ISO 18924:2000
(Main)Imaging materials — Test method for Arrhenius-type predictions
Imaging materials — Test method for Arrhenius-type predictions
Matériaux d'image — Méthode d'essai pour les prédictions de type Arrhenius
General Information
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 18924
First edition
2000-08-01
Imaging materials — Test method for
Arrhenius-type predictions
Matériaux d'image — Méthode d'essai pour les prédictions de type
Arrhenius
Reference number
ISO 18924:2000(E)
©
ISO 2000
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ISO 18924:2000(E)
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ISO 18924:2000(E)
Contents Page
Foreword.iv
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 Background and theory .2
5 Experimental procedures.4
6 Calculations.5
7 Test report .6
Annex A (informative) Numbering system for related International Standards.8
Annex B (informative) Advantages and disadvantages of sealed-bag and free-hanging incubations .9
Annex C (informative) Limitations of the Arrhenius method [16] .10
Annex D (informative) Examples of Arrhenius relationships .12
Bibliography.14
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ISO 18924:2000(E)
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 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 18924 was prepared by Technical Committee ISO/TC 42, Photography.
This International Standard is one of a series of standards dealing with the physical properties and stability of
imaging materials. To facilitate identification of these International Standards, they are assigned a number within
the block from 18900 to 18999 (see informative annex A).
Annexes A to D of this International Standard are for information only.
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INTERNATIONAL STANDARD ISO 18924:2000(E)
Imaging materials — Test method for Arrhenius-type predictions
1 Scope
This International Standard specifies a test method for the prediction of certain physical or chemical property
changes of imaging materials.
This International Standard is applicable to the Arrhenius test portion of ISO 8225, ISO 9718, ISO 10602,
ISO 10977 and ISO 18919.
This International Standard is applicable to the prediction of the optical-density (D) loss or gain of imaging
materials. Photographic dye images may be produced by chromogenic processing, by formation of diazo dyes, or
by non-chromogenic methods such as dye diffusion and silver dye-bleaching processing. This standard also covers
density changes caused by
� residual coupler changes in dye images,
� excess residual processing chemicals in silver black-and-white materials,
� temperature effects on thermally processed silver images.
This International Standard is applicable to the prediction of support degradation. One such example is the
generation of acetic acid by degradation of cellulose acetate film support. Another example is the change in tensile
energy absorption of black-and-white paper support.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 8225:1995, Photography — Ammonia-processed diazo photographic film — Specifications for stability.
ISO 9718:1995, Photography — Processed vesicular photographic film — Specifications for stability.
ISO 10602:1995, Photography — Processed silver-gelatin type black-and-white film — Specifications for stability.
ISO 10977:1993, Photography — Processed photographic colour films and paper prints — Methods for measuring
image stability.
ISO 18919:1999, Imaging materials — Thermally processed silver microfilm (TPS) — Specifications for stability.
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ISO 18924:2000(E)
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
Arrhenius plot
plot of the logarithm of the time for a given change in a characteristic proportional to the reaction rate (dye loss,
tensile strength change, D yellowing, etc.) versus the reciprocal of the temperature, in kelvins
min
NOTE The Arrhenius plot may be used to predict behaviour at a temperature lower than those at which the tests are run.
3.2
glass transition
reversible change in an amorphous polymer from, or to, a viscous or rubbery condition to, or from, a hard and
relatively brittle one
3.3
glass transition temperature
T
g
approximate mid-point of the temperature range over which glass transition takes place
NOTE 1 T can be determined readily only by observing the temperature at which a significant change takes place in a
g
1)
specific electrical, mechanical, or other physical property [1] .
2)
NOTE 2 T can also be sensitive to the moisture content of the polymer (see 5.4, annex B, and C.3 of annex C for
g
information).
3.4
irrelevant physical or chemical reactions
chemical or physical reactions that take place only at high temperatures and/or humidities and do not take place at
the temperatures at which the Arrhenius predictions are to be made
NOTE Such reactions may nevertheless affect the quality of the image, binder or support.
3.5
morphological changes
changes in the physical structure of the association of the molecules
3.6
thermodynamic temperature
temperature measured on the absolute scale which is based on absolute zero (–273,15�C) and having an interval
of measurement that is equivalent to degrees Celsius
NOTE The temperature unit in the absolute scale is the kelvin.
4 Background and theory
4.1 Background
In the 1890s, Svante Arrhenius discovered that the rate of some chemical reactions is proportional to the reciprocal
of the absolute temperature. This relationship has been used with phenomena related to a chemical change, such
as the loss of a particular physical property or the change in the optical density of film. If a linear relationship exists
1)
The number in the bracket refers to the reference in the bibliography.
2)
For imaging materials containing gelatin, T is very humidity dependent.
g
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ISO 18924:2000(E)
between the logarithm of the time for a change of a particular property and the reciprocal of the temperature, then
this plot can be extrapolated to lower temperatures than those used in laboratory studies. This allows the prediction
of the time required for the change to happen at room temperature or lower.
This relationship was first used for the rates of chemical reactions [2] and was later applied to paper materials [3,4].
