表面改性/阻燃增强双功能纳米锡酸盐阻燃剂的控制合成及阻燃机理研究

Stannate is a kind of important inorganic flame retardants with non-toxicity, high efficiency, and smoke suppression function. However, stannate flame retardant has poor compatibility to polymer matrix and causes damage to the mechanical properties of the polymer matrix.Therefore, base on previous controlled synthesis of nano-stannate, this project aims to synthesize surface-modified and flame-retardancy-enhanced difunctional nano-stannate flame retardant and to study its effect on the mechanical properties of flexible polyvinyl chloride (PVC) matrix as well as flame-retarding mechanism by means of surface functional manipulation and in-situ surface modification, using nano-stannate as the inorganic core and dialkyl phosphinic acid as the modifier.By manipulating and designing the modifier, we are to replace conventional flammable organic molecule with organic flame retardant to conduct surface-modification of inorganic flame retardant in order to improve the compatibility between inorganic flame retardants and flexible PVC matrix. In the meantime, the dialkyl phosphonic acid has flame retardancy, making it feasible to improve the flame retardancy by making use of the synergistic effect between the modifier and the stannate. By controlled synthesis of the scale of nano-stannate, design of the modifier chain, and manipulation of modified density of the modifier, proven the relationship between the scale of flame retardant, the component of the modifier, and the modified density with the mechanical and flame retardancy in flexible PVC, to reveal dispersion mechanism and synergistic flame-retarding mechanism of difunctional flame retardant. This research, hopefully, is to help to establish theoretical guide for the design, synthesis and application of novel surface-modified and flame-retardancy-enhanced flame retardants.

锡酸盐是一种无毒、阻燃效率高并且具有抑烟功能的重要无机阻燃剂。但是，锡酸盐同其它无机阻燃剂一样与高分子材料相容性差，损害基体材料的力学性能。在前期控制合成纳米锡酸盐的工作基础上，本项目拟通过表面功能调控的方法，以纳米锡酸盐为核，有机阻燃剂二烷基次膦酸为修饰剂，采用原位表面修饰的方法制备表面改性/阻燃增强双功能纳米锡酸盐，并研究其在软质聚氯乙烯（PVC）中的力学性能和阻燃机理。通过对修饰剂链的调控设计，利用二烷基次膦酸替代可燃性有机分子表面改性剂，解决相容性问题；利用具有阻燃功能的修饰剂与锡酸盐的协同阻燃作用提高阻燃效率；通过对纳米锡酸盐尺度控制合成、修饰剂链的调控设计、修饰剂修饰密度调控，探明阻燃剂尺度、修饰剂链组份、修饰密度与软质PVC的力学和阻燃性能之间的关联理论，揭示双功能阻燃剂的分散机制和协同阻燃机理。最终为研发新型表面改性/阻燃增强双功能无机阻燃剂的设计、合成提供理论依。

羟基锡酸锌（ZHS）是一种无毒、阻燃效率高的无机阻燃剂。但是，ZHS同其它无机阻燃剂一样与高分子材料相容性差，损害基体材料的力学性能。本项目通过表面功能调控的方法，以纳米ZHS为核，有机磷阻燃剂2-羧乙基苯基次膦酸（CEPPA）和磷硅阻燃剂9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物衍生物（DOPO-VTS）替代传统的非阻燃功能表面改性剂，制备了CEPPA-ZHS和DOPO-VTS-ZHS纳米杂化阻燃剂。研究了其合成方法及其在聚合物中热稳定性、分散性能和阻燃机理。此外，将ZHS和氧化石墨烯（GO）结合，制备ZHS/GO纳米杂化阻燃剂。研究了其在PVC中的热稳定性、分散性能和阻燃机理。主要研究内容和结果如下：.1. 以CEPPA为表面改性剂，制备了CEPPA-ZHS纳米杂化阻燃剂。确立了CEPPA和ZHS之间的键合作用方式为氢键。与非阻燃表面改性剂硬脂酸（SA）对比，CEPPA有如下作用：（1）与SA作用相同，可以提高ZHS在PVC和EP中的相容性，避免力学性能恶化，提高ZHS在EP中储能模量；（2）与SA不同，CEPPA可以提高PVC和EP的初始分解温度和增加残炭量；（3）与SA不同，CEPPA能增强ZHS的阻燃性能，即增加聚合物的氧指数、减小其热释放峰值、总热释放量、总烟释放量和烟释放速率。主要原因是除ZHS的阻燃作用外，CEPPA分解产生的PO•，不仅可以捕获HO•，抑制分子链降解的自由基连锁反应；而且，部分CEPPA被氧化成的聚偏磷酸，其一方面可促进聚合物脱水成炭，另外其本身覆盖到聚合物表面上，形成保护层。.2、以DOPO-VTS为表面改性剂，制备了DOPO-VTS-ZHS纳米杂化阻燃剂。确立DOPO-VTS在反应过程中通过Si-OH键与ZHS表面的羟基形成氢键键合到ZHS的表面。DOPO-VTS可以提高ZHS在PVC中相容性，提高PVC的拉伸性能。DOPO-VTS除与CEPPA阻燃机理相同外，因还含有硅，可燃烧生成二氧化硅，其不仅增加残碳量，而且可与炭化物构成复合无机层，提高炭层的热稳定性和抗氧化性。.3. 以ZHS和GO相结合，制备了新型的ZHS/GO纳米杂化阻燃剂。ZHS可以阻止GO的堆叠，GO可以防止ZHS的团聚，因此，ZHS/GO在PVC中有良好的分散性能，能增强PVC的力学性能；同时，利用GO的成碳作用和屏障效应，可提高ZHS的阻燃性能。