Flow-cure properties characterization

Curing Study. Although the data on the mechanical properties of the uncured inks provide information that is useful in fabricating the inks, no explanation for the poor performance of BK-62 was found. As a result, experiments aimed at examining the cure behavior of the inks were conducted. Samples of the inks were cured on a heated 2 roller apparatus, and, after various curing times, small portions of ink were removed and characterized for oscillatory and short term steady flow viscosity. In view of the complexity of the oscillatory behavior, most of the emphasis is on the steady flow tests however, it is useful to examine the general trends exhibited in the oscillatory data. 

Rheological properties of mineral-filled and mineral/glass-fibre-filled unsaturated polyester DMCs have been presented by Gandhi and Bums (1976), who found that a simple power law was useful to characterize the chemorheology of both systems (note that limited cure effects during compressional flow are assumed). This work was extended by a series of... 

Flow and cure models require important material properties as input. These are permeability of the fiber preform and reaction kinetics of the resin, respectively. The accuracy of the models depends on the accuracy in characterizing these properties. 

The technique measures changes in the properties of a polymer as it is subjected to a periodic electric field. This produces quantitative data from which can be determined the capacitive and conductive nature of materials. Molecular relaxations can be characterized and flow and cure of resins monitored. 

Another method to measure flow properties after application involves the application of microdielectric measurements that have shown promise for characterizing fihn formation and cure (5,10-13). In this technique, the paint is applied to a thin, flat sensor connected to a frequency generator, an impedance analyzer and a computer. The sensor monitors the dielectric properties of the paint film at and near the interface between the sensor and the coating. The dielectric parameter used to estimate flow is called ion viscosity, but really is electrical resistivity rather than a trae viscosity. Ion viscosity is a measure of both the number and mobility of ions in a specimen. It is affected by changes in temperature, loss of solvent, crosslinking and other chemical reactions, formation of physical structure (such as by a thixotrope), ionic impurities, and ionic additives. The advantage of this technique is that measurements can be made in situ during application, flash, and the bake. 

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