ABSTRACT

Low molar ratio urea–formaldehyde (UF) resin adhesives are primarily used for the reduction of formaldehyde emission (FE) from wood-based composites, at the expense of poor reactivity and adhesion. This study aimed to enhance the performance of low molar ratio UF resins via in-situ modification, via the addition of octadecylamine (ODA)-modified bentonite (ODA–BNT) nanoclay. The molecular weights, curing behavior, chemical groups, and crystallinity of modified UF resins with different levels of ODA−BNT were characterized by gel permeation chromatography, differential scanning calorimetry, Fourier-transform infrared spectroscopy, and X-ray diffraction (XRD). The ODA–BNT/UF resins showed better reactivity and lower activation energy compared with neat resins. The XRD results clearly showed that ODA–BNT in modified UF resins had been intercalated. A 5% ODA−BNT addition resulted in a decrease in the crystallinity of the modified UF resins, leading to better adhesion strength and lower FE compared with neat UF resins. These results suggest that intercalation of ODA–BNT in low molar ratio UF resins improve their cohesion through the formation of a larger branched network in their cured state.

摘要

低摩尔比脲醛 (UF) 树脂粘合剂主要用于减少木基复合材料的甲醛排放 (FE)，但代价是反应性和附着力较差。本研究旨在通过添加十八胺（ODA）改性膨润土（ODA-BNT）纳米粘土，通过原位改性来提高低摩尔比超滤树脂的性能。通过凝胶渗透色谱、差示扫描量热法、傅里叶变换红外光谱和 X 射线衍射 (XRD) 表征了具有不同 ODA-BNT 含量的改性 UF 树脂的分子量、固化行为、化学基团和结晶度。与纯树脂相比，ODA-BNT/UF 树脂表现出更好的反应性和更低的活化能。XRD 结果清楚地表明，改性 UF 树脂中的 ODA-BNT 已被嵌入。添加 5% ODA-BNT 会导致改性 UF 树脂的结晶度降低，与纯 UF 树脂相比，具有更好的粘合强度和更低的 FE。这些结果表明，在低摩尔比 UF 树脂中嵌入 ODA-BNT 通过在固化状态下形成更大的支化网络来提高它们的内聚力。