Effect of a novel environmentally friendly additive of polyaspartic acid on the properties of urea formaldehyde resins/montmorillonite

Polyaspartic acid (PASP) is a biodegradable green material with carboxyl groups (-COOH) and amido groups (-CO-NH-). In the article, a novel urea-formaldehyde (UF) resin modified by PASP and Ca-montmorillonite (Ca-Mt) was prepared by the alkaline-acid-alkaline method. The synthesized materials were characterized by X-ray diffraction, Fourier transform-infrared spectroscopy, thermal analysis (TG-DTG), and scanning electron microscopy. The effects of viscosity, curing time, and free formaldehyde were investigated. The results showed that the layered structure of Ca-Mt was exfoliated and dispersed in the bulk of UF. The thermal stability of the modified UF was much better than that of pure UF resin. The percentage of free formaldehyde was declined from 26 to 18%. Meanwhile, the UF composites showed the short curing time and the optimum viscosity. Finally, a synthetic process of UF modified by PASP and Ca-Mt and a possible mechanism for immobilizing the free formaldehyde were suggested. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48038.