自动凯氏定氮法测定丁腈橡胶中结合丙烯腈含量

Determination of bound acrylonitrile content in nitrile rubber by automatic Kjeldahl method

采用自动凯氏定氮法测定丁腈橡胶（NBR）中结合丙烯腈含量,研究了催化剂组成、试样的消解温度和消解时间对测定结果的影响,考察了方法的精密度和准确性,并与现行的SH/T 1157—1997方法进行了对比。结果表明,采用硫酸钾和硫酸铜混合催化剂（二者质量比为8∶1）消解试样时,最佳消解温度为420℃、消解时间为2 h,方法的标准差为0.110%~0.215%,2次重复测定结果的绝对差不大于重复性限0.35%或0.45%。该方法与SH/T 1157—1997测定结果差值为0.27%~0.43%,小于规定值,方法的准确性高;与SH/T 1157—1997方法相比,该方法可同时消解的试样数从2个提高到10~20个,蒸馏时间由60 min缩短到5~10 min。

The bound acrylonitrile content in nitrile rubber（ NBR） was determined by automatic Kjeldahl method.The effects of catalyst composition,and digestion temperature,digestion time of samples on the determination results were studied,the precision and accuracy of the method were determined,and the comparison was conducted with current method SH / T1157—1997.The results showed that using K2SO4/Cu SO4（ mass ratio 8∶ 1） mixed catalyst under the optimal condition of digestion temperature 420 ℃,digestion time 2 h,standard deviation of the method was between 0.110% and 0.215%,the difference of two determination results was less than 0.35% or0.45%.The difference value between the determination results of Kjeldahl method and SH / T 1157—1997 method was 0.27%-0.43%,which was less than the specified value,and the accuracy of the method was high;by this method the samples digested at the same time increased from 2 to 10-20,distillation time reduced from 60 min to 5-10 min compared to SH / T 1157—1997.