In this work, EPDM rubber crumbs from used tyres have been treated in batch and continuous processes in order to produce a regenerated material. For this purpose, the effect of EPDM particle size, oil type, and concentration as well as processing time, temperature, and mixing intensity were controlled for treatment in an internal batch mixer and a twin-screw extruder. The degree of regeneration was quantifi ed via a modifi cation of the ASTM D6814 method based on crosslink density determination from swelling experiments. The results showed that crosslink density reduction can occur even without any addition of a chemical agent. It is also shown that some conditions can lead to an increase in crosslink density. Physical models are proposed to account for both increase and decrease in crosslink density with processing conditions.

The properties of recycled styrene-butadiene rubber (SBR) powder with polystyrene (PS) have been studied as a function of compounding conditions in an internal batch mixer. In particular, the effect of temperature (160-220°C), rotor speed (30-120 rpm), homogenization time (3-9 min), components introduction order, surface treatment of SBR powder with a PS/tetrahydrofuran (THF) solution, and addition of a coupling agent (styrene-ethylene-butylene-styrene, SEBS) were studied. The compounds were then compression moulded and samples were prepared to measure their hardness, tensile properties (modulus, strength and elongation at break) and impact strength. Morphological analysis via scanning electronic microscopy (SEM) on selected samples was also performed to determine the interfacial state between the components. From all the results obtained, an optimisation procedure is proposed allowing the best compound to be determined as a function of final application.

This work presents the effect of EPDM powder particles size on its thermomechanical regeneration process in a batch mixer. The recycled material was decomposed into six particle groups (125, 250, 355, 500, 710 and 1000 µm) to be treated separately under controlled temperature and rotor speed to determine the relation between specific surface area and bulk regeneration. In each case, EPDM crosslink density was measured using the polymer-solvent interaction described by Flory-Rehner's equation. The results showed that not only regeneration can be achieved (crosslink density reduction), but specific conditions also led to increased reticulation degree. Images of the particles before and after treatment were also analyzed and showed that aggregates presence may distort the sieving and treatment processes of the rubber particles.

Recycled Styrene-Butadiene Rubber (SBR) from ground tire rubber (GTR) was sieved into four granulometric fractions between 125 and 500 microns to determine the effect of particle size on its thermo-mechano-chemical regeneration in an internal batch mixer. Different temperatures (140-180°C) and rotor speeds (40-120 rpm) were imposed with and without the addition of a regeneration aid (aromatic oil). The results show that partial regeneration (lower crosslinking degree) is possible under specific thermo-mechanical conditions, but the addition of the aromatic oil has limited efficiency towards this regeneration.