GB/T 8810-1988 Test method for water absorption of rigid cellular plastics
Some standard content:
National Standard of the People's Republic of China
Test method for water absorption ofrigid cellular plastics
This standard is equivalent to the international standard ISO 2896-86 "Determination of water absorption of rigid cellular plastics". 1 Subject content
678. 5/7.074
GB 8810-88
ISO 2896-86
This standard specifies the test method for determining the water absorption of rigid cellular plastics and the correction method for swelling and cut surface pore volume. 2 Reference standards
GB2918 Standard environment for state adjustment and testing of plastic specimens GB6342 Determination of linear dimensions of cellular plastics and rubber 3 Principle overview
The water absorption of a specimen is calculated by measuring the change in buoyancy of the specimen immersed in distilled water for a certain period of time. 4 Soaking liquid
Distilled water stored for more than 48 hours.
5 Test apparatus and requirements
5.1 Balance accurate to 0.01g.
5.2 Cage
Made of stainless steel. It is large enough to accommodate the sample, with a weight at the bottom to offset the buoyancy of the sample, and a device on the top that can be hung on the balance. As shown in Figure 1.
5.3 The cylindrical container has a diameter of 250mm and a height of 250mm. 5.4 Low permeability plastic film such as polyethylene film. 5.5 Slicer capable of cutting to 0.1~~0.4mm thick. As shown in Figure 2 (see separate book). 5.6 Slide
Glue two glass slides into a loose-leaf shape, and place a plastic sheet with standard scale printed in the middle. As shown in Figure 3. 5.7 Projector
Universal 35mm slide projector suitable for 50mm×50mm standard samples or projection microscope with standard scale. Approved by the Ministry of Light Industry of the People's Republic of China on February 13, 1988 406
Implementation on July 1, 1988
GB8810-88
Figure 1 Cage with test sample
6 Test sample and its preparation
Cell counting slide
GB 8810-88
Figure 3 Slide device
6.1 The number of test samples shall not be less than three.
Glass slide with standard scale
Soft adhesive tape bonding
Blank coverbzxZ.net
6.2 The test sample size is 150mm in length, 150mm in width, and the volume is not less than 500cm. For products with natural or composite skin, the test sample thickness is the product thickness. For products with a thickness greater than 75mm and no skin, the test sample should be processed to 75mm, and the parallelism tolerance between the two sides shall not exceed 1%.
6.3 Sample preparation and state adjustment The sample is prepared by mechanical cutting. The surface of the sample should be flat and dust-free. Dry the sample in a desiccator at room temperature and weigh it every 12 hours until the difference between two consecutive weighings is no more than 1% of its average value. 7
Test conditions
Water temperature 23±2℃, soaking time 96h.
8 Test steps
8.1 According to the provisions of GB2918, adjust the test environment to 23±2℃ and the relative humidity to 45%~55%. 8.2 Weigh the mass of the sample ml, accurate to 0.01 g. 8.3 Measure the linear dimensions of the sample according to the provisions of GB6342. 8.4 In the test environment, pour distilled water into the cylindrical container. 8.5 Dip the mesh cage into the water, remove the bubbles, hang it on the balance, and weigh its apparent mass mz, accurate to 0.01g. 8.6 Place the sample in the mesh cage and re-immerse it in water, keeping the top of the sample about 50 mm above the water surface. Use a soft brush or stir to remove bubbles on the sample.
8.7 Cover the cylindrical container with a low-permeability plastic film. 8.8 After 96 ± 1 h or other specified immersion time, remove the plastic film and weigh the mass m3 of the mesh cage containing the sample immersed in water to an accuracy of 0.01 g.
GB8810—88
Test the swelling of the sample and make corrections for the swelling and the volume of the pores on the cut surface [see Appendix B (Supplement)]. 8.9
9Test results show
9.1 When there is no obvious non-uniform swelling phenomenon after the sample is immersed, the calculation formula is as follows: Wav = m. ±Vip- (m)+m + Vp) >× 100
Wherein: WAV -
Water absorption rate, %,
m1 ---Sample mass, g;
m2—Apparent mass of the mesh cage immersed in water, g, m3——Mass of the mesh cage immersed in water and containing the sample, g, V,——Volume of the sample after immersion, cm\
V. ——Initial volume of the sample, cm\;
V. Volume of pores on the cut surface, cm\
p——Density of water at 23℃, 0.9975g/mL. 9.2 When the sample has obvious non-uniform swelling after immersion, the calculation formula is as follows: Wav = m. +(Va- Vo)e- (m +m.)Vop
9.3 Test results
Take the arithmetic mean of the water absorption of all the tested samples. 10 Test report
The test report should include the following contents:
Type and name of foam plastic,
Detailed description of the relevant samples;
Method of preparing the sample;
Number of tested samples;
Immersion time;
The correction method used (A or B), the correction coefficient is expressed in volume percentage, S. X 100%
Si×100%
×100%
Each corrected water absorption result and average value, expressed in volume percentage; h.
