Repairing a crack (plastic pen)

[OcalaFlGuy]

Take the warnings on the MEK can VERY, VERY seriously. Please. That stuff will make you see Jesus.

 

Bruce in Ocala, Fl

[PJohnP]

Safety person here with many years of experience investigating accidents and, much more to the point, working to prevent them...

 

 

 

The precautions for using/handling these solvents involve appropriate ventilation with fresh air, handling the minimal amount of flammable solvent necessary, and ensuring that the usage is well away from ignition sources.

 

I'll try to keep some of the discussion as straightforward as possible, but it's a more complicated matter in a work environment. This is only a brief overview for the purpose of discussion, and it cannot address all conditions, locations, or solvents - this discussion is intended only as a starting point for anyone doing occasional home pen repairs with flammable organic solvents.

 

Ventilation is pretty straightforward and simple... until it isn't. Organic solvent vapours tend to be more dense than air, essentially "puddling" in the area where liquid spills occur. The areas close to liquid spills or the open mouths of containers have appreciable concentrations which do not disperse as quickly as one might expect, allowing for a person in the area to inhale those vapours. Working in a basement corner, a small closed "crafts room", or some other place without ventilation is a poor idea. As a rule of thumb, people using these solvents should ensure that there is a substantial fresh air make-up to the pen repair work area. In a workplace, this would have to be done under a designed vent system to the outdoors.

 

Depending on the specific solvent being used, there can be acute or chronic effects. Acute effects are (relatively) quick and can include (but are not limited to) lightheadedness, fainting, even fatality. Chronic effects are longer term, and include teratogenicity, cancer, birth defects, etc. The casual pen repairer at home shouldn't have chronic effects, unless the person starts to do multiple repairs in sequence over time, which is a larger issue than fixing one or two pens.

 

While users can obtain respirators with the correct organic solvent cartridges, this is a long second choice to working with correct ventilation. Where someone would be performing this effort in a workplace on an ongoing basis with these solvents, testing of the area solvent vapour concentrations would be required, along with respirator fit-tests if that option were being considered. Important note - the dust masks and cheap respirators from the local hardware shop don't meet the requirements for a workplace organic solvent respirator. Anyone who is going to start doing this in a work environment needs a much larger assessment than we're going to discuss in this thread, which includes some stringent government requirements considering acute and chronic effects from the solvents, ventilation assessments for the engineered controls, and the list goes on at some length from there.

 

The average person who does a single pen repair with some decent fresh air ventilation shouldn't have large scale deleterious effects, unless...

 

...The home pen-repairer spills the flammable solvent in a sizable mess in the area where work is being conducted..

 

Solvents like MEK (methyl ethyl ketone) and acetone are highly flammable. They're not just easily flammable, but extremely so, vaporising and igniting far more readily than most people understand because of the intrinsic chemical properties of the materials. Flash fires move far more quickly than a person can run, engulfing them and burning them. Worse, a relatively small spill can quickly form sufficient vapour for a vapour-phase explosion, igniting from even from a light switch being tripped. MEK and acetone can explode far more easily than natural gas (methane) and with more explosive impact.

 

One shouldn't have to mention it, but then, accident histories show it is necessary to say it, no smoking, no open flames, no electrical heaters, and so forth should be in the room where pen repair with organic solvents is being performed.

 

Again, using these solvents in a workplace is a much complicated discussion than we're going to address in this thread, but, like the potential for acute and chronic exposures noted above, there are a plethora of well-founded government rules intended to protect people from being crispy-fried or exploded through correct management of the storage, distribution and use of flammable liquids. Control of ignition sources in workplaces becomes a subject in and of itself.

 

One of the best controls is only using/handling a minimal volume of flammable solvent. The average person doing a single pen repair should decant the solvent outside into a much smaller container for their work, which will minimise the potential for fire and/or explosion. How small ? Well, ponder that the putative home-pen-repair-person will be fixing a crack on one pen, so think about a thimble or two's volume, not a cup-full or more ! There is no good reason for the home pen-repair person to be handling/using organic solvents in bulk quantities indoors.

 

For those folks who comment that people use these solvents all of the time, and they haven't personally had an accident or seen one, I'll comment,

 

The plural of anecdote isn't data.

 

A quick check of newspapers and other media will show accident after accident, some terribly tragic, and in many of those cases there will be a comment, "We never thought that this would happen to us/him/her."

 

A few reasonable precautions for the person fixing one or two pens along with some care in their work should suffice to protect them against chemical exposure and fire/explosion hazards.

 

 

 

 

John P.

[pokermind]

FWIW, you can no longer purchase MEK at your local hardware store in California. I read in another post that at least one other state has also adopted this restriction, but I can't remember which one. Most likely this is type of product will (eventually) only be available to professionals nation wide.

[kevanf1]

Another chemical has been mentioned, dichloromethane. I have to add my own warning about this stuff. In the short term it will cause lightheadedness possibly fainting. It has the potential, long term of causing industrial asthma and worse, it can cause heart rhythm problems and even cardiac arrest! I know, I used to use the stuff for years. I read the hazard safety sheets and heeded the warnings. Others did not and they did end up with industrial asthma

[WirsPlm]

Normal glues/epoxy don't really work too well on pens - unless you don't mind a big blob of epoxy on the pen.

You want to search for: plastic weld, plastic solvent weld or MEK.

There must be manufacturers in mainland Europe.

Try translating the terms into German and use google.de.

(MEK = methyl ethyl ketone, I think)

 

What if I don't mind a big blob of epoxy on the pen (I'm repairing for myself and would rather have to sand or polish a bit than deal with possible explosions)? I've used epoxy on lots of things before (including various plastics) and it seems like it would do the job of holding the parts together without a lot of the risks associated with plastic welding.

