The refrigeration industry produces millions of tons of waste polyurethane (PU) every year, which can cause environmental damage and human health problems. This article analyzes the use of waste PU as filler in composites made of styrene butadiene rubber (SBR) and natural rubber (NR) to produce shoe soles. The interfacial interaction of said filler was evaluated by the Flory-Rehner method (swelling) using the equation developed by Lorenz-Park. The results of this evaluation were later compared with those obtained by the Mooney-Rivlin method using the data from stress-strain tests. According to the results of the tensile strength tests, the composites filled with waste PU present stress-strain curves that are like those of metallic materials that have low elastic strength but high plastic strength. Using the Lorenz-Park equation, the filled composites examined in this study exhibited values above 0.7, which means a strong filler-rubber interaction. Scanning Electron Microscopy and Fourier-Transform Infrared Spectroscopy were used to investigate the morphology of the composites in detail.

Eco-efficient construction has emerged as a distinct new field. The reuse or recycling of residues for production of building materials has the potential to avoid incorrect disposal, decrease the volume of waste in landfills and reduce the extraction of natural resources, which deplete the environment. This study proposes a new approach to reuse lime mud (LM), mainly composed of calcium carbonate, as filler in gypsum plaster to replace gypsum in proportions of 5, 15 and 25%, tested after 7, 14 and 21 days. An elemental analysis of the residue showed calcium-rich composition and that the particle distribution was between 1 and 11 μm with a mean particle diameter around 6 μm. The density of gypsum/lime mud (G/LM) composites was reduced from gypsum (1244.9 kg/m3) to G/LM25 (1132.1 kg/m3) in 21 days. The flexural strength of gypsum after 21 days was 5.7 MPa compared to 5.4 MPa for G/LM5 (LM at 5%), the latter being a reduction of only 5.3% from the former. Even with incorporation of 25% of LM, after 21 days composites presented mechanical resistance above the standard international recommendations: compressive strength of 9.6 MPa (≥8.3 MPa recommended), axial compression strength of 8.5 MPa (≥6.0 MPa) and flexural strength of 3.7 MPa (≥2.0 MPa).

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The biodiversity of plant resources is a renewable source that can use as a sustainable component in various applications. The use of vegetable waste as a filler element in polymeric composites is part of the solid waste management policy and the sustainable development of agribusiness. In this work, the natural rubber composites were prepared with acai seed in proportions of 0, 10, 20, 30, 40, and 50 phr (per hundred rubber). The composites were homogenized in an open cylinder mixer and characterized by rheometric, morphological, mechanical, and thermal tests. The addition of the organic fillers significantly reduced the vulcanization process time. Thermogravimetric analysis and infrared spectroscopy showed that the composites were thermally stable and showed no structure changes after the vulcanization process, respectively. The Lorenz-Parks method's evaluation of matrix/filler interactions showed a strong interaction between NR/Acai. The new biocomposite can replace nonecological composites economically and sustainably.

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