Composites based on polyurethane-urea and ground rubber from car tyres: relation between structure and properties

The basis of this work is an investigation of multicomponent systems containing a reactive polyurethane-urea matrix, recycled rubber filler, and porosity. Rubber crumb with varying particle sizes obtained from used car tyres was used as the filler. As a matrix, water-curable isocyanate pre-polymer was used. Porosity was caused by the inability of the matrix to fully fill space between rubber particles, combined with foaming from matrix curing. We report on dependences of PUU/rubber system mechanical properties on the composition and structural parameters. Mechanical property values were obtained via tensile loading of prepared rectangular slabs. We found that mechanical behaviour exhibits strong correlation with a structural parameter called interspace filling, which expresses how much the matrix fills space between filler particles. Interspace filling is dependent on the degree of porosity and the volume fraction of the PUU matrix in a hypothetical nonporous material. Therefore, this work offers a simple characterization of complex materials, of which the studied porous composite is an example. Our results could contribute to the development of applications for large volumes of recycled rubber in materials used in rapid repair of roads and pavements.