Comparative study of physico-mechanical properties of polypropylene fibre-reinforced gypsum composites

Abstract

Nowadays, the growing demand of plastic is leading to an uncontrolled waste production that threats the Planet's health. Over 8 million tonnes of plastic debris go into the ocean annually because of poor end-life management. Single-use products represent one of the main sources of plastic pollution, due to its low recycling rate related to its large production. Among them, personal hygiene disposable products (e.g., non-degradable wet wipes) represent a hazardous concern to marine ecosystem because of their dumping into the sea, dragged away by wastewater currents. Classified as non-woven textiles, non-degradable wet wipes are made from polymeric fibres, mainly polypropylene (PP), that complicate their degradation in contact with water. The incorrect disposal society makes of this waste causes devasting blockages in sewerage network, with alarming environmental and economic consequences. In this sense, alternative solutions to promote the recycling of this waste are needed in support of governmental regulations. Thus, from construction sector and committed to the Circular Economy's objectives set by the European Green Deal, the present work evaluates the feasibility of using PP waste fibres from disposable wet-wipes, as alternative to commercial PP reinforcement fibres, to produce eco-friendly reinforced gypsum-based products. Two types of reinforced-gypsum composites were prepared by adding commercial polypropylene (PPF) and waste polypropylene (PPWF) fibres, respectively. Different addition levels of fibre (2, 2.5, 3 and 3.5% by weight of gypsum) were selected to develop each group of gypsum blends. Then, composites were subjected to an experimental campaign based on dry density, mechanical behaviour (flexural and compressive strength) and deformability pre-failure, following the guidelines stablished by standards and comparing the results with the control material. The results showed a slight decrease of density as the percentage of PPWF rose, when compared to reference gypsum. Despite of the fact that lower values of mechanical strength were got by composites containing PPWF compared to those reinforced by PPF, a significant improvement of flexural strength (up to ∼19.5%) was reached by mixtures with 2.5wt% PPWF content, in relation to control material. On the other hand, a decrease on compressive strength of composites with PPWF addition was observed, unlike the performance showed by gypsums with PPF content up to 2.5 wt% (∼4.5% increase). However, all the data were over the minimum strength values stablished by standard. Furthermore, greater plastic deformation was developed by fibre-reinforced gypsum before to reach the failure point, in comparison with control gypsum which presented a brittle failure. Finally, it could be inferred the effectiveness of commercial PPF to enhance the mechanical properties of gypsum composites, just as the feasibility of using recycled WPPF as eco-friendly replacement to obtain gypsums for construction applications with both mechanical and environmental improvements, so promo...