Deng Xue, Liu Zhu, Wang Zhongwei, Wu Zhigang, Li Dan, Yang Shoulu, He Shiqiang, Ji Ning
Guizhou Academy of Forestry, Guiyang 550002, China.
College of Forestry, Guizhou University, Guiyang 550025, China.
Polymers (Basel). 2025 May 20;17(10):1402. doi: 10.3390/polym17101402.
In this research, a urea-formaldehyde (UF) resin was modified with nanocrystalline cellulose (NCC) and nanofibrillated cellulose (CNF), and the properties of the modified resin were comprehensively evaluated by combining the techniques of infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that (1) the introduction of NCC and CNF significantly changed the hydrogen bonding network of the UF resin, in which CNF enhanced the internal hydrogen bonding of the resin through its long-chain structure and elevated the cross-linking density. NCC increased the crystallinity of the resin, while CNF enhanced the overall performance of the resin by improving its dispersion. (2) The composite curing agent system significantly reduced the curing temperature of the resin, resulting in a more homogeneous and efficient curing reaction, and the CNF-modified UF exhibited better thermal stability. (3) The addition of NCC and CNF significantly improved the dry and water-resistant bonding strengths of the resins. In addition, the use of complex curing agent further enhanced the bonding strength, especially in the CNF-modified system; the addition of complex curing agent increased the dry bonding strength to 1.60 MPa, and the water-resistant bonding strength reached 1.13 MPa, which showed a stronger cross-linking network and structural stability. (4) The addition of NCC and CNF led to a significant reduction in the free formaldehyde content of UF resins, resulting in respective levels of 0.17% and 0.14%. For plywood bonded with the CNF-modified UF resin, formaldehyde emissions were measured at 0.35 mg/L, which were markedly lower than the 0.54 mg/L of the unmodified sample. This further highlights CNF's effectiveness in minimizing formaldehyde release. (5) Overall, CNF is superior to NCC in improving the thermal stability, bonding strength, water resistance, formaldehyde release, and overall performance of the resin. The use of complex curing agents not only optimizes the curing process of the resin but also further enhances the modification effect, especially for CNF-modified resins, which show more significant performance advantages.
在本研究中，用纳米晶纤维素（NCC）和纳米纤化纤维素（CNF）对脲醛（UF）树脂进行了改性，并结合红外光谱（FTIR）、X射线衍射（XRD）、差示扫描量热法（DSC）、热重分析（TGA）和扫描电子显微镜（SEM）技术对改性树脂的性能进行了综合评价。结果表明：（1）NCC和CNF的引入显著改变了UF树脂的氢键网络，其中CNF通过其长链结构增强了树脂的内部氢键并提高了交联密度。NCC提高了树脂的结晶度，而CNF通过改善其分散性提高了树脂的整体性能。（2）复合固化剂体系显著降低了树脂的固化温度，导致固化反应更加均匀和高效，且CNF改性的UF表现出更好的热稳定性。（3）NCC和CNF的添加显著提高了树脂的干强度和耐水粘结强度。此外，使用复合固化剂进一步提高了粘结强度，特别是在CNF改性体系中；复合固化剂的添加使干粘结强度提高到1.60MPa，耐水粘结强度达到1.13MPa，这表明交联网络更强且结构更稳定。（4）NCC和CNF的添加导致UF树脂的游离甲醛含量显著降低，分别为0.17%和0.14%。对于用CNF改性的UF树脂粘结的胶合板，测得的甲醛释放量为0.35mg/L，明显低于未改性样品的0.54mg/L。这进一步突出了CNF在最小化甲醛释放方面的有效性。（5）总体而言，在提高树脂的热稳定性、粘结强度、耐水性、甲醛释放和整体性能方面，CNF优于NCC。使用复合固化剂不仅优化了树脂的固化过程，还进一步增强了改性效果，特别是对于CNF改性树脂，其表现出更显著的性能优势。
