Abstract
The viscosity of strongly basic resols preoared by mixing of high-molecular resols (HMR), a low-molecula resol model (saligenin) and sodium hydroxide in the various formulations was studied through the use of a Couette-type viscometer, and the effects of the formulations of the glue mixtures on their viscositties were discussed.
The amount of sodium hydroxide was in the range of 0.4 to 0.8 moles to a phenyl nucleus in the mixtures and the mixing ratio in weight of two types of HMR to saligenin was O.33, 1.00 and 3.00. Two types of novolaks, that is, high-ortho and randam novolak, were fractionated by the use of water and acetone to remove the low-molecular portion, and then the high-molecular novolaks obtained were converted into two types of HMR having about O.5 moles/100g of methylol groups and the characteristics of the original resins.
The flow curves made by single-bob method for the glue mixtures at 50% solid loading presented the following informations.
(1) Increasing the mixing ratio of HMR to saligenin and lowering the sodium hydroxide addition formed the glue mixtures to be the Non-Newtonian fluid with high viscosity.
(2) To make the glue mixtures having low viscosity and the linear relationship between the shearing stress and the velocity gradient on the flow curves, adding more than 0.6 moles of sodium hydroxide or increasing the mixing ratio of a low molecular resol (saligenin) was required.
(3) The increasing effect of the high-ortho type HMR on the viscosity of the glue mixtures was greater than that of the randam type one, indicating that the effective hydrodynamic radius of the former type of HMR in solution was greater than the radius of the latter.
