Direct moulding of rubber granules and powders from tyre recycling

SMART project (Sustainable Moulding of Articles from Recycled Tyres) is a research project financed by the European Commission with the aim of developing a new moulding process of granules and powders from tyre recycling without any addition of virgin rubber or linking agent. The so called “direct moulding” is a compression moulding process which is directly applied to rubber particles from tyre grinding. After one year of activities, the new moulding process has been deeply investigated and some results are reported in the current work for the first time. Rubber granules and powders were produced by GumiImpex (partner of the European project) thanks to different technologies: particles from tyre grinding and buffings from tyre machining. Different size distributions of rubber particles and buffings were used to produce rubber sheets with the size of 200x200x5 mm3 at the temperature of 160°C and the pressure of 3 MPa by using aluminium moulds. Tensile specimens were extracted from the sheets and tensile tests were performed and related to sample density and particle properties. Rubber densities over 1 g/cm3 have been reached for all the samples with ultimate tensile strength and maximum elongation up to 1 MPa and 80%, respectively. These mechanical data are very promising in comparison with properties of polyurethane bound rubber composites. Increasing moulding pressure and temperature would lead to higher mechanical properties, if necessary.