contact cement/patch glue question
 

hi again,

Its "ask basic questions" day for me.

When looking for something to help repair a broken plastic part on a snow scoop (the Californians are asking, what the hell is a snow scoop?) I fished around in old junk in our garage and found a can of this, would have been from previous owners and so goes back probably 20 yrs.
It smells like the stuff in patch repair kits, looks like it and even acts like it. Is there any reason this isnt the same stuff we have in those itsy bitsy tubes that come in patch kits? I get maybe a flat a year and usually patch them without issues, but if this stuff is the same, I will use it when patching at home instead of opening a new tube which will then be suspect because they always dry out afterwards, especially given I dont get flats that often.

Given the fact that every year or two I end up having to buy a new patch kit or two just to get some more glue tubes after the others have dried out, I have lots of patches, and I keep some old tubes around for using the rubber, so I guess I just need to try a patch with this stuff and see how it works.

cheers

Sheldon Brown calls the glue in patch kits "rubber cement" and who am I to argue with that. I think the actual vulcanizing agent is what applied to the patch. It works with the rubber cement to form a bond with the tube. Unvulcanized natural rubber (from rubber trees) is much more reactive than the vulcanized butyl rubber in the tube and whatever is in the patch. If the rubber in rubber cement is natural rubber, it is all set to react with vulcanizing agents and then with the patch and the tube. If it is in contact with both the tube and the patch while that reaction is taking place, then it would attach to both sides and make a bridge between the patch and the tube. I actually think this is what is going on. In a word NO, your Dural is not likely the right stuff. Bulk packaged rubber cement could be just fine though.

I think the rubber cement in stationery stores is enough different that you'll not get a patch to stick. The stuff in the patch kit is much thinner and probably has a different solvent mix to "vulcanize" the butyl rubber of the inner tube.

Contact cement is not the same even if it smells the same. Eventually contact cement will dry out and crack, where the rubber in inner tube patch kit still will be pliable.

It is not the solvent in the patch kit glue that participates in the vulcanization. It is only the natural rubber dissolved in the solvent. That is why the solvent has to dry before you can put the patch on the tube.

the rubber is useless until it is vulcanized in contact with both the tube and patch. The rubber that dries out has reacted with air instead of the vulcanizing agent. That's why it dries out. It has been oxidized. But after vulcanization the reactive sites which can be oxidized have been used up and are no longer available.

Look for $2 tubes of rubber cement on the shelves next to the auto tire patch kits in your local auto parts store or in the automotive section of your favorite big box store. They may be a little too big for your on bike repair kit, but I've used them for years for when my tiny Tip Top tubes get all petrified. It's always worked just as well as the stuff that comes with the patches.

here is the current description of the stuff I found, clearly for wood and all kinds of stuff, but not vulcanization of patches.

http://www.dural.ca/industry/contact.html

learn something everyday.

This topic has also lead to heated discussions here based on various levels of understanding of rubber chemistry. Yes, a real "vulcanizing" fluid is better for gluing patches to a bike tube.

However, I have had years of success using Rema patches and plain office supply store Elmer's Rubber Cement to glue them on. I scrub the area around the puncture with the sandpaper in the Rema kit to remove oil or residual mold release from the tube, apply a thin layer of the rubber cement extending a bit beyond where the patch will cover and let it dry for several minutes. Then I remove the foil backing from the patch, apply it over the hole and iron it down with my thumb. Glued on this way I have almost never had one fail or leak.

The beauty of this approach is that the cement comes in a larger bottle, costs little and never goes dry because it's also used for other projects around the house.

almost never--for me this is important. As I really get very few flats per year, usually about one on average, my tubes can be in use for quite a while. I'd rather not take the chance of a patch failing, what I can say is that I dont ever recall a patch leaking afterwards if put on properly. Not worth the possibility of it given how much I commute, and it would be frustrating to lose the time if it was a glue failure, especially if I am running late or just on time. So although I dont like to waste stuff, I think I will stick with "vulcanizing rubber cement". Most likely I will just try to find small tubes sold separately, or just buy another $3 patch kit. I always make sure there is one unopened tube in my little plastic box repair kit, two new ones if I am on a trip.
I do like the idea of finding a larger tube of vulcanizing stuff to have at home so as not to open the weeny ones.

thanks for your comments, it is good to know that the Elmers stuff will work very well, I appreciate that if you have used it for years with hardly any failures, that certainly is a good track record. Good to know especially if for some reason this was the other stuff available-I suspect your good technique of cleaning the area of the tube is a factor, that seems to be my experience with patching in general.

Lots of CA gets plenty of snow.

Come on, don't ruin my smartassery!

OK, if one failed repair in 20 years (my experience) is too much, that's your choice. I almost never repair the tube on the road, I carry a spare tube or two with me and repair the damaged one at home in comfort.

