Alexandre Portela

Compatibilizers that enhance sustainability and improve the miscibility of polymer blend components have garnered significant attention. This study investigates the difference between the synthetic chain extender Joncryl^® ADR 4468 and the natural epoxidized linseed oil (ELO) Merginat 8510100 as compatibilizers for thermoplastic starch/poly (butylene succinate) (TPS/PBS) blends. Blends containing 40% TPS and 60% PBS were prepared with 1, 3, and 5 phr of each compatibilizer, along with a reference with no additives. The properties of these blends were evaluated using tensile testing, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), rheology, and scanning electron microscopy (SEM). The findings indicate that while Joncryl^® ADR 4468 significantly improved tensile strength, it also resulted in a brittle fracture. In contrast, ELO batches exhibited greater ductility, albeit with lower tensile strength. These differences are attributed to the chain extension and minor cross-linking effects of Joncryl^® ADR 4468, compared to the increased chain mobility arising from ELO’s plasticizing and compatibilizing actions. Supporting evidence for these observations includes increased cold crystallization temperature (T_cc) and melting temperature (T_m), greater storage modulus along with higher complex viscosity, strengthened interfacial adhesion, and fewer morphological defects in Joncryl^® ADR 4468 blends. These results highlight the importance of selecting an appropriate compatibilizer based on specific application requirements. Overall, this study addresses the knowledge gap regarding the loadings of Joncryl^® ADR 4468 and ELO in TPS/PBS blends and provides a basis for further optimization strategies, such as the incorporation of binary compatibilizers, alternative grafting-based compatibilizers, and twin-screw blending modifications.

Poly(L-lactic acid) (PLLA) and iron (Fe) are popular bioresorbable material candidates for biomedical implants. However, PLLA coronary stents are relatively too thick compared to metallic stents when providing the same mechanical strength, while iron degrades too slowly. Recent studies show that PLLA coatings can enhance iron’s corrosion rate, and iron has strong mechanical strength, making PLLA–Fe composites ideal for bioresorbable implants. Although PLLA coatings on iron samples have been studied, research on embedding iron wires in relatively thick PLLA matrices is limited. Moreover, no studies have yet explored 3D-printed metal wire-reinforced PLLA monofilaments for biomedical applications. To address these research gaps and investigate the in vitro degradation profile of PLLA/Fe wire monofilaments for bioresorbable stents, this study first developed a novel polymer filament–metal wire coextrusion 3D printer for printing PLLA/Fe wire monofilaments. In vitro degradation tests were then conducted on both PLLA/Fe and neat PLLA monofilaments at 50 °C. Thereafter, characterizations, including mass loss, pH, surface appearance and morphology, tensile tests, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC), were performed. Results indicated that the overall degradation rate of PLLA/Fe monofilaments was higher than that of PLLA counterparts, while the degradation rate of PLLA matrix was not affected by the embedded iron wire according to molecular weight analysis. Notably, the Young’s modulus and stiffness of PLLA monofilaments were significantly improved by the iron wires during the early stages of degradation, but the reinforcement in tensile strength was negative after immersion due to the poor embedding quality of the iron wires in the PLLA monofilaments. With future improvement of the embedding quality of iron wire, the 3D-printed PLLA/Fe wire composites can have great potential in the development of biomedical devices using the novel 3D printing method, including most types of stents and bone scaffolds.

The immiscibility of thermoplastic starch (TPS) and polybutylene succinate (PBS) complicates the thermal processing of these materials. This study provides the first comparative assessment of two compatibilizers with differing reaction mechanisms, Joncryl^® ADR 4468 and epoxidized linseed oil (ELO), for the optimization of biobased TPS/PBS blends. A total of 13 batches, varying in compatibilizer and blend composition, were processed via hot melt extrusion and injection molding to produce pellets. Blends were analyzed using tensile and impact testing, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), rheology, and scanning electron microscopy (SEM). The findings suggest that both compatibilizers can improve the compatibility of these blends, as evidenced by higher glass transition temperatures (T_g) compared to the reference batch (100-0-N/A). Joncryl^® ADR 4468 batches exhibit superior tensile strength and Young’s moduli, while ELO batches demonstrate greater elongation at break. The enhanced processability observed in Joncryl^® ADR 4468 is attributed to the increased polymer chain entanglement and molecular weight, whereas ELO facilitates greater chain mobility due to its plasticizing effect. These differences arise from the distinct mechanisms of action: Joncryl^® ADR 4468 promotes chain extension and crosslinking, whereas ELO mainly enhances flexibility through plasticization. Overall, this study provides a comparative assessment of these compatibilizers in TPS/PBS blends, laying the groundwork for future investigations into optimizing compatibilizer concentration and blend composition.

