Aging of polyethylene: Non-destructive testing with mobile magnetic resonance

Magnetic Resonance (NMR: Nuclear Magnetic Resonance) is known in medical imaging as a diagnostic tool and in chemistry as a spectroscopic method for molecular structural analysis. In both cases, the object of interest is investigated with radio-frequency waves in the center of strong super-conducting magnets. High and homogeneous magnetic fields simplify the measurement process, but give rise to high equipment cost. On the other hand, weak and inhomogeneous magnetic fields can be generated with small permanent magnets, and the NMR relaxation times important for materials characterization can be measured with small and portable sensors, which are brought into contact with the object at the site of interest. Investigations of PE pipes and aged PE coatings of steel pipes demonstrate, that the morphology of partially crystalline polymers like polyethylene can well be characterized with this mobile NMR technology, and that the measured NMR parameters are of use for a state assessment of the material.

Blümich, A. Adams-Buda, M. Baias, Alterung von Polyethylen: Zerstörungsfreies Prüfen mit mobiler magnetischer Resonanz, GWF Gas Erdgas 148 (2007) 95–98.