dinone or the like); 1-alkyl substituted pyrrolidinones; 1-aryl substituted pyrrolidinones; dialkyl- and dicycloalkyl-carbodiimides having from about 5 to about 20 carbon atoms; ##STR1## wherein each R2 is the same or different and is an alkyl, cycloalkyl or aryl, having from 1 to about 12 carbon atoms.