TABLE OF CONTENTS Polyvinyl chloride (PVC) is a product based on the earth s natural resources: salt and gas or oil. Salt water electrolysis yields chlorine (in addition to caustic soda and hydrogen). Ethylene can be derived from naphtha when oil is refined or from natural gas. Chlorine and ethylene can be combined to form the monomer vinyl chloride. PVC results from the polymerisation of vinyl chloride.
PVC cannot be processed on its own due to its very low thermal stability and high melt viscosity. Therefore, it is necessary to combine with the polymer a number of suitable additives to give a wide and varied range of properties to satisfy many different end-use applications. It is this scope for generating a wide range of properties through appropriate formulation that gives PVC a broad application coverage that is unmatched by any other commodity thermoplastic. Its durability (85% is used in medium- to long-term lifespan applications), linked to its cost effectiveness, has made it the second largest commodity plastic after polyethylene (PE).
PVC is a thermoplastic, meaning that it has the property of softening or fusing when heated and hardening when cooled. Thermoplastic materials, correctly formulated, can undergo this process many times without undergoing any appreciable chemical change. PVC has primarily an amorphous structure, i.e., lacking positional order on the molecular scale, and shows typical characteristics of dimensional stability up to the glass transition temperature ( T g): creep resistance, low shrinkage, impact resistance but notch sensitive, and good transparency. T g
