In this work, the suitability of nanofibrillated cellulose (NFC) as a novel component for wood coatings has been evaluated. NFC was prepared from two different wood pulps with a high pressure homogeniser and a grinder, depending on the initial fibre size of the two pulps. The fibrillation process was monitored using viscosity measurements and scanning electron microscopy. Viscosity measurements were found to be a suitable, reliable and especially fast and easy method for process monitoring, optimization and quality assessment of the NFC fibrillation process. NFC was mixed with four different waterborne acrylic polymer emulsions and analysed regarding its rheological behaviour. The viscosity of the acrylate-NFC suspensions was dominated by the NFC, whereas the polymer type was of minor importance at the tested concentrations. The viscosity increased exponentially after NFC addition and consequently the viscosity of such suspensions would be precisely adjustable in the considered shear range. During accelerated storage at elevated temperatures, the general flow behaviour did not change; only a slight viscosity increase was observed. The study shows that rheology is an important issue that has to be taken into account when applying NFC as additive in water based coating systems and that NFC is suitable as component for coating applications.

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Composite films of nanofibrillated cellulose (NFC), derived from beech wood pulp, and 8 commercial acrylic and alkyd polymeric binders were prepared. Structural and mechanical properties of the composites were assessed by microscopy and tensile tests before and after aging. While the NFC was compatible with acrylate polymers, it formed undesired aggregates during processing with the alkyd polymers. Modulus of elasticity, tensile strength, and elongation at break of prepared films depended on the initial properties of the neat polymers. All composite films were stiffer, stronger, and less extensible than the corresponding neat polymer films. The reinforcing effect increased with increasing NFC content. Aging by artificial weathering strongly affected the mechanical properties of neat polymer and composite films. Alkyd films became, compared to the acrylate films, much stiffer and more brittle after artificial weathering. The results of the mechanical tests are regarded as promising step to use NFC as novel component in wood coatings.

Nanofibrillated cellulose (NFC) was used as biobased stabilizing agent in the heterophase polymerization of methyl methacrylate (MMA) to nanoscale poly(methyl methacrylate) (PMMA) spheres. NFC/MMA suspensions at different NFC/MMA ratios were prepared in water, and the suspension stability was evaluated before the subsequent polymerization. The resulting polymerization products as well as products from several control experiments were analyzed via optical microscopy, SEM, and isolation experiments associated with thermogravimetric analysis. PMMA spheres had diameters in the range of 150-250 nm and were regularly distributed within the NFC network, whereas NFC acted as a stabilizer during the polymerization. The appearance of the resulting PMMA spheres within the NFC network was influenced by different factors, such as the reaction conditions, the initiator, and the solubility of the monomer.

Dynamic mechanical analysis (DMA) represents an important method for understanding the mechanical behavior of surface coatings. In this work, transparent composite films of nanofibrillated cellulose (NFC), derived from beech wood pulp, and 10 different commercial polymeric binders, representative binders for wood coatings, were prepared to study the viscoelastic properties of the composite films. DMA in tensile mode was used to determine the glass transition temperature (T g ), the storage and loss modulus and the crosslinking and entanglement density before and after accelerated aging. Additionally, Fourier transform infrared spectroscopy (FTIR) was applied to corroborate the findings of the dynamic mechanical analysis. T g , moduli, crosslinking and entanglement density of prepared films depended on the initial properties of the neat polymers. The addition of 2.5 wt% NFC to the polymers had no significant influence on T g and entanglement density, while the reinforcing effect of NFC influenced the moduli of all polymers, as well as the crosslinking density of the alkyds. Accelerated aging by UV radiation at 60 °C strongly affected the viscoelastic properties of neat alkyd polymer and its NFC composite films, while the aging effect was less pronounced for the acrylates. DMA and FTIR findings confirm that unmodified NFC did not adversely change the general aging behavior of the polymers.

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