This standard specifies the determination of sulfide sulfur in vulcanized rubber and unvulcanized rubber by iodine titration. This standard is applicable to chlorine-containing rubber, nitrogen-containing rubber and hydrocarbon-containing rubber (including natural rubber). GB/T 15252-1994 Determination of sulfide sulfur content in rubber by iodine titration GB/T15252-1994 Standard download decompression password: www.bzxz.net

Method".
National Standard of the People's Republic of China
Determination of sulfidesulfur content in rubber
Iodometric method
Rubber---Determination of sulfidesulfur content-lodometric methodGB/T15252-94
This standard is equivalent to the international standard ISO8054-1988 "Rubber or vulcanized rubber-Determination of sulfide sulfur content-iodometric subject content and scope of application
This standard specifies the determination of sulfide sulfur in vulcanized rubber and unvulcanized rubber by iodometric method. This standard is applicable to nitrogen-containing rubber, nitrogen-containing rubber and hydrocarbon-containing rubber (including natural rubber). 2 Reference standards
GB/T601 Preparation of standard solutions for chemical reagent titration analysis (volume analysis) GB/T3516 Determination of rubber solvent extracts 3 Principle
After the sample is extracted with acetone, the metal sulfide is decomposed with a mixture of hydrochloric acid and acetic acid. The generated hydrogen sulfide is absorbed by cadmium acetate buffer solution, and the generated cadmium sulfide is determined by iodine titration. 4 Reagents and materials
Analytical reagents and distilled water or water of equivalent purity should be used during the analysis. 4.1 Acetone (GB/T 686).
4.2 Cadmium acetate buffer solution: Dissolve 25g dihydrate acetic acid (HG/T3--997) and 15g anhydrous sodium acetate (GB/T694) in water, add 100mL glacial acetic acid (GB/T676), and dilute to 1000mL with distilled water.4.3 Hydrochloric acid-acetic acid mixture: Mix 1 volume of hydrochloric acid (GB/T622), 5 volumes of glacial acetic acid (GB/T676) and 1 volume of water. 4.4 Surfactant solution, p=20g/L: Dissolve 2g alkylphenol ethylene oxide condensate (OP emulsifier) ​​in 100mL water. 4.5 Iodine solution c (I2) = 0.025mol/L: Weigh 6.5g iodine (GB/T675) and 20g potassium iodide (GB/T1272) and dissolve in 100mL water, dilute to 1000mL, shake well, and store in a brown stoppered bottle. 4.6 Sodium thiosulfate standard titration solution, c(Na2S2O3) 0.05mol/L Prepare and calibrate according to GB/T601. 4.7 Starch solution, p=10g/L.
4.8 Glycerol.
4.9 Pure nitrogen.
4.10 Filter paper.
5 Instruments
All ground joints are sealed with glycerol during assembly. 5.1 Rapid extraction device: See GB/T3516. Approved by the State Administration of Technical Supervision on September 24, 1994, and implemented on August 1, 1995
5.2 Pipette: 2mL, 25mL.
5.3 Burette: 50mL.
5.4 Sulfide type sulfur determination device: See Figure. GB/T15252-94
1—gas washing bottle, filled with acetic acid cadmium buffer solution; 2—separating funnel; 3—connector; 4—condenser; 5—reduction adapter; 6—conical flask, containing sample; 7—receiver; 8—absorption bottle, filled with acetic acid cadmium buffer solution; 9—gas washing bottle, filled with acetic acid cadmium buffer solution 6 Analysis steps
Weigh 0.5-2.0g of the particle sample cut into about 1mm2, accurate to 0.0001g, wrap it with filter paper extracted with acetone, extract the sample with acetone according to the method specified in GB/T3516, and the extraction time shall be not less than 4h. Take out the sample and dry it in an oven at 70℃ for 15min. Transfer the dried sample to the conical flask (6), add 100 mL of cadmium acetate buffer solution and 2 mL of surfactant solution to the absorption bottle (8), and add the same solution to the gas washing bottle (1 and 9) to a depth of about 10 mm. Assemble the reaction device according to the diagram, connect nitrogen, and then adjust the nitrogen flow rate in the absorption bottle to about one bubble per second. Slowly add 50 mL of hydrochloric acid-acetic acid mixture from the separatory funnel (2) to the conical flask, slowly heat to boiling, and continue to boil slightly for 30~~40 minutes. After stopping heating, increase the nitrogen flow rate appropriately to remove all residual hydrogen sulfide. At this time, the solution in the gas washing bottle (9) should be colorless, otherwise, it must be re-measured with a smaller sample or a slower gas flow rate. Remove the receiver (7) and add 832
GB/T 15252 --- 94
25mL of iodine solution to the receiver with a pipette to allow the iodine to react with the precipitate adhering to the receiver. After the precipitate is completely dissolved, rinse and remove the receiver, cool the solution to about 15°C, and titrate the excess iodine with a sodium thiosulfate standard titration solution. When the end point is approaching, add 3mL of starch indicator and continue to titrate until the blue color of the solution disappears. At the same time, perform a blank test.
7 Expression of analytical results
The sulfide sulfur content is calculated by the following formula, expressed in mass percentage: 0.016(Vo - Vc × 100 =
1.6(V.- V,)c
Sulfide sulfur (%, m/m) =
Where: V. —The volume of sodium thiosulfate standard titration solution consumed in titrating the blank solution, mL; V, —The volume of sodium thiosulfate standard titration solution consumed in titrating the test solution, mL; —The actual concentration of sodium thiosulfate standard titration solution, mol/L; m-
The mass of the sample,. Www.bzxZ.net
The mass of sulfur equivalent to 1.00mL sodium thiosulfate standard titration solution c(NazS,O,)=1.000mol/LJ, expressed in grams.
The analysis result is rounded to two significant figures.
Additional remarks:
This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Beijing Rubber Industry Research and Design Institute of the Ministry of Chemical Industry. This standard was drafted by the Shanghai Rubber Products Research Institute. The main drafters of this standard are Shen Yihua and Wang Jinbao. 833
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