Physical Ageing of uPVC Gas and Water Pipes

TLDR: In this paper, the authors investigated the kinetics of physical ageing of unplasticized PVC pipes using Differential Scanning Calorimetry, and a quantitative model was set up that describes the influence of ageing time and temperature on the well-known endothermic ageing peak.

Abstract: The kinetics of physical ageing of un-plasticized P VC was investigated using Differential Scanning Calorimetry. A quantitative model was set up that describes the influence of ageing time and temperature on the well-known endothermic ageing peak. The activation energy for physical ageing of 116 kJoule/mole is very close to the literature value (115 kJoule/mole). Physical ageing of uPVC pipes leads to a decrease i n impact resistance and may ‐ for uPVC water pipes ‐ decrease the water hammer resistance. To study this, Rapid Crack Propagation measurements were performed, to assess the Critical Pressure. Crack initiation was always performed where the wall was at its thickest. Thus, RCP data was obtained with about 80% less scatter than usual. Excavated uPVC gas and water pipes have absorbed varying concentrations of water (maximum uptake 0.6 %) and carbon dioxide, which both act as plasticizer. Along with physical ageing these phenomena may affect impact performance.