Use of modifiers ZSM‐5 and bentonite enhancing the hydrolytic and thermal stability of urea‐formaldehyde composites

Abstract

This research introduces a new approach using zeolite ZSM‐5 (Z) as formaldehyde (FA) scavenger in urea‐formaldehyde (UF) resins, while simultaneously investigating and comparing the structural influence of Z and bentonite (B) on different properties of UF composite. ZSM‐5 and bentonite were used to modify the in situ synthesized UF resin with a low formaldehyde/urea (FA/U) molar ratio (0.8), to reduce the free FA content in the UF resin. The fillers and modified UF composites were characterized using XRD, FTIR, TGA, DTG, and DTA. The surface of fillers and modified UF resins was observed using SEM. The content of free FA, determined by the sulfite method, for the sample UF/Z composite, was 0.06%, while for the sample UF/B composite was 0.18%. After acid hydrolysis, the content of released FA was similar for both modified resins (4.08% for UF/Z and 4.80% for UF/B). This slight difference indicates a better hydrolytic stability of UF/Z. Analysis of thermal stability showed that UF/Z starts to degrade at a higher temperature, which, together with the values of released FA, indicates that UF resin modified with ZSM‐5 is thermally and hydrolytically more stable compared to the UF/B composite. The obtained results suggest that ZSM‐5 with its microporous structure contributes better to improving the properties of UF resins than bentonite with its layered structure.Highlights Synthesis of UF resins modified with ZSM‐5 and bentonite. New approach using ZSM‐5 as a formaldehyde scavenger. Comprehensive characterization of the fillers and modified UF resins. UF/Z resin has superior hydrolytic and thermal stability over UF/B resin. The microporous structure of ZSM‐5 enhances the properties of UF.