Devulcanized Tire Rubber Research Articles

Devulcanized Tire Rubber–Waste Plastic Compounds: A Solution to Improve Storage Stability of Plastic-Modified Bitumen

Devulcanized Tire Rubber–Waste Plastic Compounds: A Solution to Improve Storage Stability of Plastic-Modified Bitumen

Recycled plastics and rubber for green roads: The case study of devulcanized tire rubber and waste plastics compounds to enhance bitumen performance

Devulcanized rubber (DVR) and waste plastics have been studied separately as bitumen modifiers, but their individual drawbacks prevent full implementation in the field. In this paper, two pelletized composites produced by coupling DVR with waste low-density polyethylene (LDPE) and polypropylene (PP) were investigated. Linear viscoelastic properties, rutting, and fatigue cracking performance were evaluated, and results were compared to those obtained on neat and polymer-modified bitumen with high styrene-butadiene-styrene content (HiPMB). The non-recoverable creep compliance was reduced with the increasing addition of DVR with either LDPE or PP, and the modified bitumen can be classifiable as “E” grade like the common HiPMB. Bitumen modified with DVR-LDPE compounds showed the best fatigue cracking performance overall, and can fully replace the industrial HiPMB. The implications of these results go beyond the sole performance improvement since these compounds can significantly reduce the environmental impact of road construction by using two waste materials simultaneously.

Utilization of devulcanized waste rubber tire in development of heat insulation composite

This study aims to investigate the possibility of recycling devulcanized rubber tires for their use as fillers for thermoplastic thermal insulators. A devulcanized rubber tire was ground into powder and then mixed with polystyrene in different proportions (0–50 wt%) using a melt extruder. The mixture was then transferred to a hot press for fabricating the final sample. The effect of devulcanized rubber tire content on the physical, thermal, and mechanical properties of devulcanized rubber tire–polystyrene composites was investigated. Thermal conductivity measurements were verified using series and parallel conduction models and the Hashin and Shtrikman model. Composites with less than 40 wt% devulcanized rubber tire content exhibited superior properties, with thermal conductivity ranging from 0.0502 to 0.07084 W/(m⋅K), density from 462.8 to 482.32 kg/m3, compressive strength from 11.66 to 7.47 MPa, and flexural strength from 40.4 to 19.26 MPa. Moreover, alkaline treatment of the devulcanized rubber tire further improved the mechanical properties and thermal stability of the composite. The results are supported by characterization techniques such as scanning electron microscopy, thermogravimetric analysis, and Fourier-transform infrared spectroscopy. The chemical treatment was found to enhance the coherence between treated devulcanized rubber tire and polystyrene. The novel devulcanized rubber tire–polystyrene composite can be used as an alternative insulation material because of its superior properties compared with those of conventional insulation materials. Furthermore, the environmental and economic implications of using devulcanized rubber tire–polystyrene composites as a new insulation material are discussed herein.

Composite Bitumen Binders Based on an Active Powder of Discretely Devulcanized Tire Rubber

Composite binders (CB) for road construction, based on bitumen and active powder of discretely devulcanized rubber (APDDR), obtained by the method of high-temperature shear grinding (HTSG), are considered. The formation of CB occurs with the introduction of APDDR in bitumen during the preparation of the asphalt mixture. The advantages of CB compared with bitumen in a wide temperature range are shown: a decrease in plastic deformations at high temperatures, an increase in fatigue life and resistance to the formation of low-temperature cracks.

Devulcanization of ground tire rubber: thermo-oxidation followed by microwave exposure in the presence of devulcanizing agent

The disposal of recycled tires is a problem that has gained considerable importance since it has involved the environmental as well as various disciplines and points of view. Currently, the burning and outdoor storage of disposed tires are forbidden practices because of their polluting effect, damage to health and the fact that they contribute to the spread of diseases due to vectors such as insects. Therefore, it is important to research alternative methods that provide added value. In this work, waste ground tire rubber was treated by applying a combination of oxidation with potassium permanganate/hydrogen peroxide, followed by microwave exposure in the presence of a devulcanizing agent. Devulcanized tire rubber was analyzed by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, cross-link density and sol fraction. Styrene butadiene rubber composites were prepared using devulcanized tire rubber and sulfur cure system. The blends were mixed in a two roll mill laboratory. The vulcanized specimens were obtained by compression molding. Curing properties, tensile and tear strength, elongation at break, hardness (Shore A units), abrasion resistance (mm3), and compression set of these rubber composites were evaluated and the morphology of the fractured surfaces from tensile specimens were analyzed with scanning electron microscopy. The results showed that microwave exposure with devulcanizing agent reduced the cross-link density and increased the soluble fraction of rubber tire. Improved flow through viscosity reduction (low torque) and higher mechanical strength were obtained by compounding styrene butadiene rubber with ground rubber tire (thermo-oxidized followed by microwave exposure with devulcanizing agent), whose market values were similar to those obtained for virgin styrene butadiene rubber/silica composite.

Rheological Property of Bitumen Modified by the Mixture of the Mechanochemically Devulcanized Tire Rubber Powder and SBS

The mechanochemically devulcanized ground tire rubber (m-GTR) prepared by solid-state mechanochemical reactor was used in the modification of bitumen with styrene-butadiene-styrene block (SBS) copolymer powder. The conventional properties (such as penetration index, softening point, 5°C ductility, and aging test) and rheological properties of bitumens modified by 8, 10, and 12 wt % m-GTR/SBS were investigated in this paper. The conventional properties except penetration of m-GTR/SBS modified bitumen were improved, compared with 5.5 wt % SBS modified bitumen. Rheological data demonstrated that all of the testing results of 10 wt % m-GTR/SBS modified bitumen were better than those of SBS modified bitumen under the condition of high temperature. The scanning electron microscope observation of the fractured surfaces showed that the m-GTR/SBS mixed powder had a better interface adhesion with matrix than SBS.

Devulcanization of carbon black filled natural rubber using supercritical carbon dioxide

AbstractNatural rubber (NR) vulcanizates filled with various contents of carbon black were devulcanized in supercritical CO2 in the presence of diphenyl disulfide as a devulcanizing reagent. The devulcanized rubbers were separated to sol and gel components using chloroform. Regardless of the carbon black content in the NR vulcanizates, sol fractions of 20–40% were obtained and the swelling ratios of the gel components were higher than the original vulcanizates. Dynamic mechanical properties of the devulcanized rubbers were also investigated. Devulcanized rubbers showed a slightly lower G′ values and slightly higher tan δ values than the initial compounds and much lower G′ values and much higher tan δ values than the vulcanizates. These results indicate that the presence of carbon black in NR vulcanizates does not disturb the devulcanization. A NR‐based truck tire vulcanizate was also devulcanized. The physical properties of recycled rubber made from virgin rubber and various contents of the devulcanized tire rubber were measured. The decrease in tensile strength was only around 10% at up to 40 phr of the devulcanized tire rubber content. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 137–143, 2005

Elastic steric stabilization of polyethylene-asphalt emulsions by using low molecular weight polybutadiene and devulcanized rubber tire

Emulsions containing 3% polyethylene were stabilized against coalescence in an asphalt medium by low molecular weight virgin polybutadiene and recycled styrene-butadiene stabilizers. The recycled styrene-butadiene steric stabilizer precursor was obtained as a thermo-mechanical devulcanized ground rubber tire in asphalt. The low molecular weight butadiene and styrenebutadiene rubbers were in situ reacted with sulfur in order to increase the compatibility of the stabilizer with the asphalt phase.