Fernando Leite

Biodegradable polymer composites are promising materials for orthopaedic applications because their lower stiffness compared with metallic implants may reduce stress shielding effects. In this study, PLA-based composites containing PEG (0–14 wt%) and flax fiber (5–10 wt%) were fabricated by compression moulding using untreated and pretreated flax fibers, with potential application in orthopaedic fixation plates. The composites were analysed by Scanning Electron Microscopy (SEM), Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC), and their tensile, flexural and impact properties were evaluated. The tensile and flexural strength and modulus of composites were improved by approximately 20–30%. SEM results showed that fiber-matrix adhesion was greater than fiber pull-out for the fibers in the fiber-treated samples compared with those containing untreated fibers. Increasing PEG content, the strength and stiffness decreased, and impact toughness increased, particularly for the intermediate-PEG formulations (S3, S4). Similar thermal stability across formulations (TGA) suggested that the effects of treatment and PEG were not influenced on thermal characteristics, but on interfacial and mechanical properties. DSC results indicated that the effects of treatment were surface-limited and not bulk. Thus, the interfacial strength was controlled by fiber treatment, and the stiffness–toughness trade-off was controlled by PEG showing that moderate PEG (S3, S4) treatment was ideal for the mechanical properties of biodegradable orthopaedic fixation.

This study investigates the development and performance of polyolefin-based packaging materials reinforced with industrial mineral residues, specifically slate powder (SP) and bivalve shell powder (BSP). High-density polyethylene (HDPE) and polypropylene (PP) matrices were compounded with these fillers and processed by extrusion blow moulding to produce final prototypes. Thermal analyses (TGA and DSC) showed that incorporating SP and BSP does not compromise the thermal stability of the polymer matrices and increases stiffness in the filled formulations. Accelerated ageing (QUV, 200 h) revealed distinct photo-oxidative behaviours. PP and PP + BSP (30%) exhibited increased fragility and moderate colour changes, whereas PP + SP (10%) retained flexibility, indicating a partial protective effect of SP. HDPE-based formulations showed higher intrinsic UV resistance, with HDPE + BSP (30%) displaying excellent colour stability. Tensile tests before and after QUV exposure confirmed that fillers increase stiffness with limited influence on tensile strength. Air permeability results indicated that neat PP and HDPE were below the detection limit. At the same time, filled formulations exhibited measurable permeability, suggesting that filler incorporation may influence gas transport through interfacial effects. Overall, the results show that SP and BSP act as reinforcing additives and can modify functional properties such as stiffness and ageing resistance. However, their influence on barrier performance depends on the formulation and permeation mechanism.

Due to the increase in the global terrorist threat, there has been a growing demand for materials that can more efficiently protect civil, industrial, and military structures against explosions. In this sense, two new commercial polyureas (A and B), that present high potential to be used as a protective coating on building facades against explosions, were compared in this work, through several tests. Chemical characterization with the Scanning Electron Microscope (SEM) of the surface of the polyureas revealed that the commercial polyurea A has a heterogeneous surface while the other polyurea has a more uniform and homogeneous surface, resulting in a more compact structure. The shock-wave attenuation ability of polyurea is believed to be controlled primarily by the hard domains. The TGA tests revealed that polyurea B has more hard segments than polyurea A in its composition. The mechanical tests performed showed that polyurea B has significantly better tensile properties-almost 3000% of maximum deformation capacity compared with approximately 115% of polyurea A. Thus, it was concluded that polyurea B has more potential to be used as a coating in building blast protection due to its exceptional elongation characteristics, a critical parameter to absorb the high frequency and intensity of blasts.