Abstract Based on measurements of the dynamic viscosity, a strategy is proposed to find an expression that relates the viscosity of an epoxy resin during curing, to the temperature, shear rate, and degree of reaction. A cure model has been fitted for the viscosity of two part epoxy / amine resins, focusing on the low extents of cure – the most important region for the mould – filling stage in the relevant process. The model can be used to predict the viscosity during cure.
The model parameters are obtained from isothermal viscosity – time measurements at constant sear rate. Examples are shown and data are given for nine different temperatures. The model is applied to simulate non – isothermal cure and compared against experimental data. The material is Epoxy resin with multifunctional cycloaliphatic diamine curing agent or in a jargon EPIKOTE resin L 20 and curing agent EPH 960. It appeared that the dynamic viscosity is a unique function of the effective shear rate (i.e. the product of frequency and strain) over a wide range of frequencies and strains after being corrected for the temperature. The effective shear rate dependence of the viscosity is described with a power law with an exponent that depends on the conversion. The effect of temperature is described with an Arrhenius-type equation with conversion dependent parameters [1]. Differential Scanning Calorimetry (DSC) is applied to determine the kinetic equation that is used, in combination with the thermal history, to obtain the conversion during the rheological measurements. The description of the viscosity gives a good prediction of the measured viscosity in the region between melting and gelation of the resins.
An investigation of the thermal / rheological response of the EPIKOTE system was used to develop a mathematical model. Because of the proportionality of viscosity to temperature at the process condition, the model can also be used to measure the extent of reaction, which is significant in the process.
Contents Acknowledgments. 2
Contents. 3
Figures List 3
Tables List 3
Equations List 3
Abstract 3
1 .         Introduction. 3
2 .         Review.. 3
2 .1.          Epoxy Resins. 3
2 .1.1.       Epoxy Resin 828. 3
2 .2.          The gel point and beyond. 3
2 .3.          Resin Transfer molding. 3
2 .3.1.       RTM
6 Hex – Flow.. 3
2 .4.          Chemorheology. 3
2 .5.          Rotational Rheometry. 3
2 .5.1.       Cone and Plate Viscometer 3
2 .6.          Modeling. 3
2 .6.1.       Kinetics Modeling. 3
2 .6.2.       Reaction Modeling. 3
2 .6.3.       Chemoviscosity Modeling. 3
3 .         Experimental 3
3 .1.          Material 3
3 .1.1.       Sample Preparation. 3
3 .2.          Instrumental Techniques. 3
3 .2.1.       Cone and Plat Viscometer 3
3 .2.2.       Differential Scanning Calorimetry. 3
4 .         Results and Discussion. 3
4 .1       Rheology. 3
4 .2       Kinetics. 3
4 .3 Chemorheology. 3
5.         Conclusions. 3
6 .         Summary & Recommendations. 3
7.         References. 3
8 .         Appendixes. 3