24

Is the rubber cement that you can buy at the stationery shop:

Elmer's rubber cement

the same as what's in the little tubes of cement that come with your patch kit:

Park tire patch

If not, then exactly what is different? What makes tire patches stick much more strongly?

  • 2
    In a word, "NO". – Daniel R Hicks Oct 30 '15 at 18:33
  • And here is the big question.. where is the best place to get the best adhesion for the money? 4 ounces of scuba gear drysuit cement = $12, LOCTITE Vinyl, Fabric and Plastic Adhesive = $3.28 (Lowes) or just keep buying Slime 5 patch kits @ $2.00 (Lowes) (Wow.. at these prices. Slime wins...) – zipzit Oct 31 '15 at 4:22
  • Zipzit, I don't think any of those with the exception of slime patch kits would work, be cause of the difference between an adhesive and devulcanizing solution. – RoboKaren Oct 31 '15 at 13:28
  • 3
    I think many of us have opened up a patch kit to find the little tube all dried out, but still with many patches unused. We've eyed the bottle of elmers with some curiousity as a replacement. – RoboKaren Jun 18 '17 at 19:06
  • 1
    @RoboKaren I know the feeling. I went around to all bike shops and none would sell me an 8oz can of vulcanizing cement. I had to go to ebay for it. Obviously, carrying 8oz of cement in the saddle bag is a non-starter, but if you make habit of carrying spare tube for on-road repairs and repair the bad tube at home, then the bulk supply of cement makes a lot of sense. 1x 8oz can of cement at the cost of 3-4 patch kits. – codechimp Jun 22 '17 at 14:56
34
+50

The "cement" used in tire tube patch kits (de)vulcanizes the rubber in the patch and of the tube. Which is a chemical process, usually using sulfur, where the rubbers bond and form a stronger bond than just an adhesive would do.

Rubber cement is just a gooey adhesive. Usually latex with acetone and other chemicals to make it more pliant. You wouldn't want to use it to patch a tube since it is not very strong, will degrade the integrity of the surrounding rubber and patch, and in general make a mess.

  • 5
    When I was a kid, and my rides around the block, I once patched a tube with rubber cement and a piece cut out of another tube. It lasted for about 3 days. Also tried with rubber cement + tire patch. Lasted even less. Meanwhile, a well applied tire patch with vulcanizing compound will outlast the tube and the tire! – Jahaziel Oct 30 '15 at 13:21
  • 2
    Agree there is vulcanization going on but according the the MSDS from the web site what is in that park tube is a type of rubber cement. – paparazzo Oct 30 '15 at 14:28
  • Some cheap patch kits sold in Asia really do contain "rubber cement" (and are labeled as such). They don't work well. They tend to come with patches which are much less stretchy than the Rema ones we all know and love. – John Zwinck Oct 30 '15 at 15:13
  • 4
    Vulcanization does occur in natural rubber when exposed to sulfur and results in a cross-linked polymer but 1) most inner tubes are made of butyl, which is a synthetic rubber made from petroleum (which is why ExxonMobil is one of the major producers of butyl rubber) and isn't cured with sulfur and 2) vulcanization of natural rubber occurs under both pressure and heat. A typical vulcanization process using natural rubber and sulfur (with accelerants) is done at around 170 deg C. (~350 deg F). – R. Chung Oct 31 '15 at 14:44
  • 1
    I edited the answer slightly because the fluid doesn't vulcanize the rubber, it devulcanizes it slightly so that it will accept new cross-link bonds (which then re-vulcanize). – RoboKaren Jun 23 '17 at 14:13
20

They are both types of rubber cement but not the same

MSDS will tell you a lot

One difference is tire uses a mainly naphtha as a solvent and the elmers does not.

Park MSDS
Elmers MSDS

Looked up a couple other vulcanizing fluids and the commonality is the use naphtha as a solvent. According to this link naphtha is also rubber solvent. A bicycle tube is vulcanized but the surface is treated to de-vulcanized (you don't want it bonding to the tire). So I suspect the naphtha is used dissolve a little bit of the tube to expose the cross links (vulcanization) and the patch has exposed cross links. The adhesive part holds the patch to the tire long enough for these cross links to hold hands. Do I have a citation - no - could not find one. That is just my analysis.

  • 8
    +1 for thinking of looking up the Material Safety Data Sheets! – Rider_X Oct 30 '15 at 15:57
  • 1
    @Frisbee do you have some sort of citation for devulcanization of the surface of tubes during manufacture? As far as I was aware, they just talc'd them to prevent tire friction. – Deleted User Oct 30 '15 at 20:51
  • @ChrisinAK "Do I have a citation - no" and I just made up the word de-vulcanized. You can call it my speculation. I do have a citation that naphtha is a rubber solvent. Talc alone would contaminate the open cross links but I suspect they do some kind of chemical neutralization of the surface. If it was contaminate alone it could be reversed with a detergent - not a rubber solvent. Naphtha is kind of harsh - would not likely use it if there was detergent alternative. I have a degree in chemical engineering but no specific expertise in this area. – paparazzo Oct 30 '15 at 21:03
  • Devulcanization is an actual thing. But it's resource intensive. I thought you were referring to your supposition of naphtha use when you stated you had no citation, I didn't realize your "the surface is treated to de-vulcanized" was also speculation. – Deleted User Oct 30 '15 at 21:11
  • @ChrisinAK Devulcanization is a thing and for recycle it means the mass as a whole. I did say surface and I do suspect they use something similar. A stack of tires has no visible talc or other contaminate and does not stick. If they did not neutralize the surface then shipping and handing would be a real problem. – paparazzo Oct 30 '15 at 21:22
9

