Composites of polyurethane (PU) and asbestos (liner) are used as internal coating of rocket motors, providing thermal protection and assuring the adhesion between propellant and the motor walls. However, the use of asbestos has been restricted due to its hazardous nature. In the present work, asbestos was replaced by hydrated alumina silicate (SA) and expandable graphite (GE) in different contents. Thermogravimetric analysis (TG) showed that the thermal stability of liners was practically unaffected by the filler replacement although the activation energy obtained for the decomposition has changed. Thermomechanical analysis (TMA) showed that coefficients of thermal expansion of SA/liners were lower than asbestos/liner. SA/liners also presented the highest tension values in mechanical tests.
Polyurethane composite; aluminosilicate; expandable graphite; thermal stability
