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An aqueous TEMPO-oxidized cellulose nanofiber (TOCN) dispersion and aqueous hydrogenated acrylonitrile-butadiene rubber (H-NBR) latex were mixed with or without applying high shear forces. The TOCN/H-NBR mixtures containing TOCN volume ratios of 0–10.0% were then converted to crosslinked composite sheets with peroxide between the H-NBR molecules by hot-pressing. When the aqueous TOCN/H-NBR mixtures were pretreated with high shear forces, the crosslinked TOCN/H-NBR composites exhibited concomitant high tensile strength, high tensile modulus, high ductility, high storage modulus, and high dimensional stability to temperature. These properties are better than those of H-NBR composites containing single-walled carbon nanotubes or carbon black at the same filler volume ratio. In the crosslinked TOCN/H-NBR comosites prepared with high shear fodrces as pretreatment, electron microscopy images showed that the TOCN elements were homogeneously dispersed in the H-NBR matrix without forming aggregates. Thermal and pulsed NMR analyses of the solvent-extracted residue of the non-crosslinked TOCN/H-NBR composite indicated that characteristic nanostructures formed in the TOCN/H-NBR interfacial phases, which may cause the excellent mechanical and thermal properties of the composite. Image 1 [ABSTRACT FROM AUTHOR]

Abstract: Interlaminar fracture toughness for mode I and II deformation were investigated for carbon fiber (CF)/epoxy laminates toughened by a carbon nanofiber/epoxy interlayer. Vapor grown carbon fiber (VGCF) and vapor grown carbon nanofiber (VGNF) were chosen as the reinforcement for the interlayer. To illustrate the effect of the interlayer on the fracture toughness of the laminates, several types of carbon fiber reinforced plastics/carbon nanofiber (CFRP/CNF) hybrid laminates were fabricated. Each laminate was composed of unidirectional carbon/epoxy prepregs with carbon nanofiber varying the interlayer thickness. Mode I interlaminar fracture toughness was evaluated by a standard double cantilever beam (DCB) test. Mode II interlaminar fracture toughness was evaluated by an end notched flexure (ENF) test using a three point bending test. The experimental results of the DCB test confirms that the mode I interlaminar fracture toughness for hybrid laminates is about 50% greater than the base CFRP laminates. Furthermore, the results of the mode II fracture toughness test confirms that the interlaminar fracture toughness for hybrid laminates is 2–3 times greater than base CFRP laminates. In addition, the results revealed the recommended range of CNF interlayer thickness is between 100 and 150μm (approximately 20g/m2 carbon nanofiber area density). The difference in the effect of the interlayer fracture properties under mode I and II deformation was discussed on the basis of fractographic observations derived from scanning electric microscope. [Copyright &y& Elsevier]

Aqueous dispersion consisting of 2,2,6,6-tegramethylpyperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TEMPO-CNFs), dodecyltrimethylammonium chloride (DTMACl), and diethylene glycol (DEG) was oven-dried at 40 °C for 1 d to prepare a dried product. The soft and bulky TEMPO-CNF/DTMACl/DEG material was added to a carboxy group-containing nitrile-butadiene rubber (XNBR) followed by removal of all the DEG molecules by vacuum drying at 80 °C for 8 h. The mixture was then subjected to kneading with high shear forces using a two-roll mill at 20–30 °C (i.e., elastic kneading), followed by pressing at 170 °C for 20 min to prepare cross-linked XNBR composite sheets consisting of TEMPO-CNF and DTMACl. The XNBR composite sheet containing 9.9 vol% TEMPO-CNF had an average tensile strength, storage modulus at 23 °C, work of fracture, and elongation at break of 19 MPa, 47 MPa, 2.7 MJ/m3, and 230%, respectively, whereas those of the reference cross-linked XNBR sheet were 11 MPa, 11 MPa, 0.9 MJ/m3, and 220%, respectively. Scanning transmission electron microscopy observation revealed unique fibrillated and cluster-like structures of the TEMPO-CNF were likely responsible for the excellent mechanical and thermal properties. The proposed process is industrially viable for conventional kneading processes to prepare composite rubber sheets with good mechanical and thermal properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Nanocellulose-reinforced polyethylene composite sheets were prepared with an in situ surface-hydrophobized, TEMPO-oxidized cellulose nanofibrils (TEMPO-CNFs) and polyethylene by thermal kneading with high shear forces (i.e., under 'elastic' kneading conditions). First, diethylene glycol (DEG) and cationic surfactant were added to a 1% TEMPO-CNF/water dispersion, and the mixture was agitated to prepare a foam. This foam was oven-dried at 40 °C for ~2 days to prepare a bulky and soft product. This oven-dried TEMPO-CNF/surfactant/DEG was added to maleic anhydride-modified polyethylene at 120–135 °C, and the mixture was elastically kneaded to prepare a TEMPO-CNF/surfactant/polyethylene master batch. The DEG and water molecules present in the oven-dried product were completely removed during kneading. The master batch was further kneaded with polyethylene to prepare TEMPO-CNF/cationic surfactant/polyethylene composite sheets. No detectable aggregates of TEMPO-CNFs were observed in the scanning electron microscopy images of the composite sheets. The yield stress and modulus of the sheets linearly increased with increasing TEMPO-CNF content up to ~8 vol%. Therefore, we successfully reinforced polyethylene with TEMPO-CNFs using our oven-drying and elastic kneading method. [Display omitted] [ABSTRACT FROM AUTHOR]