AN ATOMIC-FORCE MICROSCOPY STUDY OF THE EFFECT OF TENSILE LOADING ANDELEVATED-TEMPERATURE ON POLYVINYLIDENE FLUORIDE FROM FLEXIBLE OIL PIPELINES

Flexible pipelines and risers have been used for more than 20 years fo r the transport of oil and gas in the petroleum industry. In the curre nt study, a phase II polyvinylidene fluoride based pipeline material w as subjected to varying degrees of tensile deformation, and microtomed sections were examined by atomic force microscopy (AFM) in order to i nvestigate the resulting topographic changes. The effects of annealing at 100 and 130 degrees C on the maximum load and on topography were a lso studied. Annealing at 130 degrees C for varying lengths of time ga ve an increase in the maximum load which was found to be dependent upo n crystallization kinetics. AFM studies showed ridges running perpendi cular to the loading axis, which are attributed to flow lines resultin g from the extrusion process. In annealed samples these ridges were cl oser together than in unannealed samples. The ridges were absent in qu enched samples, but they gradually reappeared after storage at room te mperature. These observations were further verified by transmission el ectron microscopy studies.