SolarInterested provided a link to this documentation, but for ease of access, I'll just go ahead and paste it here:
With Coroplast’s very high wetted surface area and melting point all the way up over 320F, if we can find a good way to bond it, water tight, to CPVC, we could really have a great breakthrough in DIY solar! In addition, it would make for a very easy build and extremely inexpensive too. A 4 foot by 8 foot sheet of Coroplast can be obtained from your local sign shop for $15 or less! Coroplast can not only be used in collectors, but as heat exchangers in a thermal storage tank, as well as for heat distribution in your living space.
So, how do we bond Coroplast (polypropylene) to CPVC? We have one definite option, DP8005, that Mike in Texas has proven to work well in his collector. The only problem is that DP8005 requires an applicator, so the startup cost is higher. That’s okay if you are building a large array of multiple panels, but for the guy who is only building one or two panels, the cost is a bit of a hurdle. Besides, we would all like to do this as inexpensively as possible without compromising on reliability. So, here are the options that I am aware of so far and my thoughts on them:
If you want to get started now with a proven, reliable option, this is it! Here is what you will need:
3M Scotch-Weld DP8005 Acrylic Adhesive
Adhesive for DP8005 to attach coroplast to PVC, CPVC, etc.
3M Scotch-Weld EPX Plus II 10:1 Mixing Nozzle
Mixing nozzle for DP8005 to attach coroplast to PVC, CPVC, etc.
3M Scotch-Weld EPX Plus II 10:1 Plunger
Plunger for DP8005 to attach coroplast to PVC, CPVC, etc.
3M Scotch-Weld EPX Plus II Applicator
Applicator for DP8005 to attach coroplast to PVC, CPVC, etc.
Good to 212F, the only concern here is cost. With the applicator, etc., a little over $100 for startup.
Here are other options, some of which are just starting to be tested, but may work well and be less expensive:
Amazing Goop (Marine is mentioned often but all flavors seem to look good in early testing)
This is the product that is recommended by another fellow (not a Simply Solar member) who is building Coroplast collectors:
(We came up with an easier way to build than what he is doing: http://groups.yahoo.com/group/SimplySolar/photos/album/1626274866/pic/list)
Concern: Service temp limited to 150F - update - Fritz tried all four flavors of Goop. They adhered well. He then boiled them for 15 minutes and they continued to adhere!
I tried this (All purpose Goop) and it looks promising. Even though the TDS says not for PP, it adheared well and held up well with a small test in a stagnated collector.
Giving the coroplast area to be glued a light sanding is helpful. Also, try putting water on the coroplast. If it beads, rub the area to be glued with ammonia.
I'm trying this option now in my collector with two, 4' X 8' absorbers. I was generous with the glue, it took almost two, 3.7 oz tubes for each absorber. The tubes are less than $5 each, so that's fine.
Permatex 97 Super High Tack Gasket Sealant.
Scott L. highly recommended this option in his testing. Scott writes:
"I glued Coroplast to ABS black plastic and heated on the wood stove right up to boiling for many hours and the one that worked best was the 97. To peel it apart was hard work. I then made a 6" ABS header with a slot in it and glued a short piece of Coroplast in it and plugged the flutes or channels in the other end. I capped both ends of the ABS. One cap had a T with a pressure gage and a tire type air valve installed so I could add pressure.
I added up to 20lbs of air over a couple of hours at 185*F water on the stove with no problems. I even let it boil over night. The Abs did soften a bit but held its shape. The Coroplast felt the same and did not bulge or deform."
This product is good to 500F. Here is the technical data sheet:
Polymer Bonding Kits
For bonding polyethylene, polypropylene, polyurethane, nylon, polyester, UHMW's, HDPE's, UHMWPE's, Teflon®, Delrin®, silicon, Mylar®, etc.
Doug called tech help and described what we are trying to do, and was told that any of the kits for bonding polymers will work. I don't know how far 1 oz will go, but it sounds like it will make a good bond. Doug
TAP Poly-Weld Adhesive
This adhesive is made for bonding to Coroplast and other plastics. It is $13.95 a tube but does not need any applicator.
It is designed to glue PP, pvc, ABS and other plastics. It has a temperature range of -40*F to 200*F. It does require a flame treatment to the PP which is very easy to do. Try it on a scrap piece and you will find out how tough PP is.
3M™ Scotch-Weld™ High Performance Industrial Plastic Adhesive 4693H Clear, 5 oz tube
$13.05 for a 5 oz tube. Most importantly:
A clear, elastomeric adhesive with exceptional adhesion to metal and plastic. This adhesive is unique in its ability to bond hard-to-hold materials like polypropylene, polyethylene, and high-impact polystyrene.
Concerns: Only good to 160F, Heat Reactivation: Adhesive may be heat reactivated by raising the glueline temperature to 180°F.
