CPVC Coloring

[adamgnt]

Hello All,

A new rev of a product is using a 3" Schedule 80 CPVC pipe as a pressure tube and solid stock for 2 endcaps, instead our the typical anodized/painted aluminum. The product is for a long term (1-3 year) deployment in ocean water at depths up to 200m. From a sellers perspective, this is fairly high end equipment and I would prefer not to ship it out 100% gray, looking like it was glued together in the Home Depot parking lot. My issue is I can't find a supplier to sell me colored (would like yellow, but will take anything a this point) CPVC pipe in lots less than 2500 feet. That's a lot of pipe to store. Is there something inherent in CPVC manufacturing that making coloring more difficult than PVC? I thought they just impregnated it with chlorine, making it more ductile (which is why we need it). Perhaps it's not a good enough market to justify small runs.

I have also had similar difficulties identifying a paint that won't easily flake off when dinged while on our assembly floor. Any input on that front would also be welcomed.

--Adam

 

[Demon3]

CPVC (chlorinated PVC) has extra chlorine in the polymer in order to make it remain stiff to higher temperatures (i.e. it increases the Vicat and HDT). I don't think it will make it more ductile, in fact quite the opposite. Sounds like you could use normal PVC, it's cheaper too.

The other effect of CPVC is that it's not nice to process, tending to scorch in the extruder if you're not careful. The higher processing temps could make it more difficult to color (not sure) but most likely is just that it's not as common as PVC so color choice will be more limited.

Based on what you've mentioned I'd go for normal PVC.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[adamgnt]

According to my other engineers in the building, CPVC exhibits this higher ductility in the form of higher compressibility without fracture, which would be disastrous in an underwater environment.

Didn't take the time to do a research search to my standards, but for these purposes, it would seem the CPVC wikipedia page would agree:

"Mechanical properties

The principal mechanical difference between CPVC and PVC is that CPVC is significantly more ductile, allowing greater flexure and crush resistance. Additionally, the mechanical strength of CPVC makes it a viable candidate to replace many types of metal pipe in conditions where metal's susceptibility to corrosion limits its use."

I'm by no means closed minded, I'm more than happy to review some literature that lays out contrary evidence/

 

[Demon3]

Yes, plastics behave in the opposite way in compression compared to tension. You're absolutely right, sorry. 99% of the time people are looking at tensile properties and I forgot to stop and think that underwater the sea exerts a compressive force.

Polymers like polystyrene are brittle under tension and yet perform great under compression, for example as proppants for oil exploration.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[Compositepro]

It should not be too difficult to find a paint that will adhere well to CPVC or PVC. Both are joined by solvent welding. For example the pigmented cements used on the pipe does not flake-off. PVC is naturally clear and I guess that CPVC is as well. Pipe compounds contain a lot of filler (usually calcium carbonate),and this has a lot of affect on mechanical properties, sometimes good, sometimes not.

 

[unclesyd]

You might want to try using the same material as used for the cements, just use it all over instead of on the ends. I would try different paint systems starting with a high end (high pigment} outside vinyl against this primer.

You might want to contact the company mention in this paper.

http://www.reedconstructiondata.com/documents/FS/catalogs/xxxxxx10014817xxca22026/allSm.pdf

If the above link doesn't have what you need I would also look at fire protection CPVC piping.

 

[patprimmer]

I support those who say it should be easy to paint. You just need the correct solvent based paint system.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[unclesyd]

I have learned that the paint will go without the primer just clean the pipe very well.
You might try the primer to see if will give you a more durable coating.