ISO 11667:1997

Overview

ISO 11667:1997 specifies laboratory dissolution methods to determine the resin, reinforcement‑fibre and mineral‑filler contents of fibre‑reinforced plastics used as moulding compounds and prepregs. It defines two solvent‑extraction procedures - Method A (Soxhlet extraction) as the reference technique and Method B (immersion in a beaker) for simpler, routine quality‑assurance testing. The standard applies to prepregs (yarns, rovings, tapes, fabrics) and to SMC, BMC and DMC moulding compounds.

Key topics and requirements

• Two extraction methods
  • Method A - Soxhlet extraction: reference method for disputes; uses a Soxhlet apparatus to ensure complete resin removal.
  • Method B - Beaker immersion: simpler equipment for routine QA; may include ultrasonic assistance.
• Solvents: Examples suitable for common resins include dichloromethane, acetone, methyl ethyl ketone (MEK) and denatured ethanol; selection must ensure complete resin extraction.
• Specimen preparation & sampling: Test on two (or more) representative specimens; specimen masses typically 2–20 g; prepregs sampled ≥50 mm from fabric edges.
• Drying and weighing: Dry to constant mass (oven ~105 °C) and use a precise balance (accuracy ~0.5 mg) - repeat drying/weighing until mass change <1 mg.
• Separation of fibre and filler:
  • Method A separates fillers by reacting the extraction residue with hydrochloric acid (for acid‑soluble mineral fillers) and filtering;
  • Method B separates by successive filtration and washing without acid.
• Calculation and reporting: Resin content is obtained from mass loss after extraction; fibre and filler percentages are calculated from subsequent filtration/acid‑reaction masses and reported as percent of original mass. Coatings/sizings that dissolve with the resin are counted as resin.

Applications and users

• Who uses it: Materials laboratories, composite manufacturers, quality engineers, R&D teams, and certification bodies involved with prepregs and moulding compounds (SMC/BMC/DMC).
• Practical uses:
  • Routine quality control of prepreg and moulding‑compound batches
  • Material specification verification and incoming inspection
  • Failure analysis and composition auditing
  • Comparative testing where precise resin/filler/fibre proportions are required
• Limitations: Not applicable to composites with solvent‑soluble reinforcements or to materials where the resin is partially/fully cured and insoluble. Normal laboratory safety practices are required.

Related standards

• ISO 1172:1996 - calcination methods for cured materials (alternative for cured resins)
• ISO 291, ISO 472, ISO 4793 - referenced for conditioning, terminology and filter porosity grading

Keywords: ISO 11667, fibre‑reinforced plastics, moulding compounds, prepregs, resin content determination, solvent extraction, Soxhlet, SMC BMC DMC, mineral filler analysis, reinforcement fibre content.