Gluing 'oily' plastic

[justin1985]

I'm in the middle of detailing a Farish cl.90, and as part of the project I'm trying to attach the air dam, moulded in the 'oily' plastic of the bogie frames, onto the base of the plastic body. However, I've not had any luck! So far poly cement produced only a very brittle joint, and two-part epoxy failed to key well at all, and simply peeled away once the air dam was poked! I've just tried butanone, but it doesn't seem to be having any more luck ... any other suggestions?

 

Also, I've managed to split one of the air dams where I've tried to cut out the coupler pocket - trying to glue this plastic back to itself is even less successful! Butanone doesn't even seem to touch it when trying to glue it to itself!

 

Thanks

 

Justin

[Etched Pixels]

For attaching bogie sides I've had some luck with evostick, but if its got to be strong then drilling 0.3mm holes into the plastic and running wire through the parts is sometimes the best way (eg when attaching bogie sideframes). It also helps if you roughen up the material you are joining. PVA will also key to ABS type plastics to some extent so painting it in dilute PVA can make it easier to fix or paint (eg for Peco buffer stops)

[bertiedog]

You have found the insurmountable modelling problem, all nylons, polythene and many other related soft plastics have no practical safe solvent, and are therefore near impossible to glue together by a dissolving glue. As they resist solvents they also resist epoxy and even rubber glues, as the surface is dead smooth, and any flexing will throw off the glue.

 

Abrasion or mechanical roughening of the surface may work, or heat fusion, where a hot wire is used to melt the two surfaces and weld them. Evostick rubber adhesive may bond soft plastic, if it can get a grip to a roughened surface. Larger soft plastic items may respond to a hot glue gun, but this is not suitable for small delicate parts.

 

PVC plastic is a bit different, solvent glues exist along with strong rubber cements, most commonly used for plumbing joints. Flexible PVC can be joined as can butyl rubber with strong glues

 

Polystyrene and ABS have no issues, they glue and fuse well with solvents as does acrylic, perspex, and polycarbonate sheet.

 

PTFE (Teflon), is near impossible to join, do not use heat it generates a poisonous gas. Solvents exist, but are very noxious indeed and confined to factory and lab uses.

 

hope this helps,

 

Stephen.

[hollywoodfoundry]

These days it is most likely that the bogie side frames have been moulded in Acetal, the generic name for Delrin (a DuPont product). Alledgedly there is a Loktite adhesive that they claim will bond Acetal, and there is also an American glue whose makers claim will bond Delrin, but I cannot remember the name. Try Googling 'bonding delrin', it produces quite a lot of results.

[bertiedog]

These days it is most likely that the bogie side frames have been moulded in Acetal, the generic name for Delrin (a DuPont product). Alledgedly there is a Loktite adhesive that they claim will bond Acetal, and there is also an American glue whose makers claim will bond Delrin, but I cannot remember the name. Try Googling 'bonding delrin', it produces quite a lot of results.

 

The Acetal adhesives are well known, but may not be approved for home use in the EEC or UK, Bondit make several grades, but cost and toxicity issues make it an industrial process.

 

We used special glues for nylon and other difficult plastics in lab equipment we made, but this was in full protective clothing, with air respirators supplied with positive pressure air!! The stuff is based on super strong acids for nylon, and acetal requires similar acids, but in a lower strength, but still pretty lethal.

 

Very careful degreasing and abrading of the surface is still required, and also the surplus "glue" has to be safely neutralised after the joint is made.

 

The Loctite glue will work with "stiff" grades of Delrin, and "loaded" versions, where additives and fillers are contained in the plastic to give it a hard structure. The grades used for mouldings on model railways are far too soft to work with it.

 

The Loctite Delrin Glue depends on a mechanical joint, like a plug into a machined hole, the Loctite acts as a filler, and locks the plug into place. Butt joints do not work with the Loctite, only mechanical aided joints.

 

In the same way, thick grade Superglues will work with a plug joint in Acetal plastic, acting as the filler.

 

Hope this helps outline all the problems, far to much information for simple model problems, but it is best to know the background to save wasting time trying to find glues that do not work as expected or are very costly.

 

Stephen..

[justin1985]

Many thanks for the replies!

 

I think I'll just get a replacement air dam from BR Lines for the split one, and then experiment with the "plug and socket" approach using small holes and wire, as suggested by etched pixels.

 

Justin

[Butler Henderson]

I've found Evo-Stik Serious Glue to work on a number of awkward plastics icluding those used by Sanda Kan

[mikes rail]

for oily plasic parts try AC77 primer it comes in a small jar and you just brush a little on each part before gluing. I got mine from Rapid electroncesa couple of years back

[grahame]

I've successfully glued on air dams/valances and bogies side frames (in N gauge) using superglue (the type with rubber in to give a slightly flexible bond) and roughing up the joining surfaces with a file first. For additional strength pinning with a hole drilled through and length of wire or track pin with head cut off (as already suggested) does help.

