复合金属氧化物对膨胀阻燃聚丙烯的协效作用

Synergistic Effect of Compound Oxides with Intumescent Flame Retardant on the Properties of Polypropylene Composites

研究了复合金属氧化物(LDHO)对膨胀阻燃聚丙烯体系(PP/IFR)的协效作用。以层状复合氢氧化物(LDH)为前驱物通过焙烧法制备了2种LDHO,分别为镁铝LDHO(MgAl-LDHO)、镁铝铁LDHO(MgAlFe-LDHO),并通过X射线衍射对LDH和LDHO进行了表征,采用熔融共混法制备了PP/IFR/LDHO复合材料,通过极限氧指数(LOI)、UL94垂直燃烧、锥形量热等方法考察了复合材料的阻燃性能。结果表明,2种LDHO均可以提高PP/IFR体系的氧指数,并使最高热释放速率(PHRR)大幅度降低,其中MgAl-LDHO可使PHRR降低71%;热重分析表明,LDHO的加入提高了PP/IFR体系的分解温度及残炭在高温区的热稳定性,从而提高了体系热稳定性能。采用扫描电镜观察了残炭的形貌结构,发现添加LDHO后炭层更加致密、坚实,表明通过改善PP/IFR炭层的质量,LDHO起到了协效阻燃的作用。

The synergistic effect of compound oxides with intumescent flame retardant on the properties of polypropylene composites was researched. Compound oxides （MgAl-LDHO, MgAIFe-LDHO） were obtained with calcining layered double hydroxide （LDH） precursors and prepared by hydrothermal method. X-ray diffraction （XRD） was employed to characterize the structure of LDH and LDHO mentioned above, and the results indicate that the calcination of LDH at 500 ℃ gives rise to formation of ill-crystallized MgO phase and spinel phase. The PP/IFR composites with these different LDHO were then fabricated through melt blending process. The thermal stability and flame retardancy of resulting composites were investigated by thermogravimetric analysis （TGA）, limiting oxygen index （LOI）, vertical burning test（UL94） and cone calorimeter. TGA data shows that LDHO could improve the thermal stability of PP/IFR. LOI and UL94 tests show that LDHO could increase the LOI of PP/IFR composite. Cone calorimeter results reveal that LDHO could clearly enhance the char layer quality, consequently result in significant reduction of PHRR. The PHRR of PP/IFR/MgAl-LDHO composite decreases 71%, compared with that of PP/IFR composite. The char residue after cone test was characterized by scanning electron microscope （SEM）. The residue characterization demonstrates that LDHO could promote formation of the homogeneous and compact intumescent char layer. Taking all results into account, a conclusion can be draw that LDHO could be used as an effective synergistic agent for PP/IFR composites to enhance its flame retardancy through improving the char quality in the condensed phase.