FTIR spectroscopic and thermogravimetric characterization of ground tyre rubber devulcanized by microwave treatment

In this work the phenomena involved with the microwave devulcanization of ground tyre rubber (GTR) were investigated. During studies three types of GTR characterized by different content of organic compounds (elastomers, plasticizers, etc..), carbon black and ash have been analyzed. The chemical structure of GTR before and after microwave devulcanization process was studied by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Furthermore, efficiency of microwave devulcanization conducted at different time was evaluated based on the crosslinking density and sol content values. FTIR spectroscopy results shown that devulcanization of GTR causes a decrease in carbon black with generation of CO2 due to its thermo oxidation, a decrease in structural groups of elastomeric components (mainly methylene and methine) and a breaking of C-S groups and S-S bridges. The presented results indicate the strong correlation between content of SiO2 in GTR and its degree of devulcanization. It was observed that GTR with a high content of SiO2 are easier devulcanized than samples with low content of SiO2, which suggest the presence of silica fillers improve microwave devulcanization efficiencyPostprint (author's final draft

Preliminary investigation on auto-thermal extrusion of ground tire rubber

Ground tire rubber (GTR) was processed using an auto-thermal extrusion as prerequisite to green reclaiming of GTR. The reclaimed GTR underwent a series of tests: thermogravimetric analysis combined with Fourier-transform infrared spectroscopy (TGA-FTIR), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and static headspace and gas chromatography-mass spectrometry (SHS-GC-MS) in order to evaluate the impact of barrel heating solution (with/without external barrel heating) on reclaiming process of GTR. Moreover, samples were cured to assess the impact of reclaiming heating solution on curing characteristics and physico-mechanical properties. Detailed analysis of the results indicated that the heat supplied by the machinery was replaced by energy generated due to the high shearing phenomenon, what significantly influenced energy consumption and hereby lowered processing costPostprint (published version

Structural and physico-mechanical properties of natural rubber/GTR composites devulcanized by microwaves: influence of GTR source and irradiation time

Ground tire rubber from car and truck was modified using microwave irradiation at variable time. The irradiated ground tire rubber was used as filler in composites based on natural rubber. The composites, with high content of ground tire rubber, were prepared using an internal batch mixer and subsequently cross-linked at 160¿. The influence of the ground tire rubber source (car/truck) and irradiation time on structure, physico-mechanical behaviour, thermal properties and morphology of natural rubber/ground tire rubber composites was studied. The interfacial interactions between ground tire rubber and natural rubber as function of ground tire rubber source and irradiation time were evaluated by Fourier transform infrared spectroscopy, thermogravimetric analysis, tensile tests, swelling measurements and scanning electron microscopy. The results showed that irradiation of ground tire rubber slightly enhanced tensile properties and cross-link density of natural rubber/ground tire rubber composites. This effect was more evident in the case of ground tire rubbertruck because of its higher content of natural rubber and was reflected in changes in the interfacial adhesion, which were confirmed by the results of Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy analysisPostprint (author's final draft

Best Practice for the Devulcanization of Sulfur-cured SBR Rubber

In the present paper, special attention will be devoted to thermo-chemical devulcanization of sulfur-cured styrene butadiene rubber (SBR) using diphenyldisulfide (DPDS) as devulcanization aid. SBR is the main component in whole passenger car tire rubber and, at the same time, the most critical one in terms of devulcanization. This study is the first step to realize an effective devulcanization process for whole passenger car tire rubber. Diphenyldisulfide was found to be an effective agent for reclaiming of mainly natural rubber based sulfur-cured materials: DPDS acts as a radical scavenger and helps in preventing broken rubber chains to recombine. In this study, the effect of DPDS on the ratio of crosslink to polymer scission is investigated. The most important process parameter is the temperature, at which the polymer network is broken down. A reduction of the crosslink density of the devulcanizate is observed with increasing devulcanization temperature from 180C to 220C. However, above a temperature threshold of 220C, the crosslink density rises again. This is due to intra-molecular rearrangements of chain fragments of butadiene moieties from uncontrolled degradation and oxidation effects. Oxidation stabilizers are added during the devulcanization process in order to reduce the degradation and interrupt the oxidation cycles. Above a temperature threshold of 220C, a further decrease in crosslink density without creating more sol fraction can be achieved this way. The combination of DPDS and oxidation stabilizers significantly enhances the devulcanization efficiency of SBR versus the one obtained when DPDS is used alone. The results are interpreted in terms of mechanisms of main chain and sulfur bridge scissions and the degradative cycles triggered by the presence of oxyge

