Controlled Temperature and Humidity
Exposure
Scope and Field of Application
This method can be used to give an indication of how well a
painted surface will resist a wide range of temperature/humidity
conditions. If you are particularly interested in resistance to
exposure to warm humid conditions, please refer to our Resistance to Humidity
test page. Coatings intended to resist prolonged contact with
water can be tested for Resistance
to Immersion.
Like all laboratory tests, the method described here has its
advantages and limitations and these are summarised, in general
terms, on our Testing Paints for
Resistance to Weathering page.
Summary of Method
Samples are exposed in a Fisons Climatic Cabinet which is
essentially a chamber mounted above an air treatment assembly
containing a heating element, a chilled water operated heat
exchanger, water atomisers and an air recirculating system. The
chamber is equipped with temperature and humidity sensors
together with an electronic control and recording system.
We can use this equipment to test the resistance of coatings
to extremes of temperature and humidity. Temperatures can range
from -5 to +50 °Centigrade and we can advise on the relative
humidities obtainable within this temperature range.
The cabinet can be maintained at one set of conditions or it
can be cycled, for example, between hot/humid and cold/dry. A
typical specification might be:-
- Eight hours at 40°C and 95%+ relative humidity followed
by
- Sixteen hours at 20°C and 70% relative humidity.
In practice, not all possible combinations of temperature,
relative humidity and cycle time can be attained. We will be
pleased to advise on what is possible.
One consequence of the versatility of the equipment is that
there are numerous standard methods of operation. We can select
from BS, ISO, DIN and ASTM
methods for the testing of paints, varnishes, plastics, rubbers,
bituminous materials and printed items and we will be pleased to
advise on the most appropriate conditions for testing your
materials.
Sample Requirements
The chamber dimensions are 80 x 80 x 86 cm and we can
accommodate any number of samples that will fit within this
chamber provided that their total weight does not exceed 20 Kg.
We recommend that samples are run in triplicate.
If you wish, we can prepare the test panels. The quantity of
liquid paint we needs depends on the method of application. We
will be pleased to advise you regarding our requirements.
Accreditation
Although PRA is accredited to ISO 17025 by the United Kingdom
Accreditation Service (UKAS),
we are not accredited to carry out this particular test.
Please contact Peter Collins
for further details.
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