膨胀阻燃EVA的阻燃性能及机理研究

Flame Retardancy and Flame-retardant Mechanism of EVA Modified with Intumescent Flame Retardant

研究了由三嗪类齐聚物碳源(CA)和聚磷酸铵(APP)以质量比为1∶3复配组成的膨胀型阻燃剂(IFR)在乙烯-醋酸乙烯共聚物(EVA)中的阻燃作用,采用了氧指数、垂直燃烧和锥形量热法研究了IFR不同添加量对EVA阻燃效果的影响,并通过理论-实际热重分析、成炭分析等手段对IFR的阻燃机理进行分析推测。发现IFR对EVA有着良好的阻燃效果,当IFR总添加量为40%时,材料氧指数为43%,垂直燃烧可达到UL94 V-0级,热释放峰值(PHRR)由纯EVA的517 kW/m^2降低至83 kW/m^2,烟释放峰值(PSPR)由纯EVA的0.059 m^2/s降低为0.013m^2/s,平均质量损失速率(AMLR)相比纯EVA的0.048 g/s降低至0.011 g/s。通过对IFR的阻燃机理分析推测知,CA和APP在燃烧过程中相互反应生成了更加耐高温的结构,该结构在NH3的吹胀作用下形成膨胀炭层,膨胀炭层具有良好的隔热隔氧效果,从而使材料具有优良的阻燃性能。

An intumescent flame-retardant （IFR） system composed of a novel carbonization agent（CA） and ammonium polyphosphate （APP） was prepared at the mass ratio of CA/APP of 1 ： 3 for ethylene-vinyl acetate copolymer （EVA）. The flame retardancy of the EVA/IFR composites was investigated bylimited oxygen index （LOI） test, vertical burning test （UL-94） and cone calorimeter test. The flame-retardant mechanism of IFR was analyzed by means of the experimental and the theoretical TG curves of CA/APP （3 ： 1 in weight） and char-forming ability of CA, APP and IFR. The results reveal that the IFR/EVAcomposites exhibit excellent flame retardany： when the content of IFR is 40wt%, the LOI of IFR/EVAcomposite is 43, and a V-0 classification can be achieved; the peak value of heat release rate （PHRR）decreases to 83 kW/m2 compared to 517 kW/m2 for the pure EVA; the peak value of smoke production rate（PSPR） is reduced to 0. 013 m2/s compared to 0. 059 m2/s of the pure EVA; and the average mass loss rateis decreased from 0. 048 g/s to 0. 011 g/s. The analysis of the flame-retardant mechanism of IFR indicatesthat a steady structure, which is more resistant at high temperature and is the main component of the charlayer, is formed due to the reaction between APP and CA. The char layer has good thermal insulation andoxygen insulation effect in combustion, which ends the composites with excellent flame retardancy.