基于次磷酸铝的聚丙烯木塑复合材料的阻燃改性研究

Flame-retarding modification of wood flour/polypropylene composites by aluminum hypophosphite

本研究以次磷酸铝(AP)为阻燃剂,探讨了其对聚丙烯/木粉复合材料(WPC)的阻燃性能的影响,并阐明了相关的阻燃机理。实验结果证明,当AP的添加量为30 wt%时,可以使木粉含量为30 wt%的WPC通过垂直燃烧V-0级,氧指数达到25. 0%。锥形量热测试结果表明:AP的加入能够有效抑制复合材料的燃烧,30wt%AP的加入能够使木粉含量为30 wt%的WPC的热释放峰值(PHRR)降低至240 k W/m^2,与不含阻燃剂的WPC相比降低了50%;燃烧后所得的残炭的质量高达45. 2%。扫描电子显微镜(SEM),热重-红外联用(TGFTIR)和X射线光电子能谱结果表明:添加AP后,燃烧过程中WPC/AP的气相产物中会有水、二氧化碳及含PO_2-结构的物质等生成,从而赋予WPC/AP气相阻燃作用;此外,WPC/AP在燃烧中能够热解生成内外结构不同的炭层,内部炭层主要为含铝为主的交联稳定炭层,而外部炭层主要含有交联P-O-C结构等,因此,AP能够同时通过气相和凝聚相的双重作用实现WPC的高效阻燃。

In this work,inorganic aluminum hypophosphite(AP)was used as a flame retardant for wood flour/polypropylene composites(WPC).The flame retardant performance,thermal stability and flame-retardant mechanism had been well investigated.It was found that WPC containing 30 wt%wood flour passed the UL-94 V-0 rating and its limiting oxygen index reached to 25.0%when AP content was 30 wt%.In cone calorimeter test,AP efficiently improved the fire safety of WPC.The peak of heat release rate(PHRR)of WPC containing 30 wt%of wood flour was decreased from 480 kW/m^2 of WPC to 240 kW/m^2,whose reduction was as high as 50%.The char residue of flame-retardant WPC was increased to 45%.Scanning electron microscopy(SEM),X-ray protoelectron spectroscopy(XPS),thermogravimetric-Fourier transform infrared(TG-FTIR)were used to investigate the flame-retardant mechanism.It was found that AP played the flame retardant role both in the gaseous and condensed phases.In gaseous phase,water,carbon dioxide,and some substances containing PO2 - were produced.In condensed phase,the surface and inner residues with different structures were formed.For the surface residue,it contained cross-linked P-O-C structure,etc.,but there was no substance containing Al;for the inner residue,it consisted of cross-linking structure containing Al,etc.