ISO INTERNATIONAL STANDARD 8975 First edition 1989-10-01 Plastics - Phenolic resins - Determination of pH Plastiques -- Resines phenoliques - Determination du pH Reference number ISO 8975:1989(E) Copyright Intermational Organization for Standardization No reproduction or networking permitted without license from IHS Not for Resale ISO8975:1989(E) Foreword iso (the International Organization for Standardization) is a worldwide federation of national standards bodies (lsO member bodies).The work of preparing International Standards is normaily 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, govern- mental 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. Draft International Standards adopted by the technical committees are circulated to the member bodies for approvai before their acceptance accordance with iso procedures requiring at least 75 % approvat by the member bodies voting. Internationa! Standard isO 8975 was prepared by Technical Committee SO/TC61,Plastics. Annex A of this International Standard is for information only. ISO 1989 All rights reserved. No part of this publicatlon may be reproduced or utilized in any form permissioninwritingfromthepublisher. International Organizatlon for Standardization CasePostale56·CH-1211Geneve20·Switzerland Printed InSwitzerland ii No reproductic on or networking permitted without license from IHS Not for Resale INTERNATIONAL STANDARD ISO 8975:1989(E) Plastics - Phenolic resins -- Determination of pH Scope 3.2 Hydrogen phosphate buffer solution, containing 1 approximateiy 0,025 mol of potassium dihydrogen This International Standard specifies a method for phosphate (KH,PO) per litre and approximately the determination of the pH of liquid phenolic resins 0,025 mol of sodium hydrogen phosphate (NazHPO)) at the manufacturing stage or on the market. per litre, pH = 6,88 at 23 °C. Dissolve 3,39 g of potassium dihydrogen phosphate NOTE1 A variant of this method,applicable to solid (KH,PO4) and 3,53 g of sodium hydrogen phosphate phenolic resins, is described in annex A. With liquid resins having a viscosity greater than 2 Pa's, it may be neces- (Na,HPO4), previously dried by heating at 110°C to sary to use this variant, which calls for a magnetic stirrer. 130'°c for 2 h, in water and make up to 1000 ml. This solution may be kept longer by adding a crystal of thymol. Principle 3.3 Sodium tetraborate (Borax), standard solution, The potential difference between a glass electrode and a reference electrodeimmersedinthesame Dissolve 3,80 g ofsodium tetraborate deca- solution is used to determine the pH. hydrate (Na,BgO7.10H,O) in water and dilute to 1000 ml. 4 Apparatus 3 Reagents During the analysis, use only reagents of recognized 4.1 pH-meter, accurate to 0,1 pH-units. analytical grade and only distilled water or water of equivalent purity. 4.2 Electrodes Standard solutions, with acid pH (~ 4), neutral pH 4.2.1 Measuring electrode: glass electrode. (~ 7) or alkaline pH (~ 9), or buffer soiutions. 4.2.2 Reference electrode: calomel electrode. The following standard or buffer solutions are speci- fied: 4.2.3 Maintenance of the electrodes 3.1 Potassium hydrogen phthalate, standard sol- For all types of electrode, follow the manufacturer's ution, c(KCOOC,H,COOH) = 0,05 mol/l, pH = 4.00 instructions specifying the maintenance procedures at23°C. necessary to keep the electrodes in the correct condition. Dissolve 10,21 g of potassium hydrogen phthalate. In particular, clean the glass electrode at regular 2 h, in water and make up to 1000 mt. intervals as directed by the manufacturer. This solution shall be stored in a gliass vessel and NOTE 2 When not in use over a long period, gl