solvent welding polycarbonate?

[Lewis]

Hi, I'm building an overarm blade guard from polycarbonate, solvent welded with a made-for-polycarbonate cement (Caseway Industrial Products SC-325). The only info on the can is "Fast setting cement for polycarbonate, medium to high bond strength."

My question is, how fast does solvent welding work? If anybody knows this stuff in partcular, that would be great. Barring that, how long in general does it take? An hour? Four? Overnight?

The first pieces went together very well, and I've got a couple of light weights on them to keep them together. It's been a couple of hours, and I'm wondering if it's safe to take the weights off and work on it some more.

Anybody any relevant experience to share? Thanks, Lewis

[Doug Miller]

It doesn't say on the can?

No experience with polycarbonate, but FWIW, when I have solvent-welded acrylic plastic (Plexiglas), it bonded within a few minutes at most.

-- Doug Miller (alphageek at milmac dot com)

How come we choose from just two people to run for president and 50 for Miss America?

[Lewis]

Doug, Thanks for the info. No, there's nothing on the can about how long to expect the bonding to take, except the phrase "fast setting." I've been giving it an hour or two between successive pieces, and that seems to be plenty of time. Lewis

[John Crea]

When I was building with polycarbonate in the past, I recall that typically it only took a short time for the "weld" to setup - a couple hours is probably more than adequate

John

[Robert Bonomi]

"Fast"

Depends on how big the joint is. the farther it is from the 'middle' of the join to 'exposed to air', the longer.

Usually, you're dealing in the range of 'minutes' to 'a few tens of minutes', at the outside.

There is usually no 'curing' involved -- when the volatiles have dissipated, the job is done.

BTW, 'pressure' to hold the joint together doesn't mean much with this type of joinery. It's like metal-welding -- holding the pieces 'fixed and immovable' in relation to each other is the critical item. "3rd hand" jigs are wonderful.

"If in doubt, _ASK_THE_MANUFACTURER_" is my experience. :) There is often a toll-free number on the container.

[charlie b]

You need "light tight" joints - no gaps to get a good "weld". It's capillary action that draws the solvnet into the joint. As insurance, after the solvent has done its work, drill holes, insert small brads acrossed the joint and put a little solvent on each. It'll go into any space between the brad and the sides of the hole, assuming the fit is good, and semi bond the polycarb to the brad.

charlie b

[Lewis]

Thanks to all! The joints were tight; a very slow feed with an 80-tooth blade on a table saw makes a nice clean edge in polycarbonate. I was just using weights to hold things in place, not to close gaps. I wetted out the edges I was joining with solvent on a Q-tip, then put the pieces together. Then I touched the joint with a sopping Q-tip and the solvent was drawn into the joint by capillary action. A syringe would probably have been neater -- I got a few runs down the plastic faces with my Q-tip method -- but this way seemed to work well. The material is 3/8 inch, and some is joined at 45 degrees, so the center of some of the joints was fairly far from the edges. Towards the end, I sped up the process and only allowed a half an hour before handling. No problems.

I'm planning to support the blade guard with PVC pipe. In a mock-up, the 3 inch and 4 inch pipe I'll be using seem to be plenty sturdy to support the guard, and they will do double duty as support and dust collection. I don't think I've ever seen an overarm blade guard support made with PVC -- it seems to me to be a natural. Maybe I'm missing something.... Time will tell! Lewis

[Clif]

Once the guard is finished, please share details and photos so we can follow your lead as our needs arise.

Clif

[Lewis]

Will do. Should be up in a few days. Lewis