This standard specifies the method for determining the dimensional stability of rigid foam plastics under specific temperature and relative humidity conditions. GB 8811-1988 Test method for dimensional stability of rigid foam plastics GB8811-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Rigid cellular plastics
Test method for dimensional stability
Test method for dimensional stability ofrigid cellular plastics
UDC 678: 5/7. 074
：620.179
GB 8811--88
ISO 2796—1980
This standard is equivalent to the international standard ISO2796-1980 "Test method for dimensional stability of rigid cellular plastics". 1 Subject content and scope of application
This standard specifies the method for determining the dimensional stability of rigid cellular plastics under specific temperature and relative humidity conditions. The dimensional stability of rigid cellular plastics refers to the irreversible dimensional changes in the three-dimensional directions perpendicular to each other after the sample is placed under specific conditions for a certain period of time.
2 Reference standards
GB2918 Standard environment for conditioning and testing of plastic specimens GB6342 Determination of linear dimensions of foam plastics and rubber 3 Principle
Put the specimen under the specified test conditions for a certain period of time, and after conditioning it under the standard environment, measure the changes in its linear dimensions.
4 Instruments
4.1 Constant temperature or constant temperature and humidity test chamber
Any constant temperature or constant temperature and humidity test chamber that can meet the requirements. 4.2 Measuring instruments
Measuring instruments that can measure the linear dimensions of the specimen according to the requirements of GB6342. 5 Specimens and their preparation
5.1 Preparation of specimens
Cut the specimen from the sample by sawing or other mechanical processing methods, and ensure that the surface of the specimen is flat and free of cracks. If there are no special provisions, the surface of the foam plastic should be removed.
5.2 Sample size
Length 100±1mm, width 100±1mm, thickness 25±0.5mm. 5.3 Number of samples
For each selected test condition, at least three samples of each sample shall be tested. 5.4 Conditioning
The sample shall be conditioned at a temperature of 23±2℃ and a relative humidity of 45% to 55% as specified in GB2918. Approved by the Ministry of Light Industry of the People's Republic of China on February 13, 1988 and implemented on July 1, 1988
6 Test steps
GB 8811—88
6.1 According to the method specified in GB6342, measure the length (L1, L2L3) and width (W1, W2, W.) at three different positions of each sample and the thickness (T,, T2, T,, T, T) at five different points of each sample. As shown in the figure. 10
Position for measuring the size of the specimen
6.2 Select the test conditions from the following conditions or conduct the test in accordance with relevant regulations. 55±3℃
—25±3℃
10±3℃
0±3℃
23±2℃
40±2℃
When the relative humidity is 90% to 100%, use the following conditions. 40±2℃
70±2℃
70±2℃
85±2℃
100±3℃bzxz.net
110±3℃
125±3℃
150±3℃
6.3 Adjust the temperature and humidity in the test chamber to the selected test conditions, place the specimens horizontally on the metal mesh or perforated plate in the chamber, with a minimum spacing of 25mm between the specimens, and blow air to maintain air circulation. The specimens cannot be directly radiated by the heating element. 6.4 After 20±1h, remove the specimens.
6.5 Place under the conditions specified in 5.4 for 1h. 6.6 Measure the specimen dimensions as specified in 6.1 and visually inspect the specimens. 6.7 Place the specimens under the selected test conditions again. 6.8 After a total time of 48±2h, repeat the operations in 6.5 and 6.6. If necessary, the total time can be extended to 7 days and 28 days, and then the operations of 6.5 and 6.6 can be repeated.
Result expression
Calculate the dimensional change rate according to the following formula:
Er(%) =
0×100
（1）
Wherein: EL, Ew, ET
GB881188
Ew(%) r
respectively are the dimensional change rates of the length, width and thickness of the specimen, %; respectively are the average length, width and thickness of the specimen before the test, mm; L..Wo.T. -
L, W..T.
8Test report
respectively are the average length, width and thickness of the specimen after the test, mm. The test report should include the following contents:
Type and name of foam plastic;
Detailed description of the relevant samples;
Standard environment for sample conditioning and testing; Test conditions used;
Dimensional change rate of length, width and thickness of each sample after each test; Average value of absolute values ​​of dimensional change rate of length, width and thickness of three samples after each test; Results of visual inspection of the samples after each test; Any steps not specified in this standard.
Additional notes:
This standard was proposed by the Ministry of Light Industry of the People's Republic of China. This standard is under the jurisdiction of the Plastics Processing and Applied Science Research Institute of the Ministry of Light Industry. This standard was drafted by the Plastics Processing and Applied Science Research Institute of the Ministry of Light Industry. (2)
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