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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Natural tannin-based foams are three-dimensional porous materials. Many different formulations have been investigated in order to reach foams with improved performance and increased commercial attractiveness. In this sense, each different tannin pH may impart different physical and thermochemical properties to the foams, which has not yet been fully elucidated. In the present study, seven rigid tannin foams (formaldehyde/sulfur-free) were produced using tannin extracts with variable pH values ( c.a. from 2.3 to 12.2). The most acidic tannin extracts (below 4.8) yielded tannin foams with the most lightweight (apparent density below 0.077 g.cm−3), homogeneous, and hydrophobic (water solubility below 23.5%) cellular-network architectures. Also, in most cases, the smaller the tannin pH, the higher the thermal stability of the foam. Further studies may address other technological requirements needed for thermal insulation applications.