Effect of Wheat Flour on the Viscosity of Urea-formaldehyde Adhesive

It is hoped to develop new additives substituting for wheat flour used in UF-glue, which needs to investigate the interaction of flour with UF-glue as reference. This paper tested and contrasted the effects of wheat flour, maize powder, wheat starch and its mixture with gluten on the properties of UF-glue through measuring glue viscosity and slab pre-press strength. The viscosity-increasing in UF-glue and slab pre-press strengthening efficiency ordered from great to small as: wheat gluten, wheat flour, simulated flour, wheat starch, maize powder. SEM images, IR and XRD spectra do not show clear evidence of chemical reaction between flour and UF-glue around room temperature. The starch separated from mixture of flour with UF-glue keeps its crystallitic properties such as polarizing and gelatinizes when heated enough. For same compositions the viscosity of the mixture of suspension with UF-glue is bigger than that of the mixture of dry powder with UF-glue. Wheat flour and other powders containing wheat proteins have stronger influence on UF-glue than on poly(vinyl acetate) latex; the reason for this fact needs further in-depth study.