Abstract A novel urea-formaldehyde (UF) foaming resin to be used in low-density wood-based materials was facilely fabricated by mixing thermo-expandable microspheres (TEMs) with UF resin. The foaming performance and bonding strength of the new resin were investigated with specially designed paper/UF samples and bonded veneers joints, respectively. The developed resin had a good expansion effect, with an apparent density of less than 300 kg/m3 and expansion ratios of 4.5-9.8, and a uniform cellular structure inside the resin was demonstrated by scanning electron microscope observations. However, the addition of TEMs resulted in a 47.5% to 91.4% decrease in the shear strength of the resins. As the concentration of TEMs increased from 2.5% to 10.0%, the apparent density and shear strength showed similar decreasing trends. The introduction of glutaraldehyde (GA) increased the bonding strength of the resins to 69.8%-199.7%, while significantly increasing their apparent density. Increasing the concentration of TEMs would be an effective way to reduce the apparent density of the UF foaming resins, but there will be an accompanying degradation in their strength. GA could be a potential chemical modifier for TEMs/UF resins in terms of improving their bonding strength.

中文翻译：

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一种用热膨胀微球简便制备的新型脲醛发泡树脂的发泡性能和粘结强度

摘要 通过将热膨胀微球 (TEM) 与 UF 树脂混合，制备了一种用于低密度木质材料的新型脲醛 (UF) 发泡树脂。分别使用专门设计的纸/超滤样品和粘合单板接头研究了新树脂的发泡性能和粘合强度。所开发的树脂具有良好的膨胀效果，表观密度小于300 kg/m3，膨胀比为4.5-9.8，扫描电镜观察显示树脂内部具有均匀的蜂窝状结构。然而，添加 TEM 导致树脂的剪切强度降低 47.5% 至 91.4%。随着 TEMs 的浓度从 2.5% 增加到 10.0%，表观密度和剪切强度显示出类似的下降趋势。戊二醛 (GA) 的引入使树脂的结合强度提高到 69.8%-199.7%，同时显着提高了它们的表观密度。提高 TEM 的浓度将是降低 UF 发泡树脂表观密度的有效方法，但其强度会随之下降。在提高粘合强度方面，GA 可能是 TEMs/UF 树脂的潜在化学改性剂。