Hydrogenated hydroxy-terminated polyisoprene (HHTPI) based urethane network: network properties

Polyurethane (PU) networks based on hydrogenated hydroxytelechelic polyisoprene (HHTPI) and isophorone diisocyanate isocyanurate (IIPDI) were prepared and studied. Determination of the critical conversion point (pc=0.58) was obtained experimentally through rheological measurements. This value was similar to the value predicted using the Macosko Miller model. Differential scanning calorimetry (DSC) analyses show that PUs with a high degree of phase separation is obtained (81% for [NCO]/[OH]=1). This phase segregation decreased when hard segment content increased. Glass transition temperature of the soft segment, Tgs=−66 °C, was little affected by hard segment content. Thus, the resulting polyurethanes exhibit elastomeric properties. CO]/[OH]>1 ratios, a second transition at 70 °C was observed and attributed to hard segment interactions. Using swelling measurements, the solubility parameter δ, polyurethane–THF interaction parameter (χ), crosslink densities (νe) and the molecular weight between crosslinks ( M ¯ c ) were determined.