OT: Sealing broken vinyl cold packs

SWMBO is a Physical Therapist (a Physiotherapist to those of you living in the UK and the far-flung parts of former empire). The cold packs that they use are fairly costly ($15-20) and break (a couple bags a week). So I get

"Can you figure out a way to fix these?"

"Umm, ok, but why don't you find another supplier?"

"We switched to this supplier because the previous supplier's bags were worse"

"Okey doke. I need to think about this - I think these are ultrasonically welded"

"Can't you put a vinyl patch on it? Duct tape doesn't work."

"Umm, yeah, duct tape isn't gonna get you a seal, and since the break is a split in the seam, no patch will work".

"Can't you figure out how to fix these? P-l-e-a-s-e...? You can fix anything!"

"Okay, I need to think a bit about it".

The penetrating minds of the ladies and gentlemen of this forum will no doubt get the idea. So,

1. Am I right? Are vinyl seams typically U/S welded?
2. Is there a glue I could use? I was thinking of some sort of vinyl compound dissolved in a solvent, applied to the seam using a syringe (there is the problem of having a syringe full of lethal plastic/solvent in a hospital, yes...)
3. Or is U/S welding the best option. I have to think that a U/S welding apparatus is expensive.
4. What about a metal crimp?
4. Other ideas?

Given that the expensive bags are not durable, I do plan to suggest that my wife's hospital buy the absolutely cheapest product and assume it will be a use-once product. Or figure out what the gel packs contain, and make 2-300 of their own cold packs each week using zip-loc bags. Would cost about 50 cents/bag I think.

This is clearly a case where the market asks for cheap, Chinese cheap. And the Chinese are producing what is asked for. I think that the vendor may realize that his bags are breaking and that this is good for business, too, so he has no incentive to make/supply a good product.

Any help in making my sweetie a bit more relaxed about cold packs?

Thx,

Jim

Likely not good for extended use, but one more use gets you a large percentage saving anyway. I'd try squeezing some of the goop out of the split bag, to reduce bursting pressure, then seal in a Ziplock freezer bag, maybe two of them. Fold over the Ziplock closure and tape it.

Enclose a label that says "Custom made for the XXXX Health Authority"

Try a few while working on your real idea.

Mark

Would one of these work?
FoodSaver Vacuum Sealer - Official Manufacturer's Web Site - CLICK for Free Shipping Offer.

They're cheaper at Costco. Great for food too.

I've used an impulse sealer for a long time to seal parts into polyethylene bags. I'm not sure if it would work on vinyl but apparently people do weld vinyl, so maybe. Or you could rebag these in new poly bags, unless there is some reason to use vinyl. You can buy poly 'tube' in rolls several hundred feet long. You'd just need to figure out what size tubing to buy.

Did you try repairing one with a hot glue gun yet? It might be a trick to keep from melting right on through, I don't know.

Ziplocs might be okay too, although they are not permanently closed.

SWMBO is a Physical Therapist (a Physiotherapist to those of you living in the UK and the far-flung parts of former empire). The cold packs that they use are fairly costly ($15-20) and break (a couple bags a week). So I get

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If they are that costly they may be considered medical devices and must not be tampered with. Just a thought.

My local harware chain has a crafty line in reusable bag sealers which would work if the split is along an edge seam. They're essentially a rod mandrel, 4mm diameter, coaxially located inside an open-sided tube (ie C section) 6mm ID or a smidgen less, with lead-in features at one end. The mandrel extends past the flared (open) end of the C section, and is bent to form a ramp.

The otehr end of the 'tube' is closed, fixing the mandrel (central to the tube) at that end.

The idea is that the bag can be folded and this item is slid onto the fold from the open end.

They do a great job resealing heat & eat metallic-looking plastic meal sachets, such as the ones those famously affordable and tasty Indian curry meals come in. They're a very effective seal: you could stamp on the package and it probably wouldn't leak until it ruptured.

PM me if you want more info. They wouldn't be beyond the wit of man to make, and would look classy in stainless. (The hardware store ones are plastic) I'm thinking of making some like this to take on sailing trips.

Vinyl should be able to be heat welded. You say it's a seam, so I presume presents a butt joint, and no adhesive is ever going to hold in that situation. If the bag has split at the seam I guess some gel has leaked out and you therefore have a bit more material to play with. You should be able to run a new flat seam that is plastic welded. In that instance a filler rod won't even be needed. If you're not familiar with plastic welding here's a video YouTube - Plastic Welding: How to weld plastic with the Leister Triac Plastic Welding Kit it covers flexible plastics towrds the end. Otherwise do a search on plastic welding PVC.

Pete

maybe thinking outside the box

Is it feasible to put them into a heat sealable bag before using them? This MAY help control leakage. I'm assuming the leakage come from the abuse of the bag? If not, I'm way off base, sorry, wayne.

homemade said:

If they are that costly they may be considered medical devices and must not be tampered with. Just a thought.

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I see the reason for rules, but if you are correct, this is a clear case where an unholy alliance of government and industry has conspired to screw the consumer. Grrrr.

Pete F said:

Vinyl should be able to be heat welded. You say it's a seam, so I presume presents a butt joint,
Pete

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Pete, it's actually closer to a lap joint. A poorly executed one. Envision two flat rectangular pieces of plastic, with rounded edges. They essentially used an impulse weld to secure the edges almost all the way around, then filled the thing, then sealed off the last little bit of edge.

Troup said:

My local hardware chain has a crafty line in reusable bag sealers which would work if the split is along an edge seam. ...

They're a very effective seal: you could stamp on the package and it probably wouldn't leak until it ruptured.

PM me if you want more info.

Click to expand...

These sound like just the ticket, Troup, but I can't find them here in the US. For this application, I think plastic would be better, but maybe not. I will send a PM.

