Pyro = heat, lysis = breakdown into parts. Pyrolysis is chemical reaction in which large molecules are broken down into smaller molecules. Simplest example of pyrolysis is cooking in which complex food molecules are broken down into smaller & easily digestible molecules.
Waste plastic and tire are long chain molecules or polymer hydrocarbons. Pyrolysis technology is the industrial process of breaking down large molecules of plastic/tire into smaller molecules of oil, gas and carbon black. Pyrolysis of waste plastic or tire takes place in absence of oxygen, at about 350-550 degree C and reaction time is about 15-45 minutes