PEL-CAT 9640 is a moderately active trimerization catalyst used in a wide variety of rigid polyurethane and polyisocyanurate foam and non-foam applications. It improves dimensional stability in many rigid foam systems and is a useful co-catalyst in rigid spray foam. PEL-CAT 9640 belongs to what is known as the group of gel catalysts. It is recommended for use as a co-catalyst with other polyurethane and polyisocyanurate catalysts, particularly in formulations with an isocyanate index greater than 110. It has reduced trimerization activity, as compared with stronger catalysts like PEL-CAT 9540-A and PEL-CAT 9807.