The method is suitable for determining the thermal conductivity of FRP by a plate steady state method. 1 Sample 1.1 Preparation The sample is prepared according to the provisions of GB 1446 "General rules for FRP performance test methods" or directly according to product requirements. 1.2 Dimensions The specimen size shall meet the following requirements: a The side length or diameter of the specimen shall be equal to the heating plate. b The thickness of the specimen is at least 5 mm and the maximum is not more than 1/10 of its side length or diameter. 1.3 Surface The surface of the sample shall be flat and the surface irregularity shall not exceed 05 mm/m. Both sides of the sample shall be parallel. 1.4 Pretreatment The sample shall be dried to constant weight or treated according to product technical requirements at a temperature that does not cause deterioration or deformation (but not higher than 105 °C). The so-called constant weight means that the sample has a weight change of not more than 02% at a treatment temperature of 2 hours. 1.5 Quantity Not less than 3 samples per group. 2 Test conditions 2.1 Test environment The test environment conditions shall comply with the provisions of GB 1446. 2.2 Test temperature and temperature difference The hot plate temperature is not more than 250 °C, the cold plate temperature is from room temperature to the required temperature, and the temperature difference between the two sides of the sample is not less than 10 °C. 3 Test equipment The main technical parameters of the test equipment shall meet the following requirements. 3.1 Heating plate The heating plate consists of a main heating plate and a heating plate that surrounds the main heating plate and has a certain gap. The requirements are as follows: a) The length or diameter of the heating plate is generally 100 mm, and the width of the heating plate is the edge of the heating plate. It is 1/4 of the length or diameter and has appropriate insulation measures. If there are special measures and the error of the measured value of the thermal conductivity is within 8%, this value can also be changed as appropriate. B The temperature difference between the points on the surface of the main heating plate is not more than 2% of the temperature difference between the two sides of the sample under steady state, but the maximum is not more than 0.5 °C. The temperature difference between the points on the surface of the heating plate shall not exceed 5% of the temperature difference between the two sides of the sample under steady state, and the maximum shall not exceed 1 °C. The surface roughness of the heating plate should be no more than 0.25 mm/m. 3.2 Cooling plate aThe cooling plate shall have a threaded bidirectional liquid circuit. b The size of the cooling plate and the surface condition of the contact sample are the same as those of the heating plate, but the cooling plate is not spaced. 3.3 Measurement accuracy 3.3.1 Temperature The temperature measurement should be accurate to 1% of the temperature difference between the two sides of the sample under steady state, but the maximum is not more than 05 °C. 3.3.2 Power The power of the main heating plate should be measured to the nearest 1%. 4 Test procedure 4.1 Visual inspection of the sample The sample shall be visually inspected in accordance with the provisions of GB 1446. 4.2 Specimen thickness measurement The thickness of the sample is measured at least 4 times, accurate to 005 mm, and its arithmetic mean is taken. 4.3 Mounting the specimen for testing When installing the specimen, care should be taken to eliminate the air interlayer. 4.4 Adjusting the balance Adjust the temperature difference between the main heating plate and the heating plate and the main heating plate and the bottom heating plate to balance it. The thermal conductivity test error due to unbalance should not exceed 1%. 4.5 Measurement After reaching a steady state, measure the power difference between the main heating plate and the two sides of the sample. The test is over. The so-called steady state means that the temperature fluctuation of the surface of the sample within 30 minutes is not more than 1% of the temperature difference between the two sides of the sample, but the maximum is not more than 1 °C.