Liquid terpene resin, also called polyterpene resin, is a tackifier synthesized from alpha-pinene and beta-pinene by cationic polymerization. As a light-yellow transparent liquid it is added to hot-melt and pressure-sensitive adhesive formulations to raise tack and improve wet-out, and it doubles as a modifier in coatings. It dissolves in benzene, toluene, turpentine and gasoline but is insoluble in water, formic acid and ethanol, and it offers excellent radiation and aging resistance plus strong electrical insulation, which makes it a durable tackifier for adhesives that must survive heat, UV and long service life.