Technical Notebook: Recycled rubber product development and manufacturing

Vulcanized rubber, due to unique characteristics, saw most uses in automobiles. Even with the latest shifts in the industry, vehicles still ride on tires.

Today, tires consist of about 19 percent natural rubber and 24 percent synthetic rubbers, while plastics, metal, fillers and additives make up the rest. Globally, the industry produces over 1.6 billion tires annually and consumers retire around 1 billion waste tires.

Tires of extensive designs and complex manufacturing withstand the harshness of service life. Consequently, their disposal creates recycling challenges, with subsequent health and environmental impacts. Current disposal strategies to retiring tires, consisting of incineration, crumb rubber generation, and landfilling, are not effective. Waste tire rubber recovery or regeneration is highly desirable for rubber sustainability and rubber product circular economy.

Multiple devulcanization processes introduced selective cleavages of vulcanizate’s crosslinks while retaining polymeric networks. This paper reviews devulcanization methods, explored until now, such as chemical, mechanical, biological and their combinations. The paper presents additional steps necessary for turning post-consumer goods (like end-of-life tires) into engineering materials and products. While devulcanization techniques provide new sustainability pathways for ground tire rubber (GTR), the generated devulcanizate requires compounding and particular curing. The paper opens the possibility of waste rubber recoveries.