苯并噁嗪和苯并噁嗪树脂/蒙脱土混杂材料的合成与表征及其固化行为的研究

【作者】 史子兴；

【导师】 余鼎声；

【作者基本信息】 北京化工大学 ， 材料学， 2000， 博士

【摘要】 苯并噁嗪化合物，其学名为3，4-二氢—3-取代基-1，3-苯并噁嗪(3，4-dihydro-3-substituted-1，3-benzoxazine)，作为噁嗪衍生物的一种，是一类新型热固性树脂的中间体。一般由酚类化合物，伯胺类化合物和甲醛经脱水缩合反应制得，然后，在加热和／或催化剂的作用下，苯并噁嗪发生开环聚合，生成含氮且类似酚醛树脂的网状结构。因此，人们将这类新型树脂也称为开环聚合的酚醛类树脂。 本文对双(3，4-二氢—3-苯基-1，3-苯并噁嗪)的合成方法进行了研究。在传统的两步溶液法基础上首次采用了一步溶液法的合成工艺，结果表明，一步溶液法优于两步溶液法，它不仅缩短了反应时间，简化了合成工艺，提高了生产效率，而且合成过程副反应少，产物单体含量高。此外，在合成过程中溶剂的极性对噁嗪环的稳定性有重要的影响，溶剂极性越大，噁嗪环越不稳定，以至于在极性大的二噁烷为溶剂的体系中出现了类似“活性聚合”的现象。并且通过~1H-NMR、FT-IR、元素分析、NR对苯并噁嗪的结构和热开环机理进行了表征和推断。 通过DSC对苯并噁嗪单体的热开环固化行为进行了分析。采用了差减微分法分析了在升温速度为2.5℃／min-20℃／min之间的苯并噁嗪单体的非等温固化行为，结果表明，固化体系的表观活化能和反应级数随着升温速度的升高而变小；在等温固化DSC分析中，采用了n级等温固化模型和自催化反应等温固化模型对苯并噁嗪单体等温固化行为进行了分析，结果表明，n级等温固化模型只能描述进行到一定反应程度后的固化反应阶段即扩散控制阶段，不能描述起始反应阶段。而自催化反应等温固化模型由于未考虑扩散作用的影响，因此，该模型能较好地描述受扩散作用影响小(如高固化温度下)的固化反应全过程，而当固化温度较低时，扩散作用影响大，此模型只能描述固化反应的动力学控制阶段。 热固性树脂的固化过程的相态变化对固化产物的综合物理性能有重要的影响，而扭辫分析(Torsional Braid Analysis，TBA)可以研究热固性树脂固化过程中的相态变化即：从从低分子的粘流态到形成交联结构的玻璃态的全过程。目前，对苯并噁嗪固化过程的相态变化的研究尚属空白，因此对其进行研究为确定合理的固化工艺，制备性能优良的固化产物有重要的意义。本文通过对苯北京化工大学博士论文并嗯嗦固化体系的温度一力学TBA谱图分析表明，固化反应的温度主要在1 48.7℃一237.2℃之间进行，随着固化温度提高，固化体系依次进入熔化转变区(100oC一148.7oC);凝胶化转变区(148.7oC一237.2℃):玻璃化转变区(237.ZoC一327℃)。通过对苯并嗯嗦固化体系的温度一力学TBA谱图分析发现在固化温度小于200℃时，出现了独特的次级玻璃化转变，这是由于特殊的分子间作用力造成的，并且得到了TTT谱图，为苯并嚷嗦固化体系固化工艺的确定提供了依据。通过对苯并嗯嗦固化产物的温度一力学TBA谱图分析，研究了固化工艺即热历史对通过对苯并嗯嗦固化产物玻璃化转变温度的影响，比较了不同固化工艺下固化产物玻璃化转变行为，通过对固化行为的分析，得出了合理的固化工艺。 本文首次成功地制备出聚苯并嗯嗓/蒙脱土混杂材料，这对研究高阻燃性的复合材料有重要的意义。在溶液插层法和熔融插层法的基础上，首次采用熔融缩合插层法将苯并嗯嗦单体嵌入C一18有机改性蒙脱土的晶层中，然后，在一定的固化工艺下，层内和层外的苯并嗯嗦单体开环聚合，制备出了聚苯并嗯嗦/蒙脱土混杂材料，该方法既可以避免应用溶剂对环境的污染且具有反应体系的粘度小和小分子反应物容易嵌入粘土层间的优点，已获得发明专利申请号。通过TEM、XRD对该混杂材料的结构进行了表征。 聚苯并嗯嗓/蒙脱土混杂材料(BZ几边MT)是一种新型的混杂材料，由于在以热固性树脂苯并嚷嗦树脂为基体中，引入了有机改性蒙脱土，因此必然会影响苯并嗯嗦树脂(BZ)的固化行为，使其具有与苯并嗯嗦树脂不同的固化反应过程。通过对BZ乃边MT和BZ两个固化体系的非等温固化行为的比较，发现C-18改性蒙脱土对BZ的固化反应有很大的影响，BZ从MT固化体系存在两种固化反应方式即蒙脱土晶层内催化开环和层外热开环固化反应，且随着升温速率的不同，两种反应方式的比率将不同。通过对BZ舰MT固化体系的等温固化行为的研究，结果表明，n级反应模型只能描述进入扩散控制阶段的固化反应，而自催化反应模型，由于蒙脱土晶层削弱扩散作用的影响，因此，与BZ固化体系相比，能较好地描述固化反应的全过程，并在此基础上，设定了合理的工艺条件。关健词:聚苯并嗯嗦，固化，蒙脱土，混杂材料，制备，表征更多还原

