The disposal of urban solid residues is an enormous problem, especially in the case of vulcanized rubbers like tires. The old practice of landfilling is out of use due to the rising land costs, ...environmental concerns, fire risks and the possibility of proliferation of mosquitoes and other disease-carrying vectors. Devulcanization is shown to be an effective technique for making rubbers to flow and to be remolded. However, this process not only breaks down sulphur links, but also creates new other bonds, modifying the structure of the material as a whole.
In order to help understand structural modifications of ground tire rubbers (GTR) as a result of devulcanization by microwaves, this work proposes an in-depth study of the chemical modifications, flow and thermo-oxidative degradation behavior as a function of the exposure time of the GTR to microwaves. An important conclusion is that the final temperature reached by the sample is the primary factor responsible for the success of the process. Depending on the final temperature of the sample, different types of sulphur bonds can be broken. During the treatment, there is a balance between break down and formation of new bonds. Therefore, it is important to control the process carefully in order to avoid degradation of the main chains. Tires usually are composed of a mixture of synthetic and natural rubbers, wherein natural rubbers could be more degraded by microwaves because carbon black is mainly found on this phase.
For a sustainable development, recycling is a very important step, which, beyond saving the use of natural resources, can also be a solution for low-income families, providing them earnings. ...Recycling is also considered a category of green chemistry and contributes to the reduction of pollution, bringing the improvement to the public health. However, recycling of a material trying to contribute to the environment will not bring positive results if the final properties of the recycled material do not point to an application that is viable. In this sense, the aim of this work is to present a comprehensive study of the revulcanized ground tire rubber samples, previously devulcanized by the action of the microwaves under different exposure times. It is extremely important to know in depth the modifications that occurred in the recycled material during all the stages of the recycling process to which the material was subjected, in order to select the ideal application for the recycled material. The obtained results pointed out to modifications as a result of the revulcanization process, such as in the chemical structure, composition, thermal stability, and morphology.
Vulcanized residues of ethylene–propylene–diene monomer rubber (EPDM) from expanded profiles trims, called EPDM-r, were treated to remove the paraffinic oil and then devulcanized by microwaves at ...different exposure times (0, 2, 3 and 4 min). Elastomeric formulations of EPDM-r compound/raw EPDM compound containing 67 wt% of recycled phase were produced, and the characteristics of the vulcanization process, mechanical and dynamic-mechanical properties, morphology and accelerated aging of the blends were analyzed. The promising results showed that it is possible to obtain new rubber compositions containing 67 wt% of EPDM-r with similar—or even higher—mechanical properties than the Reference sample (without EPDM-r), pointing out to the potential use of devulcanized EPDM-r in several applications, as a possible solution to the destination of these materials, aiming at the sustainable development.
Highlights
Production of elastomeric blends containing a high concentration of ethylene–propylene–diene monomer rubber (EPDM), i.e. 67 wt%.
Devulcanization of the EPDM residue by microwaves irradiation.
Increasing the microwave exposure time improved the efficiency of the devulcanization process.
Extraction of the paraffinic oil from the EPDM residue (before devulcanization) improved the efficiency of the devulcanization process.
The final material has a potential application of the residues from the automobile industry itself, such as in the manufacture of new products.
Nanocomposites of NBR with different types of clays were prepared and characterized in terms of their morphology by X-ray diffraction and mechanical properties. It was observed that the ...organo-modifier agent of the clays and the molar mass of rubber had a significant influence on the dispersion of the clay lamellae during mixing on a two-roll mill. The results suggest that this simple and quick method of mixing and compounding seems to be viable to obtain reinforced materials on the nanoscale.
The rheometric measurements were used to study the kinetics of vulcanization of the nanocomposites nitrile butadiene rubber (NBR)/organically modified montmorillonite in different concentrations. The ...presence of clay has modified the rheometric properties of rubber. However the E
a values were not significantly modified with the presence of nanofiller.
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