This standard is applicable to the measurement of thermal conductivity of plastics by the guarded heat plate steady state method, and is not applicable to the measurement of plastics with thermal conductivity greater than 2.20W/(m·K). GB/T 3399-1982 Test method for thermal conductivity of plastics by guarded heat plate method GB/T3399-1982 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test method for thermal conductivity of plastics by means of tbe guarded hot plateUDC 6T8.5
GB 3399—82
This standard applies to the steady-state method of guarded hot plate to measure the thermal conductivity of plastics, and is not applicable to plastics with a thermal conductivity greater than 2.20W/(m·K).
1 Definition
1.1 Heat flux Φ: The amount of heat passing through a surface per unit time, measured in W. 1.2 Heat flux density 9: The amount of heat passing through a unit area of ​​a surface per unit time, measured in W/m. 1.3 Thermal conductivity λ: Under stable conditions, the heat flow per unit temperature gradient perpendicular to the unit area through a unit area, measured in W/(m·K).
2 Principle
2.1 This method is based on the principle of unidirectional stable thermal conduction. When the upper and lower surfaces of the sample are at different stable temperatures, measure the heat flow through the effective heat transfer area of ​​the sample and the temperature difference and thickness between the two surfaces of the sample to calculate the thermal conductivity. a Sample
3.1 The sample should be a homogeneous hard material, and the two surfaces should be flat, smooth and parallel, without cracks and other defects. For flat sample, the unevenness is required to be within 0.5mm/m.
When testing soft materials or granular materials, a technical frame is required, and the sample should be homogeneous overall. 8.2 The sample should be a representative part of the product, directly cut from the product or prepared according to the product standard requirements. 3.2.1 For the test samples of the double-plate thermal conductivity meter, the same samples should be selected as much as possible. a.3 The sample is a square or square, with a diameter or side length equal to the protective heating plate, and a thickness of not less than 5mm. The maximum thickness is determined by the instrument and should not exceed 1/8 of its diameter or side length. 8.4 Before the test, the specimen should be conditioned according to the requirements of the product standard. If there is no product standard, it should be treated for 24 hours according to the conditions of GB2918-82 "Standard Environment for Conditioning and Testing of Plastic Specimens". 3.5 Each group of specimens shall be no less than 2 pieces.
4 Test conditions
4.1 Test environment: It should meet the normal temperature and humidity specified in GB 2918-82. 4.2 Test conditions
Hot plate temperature: lower than 333K.
Cold plate temperature: room temperature or required temperature.
The temperature difference between the cold plate and the hot plate is not less than 10K, and the temperature gradient through the specimen is between 400K/m and 2000K/m. Note: If there is no dew protection, the cold plate temperature is at least 5K higher than the ambient temperature. 5 Test instrument
The instrument required by this method is a flat plate thermal conductivity instrument with a heat shield. It consists of heating plates (including main heating plates and protective heating plates), cold plates, temperature measuring instruments and calorimetric instruments.
GB3399-82
5.1 Heating plates: The diameter of the main heating plate should be at least 100mm, and the minimum width of the protective heating plate should be at least 1/4 of the side length or diameter of the heating plate. There should be a suitable gap between the main heating plate and the protective heating plate, and the flat area of ​​the gap should not exceed 8% of the area of ​​the main heating plate. The heating plate should be flat and smooth: the surface unevenness should be within 0.25m/m. The temperature is uniform, and the temperature fluctuation of the main heating plate is not more than 2% of the temperature difference between the two sides of the sample. The protective heating plate is not more than 5%. There should be an average temperature balance detector between the main and protective heating plates. 5.2 Cold plate: It should have the same size and unevenness requirements as the heating plate. 5.3 The hot plate and the cold plate have a radiation coefficient of 10.8. 5.4 Temperature measuring instrument: Use a thermocouple with a thermocouple wire diameter of less than 0.2mm to measure the temperature of the two surfaces of the sample with an accuracy of not less than 0.1K. 5.5 Calorimetric instrument: Measure the heat flow through the sample with an accuracy of 1%. 5.6 Heating power supply: The fluctuation of the heating voltage is required to not exceed +0.5%. 6 Test steps
6.1 Use a thickness measuring tool with an accuracy of not less than 0.05mm to measure the thickness of at least four places around the sample, and take the arithmetic mean as the thickness of the sample before the test.
6.2 Place the state-adjusted sample between the hot and cold plates of the instrument so that the sample is in close contact with the hot and cold plates. 6.3 Maintain the hot and cold plates at a constant temperature and maintain the selected temperature difference. The temperature reading should be accurate to 0.1K. 6.4 When the temperature difference between the main heating plate and the expansion heating plate is less than ±0.1K, the temperature is considered to have reached equilibrium. 6.5 When the temperature fluctuation of the main heating plate does not exceed ±0.1K per hour under the condition of constant heating power, it is considered to reach steady state. Measure the temperature difference between the two sides of the heat flow sample through the effective heat transfer surface three times every 30 minutes, and calculate the thermal conductivity. When the difference between each measured value and the average value is less than 1%, the test is terminated.
6.6 After the test, measure the thickness of the sample after the test according to the provisions of 6.1. Take the average value of the thickness of the sample before and after the test as the thickness of the sample. 7 Test results
7.1 For the single plate method, the thermal conductivity ^[W/(m·K)]* is calculated as follows: Qd
or into three
In the formula: AZ
Measurement time interval, s!
The heat passing through the effective heat transfer area of ​​the sample in steady state, Jgd
The difference between the hot surface temperature t and the cold surface temperature t of the sample, that is, At=! -t, Kd—specimen thickness, m
Heat flux density through the effective heat transfer area of ​​the sample, W/m2—effective heat transfer area of ​​the sample (calculated based on the distance between the centers of the gaps between the main and protective heating plates), m\. A-
.2For the double plate method, the thermal conductivity coefficient^ is calculated according to the following formula; Qd.
A=2A.AZ·Atm
or:
2△tm
wherein: Q, 42, 9~same as (1)
dm—the average thickness of sample 1 and 2, d, and d2, that is, dm=(d,+d2), m>tm———the half-mean temperature difference between the two sides of sample 1 and 2, that is, 1 W/(in-K) -0.8958 kcal/(mh-c)(1)
GB3399—82
+[(t+++2)-(ti +t2)],K;
t1, t,——are the hot surface temperatures of sample 1 and 2, K: t,——are the cold surface temperatures of sample 1 and 2, K. Formula (2) is applicable only under the following conditions: 2[(t -ti)-(t2 t2))bzxZ.net
(t++te) -(t+++2)
7.3 The test results are expressed as the arithmetic mean of each group of samples, with three significant figures. When the difference between the test result of each sample and the half-yo value is greater than 5%, the test should be repeated.
8 Test report
The test report includes the following contents:
Sample name, number and manufacturer
Sample number, size and state adjustment, bi
Ambient temperature, humidity and instrument model
d, hot and cold plate temperature, average temperature, effective heat transfer area; thermal conductivity:
Test date and personnel.
Additional Notes:
This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China and was assigned to the Physical and Mechanical Test Methods Branch of the National Technical Committee for Plastic Standardization.
This standard was drafted by the First Branch of Chenguang Chemical Research Institute of the Ministry of Chemical Industry. The main drafters of this standard are Liu Minsheng and Wu Shuyang. From the date of implementation of this standard, the original standard HG2-158-65 of the Ministry of Chemical Industry will be invalid.
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.