ISO 27448:2009

INTERNATIONAL ISO
STANDARD 27448
First edition
2009-07-15
Fine ceramics (advanced ceramics,
advanced technical ceramics) — Test
method for self-cleaning performance of
semiconducting photocatalytic
materials — Measurement of water
contact angle
Céramiques techniques — Méthode d'essai de la performance auto
nettoyante des matériaux photocatalytiques semiconducteurs —
Mesurage de l'angle de contact de l'eau

Reference number
©
ISO 2009
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ii © ISO 2009 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 27448 was prepared by Technical Committee ISO/TC 206, Fine ceramics.
Introduction
Under the illumination of ultraviolet (UV) light, photocatalysts show diverse functions, such as the
decomposition of air and water contaminants, as well as deodorization, self-cleaning, antifogging and
antibacterial actions. These functions of photocatalysts are generally based on the action of active oxygen
species such as hydroxyl (OH) radicals formed on the surface of photocatalysts. The energy- and labour-
saving nature of photocatalysis has attracted keen interest when the photocatalyst is activated by sunlight (or
artificial lighting).
Practical applications of photocatalysts, for both indoor and outdoor use, have rapidly expanded in recent
years. Many kinds of photocatalytic materials have been proposed or are already commercialized, based on
ceramics, glass, concrete, plastics, paper, etc. Such materials are produced by either coating or mixing of a
photocatalyst, in most cases, titanium dioxide (TiO ).
However, the effect of photocatalysis is not easily inspected visually, and no appropriate and official
evaluation methods have been available to date. Some confusion has thus arisen as photocatalytic products
have been introduced. Furthermore, the above-mentioned diverse functions of photocatalysts cannot be
evaluated with a single method; thus, different evaluation methods are provided for self-cleaning, water
decontamination, air purification and anti-bacterial actions, respectively.
As a result of continuing efforts to provide test methods for photocatalytic materials, this International
Standard (covering the measurement of the water contact angle) for self-cleaning performance was prepared.
For permeable, rough, or highly hydrophobic surfaces, etc., other test methods are required and are being
developed.
It must be noted that self-cleaning performance could be evaluated with photo-induced hydrophylic property
and photocatalytic decomposition ability, because many field test results concerning the self-cleaning
properties of TiO -coated materials are in good agreement with the indexes obtained by measurement of the
water contact angle and degradation of methylene blue.

iv © ISO 2009 – All rights reserved

INTERNATIONAL STANDARD ISO 27448:2009(E)

Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for self-cleaning performance of
semiconducting photocatalytic materials — Measurement of
water contact angle
1 Scope
This International Standard deals with fine ceramics.
This International Standard specifies a test method for the determination of the self-cleaning performance of
materials that contain a photocatalyst or have photocatalytic films on the surface, and which are usually made
from semiconducting metal oxides such as titanium dioxide.
This method is used to measure the water contact angle under illumination with ultraviolet light, which is one
of the indices influencing the self-cleaning performance of photocatalytic materials.
This International Standard does not include water-permeable substrates, rough surfaces which do not have
exposed water droplets, highly hydrophobic, powder or granular materials, or visible light-sensitive
photocatalysts.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 3534-1:2006, Statistics — Vocabulary and symbols — Part 1: General statistical terms and terms used in
probability
ISO 80000-1, Quantities and units — Part 1: General
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
photocatalyst
substance that carries out one or more functions based on oxidization and reduction reactions under
photoirradiation, including decomposition and removal of air and water contaminants, deodorization, and
antibacterial, self-cleaning and antifogging actions
3.2
photocatalytic materials
materials in which, or on which, the photocatalyst is added by coating, impregnation, mixing, etc.
NOTE Such photocatalytic materials are intended for use as building and road construction materials to obtain the
functions mentioned in 3.1.
3.3
fluorescent UV lamp
lamp that provides UV-A irradiation within a wavelength range of 300 nm to 400 nm
NOTE A suitable lamp is the so-called black light blue (BLB) fluorescent lamp, with a maximum wavelength of
351 nm, as described in ISO 4892-3.
3.4
hydrophilicity
property in which the surface of the photocatalytic material shows a strong affinity for water
3.5
self-cleaning
function whereby a photocatalyst, attached to a surface like a building material, prevents fouling of the surface
by utilizing at least one of the following: the phenomenon where fouling substances attached to the surface
are broken down by oxidation and reduction when irradiated with light, and/or the phenomenon where fouling
is washed away when the surface is exposed to rain or rinsed with water, due to the hydrophilicity which
manifests itself at the same time
3.6
contact angle
when a tangent line is drawn from the contact point of the solid, liquid and vapour phases (normally air) along
the curve of the liquid on the solid, the angle between the line and the solid surface is referred to as the
contact angle
3.7
initial contact angle
contact angle immediately before starting UV irradiation
3.8
contact angle after n h of UV irradiation
contact angle after applying UV irradiation for n h
NOTE The unit of time may also be days, minutes or seconds, in addition to hours.
3.9
final contact angle
contact angle at the highest water affiliation after irradiation at a constant intensity on a photocatalytic material
3.10
pretreatment of test piece
preparation of a test piece by irradiating it with UV and then applying organic substances such as oleic acid
3.11
coefficient of variation
ratio of the standard deviation to the arithmetic mean
4 Symbols
θ initial contact angle, in degrees
i
θ contact angle after n h, in degrees
n
x average of the three consecutive points, in degrees
s standard deviation of the three consecutive points, in degrees
θ final contact angle, in degrees
f
2 © ISO 2009 – All rights reserved

5 Principle
This International Standard is for the development, comparison, quality assurance, characterization, reliability,
and design data generation of photocatalytic materials.
This International Standard defines the test method, which provides a performance correlated with the
contamination that occurred during the exposure test.
This test method is to evaluate the self-cleaning performance of a photocatalytic material by obtaining the final
contact angle of a test piece on which organic substances are applied. The organic substance is first applied
to a test piece (pretreatment), which is then irradiated by UV at a constant intensity. The water contact angle
after n h can be measured during the process. This test simultaneously evaluates the decomposition of the
organic substance and change of water affiliation. When the pretreatment of a certain test piece is impossible
and the initial contact angle before UV irradiatio
...