The effect of organofunctional nanosilica on the cross-linking process and thermal resistance of UF resin

The paper investigates the effect of surface modification of fumed nanosilica with (3-aminopropyl)triethoxysilane (APTES) on the kinetics and thermal stability of urea-formaldehyde (UF) resin. In the course of the investigation, nanoparticles were modified with APTES in the ratio 1, 2, 3, 4 and 5 part by weight (PBW) per 100 PBW of SiO₂. The parameters of curing kinetics of the resin, the conversion degree and its thermal stability were determined with use of differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The effect of nanosilica silanization on the curing process of resin was evaluated by determining the gel time at 100 °C and the activation energy (E_a) of the cross-linking process, the initial and final temperature of the reaction (T_onset, T_endset), the maximum value of the exothermic peak (T_p), the amount of emitted heat (ΔH_Tp) and the conversion degree (α_Tp) that responds to T_p. With the maximum level of silica modification, we have noted a decrease in the reactivity of the resin, which is manifested by a slightly longer gel time of the resin as well as an increase in the value of activation energy of the cross-linking process. It is accompanied by a slight decrease of resin conversion degree α_Tp. The modification of silica, regardless of the amount of silane inoculated on its surface, results in the increase in the thermal stability of UF resin.