Nanofibrillated cellulose in wood coatings: mechanical properties of free composite films

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.