Most of the methods for measuring the complete drying speed cannot give very accurate results. These methods are mainly based on the measurement of the mechanical strength of the paint film during the drying process. Delinberger and Bragang Lavova proposed to measure the complete drying time of the oil-based paint film according to the reversible degree of the paint film during the drying process, that is, its solubility in various solvents. The solubility of the paint film gradually decreases during its drying process. In this method, the dry paint film is extracted using various solvents in a Soxlet apparatus. The weight loss of the paint film measured after a certain period of time and expressed as a percentage is regarded as the reversible degree of the paint film. Due to the time schedule and considerable complexity of the experiments, this method is only suitable for research work.
Yamshikoff once proposed a method of measuring the drying speed (viscosity) of varnish for dissolving rubber according to the degree of adhesion of iron chips (relevant instrument: viscometer). The coating is brought into contact with the sample by means of an electromagnetic iron. According to this principle, Osterlin and Savina designed a simple instrument for the determination of paint materials.
A particularly interesting and well-developed method for determining the complete drying of a paint film is by measuring the electrical properties of the paint film during the drying process (change in insulation strength, change in dielectric loss angle, capacitance rate change), however, these methods have not been widely adopted so far.
Determination of the complete drying rate of varnishes and paints by the pendulum method
For determining the rate at which a painted material dries completely, good results can be obtained by borrowing a pendulum Tester for determining the hardness of varnishes and varnishes. (Related instrument: drying time Tester)
When using the pendulum Tester to measure the complete drying speed of the varnish, we have confirmed that the hardness of the dried paint film has become constant from a certain moment (related instrument: Hardness Tester). The basic coordinates of the starting point where the hardness is fixed indicate the end of the complete drying process of the paint film, while the characteristics of the curvature can show the entire drying process, that is, the concept of drying dynamics.
According to the data of Lazarev and Osterlin, the drying process of the paint film (before reaching the starting point of fixed hardness) is much longer than the drying time stipulated by the technical conditions. This shows that the Tester is a very sensitive instrument, and it may even record its drying process when other instruments cannot record it.
In the case of meeting some necessary conditions, the results of the replication test can achieve high accuracy. The pendulum Tester can be used to determine the drying rate of the dried and baked paint materials at room temperature.
