Comprehensive analysis and quantification method of Non-Intentionally Added Substances (NIAS) from Alkanox 240 formed during the polypropylene extrusion process

The characterization and quantification of additives and Non-Intentionally Added Substances (NIAS) in plastic materials are crucial research topics due to their potential migration and toxicity. This research aims to understand the formation of NIAS resulting from the thermo-mechanical degradation of additives during the polypropylene extrusion process, a critical step in polymer formulation and mechanical recycling. Additionally, it seeks to develop a method for identifying and quantifying the NIAS formed. The originality of this paper lies in studying the formation of NIAS over the mixing of polypropylene (PP) and pure additives (UV 326, UV 944, Alkanox 240) through the extrusion process, rather than directly on commercially available materials, to avoid external influences such as unknown additives, residual processing agents, environmental contaminants, and degradation products from previous manufacturing steps. Therefore, the extracts from the model plastic material (PP + additives) obtained through a one-step, two-day extraction method at room temperature were analyzed using gas chromatography with flame ionization detection (GC-FID), gas chromatography-mass spectrometry (GC-MS) and Nuclear Magnetic Resonance (NMR) to identify and quantify NIAS. Five NIAS from the degradation of Alkanox 240 were identified and quantified: 2,4-di-tert-butylphenol and tris(2,4-di-tert-butylphenyl) phosphate, by GC-FID, mono[2,4-bis(1,1-dimethylethyl)phenyl] ester and bis[2,4-bis(1,1-dimethylethyl)phenyl] ester, by a combination of GC-FID and 31 P NMR, and finally dihydroxyphosphine oxide by 31 P NMR and theoretically based on the amount of 2,4-di-tert-butylphenol. This method can be applied to the identification of NIAS based on additives, as well as the quantification of both additives and NIAS, as part of the quality control process for PP materials before their application. • Process-generated NIAS were monitored during polypropylene extrusion with additives. • GC–FID/GC–MS and 31 P NMR were used for identification and quantification of NIAS. • Five NIAS originating from Alkanox 240 or Irgafos 168 were identified and quantified. • Method applicable to identify and quantify NIAS in PP materials before use or recycle.