Determination of phenolic antioxidants in polyethylene with dissolution by n‐heptane in an autoclave

Abstract

AbstractA new procedure for quantitative analysis of phenolic antioxidants in polyolefins was tested. Thereby polyethylene samples were dissolved in pure n‐heptane or in n‐heptane/isopropanol mixture (1 000/5, v/v) in an autoclave at 160–170°C under elevated pressure. After precipitation of the polymer by cooling to room temperature, the obtained solution was either directly analysed by means of HPLC equipped with an UV‐detector, or the supernatant solvent used for the extraction was evaporated in vacuum at room temperature and the residue redissolved in acetonitrile. The concentration of antioxidants in the solution was determined by isocratic HPLC. The advantage of this procedure is the short time of about 2 h needed for analysis and the good reproducibility of results (σ = 3–5%).