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.

Blown films from ethylene-propylene random copolymers (C2C3-RACOs) are used in many packaging applications today, constituting a major fraction of both mono- and multilayer packaging film constructions. Combining high processing speed and output with good mechanical and optical performance, mostly high toughness and low haze, requires understanding the structure-property-processing relations. To improve said understanding for C2C3-RACO blown films, two commercial grades with a nearly identical C2 content of ~4.4 wt% and identical melt flow rate (MFR) but different nucleation were selected. These were tested in a processing study, varying melt temperature, blow-up ratio (BUR) and neck length. The film structure was analysed by wide angle X-ray scattering (WAXS) and atomic force microscopy (AFM), and the performance by standard mechanical and optical tests. Variation of film crystallinity was found to be in the range of 62 to 65%, much smaller than in earlier cast film studies on comparable polymers. The tensile modulus is the only performance parameter for which a general positive correlation to crystallinity can be found, blown films being about 50% stiffer than the softest cast films of a comparable polymer. Ductility and toughness are enhanced by higher orientation, resulting from higher BUR and/or higher neck length. For transparency and haze, low surface roughness is decisive at comparable crystallinity, which can be achieved by increasing melt temperature.