selected from the group consisting of:(1) an ester having the structure: ##STR15## wherein R1 is hydrogen, an alkyl group having from 1 to 30 carbon atoms, or a halogen, and R2 is an alkyl group having from 1 to 6 carbon atoms, (2) an alpha-olefin having the structure: ##STR16## wherein R' and R are alkyl groups having from 1 to 7 carbon atoms, (3) a vinyl ether selected from the group consistin