磷氮协效阻燃水性聚氨酯的阻燃机理

Flame Retarding Mechanism of Flame-Retardant Waterborne Polyurethane with Phosphorus-Nitrogen Synergy Effects

通过极限氧指数、热失重-红外光谱和扫描电镜分析对磷氮协效阻燃水性聚氨酯的阻燃机理进行了研究。结果表明,N,N-双(2-羟甲基)氨基乙基膦酸二甲酯(BHAPE)对水性聚氨酯具有良好的阻燃效果,阻燃水性聚氨酯表现出典型的凝聚相阻燃机理:水性聚氨酯中的BHAPE受热到200℃以后,开始分解为磷酸,从而降低了聚氨酯硬段的分解速率;温度继续升高,产生的磷酸发生缩聚反应,形成热稳定性较高的聚磷酸,聚磷酸具有很强的催化作用,迅速使高聚物脱水炭化,在材料表面形成致密光滑无孔洞的炭层。聚磷酸富集于残留物炭层表面,与炭层共同起到隔氧隔热、抑烟的作用,从而发挥阻燃能力。

A series of flame retardant waterborne polyurethanes（ FPUs） were prepared with different contents of N,N-bis（ 2-hydroxyethyl） ammonium dimethyl ethyl ester（ BHAPE）. The flame retarding mechanism of FPUs was studied by LOI,TG-IR and SEM. The results show that BHAPE improves flame retardant abilities of waterborne polyurethane.When the temperature is above 200 ℃,BHPAE starts to decompose into phosphoric acid which decreases the decomposition rate of the first step in the polyurethane degradation. However,polyphosphoric acid is polymerized by the phosphoric acid over 300 ℃,possessing higher stability. Polyphosphoric acid involves in polyurethane dehydration and carbonization as catalyst,becoming a compact and smooth carbonaceous layer afterward which protects polyurethane from oxygen and heat.