Microbial Desulfurization of Ground Tire Rubber by Sphingomonas sp.: A Novel Technology for Crumb Rubber Composites

Abstract

This study focused on the microbial desulfurization of ground tire rubber (GTR) by Sphingomonas sp. that was selected from coal mine soil and had sulphur oxidizing capacity. GTR was immersed in the medium co-cultured with the Sphingomonas sp. for 20 days. The growth curve of Sphingomonas sp. during co-cultured desulfurization with GTR was measured and the surface chemical groups of GTR before and after desulfurization were analyzed. The crosslink density, mechanical properties, dynamic mechanical properties, and morphology of fracture surface of SBR composites filled with GTR or DGTR were studied to evaluate the microbial desulfurization effect. The results showed that GTR had low toxicity to Sphingomonas sp., so Sphingomonas sp. was able to maintain a high biomass. After desulfurization, not only a rupture of conjugated C=C bonds, but also a reduction of sulfur content had happened to GTR. The sol fraction of GTR increased from its original 4.69-8.68% after desulfurization. Desulfurated ground tire rubber (DGTR) sheets had better physical properties, and higher swelling values than GTR sheets. The DMA results showed that SBR/ DGTR composite had a reduction of molecular chain friction resistance during glass transition region and a decrease of glass transition temperature. SEM photograph further indicated a good coherency interface between DGTR and the rubber matrix.

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

“…In this study, the accelerators concentration was fixed, resulting in mechanical properties very proportional to the sulphur amount variation. In the literature, a wide range of mechanical properties values can be found, being extremely influenced by rubber compounding formulation 9,10,11 . Were also determined the percent devulcanization, considered the ratio of the crosslink density difference before (v eb ) and after (v ea ) extrusion, and the crosslink density before extrusion (v eb ), as represented in equation 4.…”

Characterization of styrene butadiene rubber and microwave devulcanized ground tire rubber composites

“…However, all of these devulcanization methods are unable to produce a product that is similar to virgin rubber. Rubber recycling technologies such as mechanical [9,10], mechanochemical [11][12][13][14][15], ultrasonic [16], chemical [17][18][19], microwave [3,[20][21][22] and biological methods [23] have been developed with the targets of higher product quality and percent yield. Devulcanization provided the advantage of rendering the rubber suitable for reformulating and recycling into usable products [24].…”

Improving the properties of reclaimed waste tire rubber by blending with poly(ethylene‐co‐vinyl acetate) and electron beam irradiation

“…Introduction 2 matrices. To overcome this problem, reclaimed tire rubber (RTR) which has regained some extent of plasticity from breaking down the vulcanized structure of the rubber through a reclaiming process could be used instead (Li et al, 2012a, Li et al, 2012b. However, the properties of RTR were found to be very inferior from all the wear and tear and recycling process of waste tire.…”