Effects of four isocyanates and four plasticizers on the thermomechanical and tensile properties of hydroxyl-terminated polybutadiene elastomers and the effect of solid particle filling

The aim of this study is to analyze effect of four different isocyanates and four different plasticizers in hydroxyl-terminated polybutadiene (HTPB) based elastomers by quantitative analysis of the shape of the loss factor (tan delta), tensile strength, deformation frequency shift of the maximum temperatures of loss moduli G" and of tan delta. The first part of the study shows intensities of the tan delta curves with the four isocyanates follow the order HDI > IPDI > H12MDI > Desmodur (TM) E305. By molecular modeling of the isocyanates and the corresponding polyurethane parts the influence of molecular geometry on tan delta are discussed. The second part of the study analyzes HTPB-IPDI elastomers with the four different plasticizers DOA, DOS, DOZ, and IDP. The IDP provides lowest T-g at about -83 degrees C, while the others provide at about -78 degrees C. In the third part, aluminum (Al-18 mu m) and ammonium perchlorate (AP-200 mu m) are added to HTPB-IPDI+DOA to analyze the effect of particle size, wt% content and particle type on the shape and intensity of the tan delta curves. From the frequency shift of the two maximum temperatures one receives activation energies Eaf. Their average values without and with plasticizer are with tan delta 178 and 165 kJ/mol and with G" 274 and 248 kJ/mol, respectively.