Determination method of thermal resistance

The cold and heat temperature difference resistance refers to the ability of the paint film to resist the damage of the paint film during the change of temperature from low to high or from high to low. According to the national standard GB4893.7-85, the measurement method of the cold and heat temperature difference resistance of the paint film is as follows:

Equipment and materials

Constant temperature and Humidity Chamber (temperature higher than 60 ℃, relative humidity 98%~ 99%), low temperature refrigerator (temperature lower than -40 ℃), balance, electric furnace, magnifying glass, bristle brush, paraffin and rosin, etc.

Detection steps:

Four samples were taken, one of which was used as a comparative sample and the other three were used as a test. The periphery and back of the specimen were closed with a mixture of paraffin and rosin (1:1 ratio).

Put the closed sample into a constant temperature and Humidity Chamber (temperature 40 ± 2 ℃, humidity 98%~ 99%) and keep it for 1 hour.

Remove the sample and immediately put it in a low temperature refrigerator (temperature -20 ± 2 ℃) for 1 hour.

Repeat the above temperature change steps, and after three cycles, place the sample in an environment with a relative humidity of 60% to 70% at 20 ± 2 ℃ for 18 hours.

Observe the specimen, using 4 times magnifying glass to observe whether there are cracks, bubbling, obvious loss of light and discoloration.

According to the agreement between the supplier and the buyer, different cycles can be selected, such as 3, 6, 9, 12, 15, 18 weeks, etc.

If cracks, bubbling, obvious loss of light, discoloration, etc. occur during the inspection process, the sample is judged to be unqualified.

The test of thermal resistance can simulate the performance of the paint film under temperature changes, help evaluate the stability and durability of the paint film, and ensure that the paint film will not be damaged or quality problems under different temperature conditions.