gluing plastic

[almudallal]

Hello
I purchased a steam engine that has a plastic piece that broke . I would want to glue it  but  I'm concerned about the glue peeling off the paint in the area around the repair site .
any idea of which glue to use without effecting the paint around the repair area

Thanks

[Doneldon]

Al-

In order to get a high quality repair you have to use an adhesive which melts the plastic parts so they are essentially welded back together. Any other kind of adhesive, like CA or epoxy, won't do the trick nearly as well and will be more likely to break again in the future. Of course melting the plastic back together risks making a mess of things and seriously damaging painted surfaces.

You shouldn't have a big problem if you closely control the amount and placement of your adhesive. You have two choices: watery liquid glue and viscous gooey glue. Gooey tube glue is easier to control but I don't think it makes as strong of a bond as the liquid products so I recommend the thin stuff. You can use a fine brush, a tiny pipette, a toothpick, two or three very small wires held tightly together or one of the special applicators made for liquid glues. I urge you not to use the nozzles found on some liquid glues or the cap-mounted brushes found in others. They are probably too large for what you need to do (something about your post leads me to believe you are looking at a small project rather that one with a large area to be glued). Which tiny applicator you use will be a function of how accessible the parts are and what you have available but any of the tools I mentioned should work. If my assumption that you are making a small repair is incorrect, the applicators supplied with your adhesive might just work great. Plan your attack -- product, applicator, holding the parts for glue application and holding them together while the glue dries -- before you open your product. Work from an angle which won't allow any excess or misdirected glue to drip on the paint or nearby plastic. Ideally, you can hold the broken parts together in their final position and let the watery glue move into the space by capillary action from a point where the adjacent paint can't be harmed.

With care and planning, you should get a strong repair without damage to the rest of your model. Good luck with this project and please let us know how it turns out.
                               -- D

[ebtnut]

Understand this, too.  There are different types of plastics and not all of them can be repaired with the common liquid cements.  Cements such as Testors are OK for styrene, but won't touch engineering plastics like Delrin.  The original Plastruct material needed its own proprietary cement as well.  I have noted that some parts of the Bachmann steam models are made from a plastic that styrene cements won't work on. 

[almudallal]

Thank you for your advice.
You are correct the project I have is very very small . It is a tiny broken part of a ladder in a tender .
The problem is that the break is flush with the top of the tender which happens to be red and the broken part is black  so that any tiny seapage of glue may ruin the red top of the tender .
If I use the watery liquid stuff you mentioned I would probably need to use a toothpick,and be very careful
Also considering what Ebtnut  mentioned about the types of plastic on the Bachmann engines , I am now considering leaving it be  and accept it as a small imperfection .

regards,

[Doneldon]

al-

You won't hurt anything by doing a tiny test on an invisible part of the tender, although I believe that solvent glues will work on Bachmann plastics. If you get a little crazing or softening, use the toothpick to put a tiny drop of the thin glue on each part of the ladder and then carefully set it in place. It will set up in a few seconds. You can also put tiny drops on both the broken ladder and the places where it attaches to the tender. Wait a couple of seconds until the solvent has almost evaporated and then install the part. That gives you a chance to slightly soften the plastic on both sides of the joint.

I advise against using viscous glue for this operation because it will squeeze out of the joint if you use too much and it won't be strong enough if you used too little. The watery solvent will get into every bit of texture on the broken ends and then weld them together.
                                                                                                                                                               -- D