A chemist on reddit answered this question fairly authoratively:

Chemist here - natural rubber is a polymer (long chain-like molecules). Vulcanizing adds cross-links (through disulfide bonds) to the rubber, basically turning the strands of rubber molecules into a net, greatly increasing strength. Bike tubes are vulcanized rubber, but the outer surfaces are treated such that all those cross-linking sulfur groups aren't reaching out and trying to grab anything. You put on some vulcanizing fluid (henceforth "glue") and a few disulfide bonds in the tube get broken and re-formed with bonds to the polymers in the glue. Once the glue dries (there's a bit of solvent that has to evaporate) the inner side of the glue spot is chemically bound to the tire. The outer side is left with a bunch of free sulfur groups waiting to grab onto some other sulfur groups. Then you peel that piece of foil off the orange side of the tire patch (which exposes the free sulfur groups left on the patch) and press it to the glue spot - you've now made millions of chemical bonds between the patch and the glue spot. It's not really glued, though - the patch-"glue"-tire system is now one single molecule all chemically bound together.

The chemical bond holding things together is why:

  • The tube has to be clean and dry - the sulfur groups reaching out for something to grab onto will grab dirt, water, and other gunk instead of the patch.

  • You can't use duct tape or regular glue - these are sticky substances that don't vulcanize the rubber together. Rubber cement may hold a patch in place but it is NOT the same stuff.

  • Glueless patches kinda suck - the vulcanizing fluid in the little tubes works better at making bonds with the punctured bike tube.

You can make patches out of old tubes - at its most basic you're vulcanizing two pieces of rubber together, so two pieces of bike tube will stick to each other. TL;DR - Vulcanization. http://en.wikipedia.org/wiki/Vulcanization

So the take-away points are:

  • The "rubber cement" in the patch kit isn't a vulcanizing glue, it's a devulcanizing compound which breaks apart the little vulcanized polymer chains allowing for new cross-linking to happen

  • the naptha in the 'glue' is a carrier fluid that is designed to evaporate quickly

This also explains why:

  • you want the patch area clean

  • you want to use the sandpaper or scraper to scrape the rubber to expose some 'fresh' rubber

  • the 'glue' has to dry absolutely before you patch (as it's not 'glue' in the sense we know it)

  • a glued patch is as strong as the original rubber -- or stronger.

2

Plain ole Elmers rubber cent uses "n-Heptane". n-Heptane will dissolve rubber, and is used as a bonding agent for many types of rubbers, plastics, etc... Very similar to naptha. But different rubber cements use different chemicals.

I am a former boxer, and now an instructor. I have literally patched hundreds of rubber speed bag bladders. Also having four kids and eight grand kids, I have patched many a bike and off-road motorcycle tire. My grandfather taught me to cut old tire tubes to make patches, and use standard rubber cement. It wasn't until I was in college that I learned that not all chemical things are created equal. I have used plain ole off-the-shelf rubber cement with no problems. But now I usually look for Elmers (because I know it has n-Heptane in it), or I look for a tire patch rubber cement in the automotive or bike section. Motorcycle shops are a good place to look as well.

So the answer to the question is: Not all rubber cements are the same. Read the SDS (formerly known as the MSDS). Have a great day.

1

While rubber cement and vulcanizing glue are different, rubber cement can be used to repair tube. The keys are: 1) use large rubber patch, 2) apply rubber cement to both patch and tube 3) let the rubber cement dry for 10-15 min before applying patch to tube.

Assumung the tube is properly sized to wheel (ie it does not stretch to make circumference) the patch will hold. The most likely cause of failure is apply patch to early: the cement solvents need to evaporare away first. Also you absolutely have to apply cement to both sides. It is a cement-to- cement adhesion process.

1

I've used elmers rubber cement to patch tires with pieces of old tube countless times over the last 20 years and can't recall any of the patches failing. I simply roughened up the tire and patch-piece (usually at least 1-inch square, I don't bother to cut them round), applied rubber cement to both areas. Allow them to dry. Then apply. Used this method for high pressure racing tires and lower pressure mountain bike tires to the same effect. I've later taken the tubes out for subsequent patching of another puncture and seen my old patch and tried to see if I could peel it off (see if it was glued strongly or not, or merely being held in place by the tire pressure) and was not able to pull them off with my bare hands, so I'd say they were pretty secure.

  • Welcome to the site - do note that your answer doesn't address the question. All you've said is that Elmer's works as a patch adhesive in your experience, which is useful info without answering the question "are they the same" ? So it probably should be a comment not an answer. Do please have a browse of the tour to learn how SE is different to most chatty web forums. And welcome - you obviously have a lot of cycling experience which is always welcome. Have a go at answering some of the other questions. – Criggie May 14 '18 at 4:40

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