Influence of process variables on chemical devulcanization of sulfur-cured natural rubber

Sabzekar, Malihe; Chenar, Mahdi Pourafshari; Mortazavi, Seyed Mohammad Mahdi; Kariminejad, Majid; Asadi, Said; Zohuri, Gholamhossein

doi:10.1016/j.polymdegradstab.2015.04.013

Cited by 77 publications

(40 citation statements)

References 27 publications

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“…In order to deepen the study of microwaves devulcanization process and its consequences, Horikx's theory can be useful. It is commonly adopted to determine the relationship between the sol fraction after the degradation of the network structure of a rubber and the relative decrease in the crosslinking density . This theory investigates two limited cases: (i) when main chain scission occurs, the relative decrease in the crosslinking density is calculated by using eq.…”

Section: Resultsmentioning

confidence: 99%

Influence of reversion in compounds containing recycled natural rubber: In search of sustainable processing

Sousa

Zanchet

Scuracchio

2017

J of Applied Polymer Sci

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The influence of rubber devulcanization by microwaves in the reversion behavior is still modestly explored in the literature. The reversion occurs due to thermal degradation of unstable crosslinkings formed during the vulcanization process. This phenomenon results in poor final mechanical properties of the artifacts. In this work, some formulations based on natural rubber (NR) with the incorporation of NR devulcanized by microwaves at different exposure times to the microwaves were vulcanized by compression molding at the same temperature and time used for the study of their vulcanization characteristics, in order to correlate the properties obtained and understand the influence of the reversion on the mechanical properties. The results showed that levels of devulcanization/degradation of the recycled phase, as well as the additional heating time influenced on the behavior of reversion and, consequently, on the mechanical properties. the influence of density and crosslinking type in the mechanical properties of rubber has been studied by various authors, 4,6,7 since the stress-strain measurement is an indirect method for determining the crosslinking density. 5Currently, a big global problem is related to disposal of solid urban residues, and materials able to make this problem much worse are the vulcanized/cured elastomers. In the same way, the search for processes and/or sustainable materials is of great value, and it is directly related to the solution of this problem, since the use of recycled materials can reduce such problem. In addition, recycling not only protects the environment, but also saves the limited petroleum resources from which the raw material originates, 8 also being a source of income for many families around the world. The recycling method used in this work is the devulcanization by microwaves.Devulcanization is a way of providing energy to destroy, total or partially, the three-dimensional network formed during vulcanization. 9 Devulcanization by microwaves is a well-established recycling technique of vulcanized elastomers. Among its

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Section: Resultsmentioning

confidence: 99%

Influence of reversion in compounds containing recycled natural rubber: In search of sustainable processing

Sousa

Zanchet

Scuracchio

2017

J of Applied Polymer Sci

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“…These processes are rarely finding sufficient results to compete with the methods of re-use as co-processing, granulation and rolling, which in turn does not reutilize much of the energy potential in NR from tires 2,3 . Among the main devulcanization methods currently searched, highlights processing by ultrasound 4,5 , microwave 6,7 , chemical method 8 , biological treatment 9 and thermomechanical 10,11 . Currently, two relevant theories attempt to explain the mechanisms of crosslink selective breaking.…”

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confidence: 99%

Devulcanization of Natural Rubber in Composites with Distinct Crosslink Densities by Twin-Screw Extruder

2017

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In this study, the effects of the devulcanization process realized by an intermeshing co-rotating twin-screw extruder (ICTSE) on three vulcanized Natural Rubber (NR) composites with different crosslink densities (CD) have been investigated. The extrusion parameters were fixed, as well as the initial material granulometry and auxiliary thermoplastic added to the process. After composites vulcanization, they were characterized accordingly their soluble fraction (SF), crosslink density (CD), mechanical properties and thermogravimetry (TGA). The extrusion was performed on the vulcanized elastomers pursuing selectively crosslink rupture and the same characterization previously cited was conducted on the devulcanized material, except the mechanical properties analysis. The extrusion demonstrate effective devulcanization, evidenced in the increasing of soluble fractions, reduction in crosslink density and thermal stability gain. These results are directly affected by preliminary differences on materials structure and presence of ethylene vinyl-acetate (EVA) on extrusion.

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“…Recycling of the vulcanized rubber is an alternative method that converts the rubber waste into value added products [5][6][7]. Devulcanization is one form of recycling, where the crosslinked bonds in the rubber chains are cleaved, and can be classified into the three broad processes of physical [8][9][10][11][12][13][14], chemical [12,13,[15][16][17][18][19][20] and biological [12,[21][22][23][24][25][26][27][28][29] devulcanization processes. Physical devulcanization generally requires a high temperature or external energy for cleavage of the crosslinked bonds and so this process has a high cost and high energy consumption, challenging its economic and environmental viability.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the rubber waste needs to be immersed in an organic solvent to allow the chemical reagents to easily penetrate into the rubbery matrix and react with the crosslink bonds. Due to the difficulty of subsequent solvent removal and prevention of exposure to toxic chemicals [12,15,16], the advanced technique of using a non-toxic supercritical fluid (carbon dioxide, methane and water) has been applied instead, but this approach requires a high cost and energy consumption [4,12,17,18]. Accordingly, biological devulcanization has been suggested as an alternative method for green technology.…”

Section: Introductionmentioning

confidence: 99%

Devulcanization of natural rubber vulcanizates by Bacillus cereus TISTR 2651

Kaewpetch¹,

Prasongsuk²,

Poompradub³

2019

Express Polym. Lett.

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The ability of Bacillus cereus TISTR 2651 to perform biological devulcanization of natural rubber cured by conventional vulcanization (CV), semi-efficient vulcanization or efficient vulcanization was studied. Among the three curing systems, B. cereus TISTR 2651 could specifically devulcanize rubber products formed from the CV system the best, removing 26.44% of the sulfur within 20 days. Moreover, B. cereus TISTR 2651 could oxidize and desulfurize the sulfide crosslinks in the CV rubber and transform them to oxygen-containing sulfur-based groups via the 4S pathway. Additionally, the molecular weight, crosslink density and gel fraction of the CV rubber were also significantly decreased from the original levels. Horikx analysis was used to propose the mechanism of bacterial devulcanization. Finally, ground tire rubber (GTR) was devulcanized by B. cereus TISTR 2651 and the percentage of sulfur removal was about 27.98 for 20 days, where similar results were also obtained. Accordingly, B. cereus TISTR 2651 can be applied for the management of rubber waste, leading towards a solution of this environmental problem.

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Influence of process variables on chemical devulcanization of sulfur-cured natural rubber

Cited by 77 publications

References 27 publications

Influence of reversion in compounds containing recycled natural rubber: In search of sustainable processing

Influence of reversion in compounds containing recycled natural rubber: In search of sustainable processing

Devulcanization of Natural Rubber in Composites with Distinct Crosslink Densities by Twin-Screw Extruder

Devulcanization of natural rubber vulcanizates by Bacillus cereus TISTR 2651

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