Enhancing mechanical properties of recycled sheet molding compound composites through catalytic and ozone activation

Abstract Currently, mechanical recycling offers a feasible approach to reduce scraps or end‐of‐life product (EoL) of glass fiber reinforced polymer composites, such as sheet molding compound (SMC), without gravely impact on energy and costs. However, the resulting material is characterized by a discontinuous bulk, limiting its application to low‐value products. In this study, a comprehensive characterization of composites made by fresh unsaturated polyester resin (UPR) and recycled SMC with a content from 10% up to 40% by weight (wt), was carried out. To enhance the chemical interactions between the inert recycled SMC and the fresh UPR, and as consequence their mechanical properties, two different transesterification catalysts, aluminum (III) sec‐butoxide and titanium (IV) butoxide at 1.0 wt%, were utilized. To further investigate the interaction between SMC and fresh UPR, an ozone treatment was carried out on SMC before blending and all the composites compared with no‐treated reference systems. Among the formulated composites, the one made by 40 wt% of SMC and titanium (IV) butoxide results to be the most performant system with a T_g around 137°C, a modulus of 3.7 GPa and strain at break around 1.42%. These results could innovate the manufacturing of recycled composites with superior mechanical properties, potentially used for applications such as cabinet, panels, or external cladding. Highlights Mechanical recycling of sheet molding compound “SMC”. Ozone treatment of SMC filler before blending with fresh UPR. Activation of filler with Al and Ti Alkoxide; –Enhanced mechanical properties for UPR + SMC40% + Ti sample; –Enhanced elongation at break for UPR + SMC20% + O3.