Glue for plastic parts

[cats think well of me]

Hi all,

I've noticed once in awhile with some assembled models of mine, namely Red Caboose kits I'd built, plastic parts I attached with CA either fall off and can sometimes be found but more often than I'd like disappear. I've been using Zap-A-Gap CA for years as it's what my local hobby shop carried but I'd like to try something different with a less fragile bond. I love CA overall and have used it to build plastic kits for decades but I'm open to trying other adhesives. I use CA for most kit assembly, and I've used Walthers Goo for attaching weights and certain parts where I'd prefer the more flexible, less brittle bond over CA. 

Alvie

 

 

[hon30critter]

Hi Alvie,

For plastic kits I would suggest trying a plastic solvent style cement. The solvents act to weld the joint together. In other words, two pieces of plastic become one. The joints are very hard to separate.

I use Tamiya Extra Thin liquid cement. It barely leaves a trace, and a little goes a long way. Perhaps others will offer suggestions for other brands, but I will only recommend what I am familiar with.

Note that any paint on the surfaces to be joined should be removed first. Also, the best way to apply the glue is to put the two pieces together and then use a brush to apply the cement to the joint. It will flow into the joint quite nicely. Tamiya has a brush built into the lid, but I often use a larger brush when doing longer joints.

If you are joining metal to plastic then CA is your best bet. I am not sure if you are aware, but CA does have a limited life expectancy once it has been opened. I would suggest buying CA in relatively small quantities and replacing the CA every few months.

Cheers!!

Dave

 

[NHTX]

     One thing that would eliminate a lot of grief would be the identification by the manufacturers/importers as to what type of plastic was used in their product so it would be possible to use the correct cement.  All cements are not suitable for all plastics.

[doctorwayne]

I originally used Testors liquid cement for plastic, but once it was used-up, I re-filled the bottle with lacquer thinner, which worked just as well, but was a lot cheaper.  I used it for many years, until governments decided that it was a dangerous product and required the manufacturers to modify its make-up.  I would guess that it was dangerous if you spent your time sniffing the open bottle or can, or drank it, but I believe that it was a dumb move.
Based on recommendations seen here, I bought a gallon of MEK (methyl-ethyl-ketone) which does act well as a solvent-type glue for styrene, although it evapourates more quickly than did lacquer thinner, and as a result, has a shorter "working-time".  It's also a lot more expensive than lacquer thinner.

About the only time I'd use ca would be for adding metal details to plastic kits, like grabirons to freight cars.  In most of those cases, there's also a mechanical connection (holes drilled and the portion protruding into the car bent-over).

I'll sometimes use ca for joining dissimilar materials, but never to assemble plastic.

Wayne

[tstage]

Alvie,

For plastic/styrene: You want a solvent that is going to meld the two surfaces together.  I use both Testors Liquid Cement and Plastruct GP Solvent Cement when assemblying kits.  The Testors is thinner than the Plastruct so I use it on "visible" joints.  The Plastruct is more agressive and I use that on hidden joints that I want to hold well.

As Wayne stated, CA is good for adhering unlike materials such as metal to plastic.  However, CA dries hard and has poor sheer strength.  When possible I like to add a "mechanical" bond - e.g. like what Wayne shows in his photo above with the stirrups.  This ensures that the stirrup does not pull back out of and/or shift position inside the holes.

Another good adhesive worth mentioning is 100% silicone adhesive - e.g. Gorilla.  This works great on affixing metal weights inside boxcars or tank cars.  (I used to use CA for that but I had a few break off and rattle around inside the boxcar.)  It holds really well but remains flexible once it cures.  Curing time: 1 hr to touch; 24 hrs for full cure.

Tom

[cats think well of me]

Thank you for your response Tom. I've used Goo for tasks like attaching metal weights inside the floors of plastic boxcars and that always worked well. 