Edited May 2, 2014 by WirsPlm

[Ron Z]

What if I don't mind a big blob of epoxy on the pen (I'm repairing for myself and would rather have to sand or polish a bit than deal with possible explosions)? I've used epoxy on lots of things before (including various plastics) and it seems like it would do the job of holding the parts together without a lot of the risks associated with plastic welding.

That's fine if it's your pen and you don't care about the impact on value. You will own the pen, as in you won't be able to sell it, or won't get more than parts value for it if you do want to sell it.

 

I've found though that it doesn't do a very good job of holding barrels together, or securing cracks. Epoxy depends in part in surface area(s) making contact. There isn't much contact area in the crack, so not much very strength. Epoxied cracks tend to just crack open again, whereas solvent welded cracks can be nearly as strong as the original material done right and given sufficient time to cure.

[scrivelry]

Ron, what would you say is sufficient time to cure - or perhaps since I am sure there are multiple factors and it may be different every time, what would you suggest as a minimal time to cure?

 

T

[OcalaFlGuy]

4-5 days. A week would be better. Within that period, the longer it cures, the stronger the weld.

 

Bruce in Ocala, Fl

[inkstainedruth]

What would be the best for celluloid? (Sorry, it may have already been mentioned, but I was in a hurry so just sort of skimmed through this thread).

The reason I ask is that the Vac Shadow Wave I got on Ebay may have a crack in the cap (in spite of another bidder's question being answered to the contrary by the seller). I can feel what seems to be a crack when I run my nail along the circumference of the cap (and looks to be roughly an inch and a quarter long); but it is a very fine crack with no crazing, and seems to be held in place by the cap band.

Admittedly, when I looked at the photos for the listing, it looked like a crack to me as well -- but I went ahead and bid, because the seller said he couldn't find it. Of course he *also* didn't say that the top jewel was missing -- but I chalk that up to him not really being a "pen" person (most of the guy's other listings were for what looked like fishing tackle). Although it might have been nice to see photos: the "better" ones of the nib, which actually showed the tines and tipping, were instigated by me; didn't occur to me to ask about the jewel....

Live and learn. Sigh.

Ruth Morrisson aka inkstainedruth

[Chi Town]

wow, that was some informative reading!!!

[Ron Z]

With celluloid, I've found that the longer you can walk away and wait, the better. I find that there are changes that don't appear or become noticable until nearly a year after the repair as the last of the solvent comes out of the material, but none of us are willing to wait that long.

 

The initial bond is pretty good, stronger after a week, better still after a month. Waiting a month alows the repair to harden to the point where it blends well with the surrounding material.

 

For other solvents/materials it's a bit shorter. Again the initial bond is quite strong and it reaches 80% strength after 24 hours, and continues to cure for the next several weeks. For Sheaffer plastics you need at least 24 hours before blending, 48 is better, with a week proving to be the most reliable and easiest to blend.

 

For epoxy, wait the full 24 hours unless you can keep the temperature elevated (but not hot) for 2-3 hours. For instance 120 degrees for some epoxies shortens the time to full strength from 24 hours to 2 - check the manufacturers application data sheets for precise information.

[RCliff]

Plastruct Plastic Weld (MEK) Is what I use. 2 fl oz bottle from upscale hobby shop...

[Ron Z]

Plastruct Plastic Weld (MEK) Is what I use. 2 fl oz bottle from upscale hobby shop...

 

Plastruct Plastic Weld is 80% - 90% methylene chloride by weight, 5%-15% MEK, which is why it works on plastics like that used by Sheaffer, and not so well on celluloid.

 

Check the MSDS on their website.

[inkstainedruth]

Just as a heads up -- my husband is going to be having lunch later this week with a good friend of ours, who has a PhD in chemistry. Her specialty is plastics! While Steve is mostly going to be talking to her about 3D printer stuff, when he told me about the lunch (mostly in terms of "you'll be even more bored than at the weekly dinners when people are talking computer stuff") I said, "Hey -- find out if she knows anything about repairing vintage celluloid!"

I will try and remind him Thursday morning before I go to the dentist (not sure what time he is meeting her) so he doesn't get a brain f*rt and forget to ask her if/what she knows. And if I get any sort of answer, I will pass the information along.

I *love* having a pet expert around, right at the time when I need one....

Ruth Morrisson aka inkstainedruth

 

edited for typos

Edited May 6, 2014 by inkstainedruth

[OcalaFlGuy]

Too bad you don't have some MEK. A little whiff and I'll bet hubby would remember...

 

 

Bruce in Ocala, Fl

[white_lotus]

I'd ask him to get her number so you can call her, and maybe you can go to lunch with her sometime to talk plastic repair!

[FarmBoy]

To a chemist they are polymers.

[Ron Z]

A chemist is likely to talk in theoretical terms, but won't be able to offer much in the way of plastic repair techniques - different expertise. I started experimenting with repairs about 10 years ago, and the process of discovery continues. The investment in time, research, practice and failures has been expensive.

[bsenn]

When repairing motorcycle bodywork or iron castings I was taught to drill a hole at the end of the crack prior to repair to ensure that there is no crack left to re-start after the repair. Is this commonly done when repairing pen sections?

 

Brian

[FarmBoy]

When repairing motorcycle bodywork or iron castings I was taught to drill a hole at the end of the crack prior to repair to ensure that there is no crack left to re-start after the repair. Is this commonly done when repairing pen sections?

 

Brian

No