Rubber rejuvenation

[phantomrebel]

Yes, quite true, but the boiling point of the mixture is a few degrees lower than the isopropanol alone. Which doesn't matter for this application, of course.

The counter argument to the water vs. hydrocarbon issue for cleaning/rejuvenating a pinch roller is that toluene or xylene diffuses into the rubber and thus takes time to diffuse out, while water and alcohol do not penetrate the rubber and are thus purely surface issues. I know this to be true, because I've used a very sensitive hydrocarbon detector (aka "nose") to register when a hydrocarbon concentration is low enough to not cause issues, using a handwavy meaning for issues. The diffusion for the hydrocarbon solvents is, of course, rapid, so very little remains after a short time in air and one can use a fan over the surface to increase the rate of diffusion. A heat source, such as a hair dryer, to encourage such diffusion is not recommended for reasons best left to the reader to work out.

I point this out not to be argumentative, but because engineers are always explaining why the guillotine blade didn't properly descend. (If you don't get the joke, you didn't go to an engineering school.)

Yes, that was my way of qualifying the "twice" as it actually is less than that in the presence of alcohol.
As to your counterargument...why are tire manufacturers concerned with water absorption if it doesn't penetrate? Water molecules are relatively small and should diffuse quite rapidly (to use my awkward relations- xylene is at least twice the size of water). Can you elaborate?

 

[Retrovert]

Yes, that was my way of qualifying the "twice" as it actually is less than that in the presence of alcohol.
As to your counterargument...why are tire manufacturers concerned with water absorption if it doesn't penetrate? Water molecules are relatively small and should diffuse quite rapidly (to use my awkward relations- xylene is at least twice the size of water). Can you elaborate?

Oh, I wasn't quibbling about the twice. I was commenting that the boiling point of the mix was actually lowered a trivial amount, so the properties weren't being upwards moved, which likely didn't make it any more vulnerable to water retention.

As far as the rubber and water, mmmm, that's from raw material and then from manufacturing. Modern tires are a blend of nature and synthetic rubber. I haven't hung out with any tire chemists, although I did have a granduncle who brokered in mountains of used tires. (Given that his company was paid to cart away the raw material, this was far more profitable than one might otherwise think.) Natural rubber is loaded with water for obvious reasons, and this must be removed in the manufacturing process. But don't forget that automobile tires are also formed in steam presses. Wee bit higher temperature and pressure than wiping a roller with a damp cloth. I believe that is the issue. Rubber normally does not absorb much moisture or car tires would become bloated and useless (like this discussion) after it rained or even in high humidity environments. Crosslinking prevents that.

So, yeah, a few hydrophilic impurities in the crosslinked rubber with open tails will grab the water here and there, sure, but compare that brief contact to soaking in toluene. The rubber has far more hydrophobic bonds which welcome hydrocarbons like long-lost brothers showing up with whiskey, coke, and hookers. Come on in, bro, the parties just getting started!

The rubber wheel is, furthermore, hard and glazed with a surface that is not very friendly. So absorption would be small. Even given capillary effects into a fractured surface with hydrophilic bonds.

Rubber will absorb a few percent of its weight in water but up to four times its weight in hydrocarbon solvents. Something like that. My interest in studying all of this was to obtain a viscoelastic rubber for sound deadening to avoid using a certain fabulously overpriced acrylic copolymer we need not mention. The substantial loading of the rubber with solvent to keep it spreadable proved problematic. I need to go back to that problem, as my neighbors are still making more noise than frat boys with a keg and a DJ.

 

[Retrovert]

First, there is no conspiracy here of scientists trying to push chemicals on people...please.

Speak for yourself!

I not only am a card-carrying member of the Super-Duper Secret Science Conspiracy Society to Push Chemicals on People (all scientists and no marketing people, hence the long slogan), but I personally offer various di-hydrogen monoxide and a certain short-chain hydrocarbon formulation to anyone who visits.

Never trust a scientist! They're LOADED WITH CHEMICALS and will suck you into their chemical lifestyle!

Particularly ones with a liquor cabinet.

Never trust a scientist who says "the first one is free".

And don't get me started on the ones with baked goods! Those are FILLED with chemicals—especially the short and long-chain polysaccharides—and will kill you! Or at least make your pants not fit...

Bwahahahahahhaha.

Second, the general formulation has indeed been used for decades for this purpose, going back to the early days of Ampex. The MG product data sheet for Rubber Renue is very clear as to be a mix of Xylene and Methyl Salicyate. Same with numerous others if you look at the MSDS database. Some are vague, some are not. Many of the old products have disappeared along with tape popularity but some remain in the market (for use on printers, for example). Maybe the legal database would reveal some cases against these companies for product damage? Doubtful but worth checking.

Exactly. When tape died the entire ecology died with it. But the rejuvenators never were any secret. Just smell them. It stinks of toluene (sweet) and methyl salicylate (wintergreen).

As far as printer platens, the cost of replacement parts for printers has dropped, as the cost of labor for a service visit has risen, to the point that the curves intersected at replacement. Labor then continued to climb far past that.

The only use for those rubber rejuvenator products sold by the gallon is, I suspect, in conveyor belts since that seems to be the main point in the literature. I can only imagine what the livers and brains of the techs look like.

