Silylation of wheat straw cellulose pulp for its valorization as rheology modifier of industrial hydrophobic fluids: Cases of castor oil and bitumen

This work explores an innovative approach to developing novel oleo- and bitumen-based dispersions, which are potentially applicable as semisolid lubricants and bitumen binders, respectively, using lignocellulosic biomass. In particular, it focuses on investigating the impact of the silylation process of wheat straw Kraft cellulose pulp (KWP) on the rheological properties of these dispersions. To this end, KWP was functionalized with tert-butyldimethylsilyl chloride (TBDMSCl), using imidazole (ImH) as a catalyst, through a simple and efficient method. Different conditions of the silylation process such as temperature (20-100 °C), TBDMSCl/ImH ratio (1/2.5-2.5/2.5), and silylation time (2-24 h) were applied to illustrate the flexibility of the proposed methodology. Modified pulps with oil and/or bitumen structuring ability were obtained, as a result of the interaction between the hydrophobic alkyl-siloxane segment-containing fibers and these hydrophobic fluids, which enhance the compatibility between both components. Oleo-dispersions with a similar viscoelastic response to lithium grease, used as a benchmark, exhibited significantly reduced coefficients of friction and wear. Meanwhile, bitumen-dispersions displayed a substantial improvement in stiffness and elasticity with the temperature. This work may offer a novel strategy for developing rheology modifiers or structuring agents for industrial hydrophobic fluids.