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 (Na 2 CO 3 ), lithium hydroxide (LiOH), and zinc acetate ((CH 3 COO) 2 Zn). 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 ( 13 C NMR). The results showed that the accelerated efficiency of these catalysts to PF resin could be ordered in the following sequence: Na 2 CO 3 > (CH 3 COO) 2 Zn > Ba(OH) 2 > LiOH. The catalysts (CH 3 COO) 2 Zn and Na 2 CO 3 increased the reaction activity of the phenol ortho position and the condensation reaction of ortho methylol. The accelerating mechanism of (CH 3 COO) 2 Zn on PF resin is probably different from that of Na 2 CO 3 , which can be confirmed by the differences in the differential thermogravimetric (DTG) curve and thermogravimetric (TG) data. Compared to the Na 2 CO 3 -accelerated PF resin, the (CH 3 COO) 2 Zn-accelerated PF resin showed different peaks in the DTG curve and higher weight residues. In the synthesis process, the catalyst (CH 3 COO) 2 Zn may form chelating compounds (containing a metal-ligand bond), which can promote the linkage of formaldehyde to the phenolic hydroxyl ortho position.
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机译：酚醛（PF）树脂是一种高性能的粘合剂，但由于其固化速度慢和固化温度高而尚未得到广泛的开发。为了加快PF树脂的固化速度并降低其固化温度，在PF树脂的合成中使用了四种金属介导的催化剂。即，氢氧化钡（Ba（OH）2），碳酸钠（Na 2 CO 3），氢氧化锂（LiOH）和乙酸锌（（CH 3 COO）2 Zn）。测量了这些催化剂对PF树脂性能的固化促进作用，并使用傅立叶变换红外（FT-IR）光谱和定量液态碳13核磁技术研究了用催化剂促进的PF树脂的化学结构。共振（13 C NMR）。结果表明，这些催化剂对PF树脂的加速效率可按以下顺序排列：Na 2 CO 3>（CH 3 COO）2 Zn> Ba（OH）2> LiOH。催化剂（CH 3 COO）2 Zn和Na 2 CO 3提高了苯酚邻位的反应活性和邻羟甲基的缩合反应。 （CH 3 COO）2 Zn在PF树脂上的加速机制可能与Na 2 CO 3的加速机制不同，这可以通过差示热重（DTG）曲线和热重（TG）数据的差异来证实。与Na 2 CO 3促进的PF树脂相比，（CH 3 COO）2 Zn促进的PF树脂在DTG曲线中显示出不同的峰，并且残留的重量更高。在合成过程中，催化剂（CH 3 COO）2 Zn可能形成螯合化合物（包含金属-配体键），可以促进甲醛与酚羟基邻位的键合。
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