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What makes a stronger bond between large parts?

CA Liquid Glue or Micro Weld

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#16 D Bellis

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Posted 21 January 2018 - 01:59 PM

MEK (Methyl Ethyl Ketone, or "Butanone") is the main ingredient in most hobby grade Liquid Cements. The pre-packaged cements also include fillers, scents and/or retarders that generally do not improve its plastic-welding properties. 

 

I have been using MEK exclusively for plastic-plastic joints for at least 2 decades. A pint (570 ml) can of MEK is about the same price as a 1 oz. (29 ml) bottle labeled "Liquid Cement", and works FAR better. 

 

Apparently MEK is also antifreeze, so I am llead to believe.

Antifreeze is not one of the common uses for MEK, nor is that use listed on any MEK data sheets.

 

D


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#17 Gigant

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Posted 21 January 2018 - 04:14 PM

MEK (Methyl Ethyl Ketone, or "Butanone") is the main ingredient in most hobby grade Liquid Cements. The pre-packaged cements also include fillers, scents and/or retarders that generally do not improve its plastic-welding properties. 

 

I have been using MEK exclusively for plastic-plastic joints for at least 2 decades. A pint (570 ml) can of MEK is about the same price as a 1 oz. (29 ml) bottle labeled "Liquid Cement", and works FAR better. 

 

Antifreeze is not one of the common uses for MEK, nor is that use listed on any MEK data sheets.

 

D

 

My personal issues with any/all forms of solvent-only (runny) cement are:

 

  1. Control. This goes both for liquid CNA and/or plastic softening/welding solvents. If I so much as blink, they run all over the place, usually away from the surfaces to be joined. Testors Non-Toxic gives me time and control, as does the Loctite CNA Control Gel.
  2. Thin/flimsy fuselage and wing halves. Simply put, unlike home-made sprue-glue or typical tube cement that adds dissolved material, the solvent-only stuff doesn't add any thickness or body to a joint. I found it works OK like for old Monogram or Aurora kits with thick, rigid plastic joining surfaces, but useless for the newer more flexible, "thin-lipped" surfaces.
  3. I have found out it is best to limit them to spot-gluing rigging with CNA, maybe a hairline joint seam gap that can be clamped closed after applying a solvent like Testors liquid or Plastic Welder, etc., to avoid a using a lot of putty, etc.

For larger gaps I use my Testors tube-glue, clamp the halves together, wipe off the excess (remember, the Non-Toxic will not damage surfaces right away), and let it set.


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:innocent: Tom

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#18 TimHepplestone

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Posted 21 January 2018 - 04:44 PM

if I’m really worried I use 5 min epoxy resin. Apply, clamp the parts , wipe of any excess on the external surfaces. Worked for me well on Revells 1/350 Enterprise. The mating surfaces on this kit were very thin and I had packed it full of wires for lighting. Result was the seams split a week after gluing. 5 min epoxy solved the problem. Only problem is when fully cured its bloody hard to sand.
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#19 1to1scale

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Posted 21 January 2018 - 04:46 PM

I have used and still use Tamiya green top extra thin for most things, and keep the thicker orange top Tamiya for when I need more time or for stronger joints. Up until now I have never had an issue with either, but I am noticing that the Hobbycraft Mustang is very slow to dry with extra thin, I may try to experiment with sprues and some ABS type PlasticWeld glue. And for when I need a super strong glue, I always have some extra thin styrene mix. Of course I have an assortment of CA glues and kickers, but I stay away from those for large joins, mainly I use them for PE or resin. And finally I have a few tubes of a/b epoxy, but I have always hated that smell.

Edited by 1to1scale, 21 January 2018 - 04:47 PM.

