ISO 2453:2020

Overview - ISO 2453:2020 (styrene‑butadiene rubber, SBR)

ISO 2453:2020 specifies a refractive‑index method for determining the bound styrene content of emulsion‑polymerized styrene‑butadiene rubber (SBR). The standard covers sample extraction, film preparation, refractometer measurement at 25 °C and the conversion of refractive index to percentage mass fraction of bound styrene. It applies to emulsion‑polymerized SBR and to extracted oil‑extended emulsion SBR that yield a film suitable for refractive‑index measurement. It is explicitly not applicable to solution‑polymerized SBR.

Key topics and requirements

• Principle: correlate the measured refractive index of a thin, solvent‑extracted SBR film with bound styrene content using a tabulated refractive‑index vs. styrene percentage or the standard formula.
• Sample preparation: cut and weigh representative pieces (following ISO 1795 sampling guidance), extract with an ethanol‑toluene azeotrope (ETA) - or acidified ETA for alum‑coagulated polymers - then dry to constant mass in a vacuum oven.
• Film formation: press extracted rubber between aluminium foil at ~100 °C to form a homogeneous sheet not exceeding 0.50 mm thickness.
• Measurement: use an Abbe‑type refractometer accurate to the fourth decimal place, maintained at 25 °C (±0.1 °C). Use α‑bromonaphthalene as contact liquid and take multiple readings (repeatability criteria specified).
• Apparatus & reagents: wide‑mouthed conical flask, reflux condenser (or Soxhlet), vacuum oven, hydraulic press or pressing plates, aluminium foil, ETA and α‑bromonaphthalene.
• Quality & precision: the standard describes required repeatability/acceptance criteria for readings and includes precision data in an informative annex.

Applications and users

ISO 2453:2020 is intended for:

• Rubber manufacturers for process control (monitoring monomer charging and product uniformity).
• Quality control laboratories performing routine bound styrene determination on emulsion‑polymerized SBR.
• Contract testing and R&D labs characterizing SBR feedstock and verifying formulations (including oil‑extended types, when film formation is possible). Practical uses include incoming raw material inspection, batch consistency checks, troubleshooting polymerization, and correlating composition with physical properties.

Related standards

• ISO 1795 - referenced for sampling and preparative procedures for raw rubber.
• ISO 2453 includes an informative Annex A with evaluated precision data.

Keywords: ISO 2453:2020, styrene‑butadiene rubber, SBR, bound styrene content, refractive index method, ethanol‑toluene azeotrope, refractometer, emulsion‑polymerized SBR, rubber quality control.