Abstract
It is known that MbOCA [4,4'-methylene-bis(2-chloroaniline)] can improve the modulus of molded foams significantly. Due to a suspected health problem, it is not used in foam production in North America. Evaluation of amine additives with structures similar to MbOCA should provide information on how amine additives change the foam matrix morphology and its mechanical properties. These data could also guide the future design of new amine additives for a MbOCA replacement.
Four additives, MbOCA, DEOA [diethanolamine], Unilink™ 4200 [N,N’-dialkylamino-diphenylmethane] and Unilink™ 4100 [N,N'-di-sec-butyl-p-phenylenediamine] were evaluated in a standard TDI molded foam formulation. A molded foam without any additive was also tested as a reference. In-situ FTIR and modulus development during foaming were used to study the reaction kinetics of the foams. The cured foam matrix morphology was evaluated using IR, SAXS, DMS as well as extraction tests. Compression sets at 75% deflection were measured for all foams.
The data show that amine reactivity plays an important role in foam matrix morphology and final properties. If the amine additive reacts too fast, the urea phase separation will occur very early. This will hinder the gelling reaction and the urea phase will be ineffective in improving hard segment packing. This will lead to a poorer compression set and foam matrix modulus, as in the case of Unilink™ 4100. When its reactivity is lower, the amine additive can get incorporated into the hard segment effectively and increase both hard segment packing and content without significantly affecting the gelling reaction. This will lead to a much improved compression set and higher modulus. This is the case for both Unilink™ 4200 and MbOCA. DEOA can be incorporated into the system, but tends to disrupt hard segment packing and results in foam with much lower hardness.
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