Overview
ISO 19403-6:2017 - Paints and varnishes - Wettability - Part 6: Measurement of dynamic contact angle - specifies an optical method to measure dynamic contact angles (advancing and receding) on solid surfaces. The standard defines how to dose and image horizontal drops, record contact angle versus time, and interpret wetting/dewetting behaviour and interfacial homogeneity. It is part of the ISO 19403 series on wettability and complements surface energy determination methods in ISO 19403-2.
Key topics and requirements
- Measurement principle: Continuous increase (advancing angle) or decrease (receding angle) of a horizontal drop volume while optically recording the three-phase contact line.
- Apparatus: State-of-the-art contact angle measuring system with digital image capture, an optical system, specimen holder and a microlitre syringe/dosing unit for continuous volume control.
- Test liquids: Must not chemically alter the surface, crosslink, form skins or have distinct yield points; high-vapour-pressure liquids measured in saturated vapour phase.
- Procedure essentials:
- Condition test panels and liquids at (23 ± 2) °C and (50 ± 5) % RH (panels for a minimum of 16 h).
- Use at least three drops per liquid and test at multiple locations to assess surface homogeneity.
- Prefer the polynomial method for image analysis; typical dosing speeds for surface energy work ~10 µl/min (reduce for high-viscosity liquids).
- Align baseline through three-phase points and minimize needle influence (recommendation: needle-to-surface distance ~1.5× needle diameter).
- Evaluation: Plot contact angle vs time; advancing/receding angles are reported when a plateau (stable value) is observed. Report contact angle hysteresis (difference between advancing and receding) as an indicator of chemical or morphological inhomogeneity. Note: the receding angle is not suitable for surface energy determination-use advancing angles per ISO 19403-2.
- Sampling and reporting: Follow ISO 15528 for specimen sampling; include environmental conditions, liquids used, dosing rate, and image-analysis method in test reports.
Applications and who uses it
- Coatings and varnish formulators assessing substrate wettability for adhesion and coating performance.
- Quality control and R&D laboratories measuring wetting, dewetting and surface homogeneity.
- Surface scientists, material engineers and manufacturers evaluating pretreatment, surface treatments or contamination.
- Companies validating surface energy or optimizing wetting in printing, adhesives, and functional coatings.
Related standards
- ISO 19403-1: Terminology and general principles (wettability)
- ISO 19403-2: Determination of surface free energy (uses advancing angle)
- ISO 15528: Sampling for paints and varnishes
- ISO 4618: Paints and varnishes - Terms and definitions
Keywords: ISO 19403-6, dynamic contact angle, wettability, contact angle measurement, paints and varnishes, advancing angle, receding angle, contact angle hysteresis.