ISO 3262-19:2021

Overview

ISO 3262-19:2021 - “Extenders ­- Specifications and methods of test - Part 19: Precipitated silica” specifies the essential and conditional requirements and the corresponding laboratory test methods for precipitated silica used as an extender. The standard defines grading, compositional limits and detailed analytical procedures (sampling, silica and carbon determinations, residue on sieve, oil absorption, pH, loss on ignition and more). It is a technical reference for manufacturers, quality laboratories and purchasers seeking consistent, comparable data for precipitated silica.

Key topics and requirements

• Grades and composition
  • Silica content: minimum 95% mass fraction for specified grades.
  • Carbon content: Grade A < 0.3%; Grade B ≥ 0.3% (carbon contributes to loss on ignition).
  • Organic surface treatment: permitted for Grade B, not for Grade A.
• Physical and chemical limits
  • Matter volatile at 105 °C: max 8% (ISO 787-2).
  • Loss on ignition: 3–8% (Grade A), 3–15% (Grade B) (ISO 3262-1).
  • Oil absorption value: 120 g/100 g (ISO 787-5).
  • pH of aqueous suspension: 3.5–9 (ISO 787-9).
• Conditional characteristics to be agreed between parties:
  • Residue on 45 µm sieve, particle size distribution (instrumental), apparent density after tamping, specific surface area.
• Analytical methods
  • Detailed procedure for silica content (HCl treatment, controlled drying, ignition at ~1000 °C, HF treatment to remove SiF4) and for carbon content, residue on sieves, oil absorption, pH and tamped apparent density.
  • Sampling according to ISO 15528.
• Safety note: use approved laboratory safety practices-hydrofluoric acid (HF) is corrosive and toxic; work in fume hood.

Applications

• Ensures consistent quality and comparability of precipitated silica used in:
  • Paints and coatings (as extenders and rheology modifiers)
  • Rubber compounding and filler formulations
  • Adhesives, sealants and other polymer systems
  • Industrial quality control and incoming material inspection
• Supports specification drafting, supplier agreements and acceptance testing where material performance correlates with silica purity, surface treatment and particle characteristics.

Who should use this standard

• Manufacturers of precipitated silica and extenders
• Independent and in-house analytical laboratories
• Quality assurance and procurement teams in paints, rubber and polymer industries
• Standards committees, regulatory bodies and product developers defining technical specifications

Related standards

• ISO 3262-1 (general test methods)
• ISO 787 series (ISO 787-2, -5, -9, -11)
• ISO 15528 (sampling), ISO 3696 (water for analysis)
• ISO 5794-1, ISO 18451-1

Keywords: ISO 3262-19:2021, precipitated silica, extenders, specifications, test methods, silica content, loss on ignition, oil absorption, pH, sampling, laboratory methods.