BS-ISO-7781-2008.pdf
BRITISH STANDARD BS ISO 7781:2008 Styrene-butadiene rubber, raw Determination of soap and organic-acid content ICS 83.040.10 ? Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:07:31 MDTNo reproduction or networking permitted without license from IHS -,-,- BS ISO 7781:2008 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 May 2008 © BSI 2008 ISBN 978 0 580 58158 8 National foreword This British Standard is the UK implementation of ISO 7781:2008. It supersedes BS ISO 7781:2001 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee PRI/23, Test methods for rubber and non-black compounding ingredients. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. Amendments/corrigenda issued since publication DateComments Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:07:31 MDTNo reproduction or networking permitted without license from IHS -,-,- Reference number ISO 7781:2008(E) INTERNATIONAL STANDARD ISO 7781 Fourth edition 2008-04-01 Styrene-butadiene rubber, raw Determination of soap and organic-acid content Caoutchouc butadiène-styrène brut Détermination de la teneur en savons et acides organiques BS ISO 7781:2008 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:07:31 MDTNo reproduction or networking permitted without license from IHS -,-,- ii Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:07:31 MDTNo reproduction or networking permitted without license from IHS -,-,- iii Contents Page Foreword iv 1 Scope . 1 2 Normative references. 1 3 Principle. 1 4 Reagents 2 5 Apparatus 2 6 Sampling and sample preparation 3 7 Procedure 3 7.1 Preparation of the test solution. 3 7.2 Method A: titration method using indicator reagent. 3 7.3 Method B: titration method using autotitrator or pH-meter . 4 8 Expression of results . 4 9 Test report . 6 Annex A (informative) Test for rosin 7 BS ISO 7781:2008 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:07:31 MDTNo reproduction or networking permitted without license from IHS -,-,- iv Foreword ISO (the 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 through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 7781 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Testing and analysis. This fourth edition cancels and replaces the third edition (ISO 7781:2001), which has been technically revised. BS ISO 7781:2008 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:07:31 MDTNo reproduction or networking permitted without license from IHS -,-,- 1 Styrene-butadiene rubber, raw Determination of soap and organic-acid content WARNING Persons using this International Standard should be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions. WARNING Certain procedures specified in this International Standard may involve the use or generation of substances, or the generation of waste, that could constitute a local environmental hazard. Reference should be made to appropriate documentation on safe handling and disposal after use. 1 Scope This International Standard specifies methods for the determination of the soap and organic-acid content of raw styrene-butadiene rubber (SBR). Method A is the titration method using indicator reagent. Method B is the titration method using an autotitrator or pH-meter. The methods depend on the extraction of the organic acids and soaps from the rubber by means of a specified solvent. In practice, therefore, it is convenient to determine both organic-acid and soap contents on separate portions of the same solvent extract. Since the soaps and organic acids present in the rubber are not single chemical compounds, the method gives only an approximate value for the soap and organic-acid content. 2 Normative references The following referenced documents are indispensable for the application 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 385, Laboratory glassware Burettes ISO 648, Laboratory glassware Single volume pipettes ISO 1042, Laboratory glassware One-mark volumetric flasks ISO 1795, Rubber, raw natural and raw synthetic Sampling and further preparative procedures ISO 4799, Laboratory glassware Condensers 3 Principle A weighed test portion of the rubber, in the form of thin strips, is extracted using an ethanol-toluene azeotrope, or, for alum-coagulated rubber, using an ethanol-toluene-water mixture. After making up to a standard volume, an aliquot portion of the extract is withdrawn and titrated with standard acid for the determination of soap and with standard alkali for the determination of organic acid. BS ISO 7781:2008 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:07:31 MDTNo reproduction or networking permitted without license from IHS -,-,- 2 4 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. Use commercially available analytical-grade buffer solutions of known pH or, in the absence of commercial buffer solutions, prepare the solutions required (4.6, 4.7 and 4.8). 4.1 Ethanol-toluene azeotrope (ETA). Mix seven volumes of absolute ethanol with three volumes of toluene. Alternatively, mix seven volumes of commercial-grade ethanol with three volumes of toluene, and boil the mixture with anhydrous calcium oxide (quicklime) under reflux for 4 h. Cool to room temperature and decant through No. 42 filter paper. 4.2 Ethanol-toluene-water mixture. Mix 95 cm3 of ETA (4.1) and 5 cm3 of water. 4.3 Sodium hydroxide solution, c(NaOH) = 0,1 mol/dm3, accurately standardized. 4.4 Thymol blue indicator. Dissolve 0,06 g of thymol blue in 6,45 cm3 of 0,02 mol/dm3 sodium hydroxide solution and dilute to 50 cm3 with water. 4.5 Hydrochloric acid, c(HCl) = 0,05 mol/dm3, accurately standardized. 4.6 Buffer solution of nominal pH 7. Dissolve 3,40 g of potassium dihydrogen phosphate (KH2PO4) and 3,55 g of disodium hydrogen phosphate (Na2HPO4) in water and make up to 1 000 cm3 in a volumetric flask. The pH of this solution is 6,87 at 23 °C. Store the solution in a glass or polyethylene vessel that is resistant to chemicals. NOTE A pH 7 buffer solution already prepared is commercially available. 