POLYTETRAMETHYLENE ETHER GLYCOL - EFFECT OF CONCENTRATION, MOLECULAR-WEIGHT, AND MOLECULAR-WEIGHT DISTRIBUTION ON PROPERTIES OF MDI/BDO-BASED POLYURETHANES

Experimental data are presented which show that hardness, modulus, and tear strength of PTMEG-based polyurethanes are mainly affected by the hard-segment (MDI/BDO) concentration. On the other hand, PTMEG molecular weight mainly influences low-temperature and dynamic properties. Resilience and hydrolytic stability are affected by both soft-segment concentration and chain length. PTMEG of narrow molecular weight distribution yields softer polyurethanes with considerably longer elongation at break. Broad molecular weight distribution is advantageous only at the low molecular weight range (650 and 1000), giving rise to improved resilence and low-temperature performance. Polyurethanes made from PTMEG of low molecular weight (M OVER BAR //n less than equivalent to 1000) have inherent drawbacks due to poor phase separation (high T//g) and limits in soft segment concentration. Optimum overall polyurethane properties can be achieved with PTMEG in the molecular weight range of 1800 to 2100.