Two series of polymer blends based on post-consumer polypropylene (rPP) and tire rubber crumbs (Trc) under the trademark ECOPLASTOMER^® PP70 with a mutual ratio of components 70/30 wt%, containing 10, 20, and 30 wt% of flame retardants, have been prepared using a twin-screw extruder. The influence of commercially available silane-treated alumina trihydrate (ATH-sil) with the eco-friendly system based on melamine phosphate (MP), aluminum hydroxide (AC), and peanut shells (PS), used as flame retardant agents, on the mechanical, thermal, and flammability properties of polymer blends was assessed – the incorporation of ATH-sil results in the appearance of peaks related to OH groups in the Fouriertransform infrared spectroscopy (FTIR) spectra. Similar observations are made for the MP/AC/PS system. differential scanning calorimetry (DSC) analysis revealed that using the selected flame retardants did not impact the melting and crystallization temperatures of the polymer. Tensile strength experienced a minor decrease, particularly in compositions containing more than 20 wt% of the flame retardants, while hardness remained unaffected by their share. Both flame retardants reduced the flammability of the modified polypropylene/rubber powder blends, and the most favorable outcomes were achieved with ATH-sil; however, only when employed at a minimum of 30 wt%. The formulated MP/AC/PS system proved more adept at reducing flammability and smoke emissions at lower flame retardant levels (up to 20 wt%).

Waste rubber management through developing blends of thermoplastics with ground tire rubber (GTR) has gained significant attention for creating sustainable, high-performance materials with enhanced properties. In this work, we developed customized graphene/polymer nanocomposites applying GTR, ethylene-vinyl acetate copolymer (EVA), and graphene nanoplatelets (GNPs), taking carbon black (CB) as the reference additive. A wide range of electrical conductivity from 10^–12 S/cm (dielectric) to 10^–5 S/cm (semiconductor) was obtained for optimized composites containing GNPs and CB, respectively. Thermal, mechanical, and flame-retardant properties looked promising for additive manufacturing, while electrical conductivity was tailored for soft electronics. In view of processability, mechanical strength, and elasticity, GNPs-incorporated EVA/GTR composites showed an edge over their CB-aided counterparts. For example, tensile strength and elongation at break of EVA/GTR blends reinforced with 20 phr GNPs were 4.8 MPa and 681%, respectively, compared to 4.0 MPa and 651% for the composite comprising an identical amount of CB. Interestingly, combining GNPs and CB enhanced the thermal stability and flame retardancy of EVA/GTR compared to only GNPs or CB. These results were promising from both sustainability and advanced functional materials perspectives.

This is an editorial article. It has no abstract.

This is an editorial article. It has no abstract.

As a complex composite material, tire rubber has always presented significant environmental and waste management concerns due to its non-biodegradability and accumulation in landfills. The devulcanization of tire rubber has emerged as a historical challenge in the field of sustainable rubber engineering since Goodyear invented cross-linking in 1839. This review provides a comprehensive analysis of waste tire recycling processes, focusing on the sources, legislation, management strategies, and utilization across different regions. It explores the multifaceted challenges of devulcanizing rubber, with a specific focus on transitioning from ground tire rubber to the concept of multi-decrosslinking: sulfur bridge breakage, rubber chain depolymerization and micro-nano sized core-shell carbon black. Ideal devulcanization has restricted the release of reinforcing fillers, resulting in devulcanized rubber mainly containing dozens of micron particles, which hinder the wide usage of devulcanized rubber. This review comprehensively assesses the current state-of-the-art techniques for tire rubber devulcanization, including physical, chemical and biological methods. It explores the intricacies of ground tire rubber as a starting material, structural evolution of ground tire rubber during the devulcanization process and the associated challenges in achieving efficient devulcanization while retaining desirable mechanical properties. Furthermore, through an in-depth analysis of recent advancements, limitations and prospects, this paper offers a complete understanding of the challenges faced in tire rubber devulcanization. Considering the technical and environmental aspects of these processes, this work contributes to multi-decrosslinking, the ongoing discourse on sustainable materials development and circular economy initiatives, which pave the way for future innovations in the field of rubber recycling.