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#20 Mark_C

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Posted 21 January 2018 - 05:34 PM

My personal issues with any/all forms of solvent-only (runny) cement are:

 

  1. Control. This goes both for liquid CNA and/or plastic softening/welding solvents. If I so much as blink, they run all over the place, usually away from the surfaces to be joined. Testors Non-Toxic gives me time and control, as does the Loctite CNA Control Gel.
  2. Thin/flimsy fuselage and wing halves. Simply put, unlike home-made sprue-glue or typical tube cement that adds dissolved material, the solvent-only stuff doesn't add any thickness or body to a joint. I found it works OK like for old Monogram or Aurora kits with thick, rigid plastic joining surfaces, but useless for the newer more flexible, "thin-lipped" surfaces.
  3. I have found out it is best to limit them to spot-gluing rigging with CNA, maybe a hairline joint seam gap that can be clamped closed after applying a solvent like Testors liquid or Plastic Welder, etc., to avoid a using a lot of putty, etc.

For larger gaps I use my Testors tube-glue, clamp the halves together, wipe off the excess (remember, the Non-Toxic will not damage surfaces right away), and let it set.

 

I use Testor's Plastic Cement, which is somewhat gentler and slower to evaporate than Tenax.  I apply it with a bow pen (seen below) which allows me to set the amount of liquid pretty precisely, and which also works as a sort of barrier to the glue running all over the place.  The gap between the bow halves has to be close enough to the plastic gap to allow an easy transfer, otherwise it's a lot of work to get the glue to leave the pen.  This takes care of your first problem.  I've not experienced the same issues you mention in #2, but if I think the joining surface is thin, I can often come in *behind* the joint with the pen, and the capillary action takes over from there. 

 

Bow pen: bead-of-ink.jpg


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#21 Gigant

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Posted 21 January 2018 - 06:08 PM

I use Testor's Plastic Cement, which is somewhat gentler and slower to evaporate than Tenax.  I apply it with a bow pen (seen below) which allows me to set the amount of liquid pretty precisely, and which also works as a sort of barrier to the glue running all over the place.  The gap between the bow halves has to be close enough to the plastic gap to allow an easy transfer, otherwise it's a lot of work to get the glue to leave the pen.  This takes care of your first problem.  I've not experienced the same issues you mention in #2, but if I think the joining surface is thin, I can often come in *behind* the joint with the pen, and the capillary action takes over from there. 

 

Bow pen: bead-of-ink.jpg

 

I must drag out my antique bow-pen ink drafting set that I bought from a pawn-shop in L.A. while I was in college studying Engineering and try that some day. I think it is buried in the same box as my delrin K&E slide-rule that I needed in college back then. I also hear they're good for painting thin stripes or canopy frames. 

 

Meantime, it is easier for me to grab a spare tube of Testors Non-Toxic stuff while getting something else from Hobby Lobby.


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#22 D Bellis

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Posted 21 January 2018 - 07:58 PM

  1. Control. This goes both for liquid CNA and/or plastic softening/welding solvents. If I so much as blink, they run all over the place, usually away from the surfaces to be joined. Testors Non-Toxic gives me time and control, as does the Loctite CNA Control Gel.

Control comes from experience. Extended working time also translates into slow evaporation, which can lead to problems after the joint is expected to be fully cured (see below). 

 

2. Thin/flimsy fuselage and wing halves. Simply put, unlike home-made sprue-glue or typical tube cement that adds dissolved material, the solvent-only stuff doesn't add any thickness or body to a joint. I found it works OK like for old Monogram or Aurora kits with thick, rigid plastic joining surfaces, but useless for the newer more flexible, "thin-lipped" surfaces.

Liquid cements weld the parts together (fusion joint), as opposed to sticking them together (mechanical joint) with CA or other types of "glues". Given that, there is rarely any need to make joints stronger than the surrounding parts, unless the glue being used isn't up to the task at hand...

 

Gap-filling is a completely different thing from assembling parts, and is treated as such. Personal philosophy on that subject is: If the parts don't fit together properly, make them fit together before applying any kind of glue. As an absolute last resort, stretched sprue or styrene shims can be used to span gaps, and then painted with MEK to weld everything together. But, everyone has their own pet method of gap-filling.

 

3. I have found out it is best to limit them to spot-gluing rigging with CNA, maybe a hairline joint seam gap that can be clamped closed after applying a solvent like Testors liquid or Plastic Welder, etc., to avoid a using a lot of putty, etc.