Análisis de los diferentes tipos de desvulcanizado en la caracterización de nuevos materiales elastoméricos formados por la mezcla de estireno butadieno-caucho natural y mezclados con neumáticos fuera de uso (GTR)

This article proposes the creation of a new material useful for the industry from the mixture with rolls of two 50% virgin elastomers, styrene-butadiene (SBR) and natural rubber (NR) with tires out of use (GTR). These tires have been previously devulcanized following a number of techniques, which will be analyzed in this article, and then mixed with the virgin elastomer SBR/NR and the corresponding additives, revulcanized this new material in order to reach the mechanical properties, thermal and of structure that allow its use in the industry. Specifically, three types of samples have been analyzed; a first one formed by the virgin elastomer (SBR/NR), a second adding to the SBR/NR, GTR in the proportion of 20 phr (parts per hundred rubber), and a third adding to the SBR/NR, GTR in the proportion of 40 phr (more percentages were used in the mechanical tests in order to provide greater validity in the results). The GTR received has been devulcanized using different techniques: without devulcanitation (dn); mechanically devulcanized (dm); chemically and mechanically devulcanized (dcm); and microwave devulcanized (dmw). All these compounds have been tested with different tests; Mechanical, Crisscrossing Density, Gravimetric Thermal Analysis and Microscopy TestPeer ReviewedPostprint (published version

Tensile and Fracture Mechanical Properties of Styrene-Butadiene Rubbers (SBR) Filled with Industrial and Pyrolytic Carbon Blacks, and Organoclay

In this work we examined effects of filler combinations (industrial carbon black (CB), pelletized pyrolytic carbon black (pCBp) and organoclay (I30.P) on the tensile mechanical and fracture mechanical properties of SBR rubbers. The performance of standard N660 CB was compared with that of pCBp when used alone or in 1: 1 blend ratio at an overall filler content of 60 part per hundred part rubber (phr). The study covered also a mix composed of 20 phr pCB, 20 phr N660 and 10 phr I30.P the hardness of which was identical to those of the (p)CB filled ones. N660 yielded better tensile properties than pCBp. By contrast, the latter yielded higher tear and trouser tear strength values than CB. I30.P increased the storage modulus value (E’) in spite of the filler content of 50 phr. Presence of organoclay and pCBp also increased the critical value of the J-integral.</jats:p

Rubberised bitumen manufacturing assisted by rheological measurements

This paper investigates the effect of processing temperature and time on the rheological properties of recycled tyre rubber-modified bitumens (RTR-MBs) produced using two different base binders and an ambient ground crumb rubber modifier (CRM). The production of the RTR-MBs was accomplished by means of a standard Brookfield rotational viscometer together with a modified impeller, dual helical impeller, to allow mixing as well as real-time viscosity measurements of the produced RTR-MBs. The rheological properties of the final RTR-MBs were determined by means of standard dynamic mechanical analysis oscillatory and multiple stress creep recovery testing using a dynamic shear rheometer. The results indicate that the low processing conditions (160°C and 60 min) are not appropriate for developing RTR-MBs with enhanced physical and rheological properties. However, allowing the crumb rubber to interact with the base binder for longer mixing times (140 min) led to the development of an enhanced rubber (polymer) network structure within the blend (i.e. swelling of the CRM particles) and superior rheological properties. At the other extreme, using high-processing conditions (200°C and 140 min) led to RTR-MBs in which the rubber network had been subjected to devulcanisation and depolymerisation with a subsequent reduction in modification