Acrylic-based polymer waterproofing material - Methods of the test, Part 4: Determination of pH value
1992 Edition

The pH meter should be calibrated using standard buffer solutions with pH values of 4 and 7, following the manufacturer’s instructions. Prior to calibration, clean the glass electrode with distilled water and dry it gently. The electrode must be conditioned by multiple uses with the test material before final readings. Ensure the meter reaches equilibrium, and verify readings by taking 2 to 3 measurements that agree within ±0.05 pH units. After calibration, rinse electrodes and store them immersed in distilled water when not in use.

For viscous samples, take 25 ml of the polymer sample and dilute it with an equal volume (25 ml) of distilled water in a 100 ml alkali-resistant glass beaker equipped with a cover and stirring rod. Immerse both the glass indicator and reference electrodes into the mixture. Gently stir the sample between measurements to maintain uniformity. Record 2 to 3 pH readings, ensuring the pH meter stabilizes before each reading and that values agree within ±0.05 pH units. Use distilled water for cleaning electrodes between measurements.

The standard mandates the use of a glass electrode as the measuring (indicator) electrode, responsive to hydrogen ion activity, paired with an appropriate reference electrode featuring a liquid junction. The pH meter must comply with IS 2711:1979, providing direct readings and high input impedance. This combination forms an electrochemical cell that accurately measures the potential difference corresponding to the pH of the acrylic polymer sample.

While IS 13435 Part 4 does not explicitly specify temperature control, good practice involves conducting calibrations and measurements at the same temperature, ideally 27 ± 5 °C. Calibration buffers should be at the sample’s temperature to minimize errors. Allow the pH meter and electrodes to reach thermal equilibrium with the sample before measuring. Utilize temperature compensation features if available, or apply manual corrections based on temperature readings. Avoid sudden temperature changes to electrodes, ensuring stable conditions throughout testing.

Multiple pH measurements taken from the same sample should be consistent within ±0.05 pH units. Typically, 2 or 3 readings are taken with brief stirring intervals, ensuring the pH meter stabilizes before each reading. This consistency criterion guarantees reliable and reproducible pH values for acrylic polymer waterproofing materials.