Consequences of annealing during long-term pressure tests on polyvinylidene fluoride pipes

The long-term behaviour of PVF2 in the slow crack growth (SCG) regime is usually predicted from burst tests. Lifetimes measured from such tests are quite long (several months at least) making accelerated tests interesting alternatives. Creep tests were performed on three-notched PVF2 samples; the morphology of the damage zone created at the notch tip is analysed and compared to that observed in pipes failed by SCG. Some differences can be interpreted from the microstructure and mechanical changes occurring during annealing. DSC experiments, tensile and accelerated tests are performed to evaluate these changes.