plastic epoxy recommendations

RodneyWright · **Posted:** Wed Jun 07, 2006 5:33 pm

OK, here's one for you.... I have rescued a very nice open fabric Herman Miller chair that was being used in the monitoring center and was going to be tossed in the dumpster. The seat frame is cracked, but otherwise in very good shape and all the controls work. I've contacted HM, but I'm getting resistance to warrenty work on the chair since I was not the original purchaser, but I'm not giving up yet.

All that aside, what would you recommend for an epoxy to fix the seat frame. It's a sharp angle tear that actually left plenty of contact patch for a glue surface. It's also an irregular tear and left an uneven surface, which I think is great because it's not smooth and flat, lot's of hills and valleys in the tear area. The seat frame also looks to be and injection molded plastic and very hard.

I figure I have one shot at making this work if HM doesn't cover the repair. I've played w/ some of the epoxy mixes from Lowes, but most fail and don't hold up to their advertised results. Any recommendations out there?

thanks

Bernie Baake · **Posted:** Wed Jun 07, 2006 6:55 pm

Rodney,
I don't know what will stick to your chair I'm not familar with epoxying plastics. What I am familar with however is the polyester resins and pseudo epoxies that will stick to nothing but themselves. West Marine sells West system epoxy resin. A true epoxy, and this is the stuff boat builders use to repair fiberglass hulls when they're fractured or holed. Epoxy resin costs about four times as much as polyester resin and holds twenty times better.

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Can you post a pic? Is it in a highly load-bearing area like the bottom? A patch would be uglier but probably stronger -- if it's on the underside of the frame bolt a piece of aluminum or steel to it.

If it's not in a highly stressed area (like the back) then probably any old epoxy will do. I have tried a few of the specific "plastic epoxies" from various places with good results. They stick to smooth plastic better.

Also if there wasn't much plastic deformation at the fracture and the pieces fit together really tightly then superglue might work too.

Last crazy thought -- if it's a thermoplastic composite (if it was injection molded it's more than likely thermoplastic and not thermoset) and you want a really pretty repair you could somehow put the frame in a jig, maybe make a plaster mold of the broken section, then apply some heat tape and reflow the plastic

Rick Butters · **Posted:** Wed Jun 07, 2006 9:00 pm

Mike is asking the right questions -
What is the material?
Where is the broken part (load bearing, cosmetic only, etc)?

If the plastic is a thermoplastic, I would not recommend using an epoxy. An acrylic adhesive would be a better choice.

If the material is a thermoset plastic (less likely), you can use an epoxy, acrylic, or a urethane adhesive.

RodneyWright · **Posted:** Wed Jun 07, 2006 10:29 pm

here are pics of the chair and broken area. It is load bearing and quite large, but that may be a good thing. I don't know specifically what the materal is. There is no forward support past the break, so it's basically cantilevered forward past the shear point....lot's of stress here....

I appreciate everyones feedback so far....

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Rick Butters wrote:

Mike is asking the right questions -
What is the material?
Where is the broken part (load bearing, cosmetic only, etc)?

If the plastic is a thermoplastic, I would not recommend using an epoxy. An acrylic adhesive would be a better choice.

If the material is a thermoset plastic (less likely), you can use an epoxy, acrylic, or a urethane adhesive.

Hey Rick - not familiar specifically with acrylic adhesives -- is there anything avaulable off-the-shelf? Or something I already have in my glue drawer? Do you know what the solvent base usually is for acrylic adhesives? I'm also starting to wonder what "kind" of glue superglue is.

Rodney - that's a "tough break" and I'm not sure how I'd handle it. My first thought would be to use some black drywall screws on the back section where it is relatively flat (I'd drill a large hole though the first section and a small pilot hole though the back part), in combination with the "perfect" adhesive on the side piece, whatever that may be. But again my gut tells me that adhesive alone won't get the job done unless you can find a way to mechanically augment the repair. But I could be wrong!

Anyways it is an interesting repair. If you're into that kind of thing (as I am, as strange as that may be:) )

Rick Butters · **Posted:** Thu Jun 08, 2006 8:17 am

Rodney and Mike-

I'm not an adhesive expert (and I don't play one on TV), but my former employer is. See http://www.lord.com/Default.aspx?tabid=1159

Super glue is a type of acrylic resin (cyanoacrylate), but has very different properties from these two part acrylic adhesives.

Chris Brown · **Posted:** Thu Jun 08, 2006 8:26 am

Kim Reed · **Posted:** Thu Jun 08, 2006 9:14 am

If it was my chair to repair I would try and put a couple of small metal pins ( nails with heads off) in the break to help align the two pieces and give it some strength. Then I would use fibre glass tape and resin to hold the section together and add more strength to it.

RodneyWright · **Posted:** Thu Jun 08, 2006 10:37 am

Kim Reed wrote:

If it was my chair to repair I would try and put a couple of small metal pins ( nails with heads off) in the break to help align the two pieces and give it some strength. Then I would use fibre glass tape and resin to hold the section together and add more strength to it.

That actually brings up something I was thinking about. Can I use the fiberglass epoxy resin without the fiberglass and repair the chair? I know I used a simple fiberglass repair kit on canoe about 3 years ago and it's still in good shape. I think I may try that route.

And as a side note, I got hold of Herman Miller corporate and they have agreed to replace the seat frame bottom. It's a simple replacement and they don't want the old seat frame back. Once I have the new frame in place I'll try the repair on the old frame for those "just in case the replacement fails" issues.

You have to like a company that stands behind their product!!

Bernie Baake · **Posted:** Thu Jun 08, 2006 11:57 am

Rodney, epoxy resin used alone is not a strong bond, its very brittle and fractures easily, its the glass fibers in the cloth and the micro fibers in other mixing agents that give the strength to the repair. As I said West marine is a good place to start not only for the products but for instuctions on how to use the epoxies.

Chuck Frank · **Posted:** Thu Jun 08, 2006 1:39 pm

Epoxies seldom work on plastics, especially flexible plastics, same with the superglues. Unless it is actually fiberglass (identifiable by the fibers sticking out of the break) don't waste your time or money trying to use an epoxy or superglue type product. Each type of plastic requires a specific adhesive or hot melt system and some are just plain ungluable. Composits may require the use of two different systems to bond the core and the surface layers. You might ask HM what kind of plastic they use If its ABS or PVC you can use the glue they sell in the plumbing dept for those specific type of pipes. With all the manufacturers using plastic bumper covers and other plastic body parts today, better research, understanding and materials are coming out to deal with repairing them. Harbor freight sells a plastic repair kit for repairing various commonly used automobile plastics and instructions on how to determine what type plastic you are working with, but they are pretty pricey, and still no guarantee anything in there will work for this particular repair.

Todd Breakey · **Posted:** Thu Jun 08, 2006 3:13 pm

Chris Brown wrote:

Good call, but I was thinking...

It fixes EVERYTHING!!!

Richard Casto · **Posted:** Thu Jun 08, 2006 4:45 pm

Todd Breakey wrote:

Chris Brown wrote:

Good call, but I was thinking...

It fixes EVERYTHING!!!

Except for that leak on my exhaust manifold. Burning JB Weld sure does stink! :oops:

RodneyWright · **Posted:** Thu Jun 22, 2006 10:59 pm

well, good news for me I guess. HM came through and I just receive the replacement chair seat frame. Nothing like getting a $700 chair for free. I do appreciate all the comments on glue and epoxies. Good to know we have some chemists on board here :lol:

THSCC Forums

plastic epoxy recommendations

Who is online