ATR-FTIR法研究聚丙烯热氧降解过程中羰基含量变化

The Variation of Carbonyl Group Content in Polypropylene Matrix During Thermal-Oxidation Degradation with ATR-FTIR Method

以PS为内标物,利用ATR-FTIR法研究了聚丙烯热氧降解过程中羰基含量的变化。首先以不同物质的量之比的3-苯丙酸和己二酸为标样,计算了羰基(红外吸收峰1 716cm-1)与苯环单取代基团(红外吸收峰699cm-1)摩尔比与峰强的关系。通过拟合7组不同物质的量之比的羰基和苯环单取代基团的峰面积比,得到等物质的量峰强比K为6.39。从室温到220℃之间,PP/PS样品的红外谱图中未出现羰基的吸收峰;当温度达到230℃时发现有明显的羰基峰出现,此时样品中的羰基含量为(0.55±0.13)×10^(-5) mol/g;随着温度进一步升高,羰基含量快速增加,当温度为251℃时,羰基含量达到(10.41±1.13)×10^(-5) mol/g,此时温度的升高导致羰基稳定性变差,导致其分解速率增大,因此,在250~265℃羰基的增长速率减缓;当温度为265℃时聚丙烯在热氧降解过程中产生的羰基含量最高,为(11.82±1.52)×10^(-5) mol/g;当样品温度超过265℃,羰基的分解速率大于其生成速率,使得羰基含量呈下降趋势。

The polystyrene（PS）was employed as inter standard,the variation of carbonyl group content in polypropylene（PP）matrix during thermal-oxidation degradation was studied by ATR-FTIR in this work.The equimolar peak strength ratio（K）between carbonyl（1 716cm-1）and mono-substituted benzene ring（699cm-1）was calculated by fitting linear relationship between peak area ratio and mole ratio by varying the molar ratio of 3-benzenepropanoic acid and adipic acid.The Kis equal to 6.39 in this work.The FTIR results implied that no carbonyl group was generated while the temperature is less than 220℃.As the temperature increased to 230℃,an obvious carbonyl group absorption peak was found,and the carbonyl group content is（0.55±0.13）×10^-5 mol/g.After that,the carbonyl group content in PP matrix dramatically increased to（10.41±1.13）×10^-5 mol/g at 251℃.The maximum carbonyl group content in PP matrix is（11.82±1.52）×10^-5 mol/g while the temperature is 265℃.If the temperature is higher than 265℃,the stabilization of carbonyl group is deteriorated and the decomposition rate is faster than the generation rate,so the carbonyl group content in PP matrix decreased.