Using 3D-printed (3DPd) polymers and their composites as shape memory materials in various smart engineering applications has raised the demand for such functionally graded sustainable materials. This study aims to investigate the viscoelastic, shape memory, and fracture toughness properties of the epoxy-based ultraviolet (UV)-curable resin. A UV-based DLP (Digital Light Processing) printer was employed for the 3D printing (3DPg) epoxy-based structures. The effect of the hydrothermal accelerated ageing on the various properties of the 3DPd components was examined. The viscoelastic performance in terms of glass transition temperature (T_g), storage modulus, and loss modulus was evaluated. The shape memory polymer (SMP) performance with respect to shape recovery and shape fixity (programming the shape) were calculated through dynamic mechanical thermal analysis (DMTA). DMTA is used to reveal the molecular mobility performance through three different regions, i.e., glass region, glass transition region, and rubbery region. The shape-changing region (within the glass transition region) between the T_g value from the loss modulus and the T_g value from the tan(δ) was analysed. The temperature memory behaviour was investigated for flat and circular 3DPd structures to achieve sequential deployment. The critical stress intensity factor values of the single-edge notch bending (SENB) specimens have been explored for different crack inclination angles to investigate mode I (opening) and mixed-mode I/III (opening and tearing) fracture toughness. This study can contribute to the development of highly complex shape memory 3DPd structures that can be reshaped several times with large deformation.

The use of 3D printed polymers and their composites as shape memory materials in various smart engineering applications has raised the demand for such functionally graded sustainable materials. This study aims to investigate the viscoelastic, shape memory, and fracture toughness properties of the epoxy-based ultraviolet (UV)-curable resin. A UV-based DLP (Digital Light Processing) printer was employed for the 3D printing (3DPg) epoxy-based structures. The effect of the hydrothermal accelerating ageing on the various properties of the 3D printed (3DPd) components was examined. The viscoelastic performance in terms of storage modulus, loss modulus, and glass transition temperature (Tg) was evaluated. The shape memory behaviour in terms of shape fixity and shape recovery results were determined using dynamic mechanical thermal analysis (DMTA). DMTA is used to reveal the molecular mobility performance through three different regions, i.e., glass region, glass transition region, and rubbery region. The shape-changing region (Within the glass transition region) between the Tg value from the loss modulus and the Tg value from the tan delta was analysed. The temperature-memory behaviour was investigated for flat and circular 3DPd structures to achieve sequential deployment. The critical stress intensity factor values of the single-edge notch bending (SENB) specimens have been explored for different crack inclination angles to investigate mode I (opening) and mixed-mode I/III (Opening and tearing) fracture toughness. This investigation study can be employed to create highly complex shape memory 3DPd durable structures that can be reconfigured multiple times under large deformation.

This study explores the use of vat polymerization stereolithography (SLA) for fabricating mold tooling, subsequently utilized in injection molding (IM) and overmolding of tensile specimens and directly compared to those produced using metal molds. The results first find the manufacturing time for an SLA‐fabricated mold is remarkably short, approximately 6 h, presenting a substantial improvement over traditional methods. Mechanical testing revealed that the tensile specimens from the SLA‐fabricated molds exhibited the highest tensile strength among all overmolding batches. This performance was consistent with the tensile bars produced using metal molds, demonstrating the viability of SLA‐fabricated molds for overmolding applications and highlighting the potential of FDM to customize the properties of final products. However, variations in mold types impacted the dimensional tolerance and tensile strength of the final specimens. Metal mold‐fabricated tensile bars exhibited superior dimensional accuracy and maximum tensile strength (50.6–61.7 MPa) compared to those produced with SLA‐fabricated molds (46.9–55.9 MPa). These differences are attributed to the rougher surface finish inherent to the layer‐by‐layer construction of SLA and the internal stresses and defects resulting from lower thermal conductivity and uneven cooling. In conclusion, this study underscores the promising future applications of SLA‐fabricated molds in overmolding, offering reduced manufacturing costs and enhanced design freedom. The findings support the potential of SLA to revolutionize mold fabrication, thereby extending its utility and optimizing the production of polymer components with customized properties. Highlights: SLA molds compared to metal molds for direct injection molding and overmolding. FFF preforms with varied geometries were overmolded to finalize the specimens. Joint configurations in overmolding improved tensile performance. Overmolding showed better dimensional accuracy than FFF specimens. SLA mold preparation significantly reduced manufacturing costs.

Bone has the ability to heal itself; however, bone defects fail to heal once the damage exceeds a critical size. Bone regeneration remains a significant clinical challenge, with autograft considered the ideal bone graft material due to its sufficient porosity, osteogenic cells, and biological growth factors. However, limitations to bone grafting, such as limited bone stock and high resorption rates, have led to a great deal of research into developing bone graft substitutes. The P28 peptide is a small molecule bioactive biomimetic alternative to mimic the bone morphogenetic protein 2 (BMP-2). In this study, we investigated the potential of P28-loaded hybrid scaffolds to mimic the natural bone structure for enhancing the bone regeneration process. We hypothesized that the peptide-loaded scaffolds and nude scaffolds both have the potential to promote bone healing, and the bone healing process is accelerated by the release of the peptide. To verify our hypothesis, C2C12 cells were evaluated for the presence of calcium deposits by histological stain at 7 and 14 days in cultures with hybrid scaffolds. Total RNA was isolated from C2C12 cells cultured with hybrid scaffolds for 7 and 14 days to assess osteoblast differentiation. The project findings demonstrated that the hybrid scaffold could enhance osteoblast differentiation and significantly improve the therapeutic effects of the scaffold in bone regeneration.