EghtesadOnline: Few Americans care about ethylene. Many have probably never heard of it. As it turns out, this colorless, flammable gas is arguably the most important petrochemical on the planet -- and much of it comes from the hurricane-stricken Gulf Coast . Ethylene is one of the big reasons the damage wrought by Hurricane Harvey in the chemical communities along the Gulf of Mexico is likely to ripple through U.S. manufacturing of essential items from milk jugs to mattresses.