ISO 19403-1:2022

Overview

ISO 19403-1:2022 - Paints and varnishes - Wettability - Part 1: Vocabulary and general principles - defines the terminology and fundamental concepts used for wettability assessment of coatings, substrates and liquids. The standard establishes general terms and definitions for contact angles, surface free energy, surface tension, three‑phase points and related concepts, and provides informative general principles (Annex A) for interpreting contact‑angle and surface‑energy measurements. ISO 19403-1 is intended to be used in conjunction with ISO 4618 and other parts of the ISO 19403 series that specify test methods.

Key topics and technical requirements

• Vocabulary and definitions: precise terms for contact angle, base line, three‑phase point, pendant drop, fit error, shape parameter (B), interfacial energy and more.
• Surface energy concepts: distinction between surface free energy of solids and surface tension of liquids, including polar and dispersive (non‑polar) fractions.
• Wetting classifications: definitions for hydrophobic (>90° contact angle), hydrophilic (<90°), superhydrophobic (>150° with contact angle hysteresis <10°) and superhydrophilic (≈0°).
• Measurement principles: summary of the physical basis - Young equation, Dupré‑Young (work of adhesion) and Young‑Laplace equation - used to relate contact angle, interfacial energies and pendant‑drop shape.
• Surface free energy determination: explanation of the common OWRK (Owens‑Wendt / Rabel‑Kaelble) approach separating polar and dispersive components via plotting and linear regression of liquid/solid tension terms (Annex A).
• Pendant drop analysis: concept of drop contour analysis (shape parameter, capillary constant) to extract surface tension from pendant drop profiles; fit error as a quality metric.

Applications and users

ISO 19403-1 provides the vocabulary and physical principles that underpin practical wettability testing and surface characterization. Typical applications:

• Quality control and R&D for paints, varnishes and coatings (adhesion, spreading, wetting behavior)
• Surface treatment and pretreatment assessment (plasma, flame, chemical activation)
• Adhesive, printing and ink formulation where substrate wetting is critical
• Laboratory and test‑method development for contact‑angle and surface‑tension measurements

Primary users: coatings manufacturers, test laboratories, material scientists, surface engineers, adhesive formulators and standards developers.

Related standards

• ISO 4618 (paint and varnish terminology) - intended companion standard
• Other parts of the ISO 19403 series covering specific optical test methods (contact angle measurement, surface free energy determination, pendant‑drop procedures and reference materials).

Keywords: wettability, contact angle, surface free energy, surface tension, pendant drop, Young‑Laplace, hydrophobic, hydrophilic, paints and varnishes, ISO 19403-1.