DSC对苯基苯酚改性酚醛树脂固化机理研究

采用DSC技术、Kissinger法对苯基苯酚改性酚醛树脂的固化过程进行了研究,得到放热峰顶活化能为169.3 kJ/mol,远大于普通酚醛树脂(约70 kJ/mol)。理论近似凝胶温度、固化温度及后处理温度分别为414.5 K、448.9 K和483.9K。酚醛树脂的固化通常由化学反应控制和扩散控制两阶段组成。通过Ozawa法得到活化能与转化率(E-a)的变化关系表明,2种树脂固化历程存在明显差异。普通酚醛树脂固化反应进行到10%(a=10%),粘度迅速增大,反应转向扩散控制;而苯基苯酚改性酚醛树脂固化反应时粘度变化小,直至a=70%,才较快增长。这将有利于小分子的逃逸和各基团充分反应。同时高活化能也表明,反应形成了高键能的化学键,有利于提高树脂的残炭率和烧蚀性能。

Investigation on curing mechanism of phenylphenol modified phenol-formaldehyde resin by means of DSC method

The curing process of phenyl-phenol modified phenol-formaldehyde resin was investigated by means of DSC and Kissinger methods.The results show that its apparent activation energy at exothermic peak is 169.3 kJ/mol,which is much higher than that of common phenol-formaldehyde resin(about 70 kJ/mol).The theoretic approximate temperatures of gel,cure and post-treatment for modified phenol-formaldehyde resin are 414.5 K,448.9 K and 483.9 K respectively.The curing process of phenol-formaldehyde resin consists of two stages,i.e.chemical reaction control and diffusion control.The relationship between activation energy(E)and the conversion rate(a) was obtained by using Ozawa method.The result shows that curing process of two kinds of resin is obviously different,when curing reaction of common phenol-formaldehyde resin goes on 10%(a=10%),viscosity increases rapidly,and reaction changes toward diffusion control,however,curing reaction viscosity of phenyl-phenol modified phenol-formaldehyde resin changes a little,until reaction goes on a=70%,viscosity increases fast,which is favorable for escape of small molecules and sufficient reaction of all kinds of groups.At the same time,high activation energy indicates that higher-energy chemical bonds are produced during the reaction,which is favorable for improving carbon residue rate and ablative property of resin.