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

Abstract

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.

Improving the swelling, mechanical, and electrical properties in natural rubber latex/carbon nanotubes nanocomposites: Effect of the sonication method

“…In both cases, the nanocomposites showed a good relationship between analyzed properties, with good linear regression determination coefficient ( R 2 ) values. These results show that the processing and vulcanization methods were well performed, without significant degradation, contamination, or unvulcanized rubber content, since this correlation follows the literature and the rubber elasticity theory 46,47 …”

“…These results show that the processing and vulcanization methods were well performed, without significant degradation, contamination, or unvulcanized rubber content, since this correlation follows the literature and the rubber elasticity theory. 46,47 To observe the dynamic mechanical behavior of the nanocomposites, a cyclic tensile strain test was made in the filled samples dispersed by the two different sonication methods. Figure 5a shows the axial displacement behavior and axial force response at 1.5 Hz with strain ranging from 20% to 100% for the initial 10 cycles for the U1-B sample.…”

Low-Temperature Mechano-Chemical Rubber Reclamation Using Terpinene as a Swelling Agent to Enhance Bond-Breaking Selectivity

“…Among different subcritical fluids (e.g., water, ethanol, and propanol), the influence of subcritical ethanol is significantly obvious [27]. Thermoplastic polymers can also swell the crosslinking structures of rubbers [28]. Barbosa et al [28] added thermoplastic ethylene vinyl-acetate during rubber reclamation using an intermeshing co-rotating twin-screw extruder.…”

“…Thermoplastic polymers can also swell the crosslinking structures of rubbers [28]. Barbosa et al [28] added thermoplastic ethylene vinyl-acetate during rubber reclamation using an intermeshing co-rotating twin-screw extruder. The addition of the ethylene vinyl-acetate achieved effective devulcanization, evidenced in the increase of soluble fractions, reduction in crosslinking density, and thermal stability gain.…”

Characterization of waste tire rubber devulcanized in twin-screw extruder with thermoplastics

“…The principle of this method is the shear stress application on the vulcanized rubber during extrusion, which may result in selective break of crosslinks due to the strength and directionality of employed tension. [7][8][9][10][11] The crosslinks break occurs when the shear stress reaches a certain level in which the shear force overcomes the energy force of the sulphur chemical bonds C-S-, -S-S-and -S-Sx-S-. However, the breaking of main chain bonds (C-C) may occur, being an undesirable effect which cause degradation and consequent loss of properties.…”