Identifying the chemical gel point of thermoset composites using optimally windowed chirp measurements

The chemical gel point of thermoset composites is crucial to the design of manufacturing parameters in processes and industries that utilize these materials, like additive manufacturing and semiconductor packaging. However, many industrially relevant thermoset composite resins react too quickly and are too fragile to capture this behavior using traditional rheological techniques. Here, we pair Optimally Windowed Chirp (OWCh) measurements with rheology-conversion relationships to apply time-cure superposition. This data set focuses on a diglycidyl ether of bisphenol A (DGEBA) epoxy resin (Epon 826, Hexion, Ohio, USA) cured with Jeffamine D-230 (Huntsman Corporation, Texas, USA). Four resins with fumed silica (Cabot Corporation, Massachusetts, USA) mass fractions of 0 %, 2.5 %, 5 %, and 10 % were cured and observed isothermally at 70 °C. OWCh measurements for all these resins are included in this data publication. Only the rheology-conversion for the resin with 2.5 % fumed silica is reported here. The rheology-conversion relationships for the other three compositions are available in a previous data publication (https://doi.org/10.18434/mds2-2918). These results provide a way to observe how composite fillers affect the evolution of the viscoelastic spectrum, offering better understanding of the gel point. This data is described in: Romberg, S.K., Lehrman, S., Seppala, J. & Kotula, A.P. (2025) Identifying the chemical gel point of thermoset composites using optimally windowed chirp measurements, National Institute of Standards and Technology, submitted for publication.