This standard specifies the method for determining the mechanical stability of concentrated natural rubber latex. This standard applies to concentrated natural rubber latex produced from Hevea brasiliensis latex. This standard also applies to pre-vulcanized concentrated natural rubber latex. GB/T 8301-2001 Determination of mechanical stability of concentrated natural rubber latex GB/T8301-2001 Standard download decompression password: www.bzxz.net

GB/T 8301--2001
This standard is equivalent to ISO35:1995 "Concentrated natural latex, determination of mechanical stability".
The main differences between this standard and the previous version are:
Added the reference standard GB/T8300--2001 "Concentrated natural latex, wire woven mesh test sieve";
--Added two chapters "Definition" and "Sampling"; "-In the chapter "Operational procedures", the method for determining the end point is added; -The average mesh size of the wire cloth is changed to 180μm ± 7.6μm. This standard replaces GB/T8301-1987 from the date of implementation. This standard is proposed by the Ministry of Agriculture of the People's Republic of China. Determination of alkalinity" and GB/ T6003.1--1997《Golden Standard》 is under the jurisdiction of the Natural Rubber Subcommittee of the National Technical Committee for Standardization of Rubber and Rubber Products. The drafting units of this standard are: South China Tropical Agricultural Products Processing Design Institute, Food Quality Supervision, Inspection and Testing Center of the Ministry of Agriculture (Zhanjiang). The drafters of this standard are: Deng Yifeng, Huang Maofang, Chen Ying. This is the second edition of the standard. The first edition was first issued in July 1987. This standard is entrusted to the Natural Rubber Subcommittee of the National Technical Committee for Standardization of Rubber and Rubber Products for interpretation. 111
GB/T830 1-2001
ISO Foreword
ISO) (International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing international standards is normally carried out by ISO technical committees. Any member body interested in a subject for which a technical committee has been established has the right to participate in that committee. International organizations, both governmental and non-governmental, in contact with ISO may also participate in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all aspects of electrotechnical standardization. Draft international standards adopted by the technical committees are circulated to member bodies for voting. Publication as an international standard requires a vote by at least 75% of the member bodies voting.
International Standard ISO35 was prepared by Technical Committee ISO/TC45 on Rubber and Rubber Products. The fourth edition of this standard slightly revises the third edition (ISO35:1989), abolishes and replaces the third edition. 112
National Standard of the People's Republic of China
Concentrated natural latex
Determination of mechanical stability
Natural rubber latex concentrate-Determination of mechanical stabilityGB/T8301—2001
idtISO35:1995
Replaces GB/T8301—1987
Warning: Personnel using this standard should be familiar with the operating procedures of regular laboratories. This standard does not intend to involve all safety issues that may arise from the use of this standard. It is the user's responsibility to develop appropriate safety and health systems and ensure compliance with relevant national regulations. 1 Scope
This standard specifies the method for determining the mechanical stability of concentrated natural latex. This standard applies to concentrated natural latex produced from Brazilian rubber tree latex. This standard also applies to pre-vulcanized concentrated natural latex. 2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T8290--1987 Sampling of natural concentrated latex (neqISO123:1985) GB/T8298—2001 Determination of total solid content of concentrated natural latex GB/T8300—2001 Determination of alkalinity of concentrated natural latex (idtISO125:1990) GB/T6003.1—1997 Metal wire mesh test sieve (eqvISO3310-1:1990) 3 Definitions
This standard adopts the following definitions.
