Devulcanization of ground tire rubber: microwave and thermomechanical approaches

Dániel Ábel Simon,Tamás Bárány,Dávid Zoltán Pirityi

doi:10.1038/s41598-020-73543-w

Dániel Ábel Simon, Tamás Bárány + Show 1 more

Open Access

https://doi.org/10.1038/s41598-020-73543-w

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Abstract

We devulcanized ground tire rubber (GTR) in a laboratory microwave oven and an internal mixer, measured the soluble content and the cross-link density of the samples, and then used Horikx’s analysis. The results showed that microwave treatment caused severe degradation of the polymer chains, while in the case of thermomechanical devulcanization, the selective scission of covalent cross-links is more common. Four devulcanized ground tire rubber (dGTR) samples were chosen for further study and three groups of samples were produced: dGTR samples containing vulcanizing agents and different amounts of paraffin oil (dGTR-based mixtures), natural rubber-based rubber mixtures with different dGTR contents and reference rubber mixtures with dGTR-based mixtures (increased vulcanizing agent contents). Cure characteristics showed a plasticizer-like effect of dGTR. Tensile and tear strength decreased drastically with increasing dGTR content; however, elongation at break values did not follow such a trend. Mechanical properties improved with increased vulcanizing agent contents. The examined properties of the samples improved even further with the use of thermomechanically devulcanized samples. Horikx’s analysis showed that this is attributable to moderate polymer chain scission.

Highlights

We devulcanized ground tire rubber (GTR) in a laboratory microwave oven and an internal mixer, measured the soluble content and the cross-link density of the samples, and used Horikx’s analysis
The best way of disposing of waste tires and other rubber products is to turn them into a ground powder[4], which can be produced in different ways: mechanical grinding at ambient or cryogenic temperatures[5], and waterjet milling
S′max values increased because of the extra vulcanizing agents added to devulcanized ground tire rubber (dGTR) but there is no significant effect of the oil content in dGTR mixtures (A and B samples)

Summary

Introduction

We devulcanized ground tire rubber (GTR) in a laboratory microwave oven and an internal mixer, measured the soluble content and the cross-link density of the samples, and used Horikx’s analysis. We treated 50 g batches of GTR and observed an increase in sol fraction and a decrease in cross-link density, indicating devulcanization. It signified a low degree of devulcanization and suggested the degradation of the polymer chains, as shown, since the corresponding data points are closer to the random scission curve than the selective cross-link scission curve (Table 9).

Results

Conclusion