【Abstract】 In this paper, polybenzoxazine, a novel kind of thermosetting resin, which comes from heterocyclic compounds, is synthesized successfully, in order to get the new polymers that could provide excellent comprehensive performance in mechanical integrity and thermal stabilities as well as high glass transition. It is also superior to conventional thermosetting resins such as phenolic resin.Bis(3,4-dihydro-3-phenyl-l,3-benzoxazines)(abbreviated as benzoxazine hereafter) are synthesized by the reaction of the corresponding phenols, primary amines, and formaldehyde. Several methods in synthesis of benzoxazine have been adopted and compared herein. As a result, one step solution system using toluene as solvent, a new method, is preferred because it has reduced the cycle of the production and make the products less expensive, furthermore, the products have high amount of monomer , compared with two steps solution system.As we know, on the course of formulation of benzoxazine, there are many side reactions, so the 100% conversion has not reached and the products contains side products which includes dimers, trimers and higher oligmers due to the broken ring. It is therefore necessary to keep an eye on the structure of the products of benzoxazine and find the main factor of influence. By using 1H-NMR, FT-IR, and GPC to investigate the structure of benzoxazine intensively, one main factor, the solvent polarity, has been found which could change the stability of ring structure. The more polarity the solvent has, the more unstable the benzoxazine ring is, which also means if solvent is of high polarity, the products contain less monomer. In addition, the characteristic phenomena in "living polymerization" are discovered when the dioxane is employed.The behaviors of ring-opening polymerization, which play very important role in the properties of polybenzoxazine, have been studied in detail by isothermal and dynamic differential scanning calorimetry (DSC) and torsional braid analysis (TBA). In the dynamic DSC analysis, the activation energy and the order of the reaction are determined by using the difference-differentiation computational method, and theactivation energy and order of the reaction would not keep the same as the scanning rate is changed. The faster the scanning rate is, the smaller both activation energy and order of the reaction are.In the isothermal DSC analysis, two models of isothermal curing reaction, which include the nth order kinetics model and autocatalytic kinetics model, have been applied to characterize the behavior of isothermal curing reaction of benzoxazine. Both of the models have successfully copied the isothermal curing behavior in certain stage over the whole range of conversion. The nth-order kinetics model could only describe the curing behavior in diffusion control, while the autocatalytic model with two rate constants and two reaction orders, provides a good phenomenological description of the isothermal curing behavior up to the point of diffusion control for this model does not consider the diffusion control factor. In addition, as the curing temperature is high, the autocatalytic model could successfully copy the whole range of isothermal curing behavior for the diffusion control is small in high curing temperature.By using the torsional braid analysis (TBA), the isothermal and dynamic curing behaviors of the benzoxazine have been studied intensively. During the cure, the phase of benzoxazine changes from liquid to glass, which is accompanied by two phenomena, gelation and vitrification. Gelation occurs at a definite conversion for a particular formulation, which corresponds, to the incipient formation of infinite molecules and rubber-like elasticity arises after the gelation. On the course of curing from the gelation to vitrification, there are something that happens unexpectedly during the curing temperature is below 200. Before the vitrification, two kinds of sub-vitrification occur due to the special molecular interaction which becomes strong enough to change the unit of molecular movement更多还原