Natural rubber latex concentrate contains ammonia and (or other preservatives) and is a natural latex that has been concentrated in some way. 4 Principle
Dilute the concentrated latex sample to a total solid content of 55% (m/m) and stir at high speed. Record the time required to induce the first visible flocculation as a measure of mechanical stability. 5 Reagents
Ammonia solution (5.1 and 5.2) should be prepared using confirmed analytically pure ammonium hydroxide and must be stored in a sealed container. Where water is specified, carbonate-free distilled water or water of equivalent purity should be used. 5.1 Ammonia solution, containing 1.6% (m/m) ammonia (NH3), is used for concentrated latex with an alkalinity of at least 0.30% (relative to concentrated latex). 5.2 Ammonia solution, containing 0.6% (m/m) ammonia (NH), is used for concentrated latex with an alkalinity of less than 0.3% (relative to concentrated latex). 6 Apparatus
6.1 Mechanical stability tester: including the components of 6.1.1 to 6.1.3. Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on July 20, 2001, and implemented on December 1, 2001bzxz.net
GB/T8301-2001
6.1.1 Latex container: a flat-bottomed cylinder with a height of at least 90 mm, an inner diameter of 58 mm ± 1 mm, a wall thickness of about 2.5 mm, and a smooth inner surface. Polymethyl methacrylate or glass containers are suitable. 6.1.2 Stirring device: including a vertical stainless steel shaft with a tapered shaft and a length sufficient to reach the bottom of the latex container (6.1.1). The end of the shaft has a diameter of about 6.3 mm, and a horizontal smooth stainless steel disc is connected to it in an exactly coaxial position. The disc has a diameter of 20.83 mm ± 0.03 mm and a thickness of 1.57 mm ± 0.05 mm. During the whole test, the stirring speed of the stirring device shall be maintained at 14000r/min±200r/min. At this speed, the swing of the shaft shall not exceed 0.25mm. 6.1.3 Latex container (6.1.1) Bracket: The bracket shall ensure that the axis of the rotating shaft is concentric with the axis of the latex container, and the bottom of the stirring disc shall be 13mm±1mm away from the inner surface of the bottom of the latex container. 6.2 Heating method
One of the following two methods can be used:
--Water bath, which can maintain a temperature of 60℃~～80℃; a glass tube, bent into a shape that can be inserted into the latex, and circulating water with a temperature of 60℃～80C is passed through the tube. 6.3 Stainless steel wire fabric: It shall meet the requirements of GB/T6003.1, with an average mesh size of 180μm±7.6μm. 7 Sampling
Sampling shall be carried out according to the method specified in GB/T8290. Note: Storage period and storage temperature of the sample may have an adverse effect on the mechanical stability. 8 Operating procedure
Duplicate determinations shall be made within 24 hours of the first opening of the sample bottle. If the total solids content and alkalinity of the concentrated latex are unknown, they shall be determined in accordance with GB/T8298 and GB/T8300, respectively. Note: If the carbon dioxide concentration in the atmosphere near the mechanical stability tester (6.1) exceeds the normal concentration [about 0.03% (V/V)], the mechanical stability of the latex will decrease. This effect may be significant at a carbon dioxide concentration of only 0.05% (V/V). The high concentration of carbon dioxide in the atmosphere may be caused by the presence of facilities that produce carbon dioxide nearby, such as certain gas heaters or oil heaters. Dilute 100 g of latex in a glass beaker with an appropriate ammonia solution (5.1 or 5.2) to a total solid content of 55.0% (m/m) ± 0.2% (m/m), and then immediately heat the diluted latex to 36°C to 37°C (i.e. slightly higher than the test temperature) using one of the heating methods (6.2) while gently stirring. Immediately filter the heated diluted latex with a stainless steel wire cloth (6.3), and weigh 80.0 g ± 0.5 g of the filtered latex and place it in a container (6.1.1). Verify that the temperature of the latex should be 35°C ± 1°C, place the container in the specified position, and stir the latex, ensuring that the speed of the stirrer is maintained at 140001/min ± 200r/min throughout the test until the end point is exceeded. Before the end point is reached, it can be seen that the vortex depth around the stirring shaft becomes significantly shallower. The endpoint was determined by taking a drop of latex with a clean glass rod every 15 seconds and gently spreading it on a suitable surface, such as the palm of the hand, a microscope glass slide, a water surface, or a stainless steel fabric (6.3) The first appearance of floccules is the end point. To confirm that the end point has been reached, the latex can be stirred for another 15 seconds before sampling. If the number of floccules in the sample increases, it means that the end point is correct. 9 Results decay
The time (s) from the start of stirring to the end point is taken as the mechanical stability of the concentrated latex. The difference between the two test results should not be greater than 5% of their average value, otherwise, the test should be repeated. 10 Test report
The test report should include the following information:
a) This standard number;
b) All details required to identify the sample;
c) The mechanical stability of the latex, accurate to 15s;11
GB/T 8301—2001
d) The method used to check the endpoint (using the palm of the hand, microscope glass slide, water surface or stainless steel wire fabric); e) Any abnormal phenomenon noticed during the measurement; f) Any operation that is not included in this standard but is considered to be applicable; g) Test date.
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