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To investigate the structural changes upon thermal treatment of resorcinol–formaldehyde–latex (RFL) interfacial layer in a rubber-cord flexible composite, a multiscale approach was employed. High-resolution AFM mapping showed a significant increase in the modulus of the (RF) phase from 1.2 GPa to 2.3 GPa and in the latex phase (L) from 0.3 GPa to 0.8 GPa after thermal exposure at 100 °C for 10 days. The increase of the RF and L phase elastic modulus was correlated with the increase of oxygen content in the RFL layer based on SEM-EDX measurements. Furthermore, by combining finite element simulations and AFM modulus profiling, the presence of an interphase region (over 280 nm) between the RFL and the rubber regions was identified and did not deteriorate after the thermal treatment. Peel adhesion testing revealed that the increase of RF and L phase rigidity after thermal treatment was detrimental to the interfacial adhesion of the rubber composite.
Enganati et al. (Tue,) studied this question.