Wang Yongliang, Liu Baoqiang, Chen Ruiyang, Wang Yunfei, Han Zhidong, Wang Chunfeng, Weng Ling
College of Materials Science and Chemical Engineering, Harbin University of Science and Technology, Harbin 150040, China.
Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150040, China.
Materials (Basel). 2023 Jun 30;16(13):4759. doi: 10.3390/ma16134759.
Silica nanoparticles (nano-silica) were used as synergistic agents with ammonium polyphosphate (APP) and pentaerythritol (PER) to enhance flame retardancy of polypropylene (PP) in this research. The composites were prepared using a melt-mixing method. The influences of nano-silica on the fire performance of composites were thoroughly discussed, which promotes understanding of nano-silica on the flame-retardant performance of polypropylene composite. Scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS) results indicated that the nano-silica with a diameter of about 95 ± 3.9 nm were dispersed favorably in the composite matrix, which might elevate its synergistic effect with intumescent flame retardant and improve the flame retardancy of polypropylene composite. The synergistic effects between nano-silica and intumescent flame retardant on PP composites were studied using the limiting oxygen index (LOI), UL-94 test, and cone calorimeter test (CCT). The total amount of flame retardant was maintained at 30%. When the dosage of nano-silica was 1 wt.%, the LOI value of PP/IFR/Si1.0 composite reached 27.3% and its UL-94 classification reached V-1. Based on the parameters of the CCT, the introduction of nano-silica induced composites with depressed heat release rate (HRR) and peak heat release rate (PHRR). The PHRR of PP/IFR/Si0.5 was only 295.8 kW/m, which was 17% lower than that of PP/IFR. Moreover, the time to PHRR of PP/IFR/Si0.5 was delayed to 396 s, which was about 36 s later than that without nano-silica. EDS was used to quantitatively analyze the distribution of silica in charred residue. The EDS results indicated that the silica tended to accumulate on the surface during the fire. The surface accumulation characteristic of silica endows it with the enhanced flame-retardant properties of polypropylene composite at a very small dosage (as low as 1 wt.%).
本研究中，二氧化硅纳米颗粒（纳米二氧化硅）被用作与聚磷酸铵（APP）和季戊四醇（PER）的协同剂，以提高聚丙烯（PP）的阻燃性。采用熔融共混法制备复合材料。深入讨论了纳米二氧化硅对复合材料燃烧性能的影响，这有助于理解纳米二氧化硅对聚丙烯复合材料阻燃性能的作用。扫描电子显微镜（SEM）和能谱仪（EDS）结果表明，直径约为95±3.9nm的纳米二氧化硅在复合基体中分散良好，这可能提高其与膨胀型阻燃剂的协同效应，并改善聚丙烯复合材料的阻燃性。利用极限氧指数（LOI）、UL-94测试和锥形量热仪测试（CCT）研究了纳米二氧化硅与膨胀型阻燃剂对PP复合材料的协同效应。阻燃剂总量保持在30%。当纳米二氧化硅的用量为1wt.%时，PP/IFR/Si1.0复合材料的LOI值达到27.3%，其UL-94等级达到V-1。基于CCT的参数，纳米二氧化硅的引入导致复合材料的热释放速率（HRR）和峰值热释放速率（PHRR）降低。PP/IFR/Si0.5的PHRR仅为295.8kW/m²，比PP/IFR低17%。此外，PP/IFR/Si0.5的PHRR时间延迟至396s，比无纳米二氧化硅时晚约36s。利用EDS对炭化残渣中二氧化硅的分布进行定量分析。EDS结果表明，火灾期间二氧化硅倾向于在表面聚集。二氧化硅的表面聚集特性使其在非常低的用量（低至1wt.%）下就能赋予聚丙烯复合材料增强的阻燃性能。
