REVIEW OF THE RECLAIMING OF RUBBER WASTE AND RECENT WORK ON THE RECYCLING OF ETHYLENE–PROPYLENE–DIENE RUBBER WASTE

ABSTRACTRubbers do not decompose easily, and therefore, disposal of rubber waste is a serious environmental concern. Raw material costs, diminishing natural resources, and the growing awareness of environmental issues and sustainability have made rubber recycling a major area of concern. Reclaiming and recycling rubber waste is a major scientific and technological challenge facing rubber scientists today. This article reviews a number of important areas related to the reclaiming, characterizing, testing, and recycling of rubber waste. These include chemical and microbial devulcanization with particular emphasis on main chain scission and kinetics of chemical devulcanization reactions; the cutting-edge techniques for reclaiming devulcanized rubber waste by the action of large shearing forces, heat, and chemical agents: and analytical techniques and methods for characterizing composition and testing of devulcanized rubber waste, respectively. In addition, some aspects of the recycling of devulcanized ethylene–propylene–diene rubber (EPDM) waste will be reported. EPDM is used extensively in automotive components worldwide, and recycling the rubber at the end of its useful service life is of major importance to manufacturers of automotive components.

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Mechanisms Involved in the Recycling of NR and EPDM

Rubber Chemistry and Technology ◽

10.5254/1.3538830 ◽

1999 ◽

Vol 72 (4) ◽

pp. 731-740 ◽

Cited By ~ 48

Author(s):

M. A. L. Verbruggen ◽

L. van der Does ◽

J. W. M. Noordermeer ◽

M. van Duin ◽

H. J. Manuel

Keyword(s):

Natural Rubber ◽

Crosslink Density ◽

Main Chain ◽

Chain Scission ◽

Ethylene Propylene ◽

Temperature Range ◽

Lower Reactivity ◽

Ethylene Propylene Diene Rubber ◽

Diene Rubber ◽

Crosslink Densities

Abstract The thermochemical recycling of natural rubber (NR) and ethylene-propylene-diene rubber (EPDM) vulcanizates with disulfides was studied. NR sulfur vulcanizates were completely plasticized when heated with diphenyldisulfide at 200 °C. It could be concluded that both main chain scission and crosslink scission caused the network breakdown. NR peroxide vulcanizates were less reactive towards disulfide at 200 °C, and only reacted through main chain scission. For EPDM a temperature range of 200–275 °C was studied. In the presence of diphenyldisulfide at 200 °C there was almost no devulcanization of EPDM sulfur vulcanizates, and at 225 and 250 °C there was only slightly more devulcanization. A decrease in crosslink density of 90% was found when 2×10−4 mol diphenyldisulfide/cm3 vulcanizate was added and the EPDM sulfur vulcanizates were heated to 275 °C. EPDM peroxide vulcanizates showed a decrease in crosslink density of ca. 40% under the same conditions. The lower reactivity of EPDM towards disulfide compared with NR is the result of higher crosslink densities, the presence of a higher percentage of more stable monosulfidic crosslinks and the fact that EPDM is less apt to main chain scission relative to NR.

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