Regarding the performance testing methods of powder coatings, this paper mainly introduces: the determination of softening temperature and gelation time.
1. Determination of softening temperature
(1) Equipment Thermometer paper.
(2) Test procedure Heat to make the temperature of the Hot Plate reach equilibrium. Select a material with a known melting point close to the melting point of the material to be tested or use a thermometer to verify the indicated value of the temperature scale.
Spread a small amount of the powder sample to be tested on a Hot Plate to form a thin and narrow powder belt, with a length of about 2°C across the temperature range, so that the expected melting point is near the center of the temperature range. After about 1 min, brush the unmelted powder from the high temperature side to the low temperature side. Then adjust the pointer to the position where the trace of molten powder just appeared, this temperature point is the softening temperature of the powder.
2. Determination of gelation time
(1) Definition The gelation time refers to the time from melting to gelation of the hot-surface powder method at a certain temperature.
(2) Equipment furnace temperature tracker
(3) Test procedure There should be no strong ventilation around the Hot Plate, or it should be placed in a windshield surrounded by 3 sides with a height of 300mm. The temperature rise time of the Hot Plate shall not be less than 30min. The constant temperature of the Hot Plate is determined according to the requirements (usually the deviation is ±1°C), and the surface of the Hot Plate is coated with a thin layer of release agent, such as silicone oil or rubber solution. Measure 1mL of powder sample on the Hot Plate, and use a spatula to quickly spread it within a diameter of about 50mm. When the powder melts, start timing and use the stirring rod to make circular motion in the molten sample. Pay attention to the flow state of the sample. sample.
Repeat the test 3 times, each time the error should not be greater than ± 5% of the mean.