 

G.

[Mike Bellamy]

there is also an American glue whose makers claim will bond Delrin, but I cannot remember the name.

Geoff

 

You may be thinking of 'Dr Mike's' glue which is imported into UK by Paul Martin of EDM Models. Details on the NGTrains website here http://www.ngtrains.com/Pages/EDM_Models/Dr_Mikes/dr_mikes_glue.htm

 

The manufacturer's web site is here http://www.drmikesglue.com/index.html Sold in USA through Micromark http://www.micromark.com/Dr-Mikes-Formula-2-Glue-1and2-fl-oz,8534.html

 

Mike

[hollywoodfoundry]

Yes Mike, that's the one I was thinking of.

[bertiedog]

Some extra notes, I am not trying to tread on peoples recommendations, If you get it to work for you that's perfect, but it should be pointed out that the Cyno glues generally are suitable for Acetal plastic, it is not just the Dr Mike brand that will work. Set Cyano is a form of Acetal plastic anyway.

 

Acetal, if rigid enough will bond with both itself and metal like brass, quite well, the type of joint is an air exclusion one, where there is no molecular bond of any type, the bond is achieved by extremely intimate contact with the glue acting as a barrier filler, stopping the joint opening.

 

However all joints like these depend on the barrier trying to remain in place, and flexing of any type may open the contact and allow air in which breaks the bond. This why a mechanical joint, aided by glue is so much better.

 

The classic air exclusion bond is with engineering slip gauges, where the finish is so fine and flat that two slips may be "wrung" together, and remain firmly in contact without any adhesive.

 

The same action is achieved in a glue, by the same air exclusion, even when the surfaces are polished, as with two plastic moulded surfaces, or a metal to plastic surface, and this is what DrMike and all other cyano makers achieve, a good way of getting a joint, but if the surfaces flex , then the joint is broken.

 

A rubber adhesive works in the same way, adding the natural stickiness of the product, which is due to very intimate contact with the material surface.

 

It can flex and this is why they appear to bond plastics on larger joint areas.

 

Epoxy glues are air exclusion and "grip" glues, they also flex, and are the most tenacious, but fail on surfaces like polished resistant plastic, as they are more rigid than the surfaces, which flex and loose grip.

 

The final glues are solvents that dissolve the surfaces causing a molecular bond, like polystyrene and Mek for instance, and special solvents do exist for nylon and Delrin etc.

 

Delrin in particular is easier than other plastics with chemical resistance, ir responds to acids and is offered in filled varieties that are rigid and therefore glue better.

 

Unfortunately in Model Railway use the makers prefer to go for flexibility to try to help prevent breakage of small parts, and typically brakes and pipes are made of acetal plastic or nylons. Where broken or modified by cutting these simply will not glue, even with Dr Mikes glue, when a butt joint so small is involved.

 

The Dr Mikes product is good quality Cyano, but I do query some of the claims to high purity and ability to work better than other makers, they claim other makers add water, (impossible) or filler, (quite possible), which they equate to trying to down grade the other makers glues to make them inferior to their product..

 

I am not offering any personal chemical expertise on this, but can offer advice given to me by my uncle who was a top BP chemist who manufactured Cyano etc., and had a lifetime experience in plastic manufacture.

 

The Dr Mikes glue is unusually pure, but so is Loctite (brand) Henkel, Dupont, and IS etc., and all other branded Superglues will act in a similar manner to the Dr Mikes by their very nature, they form an acetal, (perspex) layer after chemical conversion by the action of oxygen, (wild simplification!).

 

Don't confuse with air exclusion setting glues like Loctite fastening compound, these are not superglues, they work in a different way, but are used as glues as well, and have the same failings as superglues on soft plastic.

 

So in the end there is no special glue for soft plastic, there are special ways of doing the joints, and there are some glues which work better than others!!!...and Dr Mikes does work well, but in my own experience so does any other superglue of repute.

 

For tiny part repairs like brakes on RTR locos etc, there is no better simple way than drilling the ends with a fine drill and adding brass wire into the holes, (interference fit), and adding a dab of superglue to help secure it.

 

Other than that a heated wire that melts both surfaces and fuses them, is the only permanent unbreakable join achievable.

 

Hope this helps clarify, it's the technique, not the actual product that helps with soft plastics,

Stephen.

[Re6/6]

Continuing on this thread....

 

...does anybody know definitively what the 'greasy' plastic in the current Hornby undergear is made from?

