Particularly in the case of PP pipes there are several different molecular structures available on the market. In the simplest case the molecular chain is built up of one and the same repeating unit often the same as the monomer shown within the brackets). The polymer is then called homo-polymer. If instead the molecular chain is built up of two different repeating units( A and B) the polymers is called copolymer. In the case of PP the homo-polymer, often designated to PP-h, the repeating unit A is the monomer propylene. In PP copolymers, designated to PP-c, the unit B is the monomer ethylene. Dependent on how the repeating units A and B are arranged in the molecular chain, distinction is made between alternating, copolymers.
Polyvinyl Chloride Pipes (PVC ) and PPR pipes can be manufactured with or without plasticizers. Examples of the former are garden hose, floor tiling and household articles. The addition of plasticizers increases material flexibility, but leads to some deterioration in other physical properties. Furthermore, some plasticizers display a tendency to migrate, escaping in the course of time so that the plastics becomes brittle. For these reasons, no pastiches are used in the manufacturer of PVC pipes for water mains and sewers. In this respect, the material is characterized as rigid PVC and this variety is termed PVC-U ( unplasticized PVC) according to ISO.

Particularly in the case of PP pipes there are several different molecular structures available on the market. In the simplest case the molecular chain is built up of one and the same repeating unit often the same as the monomer shown within the brackets). The polymer is then called homo-polymer. If instead the molecular chain is built up of two different repeating units( A and B) the polymers is called copolymer. In the case of PP the homo-polymer, often designated to PP-h, the repeating unit A is the monomer propylene. In PP copolymers, designated to PP-c, the unit B is the monomer ethylene. Dependent on how the repeating units A and B are arranged in the molecular chain, distinction is made between alternating, copolymers.
Polyvinyl Chloride Pipes (PVC ) and PPR pipes can be manufactured with or without plasticizers. Examples of the former are garden hose, floor tiling and household articles. The addition of plasticizers increases material flexibility, but leads to some deterioration in other physical properties. Furthermore, some plasticizers display a tendency to migrate, escaping in the course of time so that the plastics becomes brittle. For these reasons, no pastiches are used in the manufacturer of PVC pipes for water mains and sewers. In this respect, the material is characterized as rigid PVC and this variety is termed PVC-U ( unplasticized PVC) according to ISO.