Thermogravimetric Analysis of Composites Obtained from Polyurethane and Rubber Waste

Abstract

The thermogravimetric analysis was applied for indication of the thermal stability of polyurethane-rubber composites received from polyurethane and rubber waste. The results of the thermogravimetric analysis show that the decomposition of rubber granulate depends on the speed of heating. It starts within the temperature range from 320°C to 360°C and is completed at the temperature range from 500°C to 550°C. The evaporation of small-molecular substances probably takes place below 300°C. At temperatures above 320°C, two-stage decomposition of rubber and polyurethane-rubber waste composites was observed. The low temperature decomposition of rubber probably corresponds to the decomposition of natural rubber (NR) while the high temperature decomposition corresponds to decomposition of styrene-butadiene rubber (SBR) or/and butadiene rubber (BR). The thermogravimetric studies of the polyurethanes obtained from different isocyanates showed that the increase of thermal stability depends on the isocyanate used. The one-stage decompositions of different polyurethanes were observed. Polyurethane-rubber composites undergo two-stage decomposition. Thus, the low temperature decomposition of composites may be connected to the decomposition of suitable polyurethane and NR, and the high temperature decomposition may be connected to the decomposition of SBR or/and BR as it was observed for rubber granulate. Tested samples of composites contained polyols of the trade name Recypol® 201 and Recypol®601 received from used polyurethane foam and of rubber recyclate received from tyres in the form of a granulate of dimensions ranging from 1.5 to 2.0 mm. The percentage ratio of polyurethane glue/rubber granulate: 5/95; 7.5/92.5; 10/90 was chosen. The profiles of composites were held at the temperature of 90°C for 90 min under the load of and 2 ·106 Pa. Thermogravimetric analysis of the samples was conducted using Perkin Elmer TGA PYRIS. Measurements were performed at the temperatures from 25°C to 900°C, with heating rates of 20°C/min, 40°C/min, 80°C/min using nitrogen as the purge gas. The value of the apparent activation energy of decomposition processes of the composites is reported.