Abstract

Since their first synthesis in 1884, thermosetting and amorphous urea–formaldehyde (UF) resins have mainly been used as wood adhesives yet are known to be responsible for the release of formaldehyde, which contaminates indoor air and causes sick building syndrome. An 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 become crystalline polymers, as they form 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. Herein, recent advances in converting crystalline UF resins back to amorphous polymers through the blocking of hydrogen bonds are described, which consequently increases their cohesion, leading to a simultaneous improvement in their adhesion properties and formaldehyde emissions.

摘要

自 1884 年首次合成以来，热固性和无定形脲醛 (UF) 树脂主要用作木材粘合剂，但已知会释放甲醛，甲醛会污染室内空气并导致病态建筑综合症。减少甲醛排放的一种简单有效的方法是合成具有低甲醛与尿素 (F/U) 摩尔比 (~1.0) 的 UF 树脂。然而，低摩尔比的UF树脂成为结晶聚合物，因为它们在固化状态下在线性分子之间形成氢键，这会抑制适当的交联结构的形成，导致粘合强度差。本文介绍了通过阻断氢键将结晶 UF 树脂转化回无定形聚合物的最新进展，从而增加了它们的内聚力，