4.7 Buffer solution of nominal pH 4. Dissolve 10,21 g of potassium hydrogen phthalate (HOOCC6H4COOK) in water and make up to 1 000 cm3 in a volumetric flask. The pH of this solution is 4,00 at 23 °C. Store the solution in a glass or polyethylene vessel that is resistant to chemicals. NOTE A pH 4 buffer solution already prepared is commercially available. 4.8 Buffer solution of nominal pH 9. Dissolve 3,814 g of sodium tetraborate decahydrate (Na2B4O710H2O) in water and make up to 1 000 cm3 in a volumetric flask. The pH of this solution, when freshly prepared, is 9,20 at 23 °C. Store the solution in a glass or polyethylene vessel that is resistant to chemicals and fitted with a soda-lime carbon dioxide trap. Replace the solution after 1 month. NOTE A pH 9 buffer solution already prepared is commercially available. 5 Apparatus 5.1 Balance, accurate to 1 mg. 5.2 Hotplate. BS ISO 7781:2008 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:07:31 MDTNo reproduction or networking permitted without license from IHS -,-,- 3 5.3 Wide-mouthed conical flask, of capacity 400 cm3 to 500 cm3. 5.4 Volumetric flask, of capacity 250 cm3, complying with the requirements of ISO 1042. 5.5 Reflux condenser, complying with the requirements of ISO 4799. 5.6 Conical flask, of capacity 250 cm3. NOTE Alternatively, a Soxhlet extractor can be used instead of a reflux condenser and a conical flask. 5.7 Burette, of capacity 25 cm3, complying with the requirements of ISO 385. 5.8 Pipette, of capacity 100 cm3, complying with the requirements of ISO 648. 5.9 Automatic titrator or pH-meter, including a calomel electrode and glass electrode, accurate to within 10 mV or 0,1 pH units. 5.10 Magnetic stirrer, with a polytetrafluoroethylene-coated stirrer bar. 6 Sampling and sample preparation Sheet out 2 g to 6 g of rubber, selected and prepared in accordance with ISO 1795. Cut into pieces no larger than 2 mm × 2 mm or strips no longer than 10 mm and no wider than 5 mm. Weigh a test portion of approximately 2 g to the nearest 0,001 g. 7 Procedure 7.1 Preparation of the test solution Place a circular filter paper in the bottom of the wide-mouthed conical flask (5.3) and add 100 cm3 of ETA extraction solvent (4.1) for all rubbers except alum-coagulated rubbers. For alum-coagulated rubbers, use an ethanol-toluene-water mixture (4.2). Introduce the strips of rubber separately into the flask, swirling after each addition so that the strips are thoroughly wetted with solvent and sticking is minimized. Fit the reflux condenser (5.5) to the flask and boil the solvent very gently under reflux for 1 h. Transfer the extract to the volumetric flask (5.4), and treat the rubber with a second 100 cm3 portion of extraction solvent under reflux for 1 h. Add this extract also to the volumetric flask. Rinse the strips with three successive 10 cm3 portions of extraction solvent, add these washings to the volumetric flask and, after cooling to room temperature, adjust the final volume to 250 cm3 with appropriate extraction solvent. Alternatively, the weighed strips of sample may be wrapped in filter paper and placed in a Soxhlet extractor (see Note to 5.6) and extracted with an ETA (4.1) or ethanol-toluene-water mixture (4.2) under reflux for a minimum of 4 h. 7.2 Method A: titration method using indicator reagent 7.2.1 Procedure for determination of soap content After thorough mixing, pipette 100 cm3 of the diluted extract into the 250 cm3 conical flask (5.6), add six drops of thymol blue indicator (4.4) and titrate the solution with hydrochloric acid solution (4.5) to the first colour change (V1). BS ISO 7781:2008 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=Boeing Co/5910770001 Not for Resale, 08/14/2008 22:07:31 MDTNo reproduction or networking permitted without license from IHS -,-,- 4 Carry out a blank titration on 100 cm3 of extraction solvent taken from the same stock as was used for the test portion and using the same indicator as was used for titration of the test portion (V2). 7.2.2 Procedure for determination of organic-acid content Proceed exactly as in 7.2.1, but titrate the aliquot portion with sodium hydroxide solution (4.3), again using thymol blue indicator (4.4) (V3). Carry out a blank titration on 100 cm3 of extraction solvent using the same method (V4). 7.3 Method B: titration method using autotitrator or pH-meter 7.3.1 Procedure for determination of soap content Turn on the autotitrator or pH-meter (5.9), and allow the electronic circuit to stabilize. The temperature shown by the temperature compensator indicator shall be the same as the temperature of the test solution. Calibrate the autotitrator or pH-meter using nominally pH 7 buffer solution (4.6) and pH 4 buffer solution (4.7). Pipette 100 cm3 of the test solution into a 250 cm3 beaker containing a stirrer bar, then place the beaker on the magnetic stirrer (5.10). Insert a glass electrode and a calomel electrode into the test solution in the beaker. While stirring, titrate the test solution with hydrochloric acid solution (4.5) to pH 4,8, slowing the titration rate near the equivalence point. Record the volume of hydrochloric acid solution used at the equivalence point (V1). Carry out a blank titration on 100 cm3 of extraction solvent using the same method (V2). 7.3.2 Procedure for determination of organic-acid content Calibrate the autotitrator or pH-meter using nominally pH 7 buffer solution (4.6) and pH 9 buffer solution (4.8). Proceed exactly as in 7.3.1, but titrate the aliquot portion with sodium hydroxide solution (4.3) to pH 11,5, again slowing the titration rate near the equivalence point
