(1) Effect of temperature on viscosity
According to the hole theory of molecular thermodynamics, the viscosity-temperature relationship of low-molecular liquids can be expressed by the Andrad equation:
In the formula, A——constant;
R——gas constant;
E——flow activation energy;
T——thermodynamic temperature.
The activation energy of flow decreases with increasing temperature. For a certain liquid, within an appropriate temperature range, the positive value is approximately constant, then the above formula is rewritten as:
Experiments have proved that the above formula is also applicable to concentrated polymer solutions. For the same polymer solutions with different molecular weights, because they are very similar, they have similar viscosity-temperature relationships.
(2) The effect of base material concentration on solution viscosity
Let the solution viscosity be η, the solvent viscosity be sum, the solute volume fraction be φ, and define ηt=η/η0 as the relative viscosity (or specific viscosity) of the solution. For a dilute solution of a rigid sphere, the relationship between viscosity and solute obeys the Einsten equation:
However, the coating system is often a high-concentration solution of solvated or swollen non-spherical particles, and the solid content of modern coatings is still increasing. After many scholars' research on the extended application of this equation, there is a simple and applicable expression The formula is as follows:
This formula is applicable to low molecular weight oligomer or prepolymer solution in the range of 0~100%.
(3) Effect of solvent viscosity on solution viscosity
Usually, people are used to judging the viscosity . In fact, the viscosity of the solvent itself may change the viscosity of the solution by thousands or hundreds of mPa·s under the difference of mPa`s .
