Flame-resistant materials are key components in buildings and several other engineering applications. In this study, flame retardancy and thermal stability were conferred to a highly flammable technical thermoplastic—polypropylene (PP)—upon compositing with a carbonaceous tannin-based particulate (CTP). Herein, we report on a straightforward, facile, and green approach to prepare self-extinguishing thermoplastic composites by thermoblending highly recalcitrant particulate. The thermal stability and mechanical properties of the composites are tethered to the CTP content. We demonstrate that the addition of up to 65 wt% of CTP improved the viscoelastic properties and hydrophobicity of the PP, whereas having marginal effects on bulk water interactions. Most importantly, compositing with CTP remarkably improved the thermal stability of the composites, especially over 300 °C, which is an important threshold associated with the combustion of volatiles. PP-CTP composites demonstrated great capacity to limit and stop fire propagation. Therefore, we offer an innovative route towards thermally resistant and self-extinguishing PP composites, which is enabled by sustainable tannin-based flame retardants capable of further broadening the technical range of commodity polyolefins to high temperature scenarios.

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Aerogels are 3-D nanostructures of non-fluid colloidal interconnected porous networks consisting of loosely packed bonded particles that are expanded throughout their volume by gas and exhibit ultra-low density and high specific surface area. Cellulose-based aerogels can be obtained from hydrogels through a drying process, replacing the solvent (water) with air and keeping the pristine three-dimensional arrangement. In this work, hybrid cellulose-based aerogels were produced and their potential for use as dressings was assessed. Nanofibrilated cellulose (NFC) hydrogels were produced by a co-grinding process in a stone micronizer using a kraft cellulosic pulp and a phenolic extract from Maclura tinctoria (Tajuva) heartwood. NFC-based aerogels were produced by freeze followed by lyophilization, in a way that the Tajuva extract acted as a functionalizing agent. The obtained aerogels showed high porosity (ranging from 97% to 99%) and low density (ranging from 0.025 to 0.040 g·cm−3), as well a typical network and sheet-like structure with 100 to 300 μm pores, which yielded compressive strengths ranging from 60 to 340 kPa. The reached antibacterial and antioxidant activities, percentage of inhibitions and water uptakes suggest that the aerogels can be used as fluid absorbers. Additionally, the immobilization of the Tajuva extract indicates the potential for dentistry applications.

The objective of this study was to evaluate a two-step Pinus elliottii modification process comprising thermal treatment at different temperatures (180 °C, 200 °C, or 220 °C) for 2 h followed by vacuum-pressure treatment and in situ polymerization with a highly pure solution of poly (methyl methacrylate) (PMMA). The treated samples were then characterized based on weight loss, weight gain, density, Fourier transform infrared spectroscopy, chemical constituents, thermal stability, dimensional stability, surface hydrophobicity, morphology, color changes, and mechanical properties. Thermal modification prior to impregnation increased thermal stability (~100%-150%) in comparison with heattreated pine wood. Furthermore, after the two-step treatment, the color presented similar patterns and a lower level of water uptake (~40%-60%). Post-treatment with PMMA recovered the losses in both stiffness and strength brought by thermal modification at 180 °C and 200 °C; however, the treatment at 220 °C was found to be unsuitable for the two-step process.

Influence of chemical treatments on the thermal properties of natural fiber-reinforced hybrid composites (NFRHC)

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Based on most recently published studies, there is a large variability in both the mechanical properties of wood and sample sizes selected to evaluate them. This study aims to define sampling sufficiency for some mechanical properties of wood, which were bending strength, bending modulus, compressive strength, compressive modulus, hardness, and shear strength. The mechanical tests were carried out according to an American standard procedure on wood samples cut from clonal Eucalyptus planted in southern Brazil. Sampling sufficiency was determined by an intensive computational method based on resampling of original data using Monte Carlo simulations. The experimental tests data conformed to the normal distribution and most of the obtained sufficient sample sizes determined by Monte Carlo simulation were above those sample sizes used in most already published studies. Furthermore, properties related to wood stiffness presented smaller variabilities than their respective properties associated with wood strength, leading to smaller sample sizes for the former cases.

In this paper, nanocellulose (NC) dispersed in glycerin was incorporated into polyurethane (PU) biobased foams, using castor oil and glycerin, in a ratio of 3:1, as a biopolyol, produced by freerise pouring method. Firstly, the morphologicals properties, measureds by scanning electronic microscopy (SEM) images, were investigated and, after, the apparent density and compressives properties were measureds. The results indicated efficience in the preparation method for the biofoams and the filled foams presented a decrease in the cellular anisotropy and linear cell density and an increase in cell diameter, with a more homogenous cell structure. These morphologicals properties justify the modifications caused by the fillers in the biofoams, a larger cell, with less orientation, caused a decrease in the values of the apparent density and consequently lower values in compressive mechanical properties.