What is the X in X-mas?
propylene pro·pyl·ene (prō'pə-lēn')
A flammable gas derived from processing petroleum hydrocarbon and used in organic synthesis. Also called propene.
a colourless, flammable, gaseous hydrocarbon, C3H6, obtained from petroleum; large quantities of propylene are used in the manufacture of resins, fibres, and elastomers (see polyolefin), and numerous other chemical products. See glycol; propyl alcohol.