Optimization of composition of soy-based polyols for rigid polyurethane foams

Soybean oil-based polyols can be synthesized with different OH content. Higher OH number polyols display higher viscosity, which may limit their applications in foams. Adding glycerin to a polyol affects crosslinking density and homogeneity of the networks. It would be advantageous to use a lower OH content and a lower viscosity polyol and adjust the OH number with glycerin if the properties would stay the same. Apart from having lower viscosity, polyols with lower a OH number are easier to prepare. It has been shown that rigid foams based on the polyol having an OH number of 180 mg KOH/g have similar properties as those based on the polyol with an OH number of 208 mg KOH/g if the final OH number of the polyol system (polyol, crosslinker and water) is adjusted to the same value, although heat stability (onset of softening) of the former was lower.