Pyro = heat. Lysis = break down.Plastic Pyrolysis is chemical reaction. This reaction involves molecular breakdown of larger molecules into smaller molecules in presence of heat. Pyrolysis is also known as thermal cracking, cracking, thermolysis, depolymerization, etc.
At any given temperature the molecule is in vibrating stage. This is called molecular vibration. The frequency at which molecules vibrates is the directly proportional to the temperature of molecules. During pyrolysis the object’s molecules are subjected to very high temperatures leading to very high molecular vibrations. At these high molecular vibrations, every molecule in the object is stretched and shaken to such an extent that molecules starts breaking down into smaller molecules. This is pyrolysis.
Simplest example of pyrolysis is food cooking. When you cook food the temperature of food increases leading to higher molecular vibrations and breakdown of larger complex molecules into smaller and simple molecules. After cooking larger food molecules are pyrolyzed into smaller in simpler molecules which are easy to digest.