Abstract
Rubber has become an indispensable material for the technological development of civilization, including simple balloon and complex rocket propellant. Rubber Industry worldwide is using on an average 50% of raw materials. These materials were mostly petroleum-based, except natural rubber (NR), steel cord and bead wire. Using of these petroleum-based raw materials not only depletes natural resources, but also produces more extreme environmental hazards. The waste tire rubber problem is of great magnitude and has far reaching environmental and economic implications. There are some ways for recycling of rubber, such as reclaiming technology, surface treatment, grinding and pulverization technology, devulcanization technology. Methods of devulcanizing rubber (or elastomers) have been researched almost since the time of the discovery of the rubber/sulfur vulcanization process. By devulcanization process the cross-links in the structure of rubber are broken and devulcanized rubber can be revulcanized into a raw material for rubber industry, which is a highly valued form of waste rubber. This study provides a review of the recent advances in understanding of methods of recycling rubber and claims that the capacity of thermomechanical and mechanochemical devulcanization methods of recycling waste tire rubber can be improved in future studies.
Highlights
The annual consumption of natural rubber is more than 15 million tons, and the output of rubber products is more than 31 million tons worldwide [1]
De et al [29] reclaimed sulfur cured natural rubber vulcanizates using a vegetable product based on diallyldisulphide, which they called renewable resource material (RRM).Verbruggen et al [30] have studied the thermo-chemical action of diphenyl disulphide on sulfur vulcanized NR and EPDM vulcanizates and concluded that both main chain and crosslink scissions caused the network breakdown resulting in a recyclable powder
It can be achieved by a simultaneous chemical, thermal and mechanical action at nominal shearing in a twin screw extruder (TSE)
Summary
The annual consumption of natural rubber is more than 15 million tons, and the output of rubber products is more than 31 million tons worldwide [1]. The main source of waste rubber products is discarded waste tires, rubber pipes, rubber belts, rubber shoes, edge scraps, and waste products that are produced in the rubber processes and others [2]. The handling of such large volumes of discarded elastomeric materials poses a serious environmental problem that must be faced by the scientific community. The devulcanization and reutilization of cross-linked elastomers are very difficult because of the threedimentional network. This network makes the material insoluble and nonmelting. Currently no technique exists that revertses maximum mechanical property of vulcanized natural
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