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

The degree of cross-linking and curing is one of the most important values concerning the quality of cross-linked polyethylene (PE-X) and the functionality of adhesives and resin-based components. Up to now, the measurement of this property has mostly been time-consuming and usually destructive. Within the shown work the feasibility of single-sided nuclear magnetic resonance (NMR) for the non-destructive determination of the degree of cross-linking and curing as process monitoring was investigated. First results indicate the possibility of distinguishing between PE-X samples with different degrees of cross-linking. The homogeneity of the samples and the curing kinetics of adhesives can also be monitored. The measurements show good agreement with reference tests (wet chemical analysis, differential scanning calorimetry, dielectric analysis). Furthermore, the influence of sample temperature on the characteristic relaxation times can be observed.