Abstract
A polyurethane consisting of a poly(propylene oxide) soft segment and a diphenylmethane diisocyanate—hydroquinone di‐(b̃‐hydroxyethyl) ether (HQEE) hard block has been characterized over the composition range of 30 to 60 percent hard block. The flexural modulus varied from 60 to 900 MPa over this composition range. The elongation was approximately 250 percent at the lower hard block contents but fell below 100 percent at 60 percent hard block. Differential scanning calorirnetric measurements showed that the crystallinity associated with the hard phase increased with increasing hard block content but decreased with increasing cure temperature. The heat sag was found to decrease with increasing hardblock and increase with increasing cure temperature. A material with properties comparable to current fascia materials had a significantly better heat sag resistance than a current RIM (reaction injection molding) polyurethane. The combination of the solid chain extender, HQEE, and a solid catalyst, zinc stearate, lowing it to be processed as a one‐component resin having a pot life of greater than 8 h at 20°C al‐injection molding machines. The one‐component nature of the resin has made it possible to use a continuous in‐line mexer and to reduce the amount of scrap by using cold runner molds. In addition, any scrap that is generated can be used as regrind in the system.