BS ISO 8332:2018 pdf download – Rubber compounding ingredients — Sulfur — Methods of test
This document specifies methods of test for determining the main physical and chemical properties of sulfur used for compounding dry rubber.
Several of these properties can be determined by more than one test method and the user can choose the most appropriate method following the description of the test method principles provided under the corresponding clauses.
NOTE Typical levels for the relevant properties of sulfur for use as a rubber compounding ingredient are contained in Annex A, for information only.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 565, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of openings
ISO 3704, Sulphur for industrial use — Determination of acidity — Titrimetric method
ISO 3705, Sulphur for industrial use — Determination of arsenic content — Silver diethyldithiocarbamate photometric method
ISO 4793, Laboratory sintered (fritted) filters — Porosity grading, classification and designation
ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling
3 Terms and definitions
No terms and definitions are listed in this document.
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4 Physical and chemical properties
After sampling with a stainless-steel sampling tool in accordance with ISO 15528, the physical and chemical properties of sulfur used as a rubber compounding ingredient shall be determined by the following test methods.
5 Determination of total sulfur content
5.1 Principle
The sulfur in a test portion is first converted to thiosulfate, to which an excess volume of iodine solution is added, then determined by back titration with a sodium thiosulfate solution.
5.2 Reagents
During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity.
5.2.1 Sodium sulfite solution, 50 g/dm 3 . Dissolve 50 g of anhydrous sodium sulfite in 1 dm 3 of water.
5.2.2 Standard volumetric iodine solution, c(l 2 ) = 0,05 mol/dm 3 , freshly prepared and standardized.
5.2.3 Standard volumetric sodium thiosulfate solution, 0,1 mol/dm 3 solution, freshly prepared and standardized.
5.2.4 Formaldehyde solution, 37 % (by mass).
5.2.5 Glacial acetic acid.
5.2.6 Wetting-out solution, consisting of a 20 g/dm 3 solution of an alkylaryl sulfonate (e.g. sodium dodecylbenzene sulfonate) in water.
5.2.7 Soluble-starch solution, freshly prepared.
5.3 Procedure
5.3.1 Weigh, to the nearest 0,1 mg, 0,2 g of the sulfur sample (m 0 ) on a tared watch glass. Using a Pasteur pipette, add approximately 1 cm 3 of wetting-out solution (5.2.6). Transfer the mixture to a 200 cm 3 flask via a small glass funnel using a stream of the sodium sulfite solution (5.2.1) from a 50 cm 3 measuring cylinder. Add a few antibumping granules, fix a reflux condenser in position and place the whole on an electrically heated oil-bath. Adjust the oil-bath temperature to 130 °C. Stir the contents of the flask for 1 h under reflux, and complete the reaction. If undissolved sulfur remains visible in the flask, continue the heating process as long as necessary. Wash the walls of the condenser with water and collect the washings in the flask. Cool the contents of the flask to 25 °C. Transfer the contents of the flask to a 100 cm 3 volumetric flask. Make up to the mark with water. NOTE Reaction of 20 % oil-treated sulfur takes about 3 h to 4 h.
5.3.2 Place exactly 30 cm 3 of iodine solution (5.2.2) into a 200 cm 3 conical flask from a burette, and add 10 cm 3 of acetic acid (5.2.5) to it using a pipette.
5.3.3 Place 10 cm 3 of test solution from the 100 cm 3 volumetric flask in 5.3.1, using a pipette, into a 100 cm 3 beaker. Add 2 cm 3 of formaldehyde solution (5.2.4) and stir using a magnetic stirrer for 2 min. After a 5-min rest, add the solution to the conical flask in 5.3.2. Wash the walls of the beaker and add the washings to the conical flask. While swirling the conical flask, add 1 cm 3 of the starch solution (5.2.7) and titrate with the sodium thiosulfate solution (5.2.3) until the dark-blue colour vanishes. V 1 is the volume, in cubic centimetres, of the sodium thiosulfate solution used for this titration.
5.3.4 Carry out a blank determination omitting the test portion. V 0 is the volume, in cubic centimetres, of the sodium thiosulfate solution used for this titration.