Kuriyama, Narisawa, Shiina, Kotaki
Additional Information - Posters # 1998 Gothenburg
Unplasticized polyvinylchloride (PVC-U) is extensively used in the pressure pipe applications. These pipes are usually designed to have 50 year lifetime. Although their service performance is generally very satisfactory , there has been a number of cases where the pipes fail at unexpectedly short times. One of the major causes of these early failures is faulty installation which leads to point loading such as is encountered in the case of the presence of stones pressing against the pipe wall. Another cause is manufacturing defects such as inclusions, voids and surface defects. These defects act as internal stress concentrators (!).
The resin properties, mold geometry and molding conditions are responsible for this manufacturing performance. Especially, the degree of gelation is an important processing factor which significantly influences the mechanical properties of the pipe. There are some studies which tried to correlate the gelation of the PVC-U pipes with fracture toughness °°”, However, there have been few studies which make clear the fracture micro-mechanism in relation to the level of gelation. In this study, we describe the toughening mechanisms of PVC-U pipes of several degrees of gelation based on microscopic observations.