No abstract

The use of formaldehyde-free, biomass-based composites has gained increasing attention in recent years because of their environmental benefits and superior strength properties. In this study, oriented cotton stalk board (OCB) was fabricated with an environmentally friendly, waterbased konjac glucomannan-chitosan-polyvinyl alcohol (KCP) blend adhesive using hot pressing technology. The effects of pressing parameters on the physical and mechanical properties of oriented cotton stalk board were examined in order to obtain optimal pressing parameters. Interfacial bonding surface was also examined with a scanning electron microscope and a fluorescence microscope. The optimal physical and mechanical properties were obtained at a pressing temperature of 150 °C for 15 min with a target density of 0.8 g/cm 3 during hot pressing. Adhesive content and hot pressing pressure had significant influences on adhesion. Mechanical interlocking was also observed between cotton stalks and the adhesive. OCB with KCP blend adhesive has comparable mechanical properties to that with urea formaldehyde resin or phenolic formaldehyde resin. OCB resinated with KCP blend adhesive is environmental friendly and has potential applications in furniture and interior decoration with less stringent requirements for water resistance.

Polypeptide was used to improve the water resistance of konjac glucomannan (KGM)-chitosan-based wood adhesives. With identical solid content, the tensile strength in wet state was increased by the addition of polypeptide and a maximum tensile strength of 2.34 MPa was reached. To examine the physical and chemical changes induced by the addition of polypeptide, the structure, viscoelasticity, morphology, and miscibility of the adhesive blends were determined by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, rheometry, and scanning electron microscopy. Results indicated improvements in mechanical properties were related to the formation of intermolecular hydrogen bonds and covalent bonds between KGM, chitosan, and polypeptide, which was enhanced by increasing the polypeptide concentration. Good miscibility existed between KGM, chitosan and polypeptide, as well as good wettability between the adhesive blends and wood veneer.

An environmentally-friendly wood adhesive was developed by blending konjac glucomannan (KGM), chitosan (CH), and polyvinyl alcohol (PVA) together. The viscosity of the KGM-CH-PVA (KCP) blend adhesive was determined, and the morphology of the film was observed using scanning electron microscopy (SEM). The KCP blend adhesive was applied to plywood during the manufacturing process, and the effects of the KGM, CH, and PVA contents on the bond strength was investigated. Results showed that KGM greatly increased the viscosity of the KCP blend adhesive, whereas the addition of PVA decreased the viscosity in the test range. The SEM observations showed that the KCP blend adhesive was homogeneous. The bond strength of the plywood that was treated with KCP blend adhesive increased with increasing KGM and CH concentrations, and desirable performance could be obtained with a total solids content of 4.6%. The KCP blend adhesive with 2.0% KGM, 2.0% CH, and 0.6% PVA exhibited a comparable bond strength with phenol formaldehyde. Findings suggest that the KCP blend adhesive can be used as a wood adhesive with all raw materials, having the advantage of being environmentally friendly.