Song Kunpeng, Wang Yinjie, Ruan Fang, Yang Weiwei, Liu Jiping
School of Materials Science and Engineering, Beijing Institute of Technology, 5 Zhongguancun South Street, Haidian District, Beijing 100081, China.
Polymers (Basel). 2020 Oct 29;12(11):2534. doi: 10.3390/polym12112534.
Derivatives of 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[,]undecane-3,9-dioxide (SPDPC) are of increasing interest as flame retardants for polymeric materials. In addition, SPDPC is also an important intermediate for the preparation of intumescent flame retardants (IFRs). However, low efficiency and undesirable dispersion are two major problems that seriously restrain the application of IFRs as appropriate flame retardants for polymer materials. Usually, the functionalization or modification of SPDPC is crucial to acquiring high-performance polymer composites. Here, a small molecule spirocyclic flame retardant diphenylimidazole spirocyclic pentaerythritol bisphosphonate (PIPC) was successfully prepared through the substitution reaction between previously synthesized intermediate SPDPC and 2-phenylimidazole (PIM). Phenyl group and imidazole group were uniformly anchored on the molecular structure of SPDPC. This kind of more uniform distribution of flame retardant groups within the epoxy matrix resulted in a synergistic flame retardant effect and enhanced the strength of char layers to the epoxy composites, when compared to the unmodified epoxy. The sample reached a limiting oxygen index (LOI) of 29.7% and passed with a V-0 rating in the UL 94 test with the incorporation of only 5 wt % of as-prepared flame retardant PIPC. Moreover, its peak of heat release rate (pHRR) and total heat release (THR) decreased by 41.15% and 21.64% in a cone calorimeter test, respectively. Furthermore, the addition of PIPC has only slightly impacted the mechanical properties of epoxy composites with a low loading.
3,9-二氯-2,4,8,10-四氧杂-3,9-二磷杂螺[5.5]十一烷-3,9-二氧化物（SPDPC）的衍生物作为聚合物材料的阻燃剂越来越受到关注。此外，SPDPC也是制备膨胀型阻燃剂（IFR）的重要中间体。然而，低效率和不理想的分散性是严重限制IFR作为聚合物材料合适阻燃剂应用的两个主要问题。通常，SPDPC的功能化或改性对于获得高性能聚合物复合材料至关重要。在此，通过先前合成的中间体SPDPC与2-苯基咪唑（PIM）之间的取代反应成功制备了一种小分子螺环阻燃剂二苯基咪唑螺环季戊四醇双膦酸酯（PIPC）。苯基和咪唑基均匀地锚定在SPDPC的分子结构上。与未改性的环氧树脂相比，这种阻燃基团在环氧基质内更均匀的分布产生了协同阻燃效果，并增强了环氧复合材料炭层的强度。仅加入5 wt%制备的阻燃剂PIPC时，样品的极限氧指数（LOI）达到29.7%，并在UL 94测试中达到V-0等级。此外，在锥形量热仪测试中，其热释放速率峰值（pHRR）和总热释放量（THR）分别降低了41.15%和21.64%。此外，PIPC的加入对低负载环氧复合材料的力学性能影响很小。
