Yi Zhao, Zhang Jizhi, Zhang Shifeng, Gao Qiang, Li Jianzhang, Zhang Wei
Ministry of Education (MOE) Key Laboratory of Wooden Material Science and Application, Beijing Key Laboratory of Wood Science and Engineering, School of Materials Science and Technology, Beijing Forestry University, Beijing 100083, China.
Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (MOE), School of Materials Science and Engineering, Shandong University, Jinan 250061, China.
Polymers (Basel). 2016 Apr 26;8(5):159. doi: 10.3390/polym8050159.
Phenol-formaldehyde (PF) resin is a high performance adhesive, but has not been widely developed due to its slow curing rate and high curing temperature. To accelerate the curing rate and to lower the curing temperature of PF resin, four types of metal-mediated catalysts were employed in the synthesis of PF resin; namely, barium hydroxide (Ba(OH)₂), sodium carbonate (Na₂CO₃), lithium hydroxide (LiOH), and zinc acetate ((CH₃COO)₂Zn). The cure-acceleration effects of these catalysts on the properties of PF resins were measured, and the chemical structures of the PF resins accelerated with the catalysts were investigated by using Fourier transform infrared (FT-IR) spectroscopy and quantitative liquid carbon-13 nuclear magnetic resonance (C NMR). The results showed that the accelerated efficiency of these catalysts to PF resin could be ordered in the following sequence: Na₂CO₃ > (CH₃COO)₂Zn > Ba(OH)₂ > LiOH. The catalysts (CH₃COO)₂Zn and Na₂CO₃ increased the reaction activity of the phenol position and the condensation reaction of methylol. The accelerating mechanism of (CH₃COO)₂Zn on PF resin is probably different from that of Na₂CO₃, which can be confirmed by the differences in the differential thermogravimetric (DTG) curve and thermogravimetric (TG) data. Compared to the Na₂CO₃-accelerated PF resin, the (CH₃COO)₂Zn-accelerated PF resin showed different peaks in the DTG curve and higher weight residues. In the synthesis process, the catalyst (CH₃COO)₂Zn may form chelating compounds (containing a metal-ligand bond), which can promote the linkage of formaldehyde to the phenolic hydroxyl position.
酚醛（PF）树脂是一种高性能粘合剂，但由于其固化速度慢和固化温度高，尚未得到广泛开发。为了加快PF树脂的固化速度并降低其固化温度，在PF树脂的合成中采用了四种金属介导的催化剂；即氢氧化钡（Ba(OH)₂）、碳酸钠（Na₂CO₃）、氢氧化锂（LiOH）和醋酸锌（(CH₃COO)₂Zn）。测定了这些催化剂对PF树脂性能的固化加速效果，并通过傅里叶变换红外（FT-IR）光谱和定量液体碳-13核磁共振（C NMR）研究了用催化剂加速后的PF树脂的化学结构。结果表明，这些催化剂对PF树脂的加速效率顺序如下：Na₂CO₃ > (CH₃COO)₂Zn > Ba(OH)₂ > LiOH。催化剂(CH₃COO)₂Zn和Na₂CO₃提高了酚位的反应活性和羟甲基的缩合反应。(CH₃COO)₂Zn对PF树脂的加速机理可能与Na₂CO₃不同，这可以通过差示热重（DTG）曲线和热重（TG）数据的差异得到证实。与Na₂CO₃加速的PF树脂相比，(CH₃COO)₂Zn加速的PF树脂在DTG曲线上显示出不同的峰，并且具有更高的重量残留率。在合成过程中，催化剂(CH₃COO)₂Zn可能形成螯合化合物（含有金属-配体键），这可以促进甲醛与酚羟基位置的连接。
