Effect of aging in hot chlorinated water on the mechanical behavior of polypropylene for solar-thermal applications

Polypropylene (PP) is increasingly considered as a material choice for pressurized components in solar-thermal systems. In these systems, the materials are exposed to superimposed mechanical and environmental loads. The objective of this research is the characterization of the mechanical behavior of three different black-pigmented polypropylene (PP) grades immersed for up to 750 h in chlorinated water (5 ppm chlorine content) at an elevated temperature of 60°C. Hence, values for strain-at-break and essential work of fracture were determined by tensile tests. For the strain-at-break values and for the essential work of fracture values a similar exposure dependence was obtained. Depending on the PP grade, time-to-embrittlement values of 250 h and 750 h were achieved. For one PP grade, both testing methods led to an identical time-to-embrittlement value of 750 h.