Term from organic chemistry. PAO is the acronym for "Poly Alpha Olefins", synthetic isoparaffins with short main and long side chains. Starting substances are either short-chain polyethylenes (e.g. hexene or octene) or olefinic fractions obtained from cracking processes and separated into relatively different fractions by distillation processes. Low molecular PAOs are e.g. the main component of synthetic engine lubricating oils. Higher molecular PAOs (resins) are used for adhesives. S.a. PAH, MOSH, MOAH.