ISO 27448:2009

Overview

ISO 27448:2009 specifies a standardized test method to evaluate the self-cleaning performance of semiconducting photocatalytic materials by measuring the water contact angle under ultraviolet (UV) illumination. Targeted at fine ceramics and common photocatalytic coatings (typically metal-oxide semiconductors such as titanium dioxide, TiO2), the method quantifies photo-induced hydrophilicity - one key index correlated with self-cleaning behavior. The standard excludes water-permeable substrates, very rough or highly hydrophobic surfaces, powders/granular materials, and visible-light-sensitive photocatalysts.

Key Topics and Requirements

• Principle: Apply an organic contaminant (oleic acid) to a test piece, irradiate with a controlled UV source, and monitor reduction in water contact angle as photocatalytic decomposition and hydrophilicity develop.
• Test pieces: Standard-size flat specimens (recommended 100 mm ± 2 mm square), prepared in quintuplicate for reproducibility.
• Pretreatment: Remove organics by UV (2.0 mW/cm²) then apply oleic acid either manually (2.0 mg ± 0.2 mg per 100 cm²) or by dipping (0.5% oleic acid in n‑heptane, lift 60 cm/min, dry 70 °C for 15 min).
• UV source and intensity: Use a BLB (black light blue) fluorescent lamp (peak ≈351 nm). Irradiation intensity is measured with a calibrated radiometer and adjusted to specified values (e.g., (2.0 ± 0.1) mW/cm² or (1.0 ± 0.1) mW/cm² depending on pretreatment).
• Contact angle measurement: Use a contact angle meter (0–180°, readout accuracy 0.1°) to record initial angle at five points, then at intervals during UV exposure. Final contact angle is computed from three consecutive measurements when coefficient of variation ≤ 10% (or when angle ≤ 5°).
• Environmental conditions: Laboratory temperature recommended 23 °C ± 5 °C and relative humidity 40–70%.
• Reporting: Include test conditions, specimen description, lamp and instrument details, pretreatment and irradiation times, and initial/final contact angles.

Applications and Users

ISO 27448:2009 is practical for:

• Manufacturers of photocatalytic ceramics, glass, tiles, concrete, coatings and building materials - for product development and quality assurance.
• Independent testing laboratories validating self-cleaning claims.
• R&D teams optimizing photocatalyst formulations (e.g., TiO2 coatings) and UV-activated surface treatments.
• Specifiers, architects, and regulators assessing performance metrics for façade, glazing, and exterior materials.

Keywords: ISO 27448, self-cleaning performance, photocatalytic materials, water contact angle, photocatalyst, titanium dioxide, UV irradiation, contact angle measurement, hydrophilicity.

Related Standards

• ISO 3534-1: Statistics - vocabulary and symbols (used for variability calculations).
• ISO 80000-1: Quantities and units (rounding and units).
• ISO 4892-3: Guidance on fluorescent UV lamps (BLB lamp reference).