Description:
AbstractRigid PVC pipes prepared from a particle‐free, tin‐stabilized formulation were subjected to constant internal pressure tests (16 MPa, 60°C), originally in order to study the scattering in time‐to‐failure of pipes free from crack‐initiating particles. Although many efforts were made to produce pipes free from all possible foreign particles, most failures were initiated by particles. The particles in this case were soft and rubbery, Particles of this kind have previously never been found in any of the several hundred fracture surfaces in lead‐stabilized PVC pipes containing calcium carbonate studied in this laboratory. The possible origin of the soft particles is discussed. The results suggest that soft particles represent serious flaws. Besides a full‐grown (penetrating) crack, some of the pipes also contained growing, particle‐induced cracks. In these cases the penetrating crack always contained the largest particle. The presence of growing cracks in fractured pipes indicates the crack propagation rate in rigid PVC to be rather low at the test temperature and stress level used. Fracture surface morphology and creep thinning of the pipe wall at the point of fracture most likely were strongly affected by physical aging during the test period.