Polyolefin - Polyolefins are the largest group of thermoplastics, often referred to as commodity thermoplastics, they are polymers of simple olefins such as ethylene, propylene, butenes, isoprenes, and pentenes, and copolymers and modifications thereof. The term polyolefins means "oil-like" and refers to the oily or waxy feel that these materials have. Polyolefins consist only of carbon and hydrogen atoms and they are non-aromatic. Polyolefins are usually processed by extrusion, injection molding, blow molding, and rotational molding methods. Thermoforming, calendering, and compression molding are used to a lesser degree. An inherent characteristic common to all polyolefins is a nonpolar, nonporous, low-energy surface that is not receptive to inks, and lacquers without special oxidative pretreatment. The two most important and common polyolefins are polyethylene and polypropylene and they are very popular due to their low cost and wide range of applications.