Kinetics of isothermal degradation studies of nanosilica-polyurethane composites

J. VEGA-BAUDRIT; P. VÁZQUEZ; J.M. MARTÍN-MARTÍNEZ

Barcelona - España

Jornada; VII Jornadas sobre Adhesivos en EUROCOAT; 2006

EUROCOAT

Polyurethanes thermoplastics adhesives containing fumed silicas with different degree of silanization were prepared and characterized using FTIR spectroscopy, transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and isothermal thermogravimetric analysis. The effect of the presence of nanosilicas with different hydrophilic degree in the thermoplastic polyurethanes was investigated. An analysis of the isothermal methods to evaluate kinetic parameters of decomposition of solids from isothermal thermogravimetric data is presented.   In TPU nanocomposites, the segmental incompatibility on the TPU was increased with the presence of the hydrophilic nanosilicas. The formation of hydrogen-bonds between soft segments chains from TPU and the silanol groups on the silica surface was favoured. Therefore, TPU became well-organized and consequently crystallinity was increased. The results obtained show that fumed nanosilica improved thermal properties. Kinetic parameters were studied using degradation standard equation and Arrhenius method. When the temperature of the isothermal analysis was increased, an increased of the rate constant was obtained. The nanosilica in TPU decreases the kinetics of decomposition due to the increase of the interaction between the polyurethane soft segments. The silanol groups on the silica surface enhance the phase separation and improved the thermal properties. Finally, the fumed nanosilica in TPU-nanocomposites changed the thermal degradation mechanism.