title: Biocomposites from Natural Rubber: Synergistic Effects of Functionalized Cellulose Nanocrystals as Both Reinforcing and Cross-Linking Agents via Free-Radical Thiol-ene Chemistry.
abstract: Natural rubber/cellulose nanocrystals (NR/CNCs) form true biocomposites from renewable resources and are demonstrated to show significantly improved thermo-mechanical properties and reduced stress-softening. The nanocomposites were prepared from chemically functionalized CNCs bearing thiols. CNCs served as both reinforcing and cross-linking agents in the NR matrix, and the study was designed to prove the cross-linking function of modified CNCs. CNCs were prepared from cotton, and the cross-linkable mercapto-groups were introduced onto the surface of CNCs by esterification. Nanocomposite films were prepared by dispersing the modified CNCs (m-CNCs) in NR matrix by solution casting. The cross-links at the filler-matrix (m-CNCs-NR) interface were generated by photochemically initiated thiol-ene reactions as monitored by real-time FTIR analysis. The synergistic effects of reinforcement and chemical cross-linking at the m-CNCs-NR interface on structure, thermo-mechanical, and stress-softening behavior were investigated. Methods included field emission scanning electron microscopy (FE-SEM), swelling tests, dynamic mechanical analysis, and tensile tests. Compared to biocomposites from NR with unmodified CNCs, the NR/m-CNCs nanocomposites showed 2.4-fold increase in tensile strength, 1.6-fold increase in strain-to-failure, and 2.9-fold increase in work-of-fracture at 10 wt % of m-CNCs in NR.
authors.affiliation: †Wallenberg Wood Science Center, Royal Institute of Technology, 100 44 Stockholm, Sweden.
authors.forename: Bipinbal
authors.initials: B
authors.lastname: Parambath Kanoth
authors.affiliation: ‡Department of Fibre and Polymer Technology, Royal Institute of Technology, 100 44 Stockholm, Sweden.
authors.forename: Mauro
authors.initials: M
authors.lastname: Claudino
authors.affiliation: †Wallenberg Wood Science Center, Royal Institute of Technology, 100 44 Stockholm, Sweden.|‡Department of Fibre and Polymer Technology, Royal Institute of Technology, 100 44 Stockholm, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Johansson
authors.affiliation: †Wallenberg Wood Science Center, Royal Institute of Technology, 100 44 Stockholm, Sweden.|‡Department of Fibre and Polymer Technology, Royal Institute of Technology, 100 44 Stockholm, Sweden.
authors.forename: Lars A
authors.initials: LA
authors.lastname: Berglund
authors.affiliation: †Wallenberg Wood Science Center, Royal Institute of Technology, 100 44 Stockholm, Sweden.|§School of Biotechnology, AlbaNova University Centre, Royal Institute of Technology, 106 91 Stockholm, Sweden.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhou
keywords: cellulose nanocrystals; interface; mechanical properties; nanocomposites; natural rubber; thiol−ene chemistry