ISO 19403-2:2017

Overview

ISO 19403-2:2017 - Paints and varnishes - Wettability - Part 2 defines a standardized test method for contact angle measurement to determine the surface free energy of solid surfaces. The method is intended for characterizing substrates and coatings and is based on state-of-the-art contact angle measurement using the drop projection method in penumbral shadow. The standard supports calculation of total surface free energy and its polar and dispersive fractions using established models (preferably Owens‑Wendt‑Rabel‑Kaelble (OWRK) or Wu for polymers and coatings).

Key Topics

• Principle: deposit a minimum of three drops of at least two test liquids onto a flat specimen and measure contact angles; calculate surface free energy from averaged angles and known liquid surface tensions.
• Test liquids: recommended choices include water, di-iodomethane, ethylene glycol (values and polar/dispersive fractions are provided). Liquids must be analytical grade and must not chemically or physically affect the surface.
• Measurement methods: static (single drop) and dynamic (progressive contact angle) modes are described, using digital image capture and analysis.
• Apparatus: contact angle measuring system with dosing unit (microlitre range), optical imaging and analysis; attention to alignment, lighting and image resolution.
• Test conditions and sampling: standard atmosphere at (23 ± 2) °C and (50 ± 5) % RH; specimens conditioned for ≥16 hours; recommended minimum specimen size ~10 × 10 cm.
• Volumes and dosing: typical drop volumes 2–6 µl (di‑iodomethane 1–3 µl); typical dosing rates for dynamic tests ~10 µl/min.
• Influencing factors: morphological and chemical homogeneity affect results; powders are excluded from this part of the standard.
• Evaluation: calculation methods include OWRK and Wu; precision, repeatability and reporting requirements are specified.

Applications

ISO 19403-2 is practical for:

• Quality control and surface characterization in the coatings, paints, plastics and adhesives industries.
• Evaluating substrate wettability prior to painting, coating, printing or bonding.
• R&D for surface treatments, primers, and formulation development to improve adhesion and spreading.
• Material selection and failure analysis where surface energy influences performance (wetting, adhesion, coating uniformity).

Who uses it:

• R&D scientists, quality engineers, surface chemists, coating formulators, and testing laboratories performing contact angle and surface energy analysis.

Related Standards

• ISO 19403-1: Terminology and general principles (wettability series)
• ISO 4618: Paints and varnishes - Terms and definitions (See ISO bibliography for supplementary guidance on liquids and powder measurement techniques.)

Keywords: ISO 19403-2, contact angle measurement, surface free energy, wettability, OWRK method, Wu method, paints and varnishes, drop projection, coatings, substrate characterization.