Advanced nanocellulose-based gas barrier materials: Present status and prospects

Nanocellulose based gas barrier materials have become an increasingly important subject, since it is a widespread environmentally friendly natural polymer. Previous studies have shown that super-high gas barrier can be achieved with pure and hierarchical nanocellulose films fabricated through simple suspension or layer-by-layer technique either by itself or incorporating with other polymers or nanoparticles. Improved gas barrier properties were observed for nanocellulose-reinforced composites, where nanocellulose partially impermeable nanoparticles decreased gas permeability effectively. However, for nanocellulose-based materials, the higher gas barrier performance is jeopardized by water absorption and shape deformation under high humidity conditions which is a challenge for maintaining properties in material applications. Thus, numerous investigations have been done to solve the problem of water absorption in nanocellulose-based materials. In this literature review, gas barrier properties of pure, layer-by-layer and composite nanocellulose films are investigated. The possible theoretical gas barrier mechanisms are described, and the prospects for nanocellulose-based materials are discussed.

Photocatalytic degradation of surface-coated tourmaline-titanium dioxide for self-cleaning of formaldehyde emitted from furniture

Formaldehyde emission is an intrinsic property derived from aldehyde-based resin that is used in wood-based composites. To reduce formaldehyde emission from plywood, the composite catalyst of tourmaline-titanium dioxide (T-TiO₂) was fabricated by the sol-gel method. Furthermore, the impregnated paper loaded with the T-TiO₂ composite catalyst was used to decorate the surface of 5-layer poplar plywood. The physicochemical structure, photocatalytic activity of T-TiO₂ composite catalyst and its mechanism of degrading gaseous formaldehyde and generating air negative ions were assessed. The results discovered that the synergistic influence of the tourmaline and TiO₂ anatase nanocrystals achieved good photodegradation of the gaseous formaldehyde. The neat T(20%)-TiO₂ catalyst offered a higher formaldehyde removal efficiency (92.2%) than other catalysts, possessing 800 ions/cm³ of air negative ions concentration after 10-h visible light irradiation. The poplar plywood with a load of 3% T(20%)-TiO₂ catalyst can stably induce the degradation formaldehyde into air negative ions with a concentration of 1200 ions/cm³ in visible light. The impregnation process of paper was feasible to be industrialized and the decorated wood-based composites can be widely applied in the furniture industry.