 

It has been suggested on here that it is 'Acetal'. Any confirmation of this please? I'm still in search of that elusive adhesive.

[brian777999]

I am in the process of fixing some Kadees to the underside of some old Hornby wagons. These wagons seem to be made of that same 'greasy' black plastic. I have tried the usual Revell polystyrene glue, superglue and Araldite but none of them will hold. I often use an M2 socket cap on vans where the screw and nut will not show on the inside of the van but these wagons or Lowfits and it cannot be hidden. There must be some sort of glue that will hold. What is the actual plastic they used on those old Hornby underframes ?

 

NOTE : I live in Australia. I am thinking of trying Loctite plastics bonding system. Has anybody tried that yet ?

 

https://www.loctiteproducts.com/en/products/fix/super-glue/loctite_plasticsbondingsystem.html

Edited August 21, 2020 by brian777999

[justin1985]

I remember a tip from @CF MRC, I think, to use a soldering iron tip to slightly melt some paper or similar with a weave texture into engineering plastic, to help it provide a key for normal glues like epoxies. I haven't actually had call to try it since, but Tim might be able to confirm? 

[ejstubbs]

I've used canopy glue with some success to bond plastics that aren't susceptible to solvent-type cements.  For example, glueing Kadee whisker coupling gear boxes in to modified Airfix coach bogies (which I think are made of a similar sort of plastic to the Hornby underframes you describe:

 

[brian777999]

Thanks for the tip. I already have a bottle of that which I had forgotten about. I will give it a go today. I also tried PLASTIC MAGIC yesterday but it is useless. Anybody thinking of trying that can save their money. It won't even glue styrene to styrene !

 

 

 

[kevinlms]

3 hours ago, brian777999 said:

Thanks for the tip. I already have a bottle of that which I had forgotten about. I will give it a go today. I also tried PLASTIC MAGIC yesterday but it is useless. Anybody thinking of trying that can save their money. It won't even glue styrene to styrene !

 

 

 

Have you tried this one, allegedly sticks those slippery plastics, such as Polyethylene (PE) and Polypropylene (PP)

 

https://www.selleys.com.au/products/adhesives/minor-repairs/selleys-all-plastic-fix/

 

And this one being a 2 part version

 

https://www.loctite-consumer.com.au/en/products/superglue-all-plastics.html

 

Can't say I've tried either product, so hope they don't waste your money!

[GWR-fan]

I believe the word "bond" is significant in describing a glues success in joining two difficult to attach plastics.  To me,   bond implies intermollecular attachment giving a superior strength to the join.  I really cannot see how a manufacturer can use the term when in all probability there is no chemical interactions at the join surface.  I think a more appropriate term is "stick",  as no doubt a join is made but it has no real strength and subject to failure when stress is applied to the join.   When joining styrene type plastics a solvent is used to "weld" the pieces together.  I used to use a plumbers priming liquid (about 60% acetone) to join ABS plastics when doing a lot of modification to LGB locomotives and rolling stock.  This was far less expensive than using proprietary ABS glues such as from Plastruct,   which are predominantly acetone anyway.

 

Several years ago when building radio control fast electric boats with some made from ABS type plastics,   I used an expensive West System epoxy glue that was also suitable for bonding polyethylene type plastics.  To use on slippery plastics,   the polyethylene surface needed to be sanded with a very coarse 80 plus grit paper and the plastic surfaces to be joined  "burned" with a blow torch.  This gave a superior bond but no doubt the process would be totally unsuited to model trains.  The advertising with the product demonstrated a polyethylene kayak/canoe being sawn in half with a chainsaw,  The surface was prepared and the epoxy applied.  The canoe was then thrown from a bridge and having survived the fall was then used.  If it takes so much trouble to join these slippery plastics then I fail to see how a glue as referenced could successfully "bond" a surface.  Any join would be temporary and not subject to stress of any kind.

[brian777999]

5 hours ago, kevinlms said:

Have you tried this one, allegedly sticks those slippery plastics, such as Polyethylene (PE) and Polypropylene (PP)

 

https://www.selleys.com.au/products/adhesives/minor-repairs/selleys-all-plastic-fix/

 

And this one being a 2 part version

 

https://www.loctite-consumer.com.au/en/products/superglue-all-plastics.html

 

Can't say I've tried either product, so hope they don't waste your money!

 

I have not seen the Selleys product before but I will take note of it. The Loctite version (available from Bunnings) is my next choice if the canopy glue does not work as suggested above. 

 

Update : the canopy glue seems to be holding quite well. I will leave it overnight and test it again tomorrow.

[brian777999]

The canopy glue is excellent ; glued items can be removed but you need pliers to twist and pull to do it. That should be good enough to hold Kadees in place. I have started using this glue for other things too.