Ultrahigh-Molecular-Weight Poly(1-octene): Synthesis and Drag Reduction Performance

Ultrahigh-molecular-weight poly(α-olefin) drag-reducing agents were prepared by low-temperature bulk polymerization of coal-derived 1-octene using a Ziegler–Natta catalyst system. The effects of polymerization temperature, cocatalyst, Al/Ti molar ratio, and reaction time on monomer conversion and viscosity-average molecular weight (Mη) were investigated. Optimal conditions employed triisobutylaluminum at Al/Ti = 20, with polymerization at −5 °C for 24 h followed by 0 °C for 48 h, affording 95.4% conversion and an Mη of 1.21 × 107 g mol–1. Reducing Al/Ti to 10 increased Mη to 1.77 × 107 g mol–1 but decreased conversion to 43.2%. Rotational rheometry showed that the polymer concentration yielding maximum drag reduction decreased markedly as molecular weight increased. Measured in toluene at a Reynolds number (Re) of 2500, the sample with Mη = 1.77 × 107 g mol–1 achieved 16.6% drag reduction at 5 ppm, comparable to 17.1% at 10 ppm for a commercial sample.