Devulcanization Technologies for Recycling of Tire-Derived Rubber: A Review (original) (raw)

Feedstock Recycling of Rubber A Review on Devulcanization Technologies

Vulcanized Rubber, as elastomer, is difficult to recycle. Today, the main end of life routes of tyres and other rubber products are landfilling, incineration in e.g. cement plants, and grinding to a fine powder, with huge quantities lacking sustainable recycling of this valuable material. Devulcanization, i.e. the breaking up of sulfur bonds by chemical, thermo-physical or biological means, is a promising route that has been investigated for more than 50 years. This review article presents and update on the state-of-the art in rubber devulcanization. This review article addresses established devulcanization technologies and novel processes described in the scientific and patent literatures. It is expected that the public discussion of environmental impacts of thermoplastics will soon spill over to thermosets and elastomers. Therefore, the industry needs to develop and market solutions proactively. Tyre recycling through devulcanization has a huge lever, since approx. 30 million tons...

Current progress in waste tire rubber devulcanization

Chemosphere, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

A novel devulcanization technology for vulcanized natural rubber

Journal of Applied Polymer Science, 2006

Devulcanization of waste rubber poses a challenging environmental, economical, and disposal problem in the world because of their cross-linked three-dimensional network structure. Devulcanization of gum natural rubber vulcanizate containing three different sulfur/accelerator ratios was carried out in 90°C for 10 min with the help of open two-roll cracker cum mixing mill in presence and absence of thiol acid as a devulcanizing agent. The vulcanizate properties markedly depended on devulcanizing agent and also devulcanization techniques. Revulcanized rubber obtained by devulcanizing with thiol acid offered better mechanical properties. Decrease in scorch time and increase in rheometric torque were observed for revulcanized rubber containing devulcanizing agent. The onset degradation temperature largely depended on presence of thiol acid. IR spectroscopic results revealed that the main polymeric chain did not oxidize at the time of milling above the room temperature. Increase in storage modulus and decrease in loss modulus were observed for revulcanized rubber from DMA study. The SEM was considered to study the failure mechanism and homogeneity of the vulcanizate. By adopting this devulcanization technique, more than 85% mechanical property of vulcanized natural rubber was retained. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2831–2840, 2006

New Route of Tire Rubber Devulcanization Using Silanes

Polymers

The disposal of tires at the end of their lifespan results in societal and environmental issues. To tackle this, recycling and reuse are effective solutions. Among various recycling methods, devulcanization is considered to be a very sustainable option, as it involves the controlled breakdown of crosslinks while maintaining the polymer backbones. The objective of this study is to develop a sustainable devulcanization process for passenger car tire rubber using silanes. In this study, a thermo-mechanical–chemical devulcanization process was conducted to screen six potential devulcanization aids (DAs). Silanes were chosen as they are widely used in tire rubber as coupling agents for silica. The efficiency of the devulcanization was studied by the degree of network breakdown, miscibility of the devulcanized material, and mechanical properties of the de- and revulcanized material. Compared to the parent compound, a 55–60% network breakdown was achieved for the devulcanizate along with 5...

Mechano-chemical recycling of sulfur cured natural rubber

Polimery, 2007

Mechano-chemical recycling of sulfur cured natural rubber Summary-The disposal of cured rubber has become a major environmental problem. Discarded rubber was devulcanized by an open two-roll cracker-cum mixing mill both in the presence or absence of diphenyl disulfide at 120 o C (Mechano-Chemical Process, MCP), and then the obtained devulcanized mass was revulcanized again by the addition of sulfur and N-cyclohexyl-2-benzothiazyl sulfonamide (CBS). A new look at the devulcanization mechanism and the influence of the devulcanizing agent on the mechanical properties of the ultimate revulcanized rubber are presented in this paper. Rheometric characteristics show that both the scorch time and curing rate were low for revulcanized rubber. One of the most interesting observations is that the mechanical properties of revulcanized rubber obtained by devulcanizing in the presence of disulfide were better than of the revulcanized rubber obtained by devulcanizing in absence of disulfide. The formation of extra crosslinking in disulfide containing revulcanized rubber was confirmed by crosslinking density data. By adopting this devulcanization technique mechanical properties of vulcanized natural rubber were retained in more than 87 %.

