Transforming Crystalline Thermosetting Urea-Formaldehyde Resins to Amorphous Resins
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초록
내용
Since their first synthesis in 1884, thermosetting and amorphous urea–formaldehyde (UF) resins had been used as wood adhesives for more than 100 years. However, formaldehyde emission developed in 1980’s became an important health issue by contaminating indoor air and causing sick building syndrome. A easy and efficient way of reducing formaldehyde emissions is to synthesize UF resins with a low formaldehyde-to-urea (F/U) molar ratio (~1.0). However, low molar ratio UF resins are forming crystalline domains owing to the hydrogen bonds between linear molecules in the cured state, which inhibits the formation of a proper cross-linked structure and results in poor adhesion strength. This presentation reports recent advances in transforming thermosetting crystalline UF resins back to amorphous polymers through the blocking of hydrogen bonds which consequently increases their cohesion, leading to a simultaneous improvement in their adhesion properties and formaldehyde emissions.