I only take the side of this mixture because it has proven to work in some cases (Retrovert provided the reason why), has been in use many years with no ill effects (to my knowledge), and it is non-aqueous. I can't imagine how any of the ingredients would ever get on a tape, but if they did, the small amounts would likely cause little harm since archivists use similar solvents to remove adhesives from tape and in the application of lubricants to tapes. As I've said many times, I'm a huge fan of preservation and wouldn't want to do anything to damage a tape. I am in favor of caution. But I am also scientifically minded and need some sort of data or reasoning that some practice is harmful before believing it. I am not of the opinion that tapes, or records for that matter, should never be exposed to any chemical or that all chemicals are bad. On the contrary, I've found some to be beneficial (Antistats for example). I don't see any mechanism through which treating a roller with this mixture, as directed, would in any way cause subsequent damage to a tape. OTOH, I've seen many tapes damaged by old, hardened or dirty rollers.

+1 for Truth, Reason, Science, and The American Way.

 

[Retrovert]

There is no indication whatsoever that this home brew mix is a formula that "has been used and sold as commercial products for over 50 years by a wide number of companies for this same use". Just some haphazard speculation as to the ingredients. Again, and as you have admitted, the formulae of commercially established products are typically protected trade secrets. And we don't even know if such commercial rubber restoration products are suitable in this environment. And we are not talking about those formulae, we are talking about precisely this one.

The SDS/MSDS actually lists the ingredients! So does the bottle! There's no secret here!

I appreciate that you are unaware that hydrocarbons can be trivially analyzed using a mass spec or gas chromo but there's no secret if anyone went looking. One can tell by the smell what's in it.

Your colleague himself has alluded that the solvent component is intended to breakdown the rubber, to more thoroughly deposit some other chemicals into the substrate.

Swells the rubber and permits ingress of a plasticizer and/or migration of any residual plasticizer to the surface. The bonds are hydrophobic as I above explained. Doesn't break them down. I hypothesized that the swelling might crack some bonds, softening oxidized rubber, but I haven't looked into that. It was an offhand remark.

BTW: I'm not a colleague, I'm an evil genius bent on tape destruction. Bow down before me and despair. Colleagues wear lab coats and safety glasses with coke-bottle lenses. Evil Geniuses were Hugo Boss suits with polished boots. We also have cats! Plus those sticky things to remove cat hair from the suits. HUGE difference.

I think if the proponents were just honest enough to say that these home-brews may rejuvenate rubber rollers, but that users should exercise caution, as it is uncertain whether these chemicals are safe for magnetic tape media, it would come across as more sincere and thoughtful. Just like that warning on the box of rat poison; it's great at killing rats, but due precautions should be taken around people.

Fine.

Kids, stay in school and don't huff rubber rejuvenation products.

Happy? We good now?

The continuing intellectual resistance to just conceding this additional caution is really perplexing. It's as if someone really doesn't want to. Pride, ego? Who knows. I continue to think you are both sincere.

Hey! How did I get sucked into some sort of rubber rejuvenation lifestyle promoter?

Now I gotta get all new friends.

Hey, baby, come over here and let daddy rejuvenate your rubber with some chemicals. Let me swell your bonds, and plasticize your cold, rigid bonds with some hot, spicy aromatics, because it's all about us.

Beware the expert trap. It can be unattractive.

That's why you should never ask a question. Some expert might show up and answer it. And then some other "expert" will make up reasons why that first expert is wrong. Then you have a flamewar and a locked thread. Science!

That'll teach me to explain what super-duper sekret formulations contain.

 

[phantomrebel]

Man, you have to stop! My sides are aching. Wife sitting next to me on the couch wondering why I'm laughing so hard at my laptop and I can't explain. "hey baby, come over here....." OMG, classic stuff! No offense or conspiracy towards others, I just HAD to like those last few posts. Wittiest I've read in ages. Thanks!

 

[chris35745]

While I didnt waste my time reading all this bickering back and forth, I will offer up a very simple solution. WWW.terrysrubberrollers.com. The guy puts new rubber on old pinch rollers. I have used him in the past with an old dried out pinch roller for an Akai 285D RTR. Works like new and has been for the past several years. Simply download and print the order form, fill it out with all the info on your RTR, send in the old roller and a money order for the cost, and in a very few days, you will have a pinch roller with brand new, pliable rubber on it. No fuss, no muss. No need to be a biochemist and certainly no need to use weird and potentially hazardous chemicals.

 

[Catmanboo]

Ah, if I only had a printer! At any rate, this thing has 4 wheels plus the pinch roller. Already checked terry's, that may be a future project due to cost.

 

[phantomrebel]

Recommended Terry in post 66. We are all in agreement there, better to replace than try to restore! But you could buy another of these A-2060 decks for what the new rubber would cost you. It's a tough spot to be in.

 

[Catmanboo]

I may refocus on a Revox B-77 in my hoard that has some issues, it may be a bit more economical. Shame of the a-2060 is that all functions work, if not for the rock-hard drive wheels. I've noticed excessive bushing play on 2 of the wheels, ruling out any attempts to renovate those.Oh well...

 

[phantomrebel]

I may refocus on a Revox B-77 in my hoard that has some issues, it may be a bit more economical. Shame of the a-2060 is that all functions work, if not for the rock-hard drive wheels. I've noticed excessive bushing play on 2 of the wheels, ruling out any attempts to renovate those.Oh well...

The B-77 is a much better deck in every regard so this seems like a good plan. Even if you had to do a full recap and replace all the rubber it would be worth it. Lots of parts and support around too. Good idea and good luck!

 

[Catmanboo]

The B-77 is a much better deck in every regard so this seems like a good plan. Even if you had to do a full recap and replace all the rubber it would be worth it. Lots of parts and support around too. Good idea and good luck!

Agreed, but I'd really like to have a functional 3-speed deck, which the b77 ain't. Its big selling point to me so far is the 10"reel capacity, of which I have a few. Did find a parts source, Erhard audio, so I'll likely go that route. Tnx for the encouragement, man!