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EFFECTS OF EXTREME TEMPERATURES
Low temperatures encountered in building construction have no adverse effects on Koolfoam (although the possibility
of dimensional changes must be considered) Since Koolfoam softens at high temperatures there are however upper
limits to service temperatures: these are summarized in Table
1.The surface of Koolfoam can be briefly exposed to temperatures
appreciably higher than 100°C without damage, for instance when the material is bonded with hot bitumen.
DIMENSIONAL STABILITY
Like many organic materials Koolfoam has high linear thermal expansivity: 50-70 MK. Although this value is much
greater than those for most tougher building materials (steel, glass, masonry and wood all have vapour in the range
5-12 MK) the forces required to constrain the expansion or contraction of material made from Koolfoam are generally
negligible.
Thus expansion is seldom a problem and contraction is only likely to cause difficulty when large drops in temperature
are involved, In cold-store construction it is usually necessary to use special jointing systems or contraction
joints, since with units 4m long installed at 30°C the unrestrained contraction at -20°C could amount to
about 10mm.
Thermal expansion and contraction is reversible, but freshly moulded expanded Koolfoam is also subject to irreversible
contraction. This contraction, known as aftershrinkage, proceeds rapidly at first but eventually approaches a limiting
value. Once the aftershrinkage is close to the limiting value any residual aftershrinkage is of little importance.
For most purposes a residential aftershrinkage of less than 0.2% is acceptable.
Koolfoam board with densities of more than 15kg/m must be stored for some while before the residual aftershrinkage
drops to 0.2%. The storage time depends on the manufacturing conditions and the density of the board.
Adverse effects resulting from joints opening by aftershrinkage can be easily avoided by using board with rebate
edges or by using two or more layers laid to break joint.
EFFECTS OF WEATHERING
UV and other actinic radiation eventually causes yellowing and embrittlement of polystyrene, so that Koolfoam should
be protected from prolonged exposure to sunlight. The embrittlement is confined to the surface of the material,
and is not of itself harmful, but it does make the material susceptible to erosion by wind and rain. In practice
the usual paints, roofing material, etc, provide the required protection. Koolfoam used indoors is not sufficiently
exposed to UV to deteriorate: this is borne out by years of experience with ceiling tiles.
CHEMICAL PROPERTIES
Koolfoam is comparatively inert, and is unaffected by mildly acid or alkaline building materials such as Portland
cement, lime or anhydrite. It is however soluble in many organic solvents, and may be damaged by certain commonly
used paints, adhesives, wood preservatives, pasting agents, etc. In some cases vapour from these substances can
be harmful.
BIOLOGICAL PROPERTIES
Koolfoam has no nutritive value for micro-organisms, and does not rot. Under certain conditions soiled material
may carry fungi etc, but it is not itself attacked. Even soil bacteria has no effect on it.
Rodents and birds occassionally attack exposed Koolfoam, which should be protected by galvanised wire netting if
necessary.
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