This standard specifies the determination of free sulfur in vulcanized rubber by the sodium sulfite method. This standard is applicable to the determination of free sulfur in the following vulcanized rubbers: natural rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, synthetic polyisoprene rubber and rubber blends of the above rubbers. This method is not applicable to butyl rubber and unvulcanized rubber. GB/T 3514-1992 Determination of free sulfur content in vulcanized rubber - Sodium sulfite method GB/T3514-1992 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of free sulphur content in vulcanized rubber
Sodium sulphite method
Rubber, vulcanized-Determination of free sulphur content-Sodium sulphite methodThis standard adopts the international standard ISO7269--1987 "Rubber-Determination of free sulfur". 1 Subject content and scope of application
This standard specifies the determination of free sulfur in vulcanized rubber by the sodium sulfite method. GB/T 3514--92
Replaces GB3514-83
This standard is applicable to the determination of free sulfur in the following vulcanized rubbers: natural rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, synthetic polyisoprene rubber and rubbers blended with the above rubbers. This method is not applicable to butyl rubber and unvulcanized rubber. 2 Principle
Use sodium sulfite solution to extract free sulfur in vulcanized rubber to generate sodium thiosulfate, then use iodine standard titration solution to titrate the generated sodium thiosulfate, and calculate the free sulfur content by the volume of iodine standard titration solution consumed. 3 Reagents and materials
Analytical reagents and distilled water or water of equivalent purity should be used during the analysis. 3.1 Glacial acetic acid (GB 676).
3.2 Formaldehyde (GB685).
3.3 Sodium sulfite solution: 50g/L, weigh 50g of anhydrous sodium sulfite (HG3-1078) and dissolve it in appropriate amount of water, dilute to 1000mL. 3.4 Iodine standard titration solution: c (I2) = 0.05mol/L. 3.4.1 Preparation: Weigh 6.5g iodine (GB675) and 20g potassium iodide (GB1272) and dissolve them in 100mL water, dilute to 1000mL, shake well, and store in a brown stoppered bottle.
3.4.2 Calibration: Weigh about 0.07g of standard iodine trioxide that has been dried to constant weight in a sulfuric acid dryer, accurate to 0.0001g. Place in an iodine volumetric bottle, add 4.mL sodium hydroxide solution [c(NaOH)=1mol/L) to dissolve, add 50mL water, 2 drops of phenol indicator solution (10g/L), neutralize with sulfuric acid solution (c(H,SO.)=1mol/L), add 3g sodium bicarbonate and 3mL starch indicator solution, and titrate with the prepared iodine standard titration solution until the solution turns light blue. Perform a blank test at the same time. The concentration of the iodine standard titration solution is calculated according to formula (1): m
c = (V, - V,) × 0. 049 46
Wu Zhong: c-
actual concentration of the iodine standard titration solution, mol/L; approved by the State Administration of Technical Supervision on December 12, 1992. (1)
implemented on October 1, 1993
mmass of arsenic trioxide, g;
GB/T 3514--92
V,-volume of iodine standard titration solution consumed in calibration, mL; V2-volume of iodine standard titration solution consumed in blank test, mL; number I) = 1.000mol/L), the mass of arsenic trioxide expressed in grams. 0.04946-equivalent to 1.00mL iodine standard solution c3.5 starch solution: 10g/L.
3.6 Ceramic zeolite.
3.7 Activated carbon: granular, heated at 250-300℃ for 45min, cooled and set aside. 3.8 Filtered asbestos or acid-washed asbestos.
4 Instruments
4.1 Conical flask: 300mL, 500mL;
4.2 Iodine volume flask: 250mL;
4.3 Small funnel: about 50mm in diameter;
4.4 Suction flask: 500mL;www.bzxz.net
4.5 Buchner funnel: about 65mm in diameter;
4.6 Burette: 5mL or 10mL;
4.7 Heating bath: can control the appropriate heating temperature to keep the solution in a slightly boiling state. 5 Analysis steps
Weigh about 2g of the granular sample cut into pieces less than 1mm2, accurate to 0.001g, place it in a conical flask, add 100mL of sodium sulfite solution and 4-5 pieces of porcelain zeolite, cover it with a small funnel, place it in a hot bath, and heat it at a slight boiling state for 4h. Take out the conical flask, add 5g of activated carbon after cooling, shake it, and let it stand for 30min. Then filter it with a Buchner funnel (first put a qualitative filter paper on the Buchner funnel, then put a layer of asbestos, and then cover it with a filter paper. When using it, you only need to replace the upper filter paper frequently. The asbestos layer can be used many times and does not need to be replaced every time). Wash the conical flask with 25mL of hot water three times, and then wash the filter residue with 25ml of hot water. Combine the filtrate and washing liquid in the conical flask, add 10mL of formaldehyde, let it stand for 5min, then add 5mL of glacial acetic acid, shake it well, and cool it to below 15℃ in an ice bath or refrigerator. Take it out, add 5mL starch solution, and titrate with iodine standard titration solution until the solution turns blue and does not fade within 30s. This is the end point. At the same time, do a blank test. 6 Expression of analytical results
Free sulfur is expressed as the mass percentage of sulfur and calculated according to formula (2); (V - V.) c × 0. 032
Free sulfur (%) -
Where: V—volume of iodine standard titration solution consumed by the sample, mL; V. The volume of the iodine standard titration solution consumed in the blank, mL; c--the molar concentration of the iodine standard titration solution, mol/L; m--the mass of the sample, g;
0.032--the mass of sulfur equivalent to 1.00mL of iodine standard titration solution Tc (the result can be retained to two significant figures. 7 Parallel determination tolerance
Free sulfur content
0.1% ~~0.5%
Full tolerance
≤0.025%
I2)-1.000mol/LJ, expressed in grams. (2)
Additional remarks:
≤0.005%
GB/T3514-92
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China and 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 Beijing Rubber Industry Research and Design Institute of the Ministry of Chemical Industry, and the main drafters of this standard were Wu Peizhi and Dai Meiying.
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