ISO 4608:2023

Overview

ISO 4608:2023 - Plastics - Homopolymer and copolymer resins of vinyl chloride for general use - Determination of plasticizer absorption at room temperature - specifies a laboratory method to measure how much plasticizer a PVC general‑purpose or filler resin absorbs at ambient conditions. The test gives a practical indication of plasticizer uptake for producing dry blends and for quality control of vinyl chloride resins used in plasticized formulations.

Key topics and requirements

• Scope: Applicable to PVC general‑purpose resins and filler resins designated “G” and “F” in ISO 24024‑1.
• Principle: An excess of plasticizer is mixed with a weighed amount of resin, centrifuged, and the plasticizer retained by the resin is determined gravimetrically.
• Apparatus & materials:
  • Balance with accuracy ±0.1 mg.
  • Burette or dispenser (see ISO 8655‑2).
  • Horizontal‑rotor centrifuge with acceleration at the tube bottoms of 24 500 to 29 500 m·s‑2 (60 min) and temperature ≤ 30 °C.
  • Centrifuge tubes (conical bottom with ~0.8 mm hole or with sieve plate) and sheaths.
  • Cotton wool (100 mg ± 2 mg) or filter paper; alternative absorbents allowed if equivalent.
• Plasticizers covered: Bis‑(2‑ethylhexyl) phthalate (DOP, CAS 117‑81‑7) and Bis‑(3,5,5‑trimethylhexyl) phthalate (DINP, CAS 28553‑12‑0 / 68515‑48‑0), with specified density, refractive index and viscosity limits as per ISO 1385‑1. Note: DOP use is now restricted in Europe for hazard reasons (CLP/REACH).
• Procedure highlights: Blank measurement of absorbent, weigh tube + absorbent, add specified resin mass and a measured volume/length of plasticizer, centrifuge, reweigh and compute absorbed plasticizer. Results reported as parts per hundred resin (phr).
• Reporting: Include reference to ISO 4608:2023, sample ID, plasticizer type, centrifuging conditions, quantities used, test result, deviations, and date.

Applications and users

• Quality control laboratories in PVC resin manufacturing.
• Compounders and processors producing plasticized dry blends and formulations.
• R&D and material development teams evaluating resin/plasticizer compatibility.
• Regulatory and compliance testing where plasticizer uptake affects product performance or safety. The method supports decisions on plasticizer selection, dry‑blend formulation, batch acceptance and troubleshooting of mixing/compatibilization issues.

Related standards

• ISO 24024‑1 - designation system for PVC resins
• ISO 1385‑1 - phthalate ester test methods
• ISO 8655‑2 - piston‑operated volumetric apparatus (pipettes)

Keywords: ISO 4608:2023, plasticizer absorption, PVC, vinyl chloride resins, DINP, DOP, centrifuge method, room temperature absorption, dry blend, plasticizer uptake.