木质素在丁腈橡胶阻燃中的应用

EFFECT OF LIGNIN ON FLAME RETARDATION OF NBR

研究了木质素在丁腈橡胶（ＮＢＲ）中的阻燃效果及阻燃机理。结果表明，随木质素用量增加，氧指数增ＩＯ大，但生烟量（ＳＬ）也随之增多。这与一般阻燃剂的作用相符。但是，在木质素／ＮＢＲ共混体系中加入Ａｌ（ＯＨ）３，则会增大ＩＯ又使ＳＬ下降。木质素／ＮＢＲ共混硫化橡胶燃烧残渣的ＳＥＭ照片表明，残渣表面生成了光滑的炭层，炭层表面有大小不等的孔洞。估计木质素分子结构中的苯环对ＮＢＲ的碳化起了催化作用，而内部有机物热分解生成的低分子气体，冲破表面薄弱处造成了孔洞。加入Ａｌ（ＯＨ）３后，由于Ａｌ（ＯＨ）３受热产生的水蒸汽，在熔融木质素中膨胀，水蒸汽逸出则使残渣表面形成疏松的结构，更有利于隔绝火焰产生的高温，延缓了有机物的分解，从而使ＩＯ提高而ＳＬ下降。

The effect and its mechanism of Lignin on flame retardant of NBR have been studied. It is shown that the oxygen index( IO ) and the smoke level( SL mg/g) go up with an increasing of Lignin loading, which is in accordance with the nature of common flame retarder that the smoke level increases while the oxygen index is enhanced. However, the blending of Al(OH) 3 into the Lignin/NBR compound can result in significant increment of oxygen index and decrement of smoke level. One instance is that a system with 100 phr Lignin and 40 phr Al(OH) 3 can be self retardant ( IO above 26), and simultaneously maitain the fime elasticity). The SEM observations of the combustion residues of Lignin/NBR compound reveal that the residues are covered by a smooth coat of carbon, which has several big or small holes in its surfaces. It is presumably due to the benzene rings in the molecuar structure of Lignin catalyzing the carbonization of NBR and the low molecular gas which is produced by the internal organism when heated breaking through the weakness of the carbon coat. With the corporation of Al(OH) 3, the water vapour which is produced by Al(OH) 3 when heated swells in the melt Lignin and leaves some holes after escape, this results in a looser structure to isolate the high temperature from the flame and retard the decomposition of the internal organism. Hence, the IO is increased while the SL is decreased.