Average cell diameter of each sample and average value of all tested samples, expressed in millimeters; i.
Observed anisotropic characteristics of the sample;
Observed phenomena related to the performance of the material. (1)
(2)
A1 Principle
GB 8810--88
Appendix A
Determination of average cell diameter
(Supplement)
Cut the sample with a slicer, and its thickness should be less than the diameter of a single cell. Insert the sample into a scaled slide, and then use a projector to project its image onto the screen. Within the specified length, determine the number of cells or cell wall sections, calculate the average chord length from this number, and then use a mathematical formula to convert the average chord length into the average cell diameter. A2 Samples
A2.1 Number of samples
For foam plastics with uniform and symmetrical cell sizes, the average cell diameter of a test piece is usually used to represent it; for foam plastics with obvious anisotropy, a test piece needs to be cut from each of the three main directions, and the cell size is measured and represented by its average value. A2.2 Sample size
Cut a 50mm×50mm, original thickness sample from the sample to be tested. A3 Test steps
A3.1 Cut a test piece from the sample at random, and its thickness should be less than the diameter of a single cell to ensure that the image is not hidden due to the overlap of the cell wall. The optimal slice thickness should be determined by the average cell size of the foaming material, and the smaller cell diameter is used as the slice thickness. A3.2 Insert the sheet into the slide, adjust the ruler coordinates so that its zero point is at the top of the measurement area, and reinstall the slide. A3.3 Insert the slide into the projector and adjust the focus so that its image is clearly imaged on the wall or screen. A3.4 Measure the average cell chord length t from the projected image. First, determine the number of cells (or cell walls) within the 30mm length of the ruler, and then divide the straight line length by the number of cells to obtain the average cell chord length t. If the test piece length is less than 30mm, determine the number of cells at the maximum length.
A3.5: When the cell structure is anisotropic, the average cell diameter is measured in three main directions and expressed as the average of the three results.
A4 Calculation
Calculate the average cell diameter by formula (A1):
Where: D—
average cell diameter, mm;
-average cell chord length, mm.
The result should be kept to two significant figures.
·（Al）
GB8810-88
Appendix B
Correction of swelling and cut surface pore volume
(Supplement)
This method is used for volume correction when there is no obvious non-uniform swelling of the sample. B1
Measure the linear dimensions of the sample within 4 hours after taking it out of the water. The correction coefficient S. for uniform swelling of the sample is: V,- Vo
Where: V. — Initial volume of the sample, cm\; V, Volume of the sample after immersion, cm\.
Where: l— Initial length of the sample,mm;
d-initial thickness of the sample, mm;
b-initial width of the sample, mm.
Wherein:
-length of the sample after immersion, mm;
thickness of the sample after immersion, mm;
bi-width of the sample after immersion, mm.
B2 Correction of pore volume of cut surface
h·di·bi
(B1)
(B2)
B2.1 According to the method described in Appendix A, slice the same sample as that for the water absorption test, measure the average pore diameter D of the sample, and calculate the pore volume V of the cut surface according to the following formula. .
B2.1.1 For samples with natural skin or composite skin, the calculation formula is: V. 0. 54 D(ld + bd)
Wherein: V. Volume of pores on the cut surface, cm~, D—average pore diameter, mm;
Initial length of the sample, mm,
Initial thickness of the sample, mm;
Initial width of the sample, mm.
B2.1.2 For samples with cut pores on each surface, the calculation formula is: V. =- 0.54 D(ld + bd + lb)500
·(B4 )
B2.2 If the average pore diameter of the sample is less than 0.50 mm and the sample volume is not greater than 500 cm411, the correction factor for the volume of pores on the cut surface can be ignored.
GB8810—88
B3When the sample has obvious non-uniform swelling, use this method to perform the combined correction of non-uniform swelling and cross-section pore volume. Use a cylindrical container similar to 5.3 with an overflow port, fill it with water until the water flows out of the overflow port. When the water surface is stable, place a container with a scale under the overflow port to collect the overflowed water. The volume of the container shall not be less than 600cm, and the measurement accuracy shall be ±0.5cm (calibrated by weighing method).
Take out the sample and mesh cage from the original test container, wait for the surface water to dry (about 2min), carefully immerse the sample and mesh cage into the container filled with water, measure its drainage volume V2, and repeat the above process with an empty mesh cage to measure the drainage volume V3. The combined correction coefficient S1 of non-uniform swelling and cross-section pore volume is: S, = V,- e - v.
Initial volume of the sample, cm;
Where.V. —
V, the drainage volume of the mesh cage with the sample added, cm\; V: — the drainage volume of the empty mesh cage, cm.
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 Plastic Processing and Applied Science Research Institute of the Ministry of Light Industry. This standard was drafted by the Wuhan Plastics Research Institute. The main drafter of this standard is Yang Xuewu.
·(B6)
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