Installation Instructions

26 SABIC Innovative Plastics
Condensation/Chemical Resistance
Condensation
Condensation is formed when moisture in the
atmosphere changes back to water as it comes into
contact with a surface at a temperature below the
‘dewpoint’ of the surrounding air.
Water droplets on the surface of the glazing reduce
light transmission, and, if they fall, can spoil plants or
damage sensitive goods and equipment underneath.
Lexan Thermoclear Dripgard sheet has a special
one-sided coating that inhibits the formation of
condensation droplets. The coating lowers the surface
tension and the droplets form a thin layer of water over
the whole surface of the sheet.
When the sheet is correctly installed, this thin,
transparent water lm runs off the sheet surface into
the prole drainage system without falling to the
ground and without affecting the light transmission
values of the glazing.
Fig. 11 shows a typical condensation prediction chart
showing the relationships between internal and external
temperatures, relative humidity and the U-value. The
dotted lines on the chart illustrate clearly how glass
with a high U-value is more prone to condensation than
Lexan Thermoclear Dripgard sheet.
Example:
Chemical Resistance
Lexan Thermoclear sheet has been successfully used in
combination with many building materials and glazing
compounds. Taking into account the complexity of
chemical compatibility, all chemicals which come into
contact with polycarbonate should always be tested in
the particular application. For sheet products, the most
common materials are sealants, gaskets and the various
cleaning media. Chemical compatibility testing is an
ongoing process at SABIC Innovative Plastics and many
standard products have already been tested.
A complete list of recommended cleaners, gaskets and
sealants is available upon request. However, a shortened
list of some of the more common compounds is shown
below.
When using glazing compounds it is essential that the
sealant system accepts a certain amount of movement
to allow for thermal expansion, without loss of adhesion
to the frame or sheet. Momentive Silicones’ sealants are
generally recommended for use with Lexan Thermoclear
sheet, see Table 14. It is strongly advised when using
other sealing compounds to check compatibility before
use.
11. Condensation
Prediction Chart showing
the telationships between
internal and external
temperatures, relative
humidity and the U-value
Inside temperature: 20°C
Outside temperature: -10°C
Condensation will occur on:
A Glass U-value 5.8 w/m
2
K at a humidity content of: 32%
B LTC 6 mm U-value 3.56 w/m
2
K at a humidity content of: 50%
C LTC 20 mm U-value 1.8 w/m
2
K at a humidity content of: 68%
Table 14: Recommended Sealants
Sealant Supplier
Silpruf Momentive
MultiSil Momentive
Table 15: Recommended Gasket Systems
Gasket Type* Supplier
EPDM
Chloropene, RZ4-35-81
Helvoet
EPDM
4330, 4431, 5530, 5531
Vredestein
EPDM
3300/670, 64470
Phoenix
* more grades available
Compatible Neoprene, EPT or EPDM rubbers with
an approximate Shore Hardness of the A65 are
recommended, and compatibility reports for different
rubber types are available upon request.
In case of doubt about any aspect of the chemical
compatibility of the Lexan Thermoclear sheet range,
always consult your nearest SABIC Innovative Plastics
Sales Ofce for further advice.
11
40
30
20
10
0
-10
- 0.5
100
80
60
40
20
0
C
B
A
20
10
0
30
-10
0
10
20
30
U-value (W/m
2
K)
U-value (W/m
2
K)
Outside temperature (°C)
-20
-30
-40
2.3
3.0
3.8
5 6
1
Inside temperature (°C)
Relative humidity content (%)