CA works great for rigging and other small jobs where relatively weak mechanical joints are acceptable.

 

I never understood why anyone would apply liquid cement to a parts and then join them. The whole point of liquid cement is to join the parts and apply the cement to the assembled joint - the cement wicks into the joint no mater how tight-fitting it may seem to be. In the case of MEK, simply hold them together if need be for about 10 seconds, and the joint is solid forever. Off-the-shelf liquid cements can take longer, sometimes MUCH longer. 

 

The other problem with off-the-shelf liquid cements is that they can take so long to evaporate that they're still off-gassing after the paint is applied, and can stain the paint job from the inside out. This is also not an issue with MEK due to its quick evaporation. 

 

So, lumping all liquid cements into one pile is a mistake because they are not 'all created equal'. 

 

DISCLAIMER: All of the above relates to styrene-to-styrene joints as found in typical plastic model kits. Resin, metal, wood and other materials all require different methods and adhesives. 

 

HTH,

D


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#23 Gigant

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Posted 21 January 2018 - 11:57 PM

Control comes from experience. Extended working time also translates into slow evaporation, which can lead to problems after the joint is expected to be fully cured (see below).                                                                                                                                                                                                                                          

 

I agree-so why should I get experience with something I don't need or want, when what I have and use works fine?

 

 

Liquid cements weld the parts together (fusion joint), as opposed to sticking them together (mechanical joint) with CA or other types of "glues". Given that, there is rarely any need to make joints stronger than the surrounding parts, unless the glue being used isn't up to the task at hand...

 

So does the solvent in all Testors products, whether the more viscus tube-type cements, both regular and non-toxic.

 

 

Gap-filling is a completely different thing from assembling parts, and is treated as such. Personal philosophy on that subject is: If the parts don't fit together properly, make them fit together before applying any kind of glue. As an absolute last resort, stretched sprue or styrene shims can be used to span gaps, and then painted with MEK to weld everything together. But, everyone has their own pet method of gap-filling.

 

Only if you choose to handle the situation in that manner. I have frequently successfully done both at once with tube-type cements.

 

 

CA works great for rigging and other small jobs where relatively weak mechanical joints are acceptable.

 

There again, it depends.

 

Loctite's CNA Control Gel when used in multiple applications around the perimeter of larger assemblies has worked fine for my 1/32 HC/Trumpeter F4F, Monogram 1/32 F3F, Lindberg He-111, Accurate Miniatures Grumman TBF, etc., etc.

 

 

I never understood why anyone would apply liquid cement to a parts and then join them. The whole point of liquid cement is to join the parts and apply the cement to the assembled joint - the cement wicks into the joint no mater how tight-fitting it may seem to be. In the case of MEK, simply hold them together if need be for about 10 seconds, and the joint is solid forever. Off-the-shelf liquid cements can take longer, sometimes MUCH longer. 

 

I never said I did.

 

Notice, I said "a hairline joint seam gap that can be clamped closed after applying a solvent like Testors liquid or Plastic Welder, etc., to avoid a using a lot of putty, etc."

 

In case it is not obvious, this incorporates the usual "wicking-action method", as a gap no wider then a hairline would allow nothing much else.

 

 

The other problem with off-the-shelf liquid cements is that they can take so long to evaporate that they're still off-gassing after the paint is applied, and can stain the paint job from the inside out. This is also not an issue with MEK due to its quick evaporation. 

 

I have never experienced this since I never paint a model before letting it sit overnight.

 

And this goes back to building Monogram's 1/48 B-17 when it was first released as well as per a scale model builder's magazine build/review article, using the recommended Liquid Cement at that time, incorporating the tedious "assemble, hold fuselage halves together, apply by wicking-action" technique.

 

 

So, lumping all liquid cements into one pile is a mistake because they are not 'all created equal'. 

 

What I am referring to are the typical liquid cements the average consumer encounters at the model kit section at the local Hobby Lobby store (the Loctite products are two aisles over, same store), and I have bought them all, and they pretty much all behave alike, except for the non-toxic's tendency to take a little longer to dissolve/weld the plastic, and thus longer to set-up, the solvent types pretty much do all act the same.

