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首页> 外文期刊>Journal of Applied Polymer Science >Accelerated cure of phenol-formaldehyde resins: Studies with model compounds
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Accelerated cure of phenol-formaldehyde resins: Studies with model compounds

机译：酚醛树脂的加速固化：模型化合物的研究

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2-Hydroxymethylphenol (2-HMP) and 4-hydroxymethylphenol (4-HMP) were used as model compounds to study the reactions that occur during cure of phenol-formaldehyde (PF) resin to which cure accelerators (ethyl formate, propylene carbonate, gamma-butyrolactone, and triacetin) have been added. The addition of cure accelerators significantly increased the rate of condensation reactions. The cure accelerators were consumed during the reaction, indicating that they do not act as true catalysts. Major dimeric and trimeric reaction products were isolated and their structures determined. The results are consistent with a mechanism in which the hydroxyrnethyl group of 2-HMP (or 4-HMP) is first transesterified by the cure accelerator. The ester group is then displaced by reaction with the negatively charged ortho or para position of a second molecule (S,2 mechanism) or is converted to a reactive quinone methide intermediate, which subsequently reacts with the negatively charged ortho or para position of a second molecule (quinone methide mechanism). When accelerators were added to the reaction mixture, the self-condensation of 2-HMP was faster than that of 4-HMP. As is well documented in the literature, the exact opposite is true without added accelerators. This result would seem to indicate that the phenolic oxygen helps activate the esterified ortho-hydroxymethyl group. The number and nature of crosslinks in a PF resin cured with added cure accelerator might be different than those in a PF resin cured without an added cure accelerator. (C) 2002 Wiley Periodicals, Inc. [References: 19]
机译：使用2-羟甲基苯酚（2-HMP）和4-羟甲基苯酚（4-HMP）作为模型化合物来研究在酚醛（PF）树脂固化过程中发生的反应，固化促进剂（甲酸乙酯，碳酸亚丙酯，γ -丁内酯和三醋精）。固化促进剂的添加显着提高了缩合反应的速率。固化促进剂在反应过程中被消耗掉，表明它们不是真正的催化剂。分离出主要的二聚和三聚反应产物并确定其结构。该结果与其中2-HMP（或4-HMP）的羟甲基首先被固化促进剂酯交换的机理一致。然后，该酯基通过与第二个分子的带负电荷的正或对位反应而置换（或转化为反应性醌甲基化物中间体），然后与第二个分子的带负电荷的正或对位进行反应分子（甲基苯醌机理）。当将促进剂添加到反应混合物中时，2-HMP的自缩合比4-HMP的自缩合快。如文献中充分记录的，没有添加加速器的情况恰恰相反。该结果似乎表明酚氧有助于活化酯化的邻羟甲基基团。用添加的固化促进剂固化的PF树脂中的交联键的数量和性质可能与不添加固化促进剂的PF树脂中的交联键的数目和性质不同。 （C）2002 Wiley Periodicals，Inc. [参考：19]

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