How to measure the heat resistance of paint film?

1 Definition, Purpose and Significance

2 Relevant standards

GB/T 1735-79(89) Determination of heat resistance of paint film

3 Introduction to key points of inspection methods

3.1 Test Principle

After the sample reaches the temperature and time specified in the product standard, check the surface of the paint film. It is also possible to continue other performance tests after the heat resistance test, such as impact, bending, scratch tests, etc.

3.2 Materials and Instruments

Thin steel plate: 50mmxl20mmx(0.45~0.55)mm;

Blast constant temperature oven;                                                               

 Box-type resistance furnace (muffle furnace).

3.3 Operation points

After adjusting the oven (or muffle furnace) to the temperature specified in the product standard, put the three samples in. After the specified time, take out the samples, cool to room temperature, and compare them with the samples left in advance.

3.4 Result Judgment

Check whether the paint film has discoloration, foaming, peeling, wrinkling, cracking, etc. or check according to the product standard. Whether it is qualified or not is according to the product standard.

The evaluation of paint film discoloration, blistering, cracking, etc. can refer to the provisions in GB/T 1766-1995 "Methods for Rating Aging of Paints and Clearcoats".

3.5 Precautions

3.5.1 Substrate material, substrate treatment and paint film thickness should be in accordance with product standards. The uniformity of film thickness and the dryness of the paint film: 1. Whether there are defects on the surface of the paint film (such as the size of brush marks, whether there is willingness or not) Particles, shrinkage cavities) may affect the test results of its performance.

3.5.2 The heat-resistant temperature should be adjusted accurately and kept within the allowable deviation range. The time should be in accordance with the regulations, neither too long nor too short. 

3.5.3 According to the method standard, the sample should be placed in the oven after the temperature reaches, and taken out after the time is up, that is, sudden heating and quenching. However, some coating product standards require that as the oven heats up and cools down, the heat resistance time should be calculated from the time when the specified temperature is reached, and the temperature should be lowered after the time expires.