Hydrophobic modification of bagasse cellulose fibers with cationic latex: Adsorption kinetics and mechanism

• Latex with core–shell structure was synthesized to render bagasse fibers hydrophobic.
• Two-stage equilibrium of adsorption was observed and fitted with kinetic models.
• The extra-added cationic surfactant enhanced the adsorption efficiency of latex.
• Various driving forces for adsorption were discussed to reveal adsorption mechanism.

The modification of the bagasse cellulose fiber by the adsorption of cationic poly latex with core–shell structure on fiber surfaces was conducted in attempt to enhance the interfacial compatibility between hydrophilic fibers and the hydrophobic substrates for various applications. A two-step semi-batch emulsion polymerization was employed for constructing core–shell latex. TEM and dynamic light scattering (DLS) analysis indicated that the core–shell latex possessed a broad particles size distribution, which led to the adsorption of the latex on fiber proceeding via two-stage equilibrium mainly due to the effect of latex particle size. The pseudo-first-order kinetic model was appropriate for the description of the kinetics of the first stage equilibrium at high latex concentration and the entire adsorption process at low concentration. In contrast, the pseudo-second-order kinetic model fitted the second equilibrium at high latex concentration well. The activation energy calculated suggested that the number of activated molecules was increased as the increase of adsorbent concentration, which might change the dominant adsorption mechanism. This also addressed the reasons for the abnormal adsorption behavior with the extra-added emulsifier. In addition, the surface property of the modified cellulose fibers was also investigated via contact angle measurements. The results proved that the cellulose fiber modified with the latex became hydrophobic, allowing the as-modified cellulose to be potential reinforcements for biocomposite. Finally, the adsorption mechanism was proposed according to the adsorption process mainly governed by electrostatic interactions, hydrogen bond, π–π stack and chain entanglement.

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