[5]
This theory became the basis for TAPPI Standard 453 . The approach was also applied to textiles [6] and to
physical properties of photographic film supports [7,8]. More recently, it has been used to predict the fading of both
chromogenic and non-chromogenic photographic dyes [9,10,11].
Predictions based on the Arrhenius equation require the reactions to be run under a series of temperatures at
either constant relative humidity (free-hanging) or constant moisture content inside the enclosure. The investigator
shall determine which of the above conditions is more relevant to the system being tested.
There may also be cases where elevated temperatures cause different reaction pathways from those occurring at
ambient or sub-ambient conditions. In these cases, the plot of the logarithm of time versus the reciprocal of the
absolute temperature will be non-linear and great caution shall be taken in drawing conclusions. Only the linear and
lower temperature portion of the plot can be extrapolated to ambient conditions or below.
The drawback to elimination of higher temperature data is that the experiment will then take longer because of the
slow reaction rate at lower temperatures. Patience is the only solution for getting the correct answer when this
happens. When incubations are limited to a few of the higher temperatures, this can lead to incorrect or misleading
results and shall be done with extreme caution.
Confidence in the Arrhenius methodology is obtained when predictions for phenomena with reasonably short
lifetimes correspond to the real-time results. Such data do exist for the fading of photographic dyes [12,13] and the
stability of cellulose ester film supports [8,14].
4.2 Theory
The basic relationship in the study of chemical reaction rates is the Arrhenius equation:
–E
logkC��
2,30 RT
where
k is the rate of reaction (change per time);
E is the energy of activation for a specific reaction;
R is the gas constant;
T is the temperature (in kelvins);
C is a constant for the specific reaction.
By combining all the constant terms (E/2,30 R) into a constant "a" and measuring the time for a given change, this
equation can be rewritten as:
a
log (time)�� C
T
Consequently, when the logarithm of the time is plotted against the reciprocal of the absolute temperature, a
straight line is produced. This relationship can be used to predict the time required for a given change to occur at
lower temperatures where the reaction might require hundreds of years. This is done experimentally by determining
the time required for a given change at a number of elevated temperatures (where the times required are
reasonable), plotting these points, and extending the straight-line graph to the lower temperatures of interest. This
"Arrhenius method" of predicting long-term ageing behaviour is widely used and accepted by experts in the
photographic industry.
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ISO 18924:2000(E)
In the chemical literature, the equation has been widely applied to relatively simple, chemical reactions where both
reactants and products have been identified. However, there may be circumstances in which the fit of the Arrhenius
prediction line is less than perfect. In these cases, there may be more than one reaction occurring and this may
result in non-linear behaviour or two distinct linear portions to the prediction line. In other situations, physical
properties are measured, although the changes are the result of chemical reactions. More details of these
phenomena are given for information in annex C. However, despite the complex reactions involved, this equation
applies very well to many complicated reactions that occur with photographic materials.
4.3 Effects of relative humidity
The Arrhenius method is run at either constant relative humidity or constant moisture content in the enclosure. It
should be noted that many of the responses evaluated by the Arrhenius method are humidity dependent and that
rates can change quite drastically as a function of relative humidity [15].
The effect of moisture may be determined by several separate experiments at multiple temperatures, with each
experiment at a constant relative humidity or moisture content.
5 Experimental procedures
5.1 Outline of Arrhenius test
An Arrhenius test should have the following steps that are explained in more detail in several of the references
[16,17].
a) Prepare specimens; this may include exposing, processing, cutting, trimming, etc.
b) Take initial readings of the property of interest on the non-incubated specimens.
c) Incubate the specimens at a minimum of four temperatures, using either the free-hanging or the sealed-bag
technique (see 5.3).
d) Measure the property of interest on the incubated specimens after different incubation times.
e) Determine the incubation time at each incubation temperature for the property of interest to reach a
predetermined level.
f) Plot the log of the incubation time determined in (e) against the reciprocal of the thermodynamic temperature
to obtain an Arrhenius plot.
g) Predict the time for the property of interest to change the desired amount at the desired temperature by
extrapolation of the Arrhenius plot.
Examples of Arrhenius plots are given in annex D.
5.2 Requirements for a meaningful Arrhenius test
Although a straight line can be drawn between two points and an Arrhenius prediction may be made by plotting the
results of two different incubation temperatures, there can be no evaluation of the statistical significance of this
experiment unless three or more temperatures are used. Because a smaller number of data points is apt to lead to
a strongly biased prediction, a minimum of four temperatures shall be run for each prediction.
If the effect of relative humidity needs to be considered, experiments at different relative humidities shall be studied.
The relative humidities shall be at least 10 % RH apart, and preferably should be 20 % RH apart. The tests shall be
run at a humidity range representing the anticipated storage of the material.
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ISO 18924:2000(E)
5.3 Sealed-bag versus free-hanging testing
Two test methods, known as the "sealed-bag" and the "free-hanging" methods, are available for accelerated
stability testing. These kinds of test conditions tend to give somewhat different results.
In the sealed-bag method, the photographic material is stored in a sealed container with very little air. Pre-
equilibration of the samples to a constant relative humidity is necessary before they are s
...
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