BS-ISO-7781-2001.pdf

BRITISH STANDARD BS ISO 7781:2001 Styrene-butadiene rubber, raw Determination of soap and organic-acid content ICS 83.060 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:42:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 7781:2001 This British Standard, having been prepared under the direction of the Materials and Chemicals Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 7 February 2002 © BSI 7 February 2002 ISBN 0 580 38976 6 National foreword This British Standard reproduces verbatim ISO 7781:2001 and implements it as the UK national standard. It supersedes BS 7164-9:1997 which is withdrawn.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, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to iv, pages 1 to 6, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:42:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Reference number ISO 7781:2001(E) INTERNATIONAL STANDARD ISO 7781 Third edition 2001-12-01 Styrene-butadiene rubber, raw Determination of soap and organic-acid content Caoutchouc butadiène-styrène brut Détermination de la teneur en savons et acides organiques Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:42:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:42:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 7781:2001(E) iii Contents Page Foreword.iv 1 Scope1 2 Normative references1 3 Principle1 4 Reagents.2 5 Apparatus.2 6 Sampling and sample preparation.3 7 Procedure.3 8 Expression of results4 9 Test report5 Annex A (informative) Test for rosin.6 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:42:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 7781:2001(E) 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 3. 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 International Standard 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 analyses. This third edition cancels and replaces the second edition (ISO 7781:1996), which has been technically revised. Annex A of this International Standard is for information only. Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:42:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI INTERNATIONAL STANDARD ISO 7781:2001(E) 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. 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 suitable for non-oil-extended styrene-butadiene rubbers. Method B is applicable to oil-extended styrene-butadiene rubbers. 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 normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 385-1:1984, Laboratory glassware Burettes Part 1: General requirements ISO 648:1977, Laboratory glassware One-mark pipettes ISO 1042:1998, Laboratory glassware One-mark volumetric flasks ISO 1795:2000, Rubber, raw natural and raw synthetic Sampling and further preparative procedures ISO 4799:1978, Laboratory glassware Condensers 3 Principle A weighed test portion of the rubber, in the form of thin strips, is extracted by ethanol-toluene azeotrope, or, for alum-coagulated rubber, 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. Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:42:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 7781:2001(E) 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 7 volumes of absolute ethanol with 3 volumes of toluene. Alternatively, mix 7 volumes of commercial-grade ethanol with 3 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. 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. 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. 5 Apparatus 5.1 Balance, accurate to 1 mg. 5.2 Hotplate. 5.3 Wide-mouthed conical flask, capacity 400 cm3 to 500 cm3. 5.4 Volumetric flask, capacity 250 cm3, complying with the requirements of ISO 1042. Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:42:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 7781:2001(E) 3 5.5 Reflux condenser, complying with the requirements of ISO 4799. 5.6 Conical flask, capacity 250 cm3. NOTE Alternatively, a Soxhlet extractor may be used instead of a reflux condenser and a conical flask. 5.7 Burette, capacity 25 cm3, complying with the requirements of ISO 385-1. 5.8 Pipette, 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 or 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 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. NOTE 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 ETA (4.1) or ethanol-toluene-water mixture (4.2) under reflux for a minimum of 4 h. 7.2 Method A (for non-oil-extended SBR) 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). 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). Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 07:42:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 7781:2001(E) 4 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 (for oil-extended SBR) 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 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. Record the volume of sodium hydroxide solution used at the equivalence point (V3). Carry out a blank titration on 100 cm3 of extraction solvent using the same method (V4). 8 Expression of results 8.1 Calculate the soap content using the equation 121s s 0,25()VVcK w m ¥-¥¥ = where ws is the soap content, as a percentage by mass; V1 is the volume, in cubic centimetres, of hydrochloric acid solution used to titrate the rubber extract; V2 is the volume, in cubic centimetres, of hydrochloric acid solution used to titrate the blank; c1 is the actual concentration, in mol/dm3, of the hydrochloric acid solution (4.5); m is the mass, in grams, of the test portion; Ks is the appropriate factor selected from the following: 306 when the soap i