Removal of impurities from low-density polyethylene using supercritical carbon dioxide extraction

Abstract

Recently, extraction of impurities such as oligomers, solvent residues, and side products that are present during the production of polyethylene (PE) have attracted attention. These impurities increase the toxicity of PE and may even contaminate the packed products. Therefore, polymer industries put an increasing effort to remove them. In recent times, supercritical carbon dioxide (SCCO2) extraction has gained much attention because CO2 is considered to be cleaner, less expensive, and more environment-friendly than other materials used in the conventional methods. In the present study, aliphatic hydrocarbons such as eicosane, tetracosane, nonadecane, that are present on the surface of low-density polyethylene (LDPE) were extracted using SCCO2. Extraction condition of 22 MPa at 60 °C for 4 h was demonstrated to have better extracting capabilities than Soxhlet extraction. Thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM) demonstrated that LDPE properties were not altered.