工业化聚丙烯树脂中挥发性有机物的溯源及形成机理

Traceability and formation mechanism of volatile organic compounds in industrialized polypropylene resin

分析了75种牌号聚丙烯(PP)树脂总挥发性有机物(TVOC)含量的分布区间,对PP粉料和粒料的挥发性有机物(VOC)进行了溯源,揭示了工业化生产过程中VOC的形成机理,为进一步从源头开发低VOC的PP树脂提供技术支持。实验结果表明,市售主流PP树脂的TVOC含量在13.5~500μg/g;所有PP树脂中的VOC均含有不同分子量的烷烃和烯烃,多为C_(6)H_(14),C_(9)H_(20),C_(12)H_(26),C_(15)H_(32)等碳原子数为3的倍数的烷烃和少量的C_(6)H_(12)和C_(9)H_(18)。VOC的形成主要来源于两部分:聚合过程中产生的低聚物以及由熔融挤出造粒过程中PP热机械降解产生。提出了不同阶段VOC分子层面的形成机理,其中,来源于低聚物的烃类VOC存在较多同分异构体,主要由丙烯定向聚合复杂机理导致;熔融降解产生的VOC主要由形成的不同端基的PP分子产生。此外,降解法PP树脂的VOC还包括过氧化物自由基分解残留。

The distribution range of total volatile organic compounds(TVOC)content of 75 grades of polypropylene(PP)resins was analyzed.The traceability analysis of volatile organic compounds(VOC)was carried out from PP powders and pellets,and the formation mechanism of VOC in the process of industrial production was revealed,which provided technical support for the further development of PP resin with low VOC content.The results showed that the TVOC content of mainstream PP resins was among 13.5μg/g to 500μg/g in different intervals.The types of VOC from PP resin contained alkanes and olefins with different molecular weights and a small amount of C_(6)H_(12)and C_(9)H_(18).Most of alkanes were compounds with multiple of three carbon atoms such as C_(6)H_(14),C_(9)H_(20),C_(12)H_(26)and C_(15)H_(30).Moreover,the VOC of PP resins mainly came from two parts,one was the oligomers produced in the polymerization process,and the other was produced by PP degradation in the process of melt extrusion granulation.The formation mechanism of VOC at the molecular level in different stages was proposed.There were many isomers in oligomer hydrocarbon,which was mainly caused by the complex mechanism of propylene directional polymerization;the VOC produced by melt degradation of PP was mainly produced by the molecular structure of PP with different end groups.In addition,the VOC of PP resins with degradation method also included the residue of free radical decomposition of peroxide itself.