The heat resistance of the paint film refers to the ability of the paint film to resist discoloration, softening, bubbling and other phenomena when heated. According to the national standards GB489.2 and GB4893.3, the heat resistance of the paint film is divided into two types: dry heat resistance and damp heat resistance. The following is the determination method of the heat resistance of the paint film:
1. Determination of moisture and heat resistance of paint film:
Equipment and materials: brass copper test cup, electric furnace, balance, crucible pliers, thermometer, thermal insulation pad, nylon spinning, stainless steel pointed tweezers, distilled water, heating medium, observation box, etc.
Test conditions: The laboratory temperature is 20 ± 2 ℃, and the relative humidity is 60%~ 70%. The test temperature is selected within the range of 55 ℃, 70 ℃, and 85 ℃ according to product standards or protocols.
Detection steps: Select three detection areas with a diameter of 50mm on the sample, and record the color, gloss and surface condition of the paint film in the area. Then inject mineral oil at a specific temperature into the copper test cup, heat it to the required temperature, and then place the test cup on the detection area. Between the test cup and the sample, there is nylon spinning soaked in distilled water. After standing for 15 minutes, remove the test cup and nylon spinning to absorb the liquid on the surface. After standing for 16 to 24 hours, observe the imprints, discoloration, bubbling, etc. in the detection area, and evaluate it according to the grading standard.
2. Determination of dry heat resistance of paint film:
Instruments and materials: the same as the damp heat resistance method.
Detection steps: The test temperature is selected between 70 ℃, 80 ℃, 90 ℃, 100 ℃ and 120 ℃. The detection steps are roughly the same as those of the damp heat resistance method, except that no wet nylon spinning is placed between the copper test cup and the sample. Finally, the changes of the sample are observed under natural light in the observation box, and the evaluation is carried out according to the grading standard.
Heat resistance testing of paint films can help evaluate the performance of coatings in high temperature environments to determine their suitability and durability. According to different product standards or requirements, different test temperatures can be selected, and the performance of paint films can be evaluated according to grading standards.
吕仕铭 杜长森 周华 - 《《涂料用颜料与填料》》