Hill, that's why I added the comment at the end of my post, thinking that "hardly ever" could mean anything. So 1 in 20 years, that nothing. I too repair them at home after being sure of getting the thing out of the tire that did the first one.
Given your track record, I would have no problem using the Elmer's stuff. Thanks again.

I will say that nearly nothing will make a patch air tight if the puncture is right on or very near a molding seam in the tube. The ridge keeps the patch from clinging right over the hole and leaves an air channel. After a couple of failures (not related to the glue) I just give up and discard those outright. However, if the tube is clean and dry and the hole is in a suitable spot, I have excellent success with the cheap rubber cement.

You experience confirms, I think, that the vulcanizing ingredients are on the Rema patch, not in the cement. The cement just opens up the pores of the tube and supplies natural rubber to bridge between the tube and the patch. Or so I think. The patch is covered with a film for some reason after all.

That's exactly my experience with holes near the seams, not worth the effort. If I was in the middle of nowhere and had limited spares, maybe. I just usually rotate them out with the old "bad" tubes I keep hanging in the garage for cutting off bits to use as protection sections for mounting stuff or whatever. (I cut them once to not mix up with other tubes). An old tube can be handy for stuff sometimes. I have a little section in my trip tool kit, handy if you ever have to use a plumber type clamp so not to scratch a frame, or to stop something slipping, that sort of stuff.

If it makes you feel better the Rema company has really big patches and big cans of the fluid,
shipped to Truck tire shops for inner tube repairs in their tires.

I do feel better
Knowing they exist
Although I suspect strongly
They might be too big
;-)

I've had a somewhat different experience with the office supply rubber cement- It's way too thick and even if the inner tube is scuffed up plenty, the patches just don't stick as well as when using the special "vulcanizing" cement in the little patch-kit tubes. YMMV. I think it's the solvent mix used in the patch kits versus the solvent in the office supply stuff.

I put vulcanizing in quotes, because vulcanizing is a heating process (Vulcan being the god of fire). I don't recall heating any of my bike patches. I haven't used heating since using the patches you light with a match when patching an tractor inner tube.

How's the scoop repair going?

Despite the original meaning of Vulcan and the fact that most vulcanization IS done at elevated temperature, heating is not necessary for "vulcanization" of rubber as we now know it. The most basic curing of rubber used only heat. Results were fairly poor. Bye and bye chemical curatives and accelerators were discovered which improved the process and allowed it to be carrier out at lower and lower temperatures and faster and faster. The term is now used interchangeably with "curing" and "crosslinking" to mean a chemical process which creates three dimensional structures from the previously linear rubber polymer chains. The three dimensional structures are what give "vulcanized" rubber its permanent elasticity, resistance to softening at elevated temperature, tensile strength, high elongation without breaking, resistance to oxidation, etc. The requirement for heat is usually desirable since it gives the processor a "knob" to turn to control the process and plenty of time to arrange the rubber parts in their desired configurations in the molds before the reaction starts to take place and makes it impossible to further change the shape of the rubber. Since patching a tube on the road or at home necessarily can't involve heat very conveniently, the chemistry for that is chosen to not require added heat. But it can still be properly called vulcanization.

Well I am envious of you one-flat-a-year guys. On my first ride of the new year, I had 4, 2 of which were inside the house, and one more within a block of the house. My last long ride, though, i had none.

done, slapped some of this ol contact cement all over and into the crack, let it dry then put a bunch of black hockey tape on it. I had repaired at the beginning of the winter but kicked it a bit too hard on -25c day, so had to redo it. Looks like it will hold, just have to remember not to push too hard with my boot when pushing into a big hard pile.

If this goes again, I think I will glue some old tube material onto it and then take a butane torch to it to melt it all together into a nice gooey mess that should harden up well when cooled. The contact cement should make a good flame --What can I say, the kid pyro in me is still there I guess...

I've never seen 'hockey tape' but have heard that it can fix anything. Tried patching tubes with it??

I have a plastic grain scoop that is cracked, so I'm interested in your repair.

Don't think I'll go the gooey mess route, 'tho.

wood, the crack was not very big, only about an inch 1/2 or so, right on the top part horizontal bit facing you (where you tend to push with your boot to dig into a big pile of snow). Because the horizontal part is curved to make it structurally strong, its tricky to bolt a piece of metal on it, I thought about going that route, maybe taking some pliable plumbers strap stuff with holes in it to bolt on, but just tried this glue and hockey tape to start with. I was partly kidding about melting it into a goo, but did consider doing it just so that the crack would be dealt with fully, but was concerned about screwing up and melting too much. In any case, this quick fix worked for a while and should be ok again for awhile. If not, I will have to go the "drill holes and bolt something solid" onto it, but probably would be better with something curved to match the curved top, rather than just a flat bracket. A flat bit might work too, but I like the idea of something that can flex a bit...hence the glue and tape idea.
I have a packet of two part epoxy ,but didnt want to open it just for such a small use, as it hardens after you mix the two bits together.