polyurethane foam compositions and processes to make flexible polyurethane foams are disclosed . polyurethane foam is produced in the presence of additives comprising guanidine derivatives . improvements in physical properties such as air flow , dimensional stability , tensile , tear , elongation and foam hardness is observed when these additives are present in polyurethane formulations . in addition , these additives can minimize polymer degradation under humid ageing conditions resulting in foam products with better mechanical properties .