Polyvinyl Chloride (PVC) is one of the most commonly used thermoplastic polymers in the world (next to only a few more widely used plastics like PET and PP). It is a naturally white and very brittle (prior to the additions of plasticizers) plastic. 

Some of the most significant properties of Polyvinyl Chloride (PVC) are:

Density: PVC is very dense compared to most plastics (specific gravity around 1.4)

Economics: PVC is readily available and cheap.

Hardness: Rigid PVC is very hard.

Strength: Rigid PVC has extremely good tensile strength.

Rigid PVC in particular has very high density for a plastic making it extremely hard and generally very strong. It is also readily available and very economical which combined with the long-lasting characteristics of most plastics make it an easy choice for many industrial applications like construction.