|pälē+ noun
Etymology: International Scientific Vocabulary poly- + isobutylene
: a polymer of isobutylene varying from a viscous oil to a sticky or rubbery solid ; especially : an elastomer (C 4 H 8 ) x that is formed at a low temperature (as -100° C) in the presence of a metal halide catalyst (as boron trifluoride) and that cannot be vulcanized unless a small amount of a proportion of isoprene or other diolefin has been incorporated with the isobutylene before polymerization — compare diisobutylene , synthetic rubber