Here is another coroplast to CPVC recommendation, this time from On-Hand Adhesives, Inc. (http://www.gluguru.com).
We would suggest Loctite 401 with 770 primer for the application, as it will be difficult to bond the PP. Try 20g bottle of Loctite 401, #40140 And 1.75 fl oz bottle of Loctite 770 primer # 18396.
Here is the spec sheet on the 401. High temp is 180*F which could be a problem. The other issue I see with it is the short time you have to get your materials in position before they stick. This says 15 seconds but I read elsewhere that it is 3 to 10 seconds. The cost of this and the primer may be more than the Tap glue that are designed for PP.
Price and quantity are good. Bill Jeffries did this YouTube video showing King Kaulk to stay bonded to CPVC at over 20 PSI, which is four times the pressure we may need.
Concerns: According to their Technical Data Sheet (TDS), King Kaulk is not recommended for PP (polypropylene).
If you look at the bottom of this sheet, it says not for polypropylene.
A simple hot glue gun is an interesting alternative (not the cooler type of hot glue gun that melts at 250F, but the hotter gun that melts at 380F). Many glue sticks are made from polypropylene themselves, so maybe this would work well. It likely dries too quickly for the inside fillets, but could be an option for the outside bead. There are a variety of different glue sticks for different materials.
There are many additional hot melt glues designed for polypropylene summarized at the bottom that will likely adhere better to PP, but none of those fit in a conventional, less than $10, hot melt glue gun. This option does fit in an inexpensive, "off the shelf" gun. (Just make sure you use a 380F, hot melt gun, not the cooler, 250F variety).
* Stanley Super Strength Hot Melt Glue Stick (GS500)
Hot Melt Glue Stick, Super Strength, 0.45 In, Length 4 In, Temp Range 0 to 356 F, For Wood, Plastic, Metal, Jewerly, Fabrics, Paper And Foam
It is only $2.86 with free shipping here:
In preliminary testing, it appears to adhere well. Since it dries quickly, it can not be easily applied to the interior of the pipe, but a good option might be to use Goop on the interior and this glue on the exterior. With a hot melt glue gun, it is very easy to put this glue right where you want it.
* Ad Tech, #186.
With a melting point of 315F and designed for polypropylene, this looks very promising: http://www.adhesivetech.com/industrial-services/adhesives-detail.cfm?CID=110
Here is the TDS: http://www.adhesivetech.com/pdf/ProductTechSpecsPDF-231.pdf
Thank you for taking the time to contact us. Our chemist has reviewed your inquiry and does suggest our formula 186 for your application. If you are willing to respond with your location we would be happy to refer you to a distributor in your area. Regards,
This item (186) is a bulk adhesive sold in pellet form and requires a bulk machine to use effectively. It is not available in stick form. You can obtain pricing and availability through the following distributor. Red Hill Corp 717-337-3038
* HS-325 High Performance Glue Sticks
The heat resistance is only 165*F but you can buy them for $5.56 per pound and they fit a standard 7/16" gun.
I tried HS-325, it bonded well, but melted in a stagnated collector.
* Here is a chart showing some 3M alternatvies that include polypropylene:
As we continue to explore options for bonding coroplast to CPVC, I wrote the following to 3M. Note that while I asked about CPVC, their response cited PVC:
I wish to bond coroplast (polypropylene) to CPVC. The service temperature will range from 0F to 220F. I have two questions regarding:
3M™ Scotch-Weld™ Hot Melt Adhesive 3731
1. Would you recommend this product, or can you suggest another alternative?
2. I don't need an entire, 11 pound box. Where can I purchase this product in a smaller quantity?
Thanks in advance for your prompt response.
In order to bond PVC to Polypropylene, you could use 3796. We do not sell this product, or any of our other products in smaller quantities. Sorry.
3M's Follow up:
CPVC and PVC are in the same family, and the problem with this family is the PVC as they both contain plasticizers that will attack the bond line if you don't use the proper adhesive. 3796 is the only adhesive that will work for your application.
My Note - The chart above seems to indicate that several of these will adhere well to PVC, so I'm not sure 3796 is the only option.
Most sales are by the case, but I did find an outlet that sells this by the pound, with a 2 lb minimum at $49.11 per pound.
* Another hot glue option is item 6009 on this page: http://www.gluguru.com/Hot%20Melts.htm
Here is the technical data sheet: http://tds.loctite.com/tds5/docs/HYSHM6009-EN.PDF
So, that is where we are. Some of the options above have not even been tested yet. We've found the published specs are not always reilable in either direction (some glues work in much hotter conditions than the specs indicate), so even if the spec temps look low, give it a try. We are always looking for more options. If you have a suggestion, please chime in!