This International Standard specifies a method for the determination of the pH of polymer dispersions and rubber latices (natural and synthetic) by means of a pH-meter equipped with a combined glass and silver reference electrode.
The method is also suitable for prevulcanized latex and compounds containing polymer dispersions or rubber latices, including adhesives.
NOTE 1 The accuracy of the method decreases at pH values above 11.
Users should note that this edition of ISO 976 not only represents a revision of the previous edition, but also supersedes ISO 1148:1980, Plastics —Aqueous dispersions of polymers and copolymers —Determi-nation of pH. This edition represents a harmonized version of the two standards.
One of the major changes in this new edition of ISO 976 is the use of a combined electrode rather than the separate electrodes used in the previous edition, the combined electrode being considered superior to the separate electrodes since the latter are prone to latex deposits blocking the electro-lyte junction, thus adversely affecting repeatability. Although older-type twin electrodes are capable of giving accurate results, they should be progressively replaced because of this problem of cleaning and repeatability.