ISO 13773:1997

Overview

ISO 13773:1997 specifies a laboratory method for the determination of alkalinity in polychloroprene (chloroprene) latex produced by polymerization in an alkaline emulsion. The standard describes an electrometric (potentiometric) titration procedure that quantifies total alkalinity as millimoles of HCl per 100 g of latex and separates it into two practical components: alkaline reserve (free alkali) and delta titre (saponified anionic surfactants). This method is not suitable for polychloroprene latex prepared in non‑ionic emulsions, natural rubber latex concentrates, or necessarily for other synthetic latices.

Key topics and technical requirements

• Principle: Titrate a measured latex sample with standardized HCl to the second inflection point of the titration curve (approx. pH 4–5) while recording volumes at the first (approx. pH 10–11) and second inflection points.
• Measured results:
  • Alkaline reserve (AR) - acid volume to first inflection (free alkali).
  • Delta titre (AT) - additional acid volume from first to second inflection (saponified surfactants).
  • Total alkalinity (A) - AR + AT, expressed in mmol HCl/100 g latex.
• Reagents & purity:
  • Non‑ionic stabilizer solution (alkyl phenol polyethylene oxide type) to prevent coagulation.
  • Standard HCl solution c = 0.1 mol/dm3.
  • Use distilled or analytical grade water (ISO 3696 Grade 3).
• Apparatus:
  • Automatic potentiometric titrator (or manual burette with care).
  • Combined pH electrode suitable to pH 14.
  • Non‑metallic stirrer and grounded motor.
• Conditions & sampling:
  • Temperature control at 23 °C ±1 °C.
  • Sampling per ISO 123; note that alkaline latex rapidly absorbs CO2 if unsealed.
• Precision:
  • Repeatability: within ±0.02 mmol (reproducibility not established).
• Reporting:
  • Include reference to ISO 13773, sample ID, alkalinity (to 0.1 mmol), AR and AT (0.1 mmol/100 g), recorded pH at endpoints, stabilizer amount, unusual observations, and test date/place.

Applications & users

ISO 13773 is used for quality control, incoming raw‑material inspection, formulation development, and production monitoring in industries working with chloroprene rubber latex. Typical users:

• Latex and synthetic rubber manufacturers
• QC and R&D laboratories in the rubber industry
• Raw‑material suppliers and purchasers
• Regulatory and testing laboratories concerned with latex stability and performance

Related standards

• ISO 123 - Rubber latex sampling
• ISO 976 - Determination of pH for polymer dispersions and rubbers
• ISO 3696 - Water for analytical laboratory use

Keywords: ISO 13773, polychloroprene latex alkalinity, chloroprene rubber latex, potentiometric titration, alkaline reserve, delta titre, latex quality control.