Analytical Characterisation of the Rheo-Kinetics of Epoxy Resin Systems Used in Structural Composite Manufacturing for Nigerian Infrastructure Projects

Epoxy resin cure rheo-kinetics determine the processing window, flow behaviour during infusion, and final network structure in structural composite components for civil infrastructure applications. This study analytically characterises the cure rheo-kinetics of three commercial epoxy resin systems used in composite bridge deck and repair applications across Nigerian infrastructure projects managed from Abuja, North Central Nigeria. Isothermal and dynamic differential scanning calorimetry experiments determined cure kinetic parameters including reaction enthalpy, activation energy, and pre-exponential factors, fitted using Kamal and n-th order kinetic models. Oscillatory rheometry monitored gelation time, gel point conversion, and viscosity evolution at processing temperatures of 25, 40, and 60 degrees Celsius. Time-temperature-transformation diagrams were constructed from combined thermal and rheological data. Torsion pendulum analysis characterised fully cured network viscoelastic properties and glass transition temperatures. Results indicate significant variability in gel times among the three resin systems, ranging from 42 to 187 minutes at 25 degrees Celsius, with important implications for vacuum infusion processing window management in field applications. Activation energies ranged from 55 to 78 kJ/mol, reflecting different catalyst concentrations. All three systems achieved glass transition temperatures above 80 degrees Celsius at full cure, suitable for tropical climate structural service. Time-temperature-transformation diagrams identified vitrification onset temperatures critical for demoulding schedule planning. The study provides validated rheo-kinetic databases for the three resin systems, enabling process simulation for epoxy composite manufacturing under the temperature conditions typical of Abuja construction sites. Keywords: epoxy resin, cure kinetics, rheology, structural composite, time-temperature-transformation