I'll try a variety of these thin plastic cements as I have a bunch of polystyrene kits to build up this winter (P2K, Red Caboose, IMRY) and want to go beyond just using CA and glue. CA is great for polyurethane kits. I'll also be sure to get new bottles frequently. 

Thank you again gentlemen,

Alvie

[Overmod]

Lastspikemike

I recommend you also keep CA solvent handy (literally). It doesn't have a shelf life so it is easy to keep a small supply on hand (literally). It's often described wittily such as "reverser" or the like.

I've never used anything but acetone as CA remover.  Are there now specific formulations of CA that require a different kind of "remover" to debond or remove cleanly?

(Incidentally, the ophthalmologist response to what happens if you mistake the large-size CA bottle for Visine and 'irrigate' your cornea is essentially 'anesthetic and time'.  The glue debonds spontaneously from corneal and lid-lining proteins within a few hours (and can be mechanically removed or irrigated).  The 'other' recommendation is to use erythromycin or similar antiseptic ointment, the vehicle of which helps with the debonding.  Note that the exotherm of CA as it bonds can cause corneal burns; these will need time to heal, and pose a real risk of complications like retinal detachment should they perforate.)

[MisterBeasley]

For simple plastic-to-plastic, I use Testors.  One exception is when fastening two 90 degree walls of a structure kit.  The joints are too narrow, so I usually cut a small balsa wood strip and attach both walls to that with CA.  This gives a strong joint and also prevents light leaks from inside if you illuminate the structure from the inside.

But, whatever you use, practice good glue hygiene.  Thoroughly wipe the bottle and the inside of the cap, so it will give a better seal and be easier to open the next time.  I believe CA will have a longer shelf life of it is refrigerated between uses.

[CNCharlie]

My favourite glue for plastic is Faller Expert. It also has a handy needle applicator.  

CN Charlie

[Overmod]

MisterBeasley

I believe CA will have a longer shelf life of it is refrigerated between uses.

That is true, but you must observe very strict 'humidity control' -- more than for Japanese cameras -- if you do that.

Wrap the glue very carefully in something like a plastic Baggie, preferably with one of those little desiccant packets in with it, before putting it in the fridge.  I've seen advice to 'wrap it in foil' but how much this actually cuts down on exposure to water, I don't know.  Traces of water are what usually harden CA prematurely in its container.

When you take it OUT of the fridge or freezer is the important time for discipline.  Let it come all the way up to room temperature in a DRY place -- no bathrooms, no humid air, no condensation.  If your drink shows condensation, your glue likely would, too -- and CA loves to react with water.  

[dknelson]

CNCharlie

My favourite glue for plastic is Faller Expert. It also has a handy needle applicator.  

CN Charlie 

Charlie beat me to it!  There is also Faller Super Expert (not exactly sure what the difference is) and also a Faller cement for laser cut wood kits.  It too has that needle applicator.  

Dave Nelson

[Overmod]

Lastspikemike

Not sure what to make about advice about eyelids and cornea. I mean, I am short sighted but not THAT short sighted.

It was an actual reported case.  (The description in the literature said only that the victim 'mistook' the CA bottle for one containing some sort of eye relieving potion, but there are similarities between certain commercial product packages...)

Of course, that represents about the worst possible case for introduction of CA to the eye that would be possible... so what worked there would reasonably be expected to work anywhere.

[Overmod]

Lastspikemike

The debonder stuff isn't acetone as far as I can tell. It is aggressive on model paint.

I would be worried if the stuff you have is DMF, which is a useful industrial solvent but a potent liver toxin readily absorbed through the skin as well as via lungs and GI tract.  (In all fairness OSHA calls it a 'moderate' hepatotoxin but TWA PEL is 10ppm, which is a hundredth of even the revised STEL for acetone...)

https://www.osha.gov/dts/sltc/methods/organic/org066/org066.html

A liter of the stuff runs about $100 for 99.8% pure; technical grades probably less.  Puts those little bottles in perspective.