 

I am not referring to the very toxic and much more dangerous MEK, which here can only be gotten from industrial/commercial suppliers, and then requires the responsible user to go through the process of learning to handle a potentially dangerous solvent.


:innocent: Tom

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#24 Mark_C

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Posted 22 January 2018 - 04:22 PM

Just a quick note: MEK is available at Lowe's.



#25 D Bellis

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Posted 23 January 2018 - 06:04 PM

Just a quick note: MEK is available at Lowe's.

As well as Wal Mart, Home Depot, Hardware stores, Sporting Goods stores, Boating Supply stores, Farm Equipment stores and just about everywhere else that has a general selection of common paints and thinners. 

 

Just ignore the stuff labeled "MEK Substitute" - it does NOT work as a liquid cement. On that note, the same thing goes for "Lacquer Thinner Substitute" when used to thin enamels. 

 

D


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#26 G-Man

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Posted 25 January 2018 - 06:02 PM

Like others have said, I use Gunze Mr. Cement S when joining fuselage and wing halves. I use Locktite super glue on resin pieces. I can tell you that once the Locktite hardens, it ain't coming apart. I glued the 2 halves of my Stuka nose with it, then glued 2 braces inside to make it wider, and the pieces have not separated.
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#27 Out2gtcha

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Posted 25 January 2018 - 08:28 PM

If I want to permanently (read here NEVER EVER to be taken apart again without breaking the parts themselves) there is only 1 glue I use:  Good ol JB Weld.

 

Generally speaking, I've had the plastic/resin its gluing break long before the bond the glue creates does. I've used it to actually glue 10g hardened steel plate to the inside rear quarter of my Jeep, the holds X2 RotoPax filled with x2 gal of water, and a full load of First-Aid gear.   Through thousands and thousands of miles its not failed yet.

I also used it to bond the stainless steel oleo tubes into the OOB gear for my Trumpy SU-30. What I didn't know at the time I glued them in, was there was some air pressure built up in the bottom of each gear the the thickness of the JB Weld didn't let it pop up right way. Needless to say, by morning 24 hours later, the oleo tubes had been pushed up and out of position in each MLG.  I broke (literally) almost every part of the gear off to try to get at it, and in the end the only part that remained together was the section of oleo and gear where the JB Weld had bonded the two. 


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#28 Gazzas

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Posted 26 January 2018 - 02:44 AM

If I want to permanently (read here NEVER EVER to be taken apart again without breaking the parts themselves) there is only 1 glue I use:  Good ol JB Weld.

 

Generally speaking, I've had the plastic/resin its gluing break long before the bond the glue creates does. I've used it to actually glue 10g hardened steel plate to the inside rear quarter of my Jeep, the holds X2 RotoPax filled with x2 gal of water, and a full load of First-Aid gear.   Through thousands and thousands of miles its not failed yet.

I also used it to bond the stainless steel oleo tubes into the OOB gear for my Trumpy SU-30. What I didn't know at the time I glued them in, was there was some air pressure built up in the bottom of each gear the the thickness of the JB Weld didn't let it pop up right way. Needless to say, by morning 24 hours later, the oleo tubes had been pushed up and out of position in each MLG.  I broke (literally) almost every part of the gear off to try to get at it, and in the end the only part that remained together was the section of oleo and gear where the JB Weld had bonded the two. 

I never imagined using JB Weld on plastic.  I used some on an aluminum canoe I got from a livery once.  It never failed on many fishing excursions.

 

Thanks for the tip!

 

Gaz


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#29 Out2gtcha

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Posted 26 January 2018 - 02:54 AM

I never imagined using JB Weld on plastic.  I used some on an aluminum canoe I got from a livery once.  It never failed on many fishing excursions.

 

Thanks for the tip!

 

Gaz

 

 

If permanence is what you are after, JB Weld is your glue. AAMOF I just used JB Weld to glue the resin fuselage halves together of my F7F. Its the only thing I would trust to hold a model together with nearly a full pound of lead in it. 


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