Since the discovery and usage of vulcanized rubber, rubber chemists noted that rubber, more so unvulcanized than vulcanized, degraded rapidly when exposed to the elements, namely, oxygen, ozone, heat, ultraviolet (UV) light, and so on. These early investigators later discovered that the degradation was related to reactions involving ozone and the double bonds or unsaturation in the polymeric molecular chains, which lead to a severed polymer chain. Still other reactions involved the formation and further reaction of radicals which resulted in the elastomer becoming either completely resinified (hard) or depolymerized (soft). It soon became evident that the prevention of these various forms of degradation was vital to the future of the rubber industry.