Many companies produce reclaimed rubber across the world, including Japan, China, India, the EU, and other countries. However, Japanese production has decreased in recent years. Reclaimed rubber is commonly utilized for manufacturing tire compounds, belts, hoses, rubber mats, and general-purpose rubber products. China is the biggest producer, and India is the second. The new manufacturing process uses twin high-speed screw devulcanization technology. Rubber crumb is used for producing artificial grass, modifying asphalt, and other applications. Manufacturers are seeking technology to make finer crumbs. There has been a growing demand for environmentally friendly, sustainable, and recycled rubber materials from used tires in recent years. Rubber crumb pyrolyzed products and recycled carbon black are among the most popular products in this category. Recycled carbon black is produced by more than 30 companies outside Japan. Silicone rubber can also be broken down and returned to intermediate raw materials.

The toughness enhancement and recyclability of elastomers were investigated using polymeric nanoparticles. Rotaxane (RC) as a cross-linker, which consists of one ring and one axial structure, was used to improve toughness. The RC was used to produce acrylic polymeric nanoparticles by mini-emulsion polymerization, and the elastomer film was prepared by removal of water from the aqueous dispersion. It was found that the toughness of the resulting elastomer was improved by adjusting the amount of RC within the polymeric nanoparticles. Tear tests on the resulting elastomer films showed unique crack propagation suppression behavior. While the nanoparticles adhered to each other in the film and the polymer chains penetrated into the nanoparticles to maintain their strength, they were broken down into individual nanoparticles when heated in a solvent. When the volatile components were removed from the nanoparticle dispersion, the elastomer film was regenerated, confirming the recyclability of the material.

Super engineering plastics, high-performance thermoplastic resins such as polyetheretherketone (PEEK) have been utilized as advanced materials in industries such as aircrafts, automobiles, and medical devices, owing to their high thermal stability, chemical resistance, insolubility, and mechanical strength. However, their robustness hinders their chemical recycling, or degradation, to produce oligomers or monomeric chemicals. Chemical recycling of PEEK has been particularly difficult, to the extent that it is considered impossible. To overcome this drawback, we have researched on the chemical recycling of super engineering plastics and related robust resins. Herein, we report our recent research topics on the chemical recycling of super engineering plastics: base-catalyzed degradation of super engineering plastics such as PEEK using thiols to form dithiobenzophenones and hydroquinone without collapsing the molecular architectures of the main chain. This degradation method was applicable to various super engineering plastics including polysulfone, polyethersulfone, and polyetherimide.

Microwaves are electromagnetic waves with wavelengths of approximately 1 mm to 1 m (frequencies of 300 MHz to 300 GHz) in which the electric and magnetic fields are orthogonal and can directly transmit energy toward the target object inside.
In recent years, we have developed a plastic degradation technology platform, PlaWave ^® , for the chemical recycling field, and have applied it to various types of plastics.
In this issue, we will discuss the details of this approach and how it is applied to rubber.

In Japan, the tyre industry has developed rapidly since 1960 with the advent of full-scale motorization, and since the mid-1990s, approximately 90 million ELTs have been generated annually. Tyres are made from more than 100 different raw materials to optimize performance and are vulcanized, making them difficult to recycle. Because of these characteristics, ELTs have not been properly disposed of in the past, and illegal dumping of ELTs has become a problem. However, now almost all ELTs are effectively utilized.
We will describe the history of ELT treatment, an overview of the current effective utilization of ELTs, as well as initiatives to reduce raw material consumption and ELT generation, and future challenges.

Recently, the studies for recycling technologies have been increasing based on the viewpoint both of environmental issues and securing of raw material. For tire recycling in Japan, thermal recovery is one of main usage of tire recycling. The thermal recovery, however, has the potential to emit the CO ₂ . Therefore, tire recycling root should be re-considered and to find more better environment friendly root. Material recycling of tires has been conducted by using of rubber powder or reclaim rubber. Chemical recycling are new activities for tire recycling technology. This paper shows the status of recycling activities of tires and challenge to closed loop of tires.