RP103 - Simultaneous Dielectrometry and Rheology of Model Epoxy Resins, National Research Council of Canada, A.Ajji, P.Sammut, M.M.Dumoulin; IBM Canada, E.Bellefleur and L.Boutin
ABSTRACT
To minimize flow problems during transfer molding of epoxy resins, it is important to understand the rheology of these materials and how it is affected by the chemical reaction. In fact, during the injection cycle, the epoxy resin crosslinks as a function of time and temperature, which increases its viscisity up to infinity (no flow at the gel point). As rheological measurements are costly and tedious for these resins, use of alternative techniques is desirable. Use of dielectric techniques is among the possibilities with the advantage of its ability to be implemented on the production line. However, this technique does not measure directly the flow properties of the resins. Hence, development of correlations between the dielectric and flow properties of these resins is of great interest. This paper verifies that linear correlations can be established between the rheological and dielectric properties for unreacted epoxy resins. For reacted resins, molecular weight changes must be taken into account.
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RP114 -Application of Dielectric and Thermal Analysis to the Curing of Epoxy Resins, Toshiba Corporation, T.Nakano, S.Makishima, Y.Inoue, K.Goto
ABSTRACT
Upon studying the application of dielectric analysis (DEA) to techniques for non-destructive on-line measuring of the curing process of epoxy casting resin in molds, it was found that the ionic conduction portion derived from dielectric loss factor was closely correlated to glass transition temperature and resin viscosity. A new study was undertaken using DEA, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and curing volume shrinkage measurement to investigate in more detail the relation between the electrical conductivity of resins and the degree of cure during the curing process. A relation was quantitatively determined between the equivalent resistivity derived from dielectric loss factor and the degree of cure, viscoelasticity and volume shrinkage.
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RP117 - Modeling Conductivity and Viscosity Changes During Epoxy Using DEA, DMA, DSC, Georgia Institute of Technology, Joycelyn Simpson and Sue Ann Bidstrup
ABSTRACT
Viscosity and ionic conductivity are macroscopic polymer properties that characterize polymer segment mobility and ion mobility, respectively. Numerous studies have demonstrated that viscosity and ionic conductivity are correlated prior to gelation. However, few studies have endeavored to gain a fundamental understanding or quantitative relationship between these properties. An expression relating viscosity and ionic conductivity could potentially be quite useful for cure monitoring and control of polymer processes since ionic conductivity can be conveniently measured in-situ using microdielectric sensors. In order to formulate a structure-dielectric property relationship, this research combines DSC, DMA, and DEA analysis of the isothermal polymerization of a digycidyl ether of bisphenol A epoxy resin with a tetrafunctional amine, diamino-diphenyl sulfone.
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RP041 - Dielectric Cure Monitoring During Composite Lamination; IBM Corporation, Jeffery Gotro
ABSTRACT
Oscillatory parallel plate rheometry is commonly used to measure the viscosity of neat resins during curing. The objective of this work was to use a dielectric sensor embedded in an epoxy/glass cloth prepreg layup to infer the viscosity profile during lamination. This method allowed qualitative characterization of the viscosity profile during lamination at different heating rates.
Correlations between the dielectric loss factor and the complex viscosity were established using simultaneous viscosity and dielectric measurements. Viscosity measurements during composite lamination would be virtually impossible. The dielectric method is simple and relatively inexpensive compared to the cost of most rheometers.
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