Heat stability of cured urea-formaldehyde resins by measuring formaldehyde emission

A test method for measuring formaldehyde from urea-formaldehyde (UF) resins at high temperatures was developed and used to assess the influence of the reaction pH at: synthesis on the formaldehyde emission during cure and heat stability of the cured resins without water. Additionally, C-13-CP/MAS solid-state nuclear magnetic resonance (NMR) techniques were used to investigate the structure of cured UF resins before and after high-temperature hearing. Formaldehyde emissions during cure were related to the UF resins' methylol group content. Heat stability of cured UF resin increased as the reaction pH at: resin synthesis increased. Solid-state NMR spectra show formaldehyde emission from cured UF resins after heating is mainly ascribable to decreases of methylol group and dimethylene ether linkage. Significantly it was revealed that the uron structure characteristically found in the cured UF resin synthesized under strong acid media indicated high heat stability.