CPVC/PVC in outdoor desert environment

[Jens12]

Hi,

one of our supplier wants to install a CPVC piping for a sewage treatment unit located in the desert of Ruwais/UAE. The location is only shaded by a sunshade roof without walls and the unit will be exposed to high UV radiation. In my opinion CPVC is not dedicated for long-term (20 years) outdoor duty even if the industry promises excellent weatherability. Has anybody long-term experience with such installation outdoors ?

best regards
Jens Binder

 

[Demon3]

One of the very best polymers for outdoor weathering is ASA. It has mechanical properties just very smilar to ABS. ABS contains butadiene rubber that goes yellow and brittle over time exposed to UV light or heat. ASA contains a very stable rubber and so ASA is chosen for applications where the part must remain in good mechanical condition and with good appearance for many years outdoors. Exterior car parts like the front grill are made from ASA. It is also possible to coextrude ASA onto PVC to improve the weatherability of the PVC. Many sidings in the US are made of PVC with a coextruded layer of ASA on the top for exactly that reason.

You can find ASA data at

http://www.matweb.com

or in the CAMPUS directory (you can find that through google for example). One grade I have experience of is Luran S 778TE from BASF, that can be coextruded onto PVC and even recycled with the PVC later on if needed. Other manufacturers and grades are available too.

 

[Demon3]

I should add something. If the pipe is PVC with CPVC then the CPVC acts to increase the heat distortion temperature and Vicat softening point. The grade of ASA I mentioned before will have the same effect. It can be extruded in a thicker layer to improve HDT/Vicat as it has an HDT of about 105 Celcius. Or you can actually blend it with the PVC and get an increase in HDT/Vicat. This is done commercially and it does work.