Thermomechanical reclaiming of ground tire rubber (GTR) was performed at different temperatures (60, 120, and 180 C) using a co-rotating twin-screw extruder. Obtained samples were used in styrenebutadiene rubber (SBR) blends. As reference samples, SBR compounds containing untreated GTR were used. Curing characteristics, static and dynamic mechanical properties, and morphology of the obtained blends were determined. The results show that the increase of barrel temperature during the thermomechanical reclaiming of GTR has a positive effect on the decrease of screw torque (lower machine load) and decrease of Mooney viscosity (better processing characteristics). However, mechanical properties and crosslink density of rubber revulcanizate decreased with increasing barrel temperature during the reclaiming process. SBR blends with 50 phr of reclaimed rubber showed increasing phase compatibility between SBR matrix and the reclaimed rubber, which was confirmed by mechanical properties and morphology measurements. J. VINYL ADDIT. TECHNOL., 22:213-221, 2016.

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In this article the results of research on a continuous thermomechanical reclaiming process of ground tire rubber (GTR) conducted in a twin screw extruder are presented. The effects of the rotation direction (co-rotating/counter-rotating), design of co-rotating plasticizing units and the rotational speed of the screws on the extruder working parameters, sol fraction and the degree of reclaiming in the obtained products were described. The influence of secondary vulcanization on cure characteristics as well as mechanical properties of revulcanizates, and blends of reclaimed rubber and styrene-butadiene rubber (SBR) were determined. Based on the obtained results, it was concluded that the application of counter-rotating plasticizing system (i.e. screw profile A), consisting mainly of transport elements with different pitch, increases the time during which ground tire rubber is exposed to the barrel temperature. The use of co-rotating plasticizing system, equipped with kneading elements and characterized by constant pitch, causes that the retention time of ground tire rubber in the extruder barrel is much shorter. In the case of co-rotating plasticizing system, it is also higher shear forces (then in counter-rotating screw configuration), besides temperature, acts on ground tire rubber, and converts mechanical energy into heat. Testing of styrene-butadiene rubber-ground tire rubber/reclaimed ground tire rubber (SBR-GTR/dGTR) compounds confirmed that the reclaiming process has positive influence on properties of obtained products.

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Searching for new and cost-effective methods of waste rubber recycling is a subject of research in many scientific centers in the world. In this paper there are presented results of the research of the extrusion process of cheap and environmentally friendly thermoplastic compositions containing 50% wt. of masses of ground tire rubber (GTR). The aim of this study was to determine the relationship between the mixing conditions and properties of obtained products, which is important from a technological point of view. The mixing conditions were determined by using two variables: the screw configuration (co-rotating and counter-rotating) and the type of polyethylene. In the case of both variables, thermoplastic compositions were treated with various shear forces induced by screw speed changes. The influence of mixing conditions on the extrusion process was determined (screw torque, melt flow rate) as well as static and dynamic mechanical properties of obtained materials.