SETTLING METHOD FOR DECOLORIZATION OF LOW MOLECULAR WEIGHT POLYETHYLENE

This study investigates the bleaching of low molecular weight polyethylene (LMWPE) by the settling (sedimentation) method. LMWPE is a by-product of polyethylene production whose discoloration is associated with trace amounts of conjugated, oxidized, and polar micro-fractions. The research was conducted in three stages: selection of the appropriate sample grade, determination of the optimal settling time, and evaluation of the temperature effect on the settling process. Results showed that only Grade-1 LMWPE samples are suitable for the settling method; Grade-2 samples yielded insufficient results and are recommended for bentonite adsorption treatment instead. Optimal settling conditions were established as 150 °C for 4 hours, achieving a whiteness index of 71 and a product yield of 80%. The physical and chemical properties of the bleached product were found to be close to those of the feedstock, confirming that the polymer matrix is preserved during the process. This mechanism was further confirmed by comparative infrared spectroscopy of the feedstock, bleached product, and sediment, which revealed a distinct carbonyl absorption band unique to the sediment fraction.