The aim of this study has been to fabricate a hybrid electrospun nanofibrous scaffold composed of poly(lactic-co-glycolic) acid (PLGA)/fibrin polymers to be used as a skin substitute and analyze its physical and biological properties. Fibrin was obtained from rat blood plasma, characterized and solubilized in formic acid. The final electrospinning solution concentration was 40% PLGA (w/v) and 1% fibrin (w/v). To improve spinnability, 3% PEG (w/v) was added. The scaffolds were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Water contact angle, maximum elongation, thermal stability, degree of swelling, blood compatibility, cytotoxicity and cell viability were analyzed. The characterization by SEM showed randomly oriented nanofibers with a mean diameter of 639.8 ± 241.8 nm for the PLGA/fibrin and 1051.0 ± 290.2 nm for the PLGA. FTIR spectra confirmed the presence of fibrin in the mats. Fibrin incorporation reduced the water contact angle from 118.9 ± 2.9 to 111.1 ± 2.8. The fibrin increased tensile strength and decreased elongation at break. The scaffolds demonstrated blood compatibility and fibrin incorporation improved cell adhesion and viability when direct and indirect MTT analyses were carried out. Thus, it can be concluded that the PLGA/fibrin mat is a promising material for use as a skin substitute.
Accidents involving fire occur every day around the world, affecting thousands of people and causing economic losses. Some accidents are caused by steel structure failures, which experience a significant reduction in mechanical properties at temperatures of 400-550˚C. Therefore, fire protective coatings are required for steel structures and interest in the development of intumescent coatings has increased considerably. In this study, black wattle tannin was used as a carbon source in the formulation of intumescent coatings. Concentrations of 5% and 10% of tannin were incorporated into a novolac resin. The coating was applied on a steel plate and the thermal protection was evaluated by sample exposure to a flame for 30 min. The results showed that the tannin compound could be used as a carbon source for intumescent coatings. The temperature of the samples containing 10% of this compound was almost 300 ˚C lower compared to the uncoated steel plate.
Abstract:In recent years, the consumption of plastics has been increasing and as consequence, the waste generated has also increased. Rubber tire (RT) waste is another residue which causes significant problems to society. In view of the considerable amounts of RT waste generated, this study aimed to evaluate the influence of the incorporation of RT particles into post-consumer thermoplastic matrices such as polypropylene (PP), high impact polystyrene (HIPS) and PP/HIPS blends and the modification of the physical, morphological, rheological and mechanical properties. The particle sizes of the RT used were <500 and 500-1000 µm. The RT content was 10% w/w and the weight ratio for the PP/HIPS blend was 4/1, with processing by injection molding. The results showed that the smaller (500 µm) particle size led to a decrease in the melt flow rate (MFR) of the PP/RT composites (increased viscosity) and an increase for the HIPS/RT composites. On the other hand, the larger particles (1000 µm) led to a decrease in the mechanical performance of the PP/RT and HIPS/RT blends when compared with the neat polymers (PP and HIPS post-consumer). The observed decrease in the mechanical properties of these composites was due to weak filler/matrix interactions, which can be visualized in images by scanning electron microscopy (SEM) of the fracture surface after tensile testing.
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