal transitions were investigated by differential scanning calorimetry. Finally, in vitro cell interaction was evaluated by using SAOS-2 as cell model. Indirect cytotoxicity tests (ISO 10-993) were performed to prove the absence of cytotoxic release. Cells were then directly seeded on the plates and their viability, morphology, and functionality (ALP) checked up to 21 days of culture. Results: A similar performance of PLGA_lowT and PLGA_highT plates was verified in the three-point bending test and dynamic mechanical analyses. Also, the two processing temperatures did not influence the in vitro cell interaction. Cytotoxicity and ALP activity were similar for the PLGA plates and control. Cell results demonstrated that the PLGA plates supported cell attachment and proliferation. Furthermore, energy-dispersive X-ray spectroscopy revealed the presence of sub-micron particles, which were identified as inorganic mineral deposits resulting from osteoblast activity. Conclusion: The present work demonstrated that the selected processing temperatures did not affect the material performance. PLGA plates showed good mechanical properties for application in craniofacial reconstructive surgery and adequate biological properties