基于阻燃功能化粘土的多层次复合体系的构建与机理研究

Decreasing the volatilization of flammable gas and the loss of useful component for char forming is one of the methods to improve the flame retardant efficiency for chemical intumescent flame retardant (CIFR) system. Based on this, we present the preparation of "expandable" clay by intercalating triazine derivatives-a gas source for intumescent flame retardants, which can expand the clay and foam the char during combusting. The cross-linking clay (CLC) with excellent catalysis was synthesized by introducing different metals pillared agent into the montmorillonite. The "expandable" clay and CLC using as pre-exist physical barrier coatings and catalyzer are cooperated with CIFR to compensate the slow speed of char forming through chemical reaction. The mulriple synergistic intumescent flame retardant system is thus constructed. By this, the incombustible gas produced by triazine derivatives can break the flaming factor targeting the clay, and prevent the clay from wicking effect of ordinary organic compounds used in clay modification. At the same time, the char is formed quickly promoted by CLC, and the flame retardant efficiency is thus improved. A series of triazine derivatives with different structure and CLC are designed and synthesized. The surface modification of CLC is also studied. The dispersion behaviors of clay in matrix, the matching effect between modified clay and CIFR on the intumescent char forming of polymer is adjusted and controlled by these factors. The effects of clay intercalated by triazine derivatives and CLC on char forming, char stability and strength, flame retardant efficiency are investigated. The mulriple promoting mechanism for the cross linking-charing -expanding-antiflaming process will be discovered. The optimal formulation for modified clays/CIFR/polymer system will be obtained. This work will provide a novel thought for designing and preparing of the polymer composites with high efficiency in synergistic intumescent flame retardant system.

提高膨胀阻燃剂的效率一直是人们追求的目标。减少可成炭组分的损失并提高成炭速率和质量是获得高效阻燃的有效途径。申请者提出采用膨胀型阻燃剂中的气源-三嗪衍生物对粘土进行原位插层，获得"可膨胀"粘土，在粘土层间引入多核羟基金属阳离子柱化剂制备具有催化成炭作用的交联粘土，将这两种阻燃功能化粘土与化学膨胀阻燃剂复合，构建多层次高效协同膨胀阻燃体系。燃烧时三嗪衍生物分解，产生不可燃气体，分布在粘土周围，发挥"靶向"作用，切断燃烧要素，削弱灯芯效应，同时交联粘土催化成炭，提高阻燃效率；改变三嗪衍生物结构、金属类型、表面处理、复合方式等，调控粘土在聚合物中的分散行为和燃烧时各组分膨胀阻燃的匹配性。探索阻燃功能化粘土对高质量炭层的增效作用，阐明交联-成炭-膨胀-阻燃过程中的多途径协同机理，揭示复合阻燃体系的最优组合方式。本课题的研究结果将为高效协同膨胀阻燃复合材料的设计和制备提供一种新的思路。

本项目以膨胀型阻燃剂（IFR）为研究主体，以提高阻燃效率为目标，设计了一系列多层次结构的阻燃化粘土，包括采用三嗪衍生物、季膦盐、多羟基金属氧化物、多金属氧酸盐和金属离子与三嗪树脂共改性的粘土，将这些阻燃功能化粘土分别与IFR复合，构建高效协同阻燃体系。系统研究了几种改性粘土对阻燃性能的影响，阐明了阻燃机理，揭示了插层剂和催化剂类型对阻燃效率的贡献，建立了改性粘土与膨胀阻燃剂高效协同的方法。得到的主要结论如下。.a）三聚氰胺插层蒙脱土（MA-MMT）对尼龙6（PA6）的阻燃增强作用优于Na-MMT 及OMMT。当MA-MMT及MPP含量分别为1 wt%和24 wt%时，PA6的氧指数为35.0，并达到UL-94 V-0级，其峰热释放速率及总热释放速率也比纯PA6分别降低81%和49%。MA-MMT在燃烧过程中调控炭层结构，对基体形成有效保护，并完全抑制熔滴。.b）MA-MMT与三苯基苄基膦插层MMT（BPP-MMT）与APP/PER膨胀阻燃体系有明显的协同效应，十四烷基三己基膦插层MMT（FT-MMT）由于加速该体系的热降解而存在拮抗作用。MA-MMT与APP/PER的协同作用比Na-MMT更优异，主要表现在更高的氧指数以及较低的总热释放量上。.c）铝、钛和铁氧化物改性的层柱粘土（Al-MMT、Ti-MMT、Fe-MMT）在EVA中体现了良好的协同阻燃作用。仅添加12wt%IFR和1wt%Al-MMT即可使EVA通过UL-94 V0的测试，说明Al-MMT具有最好的协同作用。而且含有Al-MMT的样品热释放速率，热释放总量等也最低；分析表明，加入Al-MMT的体系热稳定性增强，残炭量增加，因此阻燃性能提升。.d）采用镍离子和三嗪树脂共同改性粘土，得到具有剥离结构的M-MMT。结果表明，添加3wt%M-MMT和16wt%IFR时可以使PP获得UL-94 V-0级别。M-MMT促进了PP/IFR在低温时的分解，提高了在高温时的成炭量，而且降低了热释放速率和热释放总量。此外M-MMT使炭层形成了外部微孔，内部大孔的结构，给基体提供了更好的保护作用。