Looking for alternative for teflon foil 1

[Swie]

Hello all,

Some background: my company makes filling machines. The (PE) bags with the product are sealed by using so called sealing beams. The beams are pressed onto both sides of the bag and the bag is sealed using a heated element. To protect the bag, and to prevent that the bag sticks to the heating element, we use a teflon foil between the bag and the heating element. I will add some specification of the foil later. The heating elements are heated up, in high capacity machines, to about 600 degrees Celcius, or 1100 degrees Fahrenheit.

The problem is, that in some machines with high capacity, the telfon foil wears out too rapidly, primarily due too overheating.

My question is: is there a commercially available alternative for this teflon foil, with better heat resistance and similar non-sticking characteristics.

 

[Swie]

Specification of the teflon:

http://www.fluortech.nl/pdf/data/013FL non adhesive nw FluorTech.pdf

 

[Swie]

Temperatur of the sealing beams is by the way not 600 degrees Celcius. The maximum it is set to is about 220 degrees Celsius. But no one ever checked this with an temperature gauge..

 

[Pud]

You could try a PTFE filled PEEK. Or even ordinary PEEK - it's quite low friction as is. 220C will be no problem for it.

Example:

http://www.victrex.com/en/aptiv-films

H

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

 

[Swie]

Thank you Pud.

One additional requirement: it needs to be foodgraded.

I'm not sure PEEK is an option in that regard, but I will check.

 

[1gibson]

Can you use xylan coating directly on the heating elements?

http://en.wikipedia.org/wiki/Xylan_(coating)

 

[Swie]

I think not, since the heating element is just a flat copper strip. But otherwise a good suggestion.

 

[1gibson]

It can be applied to copper so take a little closer look, it's worth asking the vendors. Instead of just solving the maintenance problem, you have the opportunity to eliminate the maintenance altogether. Not saying the xylan will definitely work, but I think you are narrowing the scope of the problem too much.

Ideally the machine would last forever, require no maintenance, be infinitely fast, and free to operate. Obviously you will never achieve those targets, but you can always try to improve reliability, speed, and efficiency.

For all we know, the Teflon foil could be a "oh crap, the bags stick to our prototype and we've already completed the design, what do we do right now so we can ship these things" solution. I can buy a small bag sealer off the shelf that doesn't have sacrificial Teflon foil that requires maintenance. What does it use, how do they get away with it, and why do you feel you can't?

 

[btrueblood]

Polyimide tape might work too, it has decent release properties. Or perhaps a silicone rubber sheet...I think I like that option the best, because it has both a decent release property, and good thermal conductivity.

 

[chicopee]

Have you researched other types of equipment such as ultrasonic sealing machines?

 

[Compositepro]

There really is not anything better than teflon. The foil is considered a consumable. Proper operation and maintenance is essential to get decent performance, however. Impulse heat sealing is more complex than it seems. The foil is normally exposed to temperatures close to its decomposition limit. Exceed this limit and the foil will be ruined on the first sealing cycle. Some machines are more robust and expensive than others.

 

[lukin1977]

We have in operation many vacuum sealing machines that use the same mechanism to close the plastic bags
The teflon foils used to be damaged after one day of operation (60 cycles aprox)

I lower the voltage applied to the heating element and the problem was solved

 

[IRstuff]

I've seen something that looks like woven fiberglass over sealing strips.

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

Of course I can. I can do anything. I can do absolutely anything. I'm an expert!

 

[Swie]

Lukin1977, lowering the coltage = lowering the temperature? I do need the temperature..

 

[lukin1977]

yes. I know you need the temperature

But maybe you can lower a little the temperature and increase the sealing time and still achieve good bag closing
I am just telling you what I did and how I solved a similar problem

 

[Compositepro]

Sealing is a function of temperature and dwell time. If the Teflon is overheated it will be destroyed. The heater power must be limited so that it does not overheat the Teflon, and then the heating period must be set long enough to allow the film to reach sealing temperature. In addition a cooling dwell is required so the weld solidifies before clamping pressure is released. If you are burning the Teflon you have probably also ruined other parts that will need to be replaced. Decomposing Teflon is very corrosive (and toxic). The heating ribbon will get corroded and cause a hot spot which will cause another failure in the Teflon very soon.