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

Abstract

Waste tire rubber (WTR) supplied by a truck tire retreader were processed in an intermeshing co-rotating twin-screw extruder (ICTSE). The extrusion process evaluated the efficiency of the thermomechanical recycling in the devulcanization of WTR rubbers. Samples were prepared by varying the process parameters, the particles sizes and thermoplastics, and the latter was used as devulcanization auxiliary agents. After extrusion, samples were subjected to solvent extraction to determine the soluble fraction (SF). Subsequently, these SF were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The highest SF (29 wt%) was obtained with higher screw rotating speed and with smaller particle size. Higher SF indicated a higher degree of devulcanization. The FTIR and DSC analyses showed that natural rubber was the main rubber extracted from extruded samples. In addition, polypropylene was more effective than low-density polyethylene in the devulcanization process, promoting higher SF.

Ground Tire Rubber Modified by Ethylene-Vinyl Acetate Copolymer: Processing, Physico-Mechanical Properties, Volatile Organic Compounds Emission and Recycling Possibility

“…Nunes et al [ 27 ] investigated the effect of polypropylene or low-density polyethylene (in the range of: 15–25%wt.) on the thermo-mechanical devulcanization of GTR.…”

Incorporation of a recycled rubber compound from the shoe industry in polystyrene: Effect of SBS compatibilizer content

“…Granulometric distribution. Particle size distribution of the recycled SBRr compound was carried out according to ASTM D5644 from a 300 g sample of milled material, which was sieved and stirred for 20 min with a set of overlapping sieves and openings of 18,20,25,35,40,60,80,120, and 200 mesh.…”

“…Vulcanized rubber waste from tires and footwear is usually made of a complex mixture containing fillers, processing additives, curing agents, pigments, and stabilizers, and when improperly discarded into the environment, some of these ingredients that have low molar mass may contaminate the soil and the groundwater over time. [17][18][19][20][21] Furthermore, nowadays, the recycling of vulcanized rubbers is even more difficult as the industries improve rubber compositions with new additives in the blends aiming to increase their performance and lifetime. Also, the actual composition is unknown because it is an industrial secret.…”

Waste tires pyrolysis oil as a source of energy: Methods for refining

“…They are improved by microwave irradiation. 4 Nunes et al 5 use the extrusion process that raises the efficiency of the thermomechanical recycling in the devulcanization of the ground tire rubbers.…”