Deformation‐Window‐Dependent Rheology of Epoxy Formulations Modified With a Commercial SWCNT Masterbatch at Ultra‐Low Nominal Nanotube Contents

ABSTRACT

This study examines the deformation‐dependent rheology of an uncured epoxy resin modified with ultra‐low single‐walled carbon nanotube (SWCNT) loadings (0.001–0.010 wt%). Steady shear, oscillatory amplitude and frequency sweeps, Cox–Merz comparison, and three‐interval shear tests were combined with near‐infrared (NIR) spectroscopy. At 0.1 s ⁻¹ , apparent viscosity increased from 2.47 ± 0.02 Pa s for neat epoxy to 8.05 ± 0.02 Pa·s at 0.010 wt% SWCNT, while the η _0.1 / η ₁₀₀ ratio rose from 2.15 to 3.97. Both viscous and elastic contributions increased with SWCNT addition; however, G″ remained above G′, with no modulus crossover or low‐frequency elastic plateau. At 0.010 wt%, complex viscosity decreased by approximately 32% at the highest applied strain. Cox–Merz deviations varied non‐monotonically with composition, indicating deformation‐mode sensitivity rather than a concentration‐defined rheological transition. Following high shear, the formulations recovered 92.4%–99.7% of their initial low‐shear viscosity. NIR spectra showed concentration‐dependent changes but no distinct composition‐specific transition. Thus, increasing the amount of the SWCNT‐containing masterbatch modifies the rheological response of the uncured epoxy while preserving a predominantly liquid‐like response, without evidence requiring assignment of a sample‐spanning rheological network.