Abstract
Abstract. 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.
Highlights
1.1 Cross-linking and curingCross-linking of commodity plastics is a common method to achieve mechanical, thermal and chemical properties comparable to those of high-performance polymers (Osswald et al, 2006)
Processing time in the production of cross-linked polymers is continuously decreasing, the degree of crosslinking/curing is usually measured in the laboratory by wet chemical analysis according to DIN EN ISO 10147 (Heiduk et al, 2015)
The wet chemical analysis showed that the degree of crosslinking of PE-Xa increases with a higher amount of peroxide and, in the case of PE-Xc, a higher energy dose
Summary
Cross-linking of commodity plastics is a common method to achieve mechanical, thermal and chemical properties comparable to those of high-performance polymers (Osswald et al, 2006). Cross-linked polyethylene (PE-X) and polyamide hold the biggest market share. The market segments of thermoset injection molding, fiber reinforced composites and resin-based adhesives are steadily growing. Processing time in the production of cross-linked polymers is continuously decreasing, the degree of crosslinking/curing is usually measured in the laboratory by wet chemical analysis according to DIN EN ISO 10147 (Heiduk et al, 2015). Long measurement times for a quantitative result and the destructive character of these standard test methods inhibit a 100 % process monitoring. There are already initial efforts to realize process measurements by other methods, such as rheological tests (Heiduk et al, 2015)
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