Outdoor Weathering Performance
Solar radiation has a particularly harmful effect upon polymeric materials
initiating degradation by causing superficial surface crazing. These
crazes become sites for further erosion from water, dust, chemicals,
etc. The degree to which these conditions affect the polymer depend
largely upon environmental parameters such as geographical location,
altitude, seasonal variations, etc.
Most Multiwall PC sheet has a one sided or two sided UV-protected surfaces, giving
durability to outdoor weathering. This unique technology helps to ensure long term optical quality under intensive
UV exposure, and maintains the superior toughness of the polycarbonate
material in comparison to other thermoplastic glazing.
Typical Values of UV protected Polycarbonate Sheet
Research into the long-term effects of weathering on glazing materials
is basically focused upon measuring product performance through material
property changes, typically mechanical strength, impact resistance,
color retention, transparency etc.
A test was developed using high intensity xenon lamps to simulate natural
sunlight. Together with other suitable UV filters and programmable rain
cycles the test is able to simulate natural conditions.
MJK Multiwall Systems encourages those interest
to acquire a copy the National Greenhouse Manufacturers Association
glazing standards ( www.ngma.com ). These standards outline guidelines for UV Testing.
The heat build-up of glazing materials can be seen as a function of
the absorption of the glazing material, in some case the pigments, and the solar intensity.
In countries with intense sun radiation, and when high energy
absorbing tinted glazing is installed, heat build-up of the glazing can
be considerable. Calculations and actual measurements on installed glass
and pigmented plastics
sheet in several projects throughout Europe have shown that sheet surface
temperatures of 212°F can exist.
Multiwall PC and compact sheet is characterized by its retention of impact
strength and stiffness at elevated temperatures, even over an extended
Multiwall PC sheet retains 85% of its room temperature flexural
modulus at 176°F. The Vicat softening temperature and the Deflection
Temperature Under Load are both around 284°F.
Multiwall PC & sheet has a continuous-use temperature of 212°F*.
At the other end of the scale the minimum continuous- use temperature
has been set at -40°F. Using polycarbonate sheet at lower temperatures
is possible since the embrittlement temperature can be as low as -80°F.