Mobile NMR for Analysis of Polyethylene Pipes

Abstract

NMR relaxometry is a suitable tool to determine the morphology of semi-crystalline polymers by its ability to discriminate between rigid, mostly crystalline and soft, usually amorphous material. The NMR-MOUSE • R (nuclear magnetic resonance mobile universal surface explorer) was explored in this work to supply morphological data of poly(ethylene) pipes nondestructively. PE-100 pipes were investigated in the new state, after squeezing them flat, and after annealing well below the glass temperature. Furthermore, the change in morphology induced by a pressure load from the inside and a point load from the outside was investigated as a function of depth, and the morphology change across a welding line was imaged. A shear-band was detected by destructive high-field NMR imaging in an area of severe deformation of a pipe, where an anomalous depths profile was observed by the NMR-MOUSE. These results demonstrate that the NMR-MOUSE is a suitable tool for non-destructive state assessment of polymer pipes on the basis of laboratory reference data.

Single-sided NMR for the measurement of the degree of cross-linking and curing

“…For simplicity only T 2 instead of T 2eff will be used in the further text. The transverse relaxation of semi-crystalline polymers can be described by two components, a rapidly relaxing one deriving from crystalline and rigid amorphous areas and a slowly relaxing one from mobile amorphous regions (Blümich et al, 2005). The measurement signals can be fitted by…”

“…Another way to get suitable information is the use of echo sums (Blümich et al, 2008), also known as cumulative binning. The signal can be approximated by a sum of exponential functions…”

“…The echo sum is proportional to the signal integral which, after normalization of s(t), represents an amplitude-weighted average of the relaxation time T 2 (Blümich et al, 2008):…”

Time-Resolved Study of the Photo-Curing Process of Dental Resins with the NMR-MOUSE

“…In the characterization of polymers, unilateral NMR has been successfully used in the investigation of aging and cross-link density as a function of depth in elastomers and polyethylene [21][22][23][24][25]. The profile NMR-MOUSE Ò is made of four parallel magnets in a proper arrangement affirming that the NMR signal is collected from a thin and flat sensitive volume at a fixed distance above the magnet [26,27].…”

Qualification of automated low-field NMR relaxometry for quality control of polymers in a production setting

“…Modifications to the magnet system as well as the ability to make minute changes in the distance between the magnet surface and the sample has afforded very high resolution depth profiles on the order of ~2 µm. [23] In cases of elastomer degradation, low field instruments have been able to reproducibly detect polymer deformation, [11,12] increased crosslinking due to aging or to manufacturing imperfections, [24][25][26] or detect defects in large materials such as 1 NMR-MOUSE ® is a registered trademark of RWTH-Aachen, Germany 3 vehicle tires. Much of the time, the handheld magnet unit can be held up to the surface of the polymer part for analysis, or the test coupon can be placed directly on the magnet face.…”