Detection of softening time of coating powder

(1) Definition

The gelation time refers to the powder coating. On a Hot Plate at a certain temperature, when a certain amount is spread to a certain thickness, it melts from the beginning, and it is called gelation when the silk cannot be pulled out or cannot flow. The period from melting to gelation of powder coating is called gelation time, and the unit is expressed in s or mn.

(2) Equipment

Hot plate: brass plate with smooth surface, thickness 15-2l11mm, diameter 120mm or square 120mmx120mm. There is a hole in the middle of the side with a diameter of 7mm and a depth of 65mm for inserting a thermometer. The Hot Plate is heated by an electric furnace. It can be used with a voltage regulator or other The temperature of the equipment is controlled, and the temperature can be maintained at ±1°C (it is better to add a stainless steel plate with a thickness of 2mm and a size that can cover the surface of the electric furnace between the Hot Plate and the electric furnace to prevent the powder or coating from falling into the electric furnace).

Stopwatch or other timer: accurate to 0.2s.

Mercury thermometer: can measure 0~250℃.

Measuring spoon: 1ml.

Stirring: The size is about 2mmx10mmx150mm, and one end is sharpened. It can be made of non-thermal conductive materials such as wood, bamboo, polytetrafluoroethylene board, etc.

Metal putty scraper.

(3) Test procedure

There should be no forced ventilation around the Hot Plate, or it should be placed in a windshield surrounded by three sides with a height of 300mm. The temperature rise time of the Hot Plate is allowed to be at least 30 minutes. The constant temperature of the Hot Plate is determined according to the requirements. The surface of the Hot Plate is a thin layer of release agent. Add silicone oil and silicone rubber solution, measure 1mL of powder sample on the Hot Plate, and use a spatula. Quickly pave it flat within about 50mm in diameter. Start timing when the powder melts, and use the throwing rod to make that movement in the molten resin. Pay attention to the flow state of the resin. When it cannot be drawn or flowed, it is regarded as a gelation point, that is, stop timing, and use a scraper to remove the resin on the board.

The test was repeated 3 times, and each time the error should not be greater than ±5% of the mean value.

(4) Results

The gel time was taken as the median value of three measurements.