Mechanochemical surface activation of ground tire rubber by solid-state devulcanization and grafting

Journal of Applied Polymer Science, 2003

Cured rubber powder was successfully devulcanized under the application of high-energy ball milling. An attempt was made to improve the efficiency of devulcanization with a phenolic antioxidant (2,6-di-tert-butyl-4-methyl-phenol). In addition, the grafting of virgin natural rubber to the surface of rubber powder was promoted by milling under an inert atmosphere. The extent of mechanochemical devulcanization was studied by estimation of the sol-gel fractions and crosslink densities. Our findings suggest that the process led to a preferential breakage of sulfur crosslinks. The curing behavior of the compounds and the mechanical properties of the vulcanizates containing treated rubber powder and fresh rubber were investigated. The chemical and mechanical properties depended strongly on the experimental milling conditions, which could consequently be controlled to improve the quality of the reclaimed rubber.

Devulcanized Rubber a Solution for Scrap Tire

Proceedings of the 7th World Congress on New Technologies, 2021

Waste is a major issue around the world with approximately 2.01 billion ton of waste generated annually. which can be Rubber waste from tires is known to be a massive environmental risk to the environment as it is non-biodegradable. However, rubber is an indispensable material of the technological development, from the simplest balloon to the complex rocket propellant. The majority of tires waste are dealt with a non-environmental manner, either dumped in landfills or burnt causing negative impact on human health and environment. Unfortunately, one of the largest tires landfill in the world is located in the state of Kuwait, AlRuhayah. This site host around 50 million dead tires. This study investigates the proper waste management of accumulate tires in Kuwait based on cost, profitability, environmental impact, efficiency, net energy produced, and operation and maintenance. A comparison between reusing, rethreading, pyrolysis, mechanical grinding and devulcanization methods were applied to seek the best method for tire waste management. Out of the eight adequate methods, devulcanization was the superior option due to its efficiency, profitability and least impact on environment. Precise calculations were made concerning different aspects such as transportation, structure and expenses. The total amount of revenue for this 10-year project is $75 million US Dollars and annually produce 24 million kg of rubber. This rubber can be further processed into green concrete, pavements and aerogel. The adaption of the proposed method is of great importance to regulatory bodies to regulate and reduce the tire waste and hence improve the environment and human health.

Devulcanization of Waste Rubber and Generation of Active Sites for Silica Reinforcement

ACS Omega

Each year, hundreds of millions of tires are produced and ultimately disposed into nature. To address this serious environmental issue, devulcanization could be one of the sustainable solutions that still remains as one of the biggest challenges across the globe. In this work, sulfur-vulcanized natural rubber (NR) is mechanochemically devulcanized utilizing a silane-based tetrasulfide as a devulcanizing agent, and subsequently, silica (SiO 2)-based rubber composites are prepared. This method not only breaks the sulfur−sulfur cross-links but also produces reactive poly(isoprene) chains to interact with silica. The silica natural rubber composites are prepared by replacing 30% fresh NR by devulcanized NR with varying contents of silica. The composites exhibit excellent mechanical properties, tear strength, abrasion resistance, and dynamic mechanical properties as compared with the fresh natural rubber silica composites. The tensile strength of devulcanized rubber-based silica composites is ∼20 MPa, and the maximum elongation strain is ∼921%. The devulcanized composites are studied in detail by chemical, mechanical, and morphological analyses. Thus, the value added by the devulcanized rubber could attract the attention of recycling community for its sustainable applications.

Recycling of Waste Tyre into Silica-Rubber Compounds for Green Tyre Application

2021

The prevention of detrimental effects to environment, owing to generation of a huge amount of rubber wastes, is a big challenge across the globe that warrants a thorough investigation of recycling and reuses waste of rubber products. In this spirit a sustainable development of a devulcanization process along with the production of value added devulcanized rubber is a task of hours. The present work describes a simultaneous devulcanization and chemical functionalisation process of waste solution styrene butadiene rubber (S-SBR). This kind of rubber is generally used as the main polymer component in silica filled tread rubber compounds for high-performance passenger car tyres. As-grown ethoxy groups on the functionalized devulcanized styrene butadiene rubber (D-SBR) are exploited for the coupling between silica and the devulcanized rubber chains. We compare the mechanical and dynamic mechanical performance of D-SBR with that of virgin SBR control composites. Covalently bonding interfa...