ISO 5794-3:2011

Overview

ISO 5794-3:2011 - "Rubber compounding ingredients - Silica, precipitated, hydrated - Part 3" defines standardized evaluation procedures for determining the physical performance of precipitated hydrated silica when compounded in a blend of solution styrene‑butadiene rubber (S‑SBR) and butadiene rubber (BR). The standard specifies a model test formulation, mixing and vulcanization procedures, and the test methods used to measure rheology, cure behaviour and mechanical properties. The formulation is intended as a model compound for silica‑based passenger car tyre treads and is used for comparative evaluation, quality control and R&D.

Key topics and technical requirements

• Standard test formulation: A detailed parts‑by‑mass recipe (S‑SBR, BR, precipitated silica, TESPT organosilane, ZnO, stearic acid, oil, antioxidants, accelerators, sulfur, etc.) to be used for silica evaluation.
• Mixing and processing: Three‑stage mixing procedure aligned with ISO 2393. Example Banbury (internal mixer) parameters and roll‑mill finishing steps are provided (temperatures, filling factors, speeds and stage durations).
• Uncured mix testing: Mooney viscosity at 100 °C (ISO 289‑1) to characterize processing viscosity.
• Vulcanization and cure evaluation: Use of oscillating disc curemeter (ISO 3417) or rotorless curemeter (ISO 6502) to measure key cure parameters (ML, MH, ts1, tc(50), tc(90) or Fmax equivalents) at 160 °C.
• Mechanical testing of cured rubber: Tensile stress‑strain (ISO 37), hardness (ISO 48) after vulcanization (standard cure at 160 °C for 15 min).
• Reporting and precision: Required test report content (sample ID, formulation, uncured viscosity, cure and mechanical results, any deviations). The standard notes that precision may vary with silica and rubber type.
• Safety note: Users should follow normal laboratory practice and applicable regulatory/safety requirements.

Practical applications and users

ISO 5794-3 is used by:

• Silica manufacturers to benchmark precipitated hydrated silica in a standardized rubber matrix.
• Tyre compound formulators and tyre manufacturers for silica selection and performance prediction, especially for passenger‑car tread compounds.
• Rubber‑testing laboratories and QA/QC teams performing interlaboratory comparisons and routine evaluation.
• R&D groups developing silica‑silane coupling systems or new S‑SBR/BR blends.

Primary use cases: comparative material evaluation, formulation development, supplier qualification and quality control of silica for tyre tread applications.

Related standards

• ISO 5794‑1 (non‑rubber tests for silica)
• ISO 5794‑2 (evaluation in SBR)
• ISO 2393 (mixing and vulcanization procedures)
• ISO 289‑1 (Mooney viscosity)
• ISO 3417, ISO 6502 (curemeter methods)
• ISO 37 (tensile), ISO 48 (hardness)

Keywords: ISO 5794-3, precipitated hydrated silica, S‑SBR, BR, rubber compounding, tyre tread compound, curemeter, Banbury mixing, Mooney viscosity, silica evaluation.