This standard specifies the method for determining the swelling degree of vulcanized latex. This standard applies to general-purpose vulcanized latex from Hevea brasiliensis, and does not apply to vulcanized latex made from dry rubber. GB/T 14797.3-1993 Determination of swelling degree of concentrated natural latex vulcanized latex GB/T14797.3-1993 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Concentrated natural rubber latex
Vulcanized latex
Determination of swelling capacity
Natural rubber latex concentrate-Prevulcanized rubber latex-
Determination of swelling capacity1 Subject content and scope of application
This standard specifies the method for determining the swelling capacity of vulcanized latex. GB/T 14797.3--93
This standard applies to general-purpose vulcanized latex from Hevea brasiliensis, but not to vulcanized latex made from dry rubber. 2 Reference standards
GB8290 Sampling of natural concentrated latex
3 Principle
The swelling capacity is calculated as a percentage of the difference in diameter before and after the film expands in toluene to the original diameter. The deeper the vulcanization degree of the film, the smaller the swelling capacity. The depth of the vulcanization degree can be inferred based on the swelling capacity. 4 Reagents
4.1 Toluene: chemically pure.
4.2 CMC (carboxymethyl cellulose salt): chemically pure. Prepare 0.15% aqueous solution for later use. 4.3 Zinc oxide: chemically pure. Prepare paste for use. Weigh 20g zinc oxide, put it in a mortar, add 26mL 0.15% CMC aqueous solution, grind evenly, and prepare it before use. bZxz.net
5 Main materials and equipment
5.1 Qualitative filter paper: specification 60cm×60cm, cut into 12cm×60cm paper strips for later use. 5.2 Belt punch: punch hole $25mm, sharpen when used. 5.3 Flat blood: $90 mm.
5.4 Standard coordinate paper: specification 10mm×10mm. 5.5 Drying box: electric heating blast, control temperature 40±1℃. 5.6 Scraper: Use 3mm thick organic glass plate to make a rectangular frame with an outer shape of 100mm×25mm×40mm in length×width×height, and glue it with fluoroform. After one opening of the square frame is milled flat, a notch with a depth of 0.125mm and a length of 80mm is milled out in the center of one long side; after the other opening of the square frame is milled flat, a notch with a depth of 0.3mm and a length of 90mm is milled out in the center of one long side (these two notches should be on one large side of the square frame respectively).
5.7 Preparation of special paper: Lay a 12cm×60cm paper strip flat on a glass plate, place a scraper on one end of the paper strip (12cm side), with the 0.3mm notch of the scraper at the back and bottom, pour zinc oxide paste into the frame, pay attention to evenly spread it and move it forward slowly, so that a 0.3mm thick layer of zinc oxide paste is left on the paper, put it in a drying oven at 80℃ for 30 minutes, dry it flat, and cut it into 12cm×8cm paper strips for use.
6 Sampling
Sampling is carried out according to the method specified in GB8290.
7 Test steps
7.1 Sample preparation Spread the special paper strip (12 cm×8 cm) flat on the glass plate, place the scraper at one end of the paper strip (12 cm side), and place the 0.125mm deep notch side at the back and bottom. Pour the sample latex into the scraper and distribute it evenly, then slowly move forward, leaving a 0.125mm thick layer of latex on the paper. Place the sample paper in an electric drying oven, blow dry at 40℃ for 5 minutes, take it out and cool it at room temperature for a while. Spread the sample paper flat on the wooden board, with the glue side facing up, and punch out a circular sample with a belt punch. Pay attention to sharpening the blade. The circular sample cannot be adhered to the sample paper, torn, cut or re-punched. It must be successful in one go, otherwise it must be repeated. 7.2 Sample swelling Place the round sample in a flat weighing dish containing 30 mL of toluene, cover it and wait for a while. You can see that the film is separated from the paper. Take out the paper and discard it. Flatten the film and cover it again. Place the scale III on the coordinate paper. After 5 minutes of equilibrium swelling, you can read the diameter of the swollen sample from the coordinate paper through the glass. The number of millimeters is accurate to 1 mm, and the last digit after the integer is retained. 8 Result calculation
Degree of swelling (%) = Diameter of the sample before swelling × 100 Diameter of the sample before swelling
Each sample is measured twice, and the relative error is allowed to be within 1.2%, and then the average value is taken. The result calculation is accurate to 1%. Additional remarks:
This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard is under the jurisdiction of the Natural Rubber Standardization Subcommittee of the National Technical Committee for Rubber and Rubber Products Standardization. This standard is drafted by the South China Tropical Crop Product Processing and Design Institute. The main drafters of this standard are Zhu Musheng and Zhou Hongqing. 147
Xiarunzaoluo District
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