Effect of ground tire rubber on structural, mechanical and thermal properties of flexible polyurethane foams

Flexible polyurethane foams were modified with two kinds of ground tire rubber, untreated and thermo-mechanically reclaimed. A reclamation process was performed in auto-thermal conditions, which reduced the cost of the process and decreased the environmental impact of devulcanization (e.g., emission of gases). The reclamation process was carried out in a continuous manner using a co-rotating twin screw extruder. The foams were prepared by a single step method for the ratio of isocyanate groups to hydroxyl groups equals to one. The ground tire rubber particles were added to a polyol mixture. The impact of the rubber treatment on the properties of resulting polyurethane composites was determined by the analysis of static and dynamic mechanical properties and thermal properties. The incorporation of rubber particles into the polymer matrix caused significant changes in the cellular structure of polyurethane foam, which was confirmed by SEM images. Moreover, a higher content of ground tire rubber in the polyurethane/ground tire rubber foamed composites enhanced their cross-link density estimated from the swelling measurements. It was also confirmed by an increase of glass transition temperature measured by dynamic mechanical analysis and differential scanning calorimetry. Addition of ground tire rubber to polyurethane foams had very positive influence on their thermal stability measured by the temperature corresponding to the 2 % mass loss during degradation of material. Modification increased initial degradation temperature even by 14 °C compared to a reference sample.