This standard specifies the method for determining the dry rubber content of concentrated natural rubber latex. This standard applies to concentrated natural rubber latex produced from Hevea brasiliensis latex. GB/T 8299-2001 Determination of dry rubber content of concentrated natural rubber latex GB/T8299-2001 Standard download decompression password: www.bzxz.net

GB/T 8299--2001
This standard is equivalent to the international standard ISO126:1995 "Concentrated natural latex. The main differences between this standard and the previous version are:
-Add three chapters on definition, reagents and instruments; determination of dry rubber content".
The specific operation method for concentrated latex preserved with potassium hydroxide is added to the operation procedure chapter. This standard replaces GB/T8299-1987 from the date of implementation. 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 Sub-Technical Committee 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 main drafters of this standard are: Huang Maofang, Chen Ying, Xu Kui, Chen Xiaoguang, Wang Guilan. This standard is the second edition. The first edition was first issued in July 1987. This standard is entrusted to the Natural Rubber Sub-Technical Committee of the National Technical Committee for Standardization of Rubber and Rubber Products for interpretation. 102
GB/T8299
—2001
ISOForeword
ISO (International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of developing international standards is usually carried out by ISO's technical committees. Any member body interested in the subject of an established technical committee has the right to participate in the committee. All governmental and non-governmental international organizations in contact with ISO may also participate in this work. ISO works 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 at least 75% of the voting member bodies to vote in favor.
International Standard ISO126 was prepared by Technical Committee SC3, Technical Committee on Rubber and Rubber Products, for the Rubber Industry (including latex).
This fourth edition of the standard slightly revises the third edition (ISO126:1989), abolishes and replaces the third edition. 103
National Standard of the People's Republic of China
Determination of dry rubber content in concentrated natural rubber latex
Natural rubber iatex concentrate-Determination of dry rubber contentGB/T 8299--2001
idt. ISO 126: 1995
Replaces GB/T8299-1987
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 responsibility of the user to establish appropriate safety and health systems and ensure compliance with relevant national regulations. 1 Scope
This standard specifies the method for determining the dry rubber content of concentrated natural rubber latex. This standard is applicable to concentrated natural rubber latex produced from Brazilian rubber tree 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 are subject to revision. Parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T8290-1987 Sampling of natural latex concentrate (negISO123:1985) GB/T8298-2001 Determination of total solid content of concentrated natural latex 3 Definitions
This standard adopts the following definitions.
Concentrated natural latex natural rubber latex concentrate contains ammonia and (or) other preservatives and has undergone a certain concentration process. 4 Principle
The concentrated latex sample is diluted to a total solid content of 20% and acidified with acetic acid. The coagulated rubber is then pressed into thin sheets and dried at 70°C.
5 Reagents
In the analysis, only determined analytically pure reagents, distilled water or water of equivalent purity are used. 5.1 Acetic acid: 20g/L aqueous solution (for concentrated latex preserved with ammonia). 5.2 Acetic acid: 50g/L aqueous solution (for concentrated latex preserved with potassium hydroxide). Add 50g of glacial acetic acid to 500mL of propylene glycol and dilute to 1L with water. 6 Apparatus
Ordinary laboratory instruments and glass blood or porcelain blood, about 100mm in diameter and 50mm in depth. Note: Lead blood is not suitable for concentrated latex containing potassium hydroxide. Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on 2001-07-20 104
2001~12~01 Implementation
7 Sampling
Sampling shall be carried out in accordance with the method specified in GB/T8290.
8 Operating procedures
GB/T 8299-2001
8.1 If the total solid content of concentrated latex is unknown, it shall be determined in accordance with GB/T8298. 8.2 Carry out two parallel determinations. bZxz.net
8.3 Weigh 10 g ± 1 g of concentrated latex from a weighing bottle into the blood (6.1) using the difference method, accurate to 1 mg. Pour enough water along the inner wall of the blood to reduce the total solid content of the concentrated latex to 20% ± 1% (m/m). Carefully rotate the blood on a smooth surface to dilute the latex evenly. Depending on the actual situation, proceed with 8.4 or 8.5. 8.4 For concentrated latex preserved with ammonia, add 75 mL ± 3 mL of 20 g/L acetic acid solution (5.1) into the latex along the inner wall of the blood within 5 min, while slowly rotating the blood.
Gently press the coagulated film under the liquid surface. Cover the blood with a watch glass and heat it on a steam bath for 15 min to 30 min. If the whey is an emulsion, add 5 mL of 95% (V/V) ethanol. Then proceed with 8.6. 8.5 Add 25ml ± 5ml of 50g/L acetic acid solution (5.2) to the concentrated latex preserved with potassium hydroxide, stir with a thin glass rod, and wash the latex adhering to the glass rod into III with water. Gently press the coagulated film under the liquid surface. Cover the blood with a piece of surface blood and heat it on a steam bath for 15min to 30min. 8.6 When the whey is clear, wipe it with a large clot to collect small rubber coagulation particles. Soak the coagulated rubber in water, changing the water several times during the period, until the water is no longer acidic when tested with litmus paper. Squeeze the coagulated rubber to expel water and obtain a uniform film with a thickness of not more than 2mm. A suitable method is to carefully place the coagulated rubber on a glass plate and use a glass cylinder with a diameter of about 45mm or a small photographic film roll to roll it first along the sides and then press it towards the center.
Rinse the film thoroughly in running water for at least 5 min for concentrated latex stored in nitrogen and at least 2 h for concentrated latex stored in potassium hydroxide. Allow the rinsed film to drip for several minutes before drying in an oven. 8.7 Dry the film at 70°C ± 2°C until no white spots are visible. If the film is dried on a large surface, turn the film over two or three times during the first few hours of drying. Cool in the desiccator and weigh. Repeat the drying, cooling, and weighing operations until the weight loss after heating for 30 min is less than 1 mg.
Note: If the film is too sticky and severe oxidation is suspected at 70°C, a lower drying temperature, such as 55°C, should be used. 9.1 Calculate the concentrated latex dry content (DRC) according to formula (1) and express it as mass fraction: m×100
DRC(%)=\
wherein m - mass of the sample, g;
- mass of the dry film, g.
The result should be retained to two decimal places.
9.2 The results of two parallel determinations should not exceed 0.1% (m/m) of the mean. Otherwise, the determination should be repeated. 10 Test report
The test report shall include the following:
a) This standard number;
b) all details required to identify the sample;
c) the dry rubber content (DRC) of the concentrated latex;·(1)
GB/T 8299
d) if it is not 70°C ± 2°C, the drying temperature shall be recorded; e) any abnormal phenomenon noticed during the measurement; f) any operation not included in this standard but considered to be applicable; g) the test date.
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