脂环酰亚胺-邻苯二甲腈的协同自由基固化机理研究

Phthalonitrile resin (PN resin) constitutes an important class of high strength and high temperature polymers. However, the polymerization of the neat resin is extremely sluggish, which greatly hinders its wide application. And the problem of high curing temperature and low curing efficiency of the resin has not been resolved by adding with traditional curing agents, which usually follows a nucleophilic addition process. Recent investigation reported that the curing reaction of PN resin occurred with high efficiency through a free radical mechanism under certain alicyclic imide promotion (holding at 250-300℃ for several hours and cyano conversion close to 100%). Moreover, both of phthalonitrile and alicyclic imide hardly showed obvious homopolymerization, while significantly, for blends of them, both of copolymerization and homopolymerization can be activated. The characteristics of this kind of synergistic and selective reaction are very rare in this field, which are not the characteristics of aromatic amines or phenols. On the basis of that, the free radical curing reaction is most probably attributed to the reactive sites of alicyclic imide moiety. Therefore, in this program, a series of special structures of alicyclic imide compounds and phthalonitrile compounds were designed and synthesized, and their synergistic curing characteristics between molecular structures of alicyclic imide and phthalonitrile groups, free radical mechanism of blends and properties of cured products were studied, which could provide new methods and new ideas for better solving the bottleneck problem of application of the PN resin.

聚邻苯二甲腈树脂（PN树脂）是一类非常重要的高强耐高温聚合物。但是，其固化速度极慢，大大阻碍了PN树脂的广泛应用。传统的固化剂并未改善其热固化加工性较差（固化温度高、固化效率低）的问题，且固化机理主要以亲核加成历程为主。最新研究报道：某些脂环酰亚胺固化剂可以通过自由基历程实现PN树脂的高效固化（250-300℃等温固化数小时，氰基转化率已接近100%），并且，这些脂环酰亚胺单体很难均聚，但其与邻苯二甲腈的共混物却具有均聚和共聚都可以加速的特征。这种协同性、选择性的反应特点在本领域非常罕见，是芳胺、酚类等固化剂不具备的特征。在此基础上，本项目针对脂环酰亚胺结构可能引发自由基反应的活性位点，设计了特定结构的脂环酰亚胺化合物，并研究固化剂（基团）的分子结构与邻苯二甲腈基团之间的协同自由基固化特性、作用机理和固化物性能，为更好地解决PN树脂的应用瓶颈提供新方法和新思路。

邻苯二甲腈树脂（PN树脂）是一类非常重要的高强耐高温聚合物材料。然而，极其缓慢的热聚合反应特征大大阻碍了其广泛应用。本项目之前的研究中发现，某些脂环酰亚胺固化剂可以通过自由基历程实现PN树脂的高效固化，并且脂环酰亚胺化合物中的脂环结构很可能是实现PN树脂高效固化的一个关键反应位点。本项目针对脂环酰亚胺结构可能引发自由基反应的活性位点，设计合成了特定结构的端基和分子主链内脂环酰亚胺化合物，并研究固化剂（基团）的分子结构与邻苯二甲腈基团之间的协同自由基固化特性、作用机理和固化物性能。结果发现，四氢苯酐酰亚胺与双邻苯二甲腈的协同催化固化程度最高，六元脂环酰亚胺化合物均在不同程度上可以加速邻苯二甲腈单体的固化，拓宽了该自由基协同固化体系的适用范围，且进一步佐证了脂环结构中的亚甲基氢-CH2-（而不是次甲基氢-CH-）很可能通过类似自由基的拔氢方式参与了反应。最后，优选四氢苯酐酰亚胺和间苯型双邻苯二甲腈特种单体，以及改性的空心玻璃微珠等原料，采用熔体浸渍法（RTM）和粉末共混法（BMC），原位成型制备了一系列硬质复合泡沫材料。相关测试表征表明，BMC法制备的泡沫性能明显优于RTM法制备的泡沫。泡沫（BMC）的密度为0.47g/cm3，导热系数低于0.10 W/（m·K），在400℃内未观察到玻璃化温度，具有UL94 V0级阻燃性能。该结果为PN树脂的设计、改性和开发高性能泡沫材料提供了思路和方法。