Plastic repairs?

[inflex]

Not an electronics question obviously, but I get a lot of machines that could do with some plastic repairs. The biggest fault tends to be mount-points snapping off at the base or splits appearing along stress risers.

[inflex]

Re: Plastic repairs?

Ended up using an old trick from my R/C aircraft building days - used CA/superglue and then dusted it with bicarb to turn it to rock hard filler. Downside is that it's rather brittle but it does hold quite strong.

There was enough of the old post still left for me to place the brass inset; an oiled screw inserted let me keep it aligned right and then I glued/dusted it a few times till I had built up enough material. The oiled screw prevents the glue locking the thread.

[LDSisHere]

Re: Plastic repairs?

That is an interesting idea for repairing plastic. How much bicarb (baking soda?) do you use and how long do you wait between layers? Some laptops just have a lot of flex do to poor design / materials, how would this method hold up in such an application since you mention it is brittle? What are the advantages and disadvantages of this method compared to using epoxy? Sorry for all the questions but they make prevent me form making a big mess experimenting.

[inflex]

Re: Plastic repairs?

If you put the CA down first, then just drop a pinch of bicarb over it to fully cover the area, then about 5 seconds later blow away the excess or tip it out. WARNING: it will get quite hot, so don't get your finger on the join

As for flexy situations, so long as the area you're gluing isn't too large it should be okay. On the model aircraft (balsa/fiberglass) there'd be quite a lot of flex but the joins held up okay.

Compared to epoxy;
PRO: cheaper, faster, harder, better adhesion (at least what I've found)
CON: brittle, requires layers if you want to build up bulk

[LDSisHere]

Re: Plastic repairs?

Thanks for the fast response. I will have to give this a shot in the future and see how it works for me. I just hope I am not too messy, I could see this easily going from rescue to disaster in one quick oops.

[inflex]

Re: Plastic repairs?

Practice on some older chassis perhaps? Because of the low viscosity of most super-glues (unless you get the gel ones), it's better to reposition the parts into their right place -before- applying the glue + bicarb. Also, you don't have to rush, a drop of superglue will stay liquid for quite some time on plastic surfaces like laptop cases (though it'll set near instantly once the bicarb is applied).

[ecking767]

Re: Plastic repairs?

I use this product from Loctite call Plastics Bonding System Model # 681925

You can buy it at your local hardware store. Its work for me and its hold very strong

[LDSisHere]

Re: Plastic repairs?

I use this product from Loctite call Plastics Bonding System Model # 681925

You can buy it at your local hardware store. Its work for me and its hold very strong

I never knew they made such a product, excellent find. Apparently my local Home Depot carries this for $3.77. Looks like something to keep around because you are going to need it eventually.

Inflex's method could be applied to mixed materials, items that are not plastic that the Loctite system would not be a suitable bonding agent, or used if you have the supplies on hand and the store is closed. I am sure I will be making use of this information in the very near future.

[inflex]

Re: Plastic repairs?

Wish I could get that loctite system as cheap here. They want $25 !!!

[inflex]

Re: Plastic repairs?

Aaah, I was looking at the wrong number - anyhow, that "activator" they have with the superglue in the Loctite 681925, it's basically the same as what bicarb is doing.

[pfrcom]

Re: Plastic repairs?

Wish I could get that loctite system as cheap here. They want $25 !!!

There's Selleys Plastics Glue which looks similar

http://www.selleys.com.au/adhesives/.../plastics-glue

IIRC it was around the $8 mark from Bunnings

Didn't work well enough for me, that I'd buy it again

[inflex]

Re: Plastic repairs?

Very interesting - haven't seen that one at the local shops (but this is a small country town). Looks like they're all CA+activator combos, so for now I guess I'll be sticking with my CA+bicarb and then JB-Weld for super-serious situation, or at times I'll fabricate replacement parts out of polybeads.

[inflex]

Re: Plastic repairs?

Another job I did last night. Not quite sure how the client managed to break the primary mount post on the back-housing of the LCD, but they did.

Anyhow, a few layers of CA+bicarb has done the trick again.

[lti]

Re: Plastic repairs?

I have done a lot of plastic repairs with JB Weld. The hinges on my old Gateway laptop are held in with nothing but JB Weld because the piece of plastic that the hinges are attached to (the housing around the display - Gateway calls this the "top lid") is not available. Even if I could get a replacement top lid, there isn't much plastic around the metal inserts.

[inflex]

Re: Plastic repairs?

Lti, I use JB-Weld if the CA-Bicarb option fails. Mostly because of costs and that it takes a few hours before I can use the repair.

I do love JB-Weld, great stuff, at least half a tube holding my car engine together in some places