Welding and seal sealing tape

[@less@ndro]

Good morning guys,
I'm in love with the xpac fabric and i discovered that i can make my backpacks waterproof if i put some seal sealing tape. I see that this is possible with many machines, ultrasonic and hot air machines. i see on amazon that there is also a tape that should works with only the iron. Actually i don't have money or space for a big and expensive welding machine but i found this http://www.alibaba.com/product-detail/230V-110V-1600W-Hot-Air-Heat_60538214436.html?spm=a2700.7724838.0.0.r3aSDs  anyone know if it could work? I don't care if it's slow because i don't have a production to make but i want it to works well and don't have the tape going away after some time. If anyone is practiced with this type of machines could you please explain me the difference between the ultrasonic and the hot air?
thanks a lot guys

[stimpy]

Looks dangerous to me. I never worked with x pac. Or the machine you post the link to. But i guess that the mouth piece will be very hot. And if you touch the x pac it might get burned or something. It would be a shame to ruin a pack

[essal]

I don't know anything about the "iron on" stuff, because I've never worked with any type of seam sealing tape that works with an iron.

The formula to glue stuff is heat + pressure + time. Your heat depends on the GLT (Glue Line Temperature) required to start the process and what fabrics you are applying it to (and what the seam tape requires). Pressure depends on how you are applying it, but static hot presses are usually 4.2 MPa, a lot. Time depends on your heat, pressure and the fabrics willingness to accept the glue as well as how heat transfers (it's very common to see a 10-20 Celcius drop from a nylon/poly fabric but it's kinda like witchcraft and hard to tell without actual testing).

The thing you posted can work, but I am curious on how you'll be able to apply enough pressure. You can set up some sort of roller that it passes into AFTER you've applied the hot air.

As a note, Ultrasonic seams all require another layer of seam tape, it's really weak on it's own. US seams are used since they produce a virtually flat seam. I am unsure if RF wielded seams can hold their own but I somehow wouldn't expect it to.

[BEA-RD]

Look into a hand held "wedge welder"

[17SG]

I have experimented with ultrasonic welding as well as seam tape for tarps. I will say that the ultrasonic welding will not weld any type of fabric and to be honest I do not think the x-pac backing would be a good candidate. Even if you can get it to work I think that ultrasonic welding give a less than desirable effect. The weld itself is strong but it seems to weaken the fabric along the weld. I have used seam tape with success that had to be ironed on. Very time consuming but since you would not be using it for production that is a non-issue. If you do choose to try the seam tape I would suggest putting the iron on the highest setting and putting a Teflon sheet over the fabric. Do not put the iron directly on the tape. The tape is Melco brand and can be found here http://www.rockywoods.com/Hardware-Zippers/Seam-Sealers-Seam-Tapes/MELCO-Seam-sealing-tape-for-2-layer-fabrics. 

[essal]

Here is a video of a common design seam sealing machine:
http://www.youtube.com/watch?v=x6Tx2yT56YM

As you can see, the nozzle providing the hot air is to the right, and it feeds to the left between 2 rollers. That gives you heat + pressure + time. A machine like this will often run ~400-900 Celsius due to the speed. A static press would run ~20-30 seconds at 150 Celsius  with ~4.2 MPa. If you can somehow mimic this with a hand held tool, then you'll be alright.

I know that one manufacturer (used to) sell a prototyping machine, which was basically a hot air gun mounted to some rollers with a simple feed mechanism, so it was way smaller than any industrial machine. Maybe "home" seam sealing tape has a lower melting point than industrial stuff and an iron might work, I just wouldn't except it to hold over time, especially if you start washing and drying anything.

[@less@ndro]

thanks a lot for the answers.

I also was skeptical about something so cheap and small.

The producer of xpac fabric said that some fabricators use Bemis #3231 tape for sealing where they sew and that the fabric is not weldable.

what about these wedge welder? I found them on alibaba and they seems more reasonable than big machines but i don't know if they are good for what i want to do. I want to sell backpacks made in this way, the tape have to stay sealed and maybe ironing them is not the best thing to do.

[SunriseTacticalGear]

I think Sonobond is the machine that was next to the Brookwoods booth at Shot show 2016.
I tried a small sample and it created a very strong bond, it looked promising for a light weight, waterproof backpack.
Scott
Also a link to a gear build.http://www.sonobondultrasonics.com/news/k9-storm-inc-uses-sonobond-s-ultrasonic-sewing-machine-to-comply-with-nij-waterproof-standards

[Corvus]

I work quite a bit with seam tape. As mentioned before, it is a magical combination of heat, time and pressure which is closely guarded by the laminate and seam tape companies. I spoke to a Gore-Tex adhesives engineer for about an hour seeking some guidance or even a starting point, and all I walked away with was that I need to sort out the heat, time and pressure through trial and error because every tape and fabric has a different combination.

The sonobond machine would be a great tool to have but if not doing volume production (or in my case repair) it is cost prohibitive. For small batch work, your best bet is a heat transfer press like those used for making t-shirt transfers. These can be found for as little as $200 and go up from there. I use a George Knight DK-8

http://www.geoknight.com/products/digital-knight-6x8-label-press

This allows me to have consistent and adjustable heat and time, and I estimate pressure by measuring the height of the platen screw. I think I can put a pressure sensor inline to be more precise in my pressure, but I have had good success so far with out one.

You need temps around 250ºF for 10-25 seconds, depending on the fabric and tape. Around 345ºF you will start to see slight glossing of most Goretex® 3 layer laminates, on the face fabric. 3 layer seam tape works VERY well on XPac material.

EDIT: Just saw someone else doing 350ºF @ 5 seconds

You could try to use an iron to achieve the results you are looking for, but in my experience (going on a year now using the press) you will have inconsistent and undesirable results Vs. using the press.

As an added bonus, I have been able to do some heat welded repairs using various basting tapes and the heat press as well.

Let me know if you have any additional questions.