The influence of a hypophosphite/cyclotetrasiloxane bi-group compound (MVC-AlPi) on the efficiency of intumescent flame retardant polypropylene (PP/IFR) consisting of ammonium polyphosphate (APP) and hyperbranched triazine-based charring agent (HTCFA) was investigated through evaluating the fire behavior and thermal stability by limiting oxygen index (LOI), the vertical burning tests (UL94), cone calorimeter and thermogravimetric analysis (TGA). The scanning electron microscopy (SEM), fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the final residues. The thermal decomposition and char-forming behavior between MVC-AlPi and each IFR formulation was studied by TGA and thermogravimetry-fourier transform infrared spectroscopy (TG-IR) test. Results revealed that a little amount substitution of IFR by MVC-AlPi imparted overall improvement in flame retardancy with reduced heat/smoke release and UL 94 V-0 rating for composites with a total loading of only 18 wt% instead of 25 wt%. The thermal decomposition behavior analysis exhibited a synergistic char-forming effect after the combination of MVC-AlPi, improving high-temperature thermal stability and yield of residual char with phosphorus- and silicon-containing crosslinked structures due to the interactions between MVC-AlPi and IFR, especially APP. The introduction of silicon into the cross-linked structures generated a fishnet-like protective device covering on the char surface inhibiting bursting the foamed carbonaceous structures and buttressed cell walls not to be fractured, leading to the formation of an integrated and thick intumescent char layer, plus the factor of the early and gentle release of non-flammable gases. This lifted flame retardant efficiency mainly contributed to the condense-phase mechanism with not ignored flame inhibition of phosphorus-containing free radicals generated from MVC-AlPi pyrolysis in gas phase. This work provided a potential way to enhance the flame retardant efficiency of IFR system.

通过评估研究了次磷酸盐/环四硅氧烷双族化合物（MVC-AlPi）对由聚磷酸铵（APP）和超支化三嗪基炭化剂（HTCFA）组成的膨胀型阻燃聚丙烯（PP / IFR）效率的影响。通过限制氧气指数（LOI），垂直燃烧测试（UL94），锥形量热仪和热重分析（TGA）来确定燃烧行为和热稳定性。使用扫描电子显微镜（SEM），傅立叶变换红外（FTIR）和X射线光电子能谱（XPS）分析最终残留物。通过TGA和热重傅里叶变换红外光谱（TG-IR）测试研究了MVC-AlPi与每种IFR配方之间的热分解和成炭行为。结果显示，用MVC-AlPi少量取代IFR可使阻燃性得到整体改善，同时总载量仅为18 wt％而不是25 wt％的复合材料的热量/烟气释放降低，UL 94 V-0等级降低。MVC-AlPi结合后的热分解行为分析显示出协同成炭作用，由于MVC-AlPi和IFR之间的相互作用，提高了高温热稳定性和具有磷和硅交联结构的残余炭的产率，尤其是APP。将硅引入到交联结构中，形成了一种炭网状的保护装置，覆盖在炭表面上，可防止泡沫状碳质结构破裂和支撑的壁破裂而不会破裂，导致形成完整而厚的膨胀型炭层，以及不燃气体过早释放的因素。阻燃效率的提高主要是由于在气相中MVC-AlPi热解产生的含磷自由基对火焰的抑制作用，而对凝聚相机理起了不可忽视的作用。这项工作为提高IFR系统的阻燃效率提供了一种潜在的途径。