Short notes: The tea leaves as a filler for UF resin plywood production

The addition of green tea leaves fractions < 0.315 mm as a filler to urea-formaldehyde resin to reduction of emission of formaldehyde from three-layer birch plywood was investigated. Moreover, other properties such as bonding quality and water resistance of plywood were investigated. It was found that green tea had an ability to absorb formaldehyde. This phenomenon was caused by phenolic compounds contained in green tea leaves. The addition of green tea in the amount of 20% and 25% resulted in a decrease in formaldehyde emission from plywood comparing to the reference sample. The bonding quality test showed that the addition of tea leaves as a filler did not affect the strength properties of the tested bond lines.

The effect of a phenol-formaldehyde adhesive reinforcement with nanocellulose on the pressing parameters of plywood

Research on improving the reactivity of phenol-formaldehyde (PF) resin and the possibility of lowering the pressing parameters of wood-based materials manufactured with its participation are still progressing. Due to a number of favorable properties, nanocellulose (NCC) is gaining more and more popularity as a modifier of wood adhesives. Therefore, the objective of the study was to assess the possible reduction of plywood pressing parameters due to the reinforcement of PF resin with NCC. Based on the bonding quality results it was found that there is a possibility to reduce pressing time by 25% and pressing temperature by 7%. Moreover, the outcomes of mechanical properties (modulus of elasticity and bending strength) of manufactured plywood indicate that theoretically it could be possible to decrease the pressing parameters even more. However, the shear strength of the glue joints was considered to be a limiting factor for further reduction. The results of delamination test show that plywood bonded with phenolic resin have no tendency to delaminate. Thus, it can be concluded that NCC can be used as a modifier for PF resin which can contribute to the reduction of pressing time and pressing temperature during the plywood manufacturing process.

Properties of the water-resistant plywood glued with pf resin with the addition of tannin filler and nanoclay

The conducted study was aimed at finding the phenol-formaldehyde adhesive formulation containing both the nanoclay and the tannin filler which allows to manufacture water-resistant plywood characterized by the improved properties. The research assumed the application of six experimental variants having a different proportions of the mentioned components which were compared with the mixture prepared according to the industrial recipe. Properties of liquid mixtures such as their gelation time and viscosity were investigated. Moreover, the differential scanning calorimetry (DSC) was performed. The manufactured plywood panels were tested in terms of bonding quality, bending strength and modulus of elasticity. Studies have shown that after the adjustment in components proportions it is possible to achieve the proper viscosity level of adhesive mixtures. The results also indicated that the suitable amount of nanoclay can contribute to the acceleration of resin gel time, however, the DSC analysis showed no effect on its reactivity. The nanoclay concentrations ranging from 2 to 4 pbw (parts by weight) per 100 g of adhesive positively influenced the bonding quality of plywood. Furthermore, there was no clear tendency in case of the effect of applied formulation on the modulus of elasticity and bending strength of plywood. The mixture containing 3 pbw of nanoclay and 5.3 pbw of tannin filler was distinguished as the most beneficial taking into account the improvement in the properties of manufactured plywood.

The soy flour as an extender for uf and muf adhesives in birch plywood production

Formaldehyde emission still remains a major disadvantage of widely applied formaldehyde-containing amino resins such as UF (urea-formaldehyde) resin and MUF (melamine-urea-formaldehyde) resin. The compositions of adhesives for plywood manufacturing have to contain a proper extenders in order to adjust their viscosity. Thus, the aim of the study was to investigate the effect of protein-rich soy flour (SF) as the extender for adhesives. The composition of flours and their ability to absorb the formaldehyde were determined. Properties of liquid resins such as gel time, viscosity, pH and solid content were investigated. The possible chemical interaction between the extenders and resins were assessed with the use of FTIR spectroscopy. Plywood panels manufactured using UF and MUF adhesives with the soy flour introduced as the extender in various concentrations were tested in terms of shear strength and formaldehyde release. Studies have shown that soy flour has a favorable composition and formaldehyde-scavenging ability. The addition of SF affected resins properties such as viscosity and gel time but showed no influence on their pH and solid content. FTIR analysis has not explained the chemical interaction between resin and extender. The application of soy flour in the concentration of 15% for UF resin and 10% for MUF resin allowed to produce plywood characterized by improved bonding quality and decreased formaldehyde emission.