Preparation of EVAM-g-NSiO2 nanocomposite pour point depressant and its effect on rheological properties of model waxy oil

Abstract

Modified ethylene-vinyl acetate copolymer (EVAM) and amino-functionalized nano-silica (NSiO₂) particles were employed as the base materials for the synthesis of the nanocomposite pour point depressant designated as EVAM-g-NSiO₂. This synthesis involved a chemical grafting process within a solution system, followed by a structural characterization. Moreover, combining macro-rheological performance with microscopic structure observation, the influence of the nanocomposite pour point depressant on the rheological properties of the model waxy oil system was investigated. The results indicate that when the mass ratio of NSiO₂ to EVAM is 1:100, the prepared EVAM-g-NSiO₂ nanocomposite pour point depressant exhibits excellent pour point reduction and viscosity reduction properties. Moreover, the nanocomposite pour point depressant obtained through a chemical grafting reaction demonstrates structural stability (the bonding between the polymer and nanoparticles is stable). The pour points of model waxy oils doped with 500 mg/kg ethylene-vinyl acetate copolymer (EVA), EVAM, and EVAM/SiO₂ were reduced from 34 °C to 23, 20, and 21 °C, respectively. After adding the same dosage of EVAM-g-NSiO₂ nanocomposite pour point depressant, the pour point of the model wax oil decreased to 12 °C and the viscosity at 32 °C decreased from 2399 to 2396.9 mPa ·s, achieving an impressive viscosity reduction rate of 99.9%. Its performance surpassed that of EVA, EVAM, and EVAM/SiO₂. The EVAM-g-NSiO₂ dispersed in the oil phase acts as the crystallization nucleus for wax crystals, resulting in a dense structure of wax crystals. The compact wax crystal blocks are difficult to overlap with each other, preventing the formation of a three-dimensional network structure, thereby improving the low-temperature flowability of the model waxy oil.