If I can't find the edge sealers that Troup described, I think I'm going to try one of the Walmart edge sealers, as it's cheap and as I understand it, even the gourmet chefs now use these to pre-prepare food. So if the bag still leaks, I can still seal my New York strip steaks.

Thanks, all..

Jim

Jim

The bad news is that the product bears a New Zealand web address, but the good news is that they take orders online and deliver to the US.

Each individual pack has two at 160mm seam sealing length, and two at 220mm. (Don't be misled by the longer figures quoted which are overall lengths)

The product is called 'Magic Lock Bag Sealers' and the website is

As Seen On TV

which diverts to one of those "as seen on TV" sites, but for a change, this one has at least one worthwhile product.

You might even find a Stateside importer - there certainly seem to be several as far afield as Australia, from a quick Google search.


BTW, if I ever travel to the US again, I might just engrave a bracelet saying "I am a medical device and must not be tampered with" :-)

ULINE - Cardboard Boxes, Shipping Supplies, Packaging Materials, Plastic Bags

Any type of Poly bag and a variety of impulse sealers. I have one of their bigger sealers that I use in a little part-time venture. They have good service, I broke a part, and they faxed a print with P/N's All parts are in stock..

The fish processing plants up here make their own gelpacks and they are quite inexpensive and durable. They even get them preprinted with their own label. The machine is 1500.00.

You can also buy premade gelpacks, I keep a couple on board for "incedents" and haven't had any leaks. Frontier Packaging in has them in Anchorage, Alaska and Seatac Box in Washington have them for $0.15 to $0.20 cents a piece if you buy a case.

bosleyjr said:

Pete, it's actually closer to a lap joint. A poorly executed one. Envision two flat rectangular pieces of plastic, with rounded edges. They essentially used an impulse weld to secure the edges almost all the way around, then filled the thing, then sealed off the last little bit of edge.

Jim

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Ah yeah, I've just looked at mine and they're the same. We have a brand called SensaFlex, clearly not used professionally, but the quality certainly looks up to it. Made in the USA as a matter of fact. I ordered them through an online medical supplier when my wife was pregnant ... they arrived when my daughter was about 1 month old

If the lap joint has simply split open then it should be a piece of cake to re-weld it. You won't need anything fancy either, just something that's able to apply suitable pressure and heat simultaneously. I haven't tried it, but am picturing simply heating a bar to (I think it's about 300C for PVC but best check that) dropping it on the joint and simply forcing it down until the plastic has fused. Certainly worth a go if you have a bag you can experiment on.

Pete

try an old iron. (i mean the thing you use for laundry.)

normally pvc is RF welded, vs US welded. RF welding is how air mattresses, binders , etc are made. Heat is generated at the joint so the pvc melts from the inside out and the tool is room temp or water cooled to solidify the pvc while still under pressure. This allows thicker material to be reliably welded than if the heat was applied from outside in. I used to be in this business.
A hot air welding gun will work, ie, blowing hot air between the sheets with out a filler rod and then pressing together.
I would experiment with swimming pool liner patch kits, or use MEK, brush on and clamp.

I looked at the leak a bit more closely. Alas, it is a manufacturing defect. The seal (RF welded, as I have been corrected) was done too agreesively, weaking the bag adjacent to the seam. So the leak has smooth bag material on one side, and the imprint from the RF welder on the other. As such, unless I had access to an RF welder I don't think that the bag is fixable.

I will tell sweetie that we tried.

It seems to me that a custom bag mfr machine in which you made a batch of bags as you needed them and discarded them when they broke would be the bomb. Could have my wife's hospital's name on it, and could note

"Furnished by ________ Rehab Hospital.
Temporary Reusable Cold Pack.
Put in Freezer after use.
Do not use directly on skin - always use towel or pillocase.
Discard after 7 freeze/use cycles, or if leak develops."

J

if you are starting from scratch, then no reason not to use pe bags that are impulse sealed shut. impulse is where you have a heating element that turns on and off while the seam is under pressure. ie a bag sealer

bosleyjr said:

I looked at the leak a bit more closely. Alas, it is a manufacturing defect. The seal (RF welded, as I have been corrected) was done too agreesively, weaking the bag adjacent to the seam. So the leak has smooth bag material on one side, and the imprint from the RF welder on the other. As such, unless I had access to an RF welder I don't think that the bag is fixable.

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Nonsense, everything is fixable, it just means you have a legitimate excuse to spend many hundreds of dollars and countless hours investing in specialised tooling and time for a PVC bag worth about 25 cents

Seriously though, from your description I wonder if it would be possible to run a filler rod around the compromised seams. I'm very new to plastic welding so others with more experience may like to step in here, but my understanding is that normally a repair of this type of material in a workshop environment would be done simply with hot air between the layers and pressure to fuse them together. However I wonder if using a thin 3mm filler rod could be used much like a rigid weld? It may still be flexible enough as those bags don't exactly get turned inside out in use. Having said that, personally if the rod didn't work I'd simply get more material and make up new bags. It's not difficult, and you don't HAVE to use fancy equipment for small scale work. I just bought myself a Leister but in reality it's just a miniature heat gun! ... with an inflated price tag

Bosley, is this the kind of cold pack you mean?
50 cents apiece...
Amazon.com: Disposable Instant Cold Compress Pack 5"x6" (120 per case): Health & Personal Care

Benta.

You can make your own bags.

1 part water to 4 parts 70% IPA alcohol sealed in a polyethylene bag, then double bagged for "safety".

You may have to adjust the ratio of water to alcohol to get the best "slush" factor. But considering what a roll of PE bag materials, a impulse sealer and a gallon of IPA costs...you can make a helluva lot of bags for what they pay for five of them.

I make my own for veterinary related PT.