Solution Grafting of Maleic Anhydride on Low-Density Polyethylene: Effect on Crystallization Behavior

Maleic anhydride (MAH) was grafted onto low-density polyethylene (LDPE) by a solution approach with dicumyl peroxide (DCP) as initiator and xylene as solvent. The effects of various experimental conditions on the grafting degree (GD, wt%), such as DCP concentration (A), MAH concentration (B), reaction time (C), reaction temperature (D) and the time for initiator addition (E), were investigated by an orthogonal experiment. The results demonstrated that the DCP concentration had the greatest influence on GD, while the reaction temperature had a minimal influence on GD. A copolymer with high GD (up to 4%) was obtained under the optimum conditions. It was proven that MAH was grafted onto the LDPE successfully by FT-IR. The crystallization behavior of the grafted LDPE was studied by differential scanning calorimetry (DSC) and X-ray diffraction (XRD), and the crystallization kinetic parameters of the grafted LDPE were obtained. Compounds of paraffin and grafted LDPE were investigated by XRD. The results demonstrated that a small amount of LDPE-g-MAH could affect the crystallization behavior of paraffin. This suggested that the grafted LDPE has a potential application as a pour point depressant (PPD) for heavy oil.