PP for Buried Sewage Piping Systems

Polypropylene has, in Europe, during the last decades gradually gained a stronger position as pipe material for non pressure sewerage applications. First heterophasic PP copolymers came into use in indoor sewerage systems, e.g. in Germany and in Scandinavia. Later Structured Wall Piping systems were developed for large diameter road drainage and buried sewerage systems. During the last years. PP has started to penetrate the solid wall underground drainage and sewerage segment in outer diameter 110 to 200 mm, mainly in competition with traditional pipe materials. This development has been predominant in Scandinavia. Pipe producers have introduced stiffness class 6 kNlm2 T6 according to SS 3604, i.e. pipe series S14 according to IS0 4065. Additionally, within the European CEN standardisation, EN 1852-1 has been developed and is scheduled for implementation in Europe. In EN 1852-1 stiffness class 8 kNlm2 is allowed according to S11.2 dimensioning and stiffness class 4 kNlm2 according to S16. Recently, the development of new stiff heterophasic PP copolymers has gained momentum with an increasing pace. High Crystalline PP with high isotacticity together with controlled nucleation give products with improved Stiffnessllmpact balance. Flexural Modulus I Tensile E-modulus values have been increased by 20 to 50 % with retained or improved Impact properties. These products can be used for Stiffness Class 8 kNlm2 with solid wall pipe dimensioning S12.5 to S14, resulting in less weighurn pipe compared to other materials. The future situation is discussed, where PP material development is in front of standardisation, and will allow for new and competitive solutions for buried sewerage systems.