Abstract
An aqueous density-gradient column was used to study annealing effects in a series of epoxy resins. The crosslinking densities were varied via the monomer composition. The height of the specimens floating in the column was observed to change linearly with the square root of time during several days. The corresponding total density change typically amounts to 6 kg m−3, or 0.6%. By back-extrapolating the sample heights to time zero, accurate density values, uninfluenced by liquid absorption and other confounding effects, may be determined. Analysis of variance shows a residual error of 0.1 kg m−3, or 0.01 %, for the means of three specimens. Consistent density increases, ranging from 0.11 to 0.17%, were shown to occur upon annealing of the cured resins. The differences between samples of varying crosslinking densities were found to be significant.
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Sieber, W., Fischer, M. Annealing effects in epoxy resins examined by a refined density-gradient technique. Journal of Materials Science 28, 1639–1644 (1993). https://doi.org/10.1007/BF00363360
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DOI: https://doi.org/10.1007/BF00363360