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Evaluating Models That Predict Epoxy Conversion Using Rheological Properties



Stian Romberg, Paul Roberts, Chad R. Snyder, Anthony Kotula


Simultaneous rheology and conversion measurements of neat and composite epoxy resins reveal that conventional models neither accurately nor fully describe the relationship between rheology and conversion. We find that models predicting thermoset conversion based on mixing rules of rheological properties are quantitatively inaccurate and do not account for chemical gelation. Models based on percolation theory and the divergence of the viscosity at the gel point are more accurate but only valid before the gel point. Here, we propose the use of the generalized effective medium (GEM) model, which incorporates the divergence of rheological properties on both sides of the critical gel point. We show that the GEM model works well for both neat resins and filled systems, and the resulting parameters estimate the gel point and scaling behavior on either side of the sol-gel transition.
ACS Applied Polymer Materials


conversion prediction, rheology-conversion relationship, curve fitting, generalized effective medium model, thermoset composite, material extrusion, additive manufacturing


Romberg, S. , Roberts, P. , Snyder, C. and Kotula, A. (2024), Evaluating Models That Predict Epoxy Conversion Using Rheological Properties, ACS Applied Polymer Materials, [online],, (Accessed May 26, 2024)


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Created April 15, 2024, Updated April 29, 2024