Heat Sealimg Polypropylene

You say nothing about your current process. Specialist Polypropylene Foot Operated Sealer
size:300mm wide crimp seal x polypropylene sealer
For sealing polypropylene, a constant heat sealer is required creating a wide crimp seal. Please feel free to send in a sample of film for

Hi pageebe,

Is each layer being sealed 5 mil (0.005 in)?

Is the heat sealing automated or manual?

What are the jaws surfaces like? I have seen teflon-coated metal jaws with a waffle-shaped pattern, and I have seen ceramic fiber flexible "bars" attached to the jaws.

What is the length and width of the sealing bars?

What is the sealing contact time?

What is the sealing bar temperature?

If the seling mechanism is pneumatic, what is air supply pressure (usually in psi)?

Mike

Yes each layer is .005 in

The process is automated.

The jaw surfaces are smooth aluminum.

The contact time is approx 1.5 seconds.

The temp is 400 F.

We recieved the machine from the company that was contracted to build it with stops that maintain a .010 gap(I'm told that this is to prevent it from compromising the integrity of the plastic.... I think some pressure should be applied, but I'm not familiar with heat sealing techniques

Are the leaks through the seams themselves, or through the bag material at the edges of the seams. I have seen both. Is there any plastic residue on the Al sealing bars? 400º seems a bit high, but your polyprop may be special.

If you are getting leakage through the seams themselves, a certain amount of experimentation could well provide a solution, as suggested by Tornado below.

By the way, what does the manufacturer have to say about the issue?

Can you remove some shims or otherwise adjust the closed position to a bit less than 0.010"? I don't know the ideal amount of compression, but a few experiments with this could be informative.

Having one of the sealing jaws float on springs, instead of a rigidly defined gap is easier to maintain in a production environment

are the sealing bars plain or teflon coated aluminum?

are the jaws actuated mechanically or pneumatically?

is the tail of the bag supported during sealing?

how wide is the sealing surface?

where is 400 degrees being measured & maintained?

we have recently started using teflon coated heads, to see if the leaks are being caused by sticking to the bare Aluminum and pulling apart. This has not changed the frequency or severity of the leaks.

The bag is held flat as it is being sealed.

the temp is measured by an embedded thermocouple approx .125 in from the surface

How wide is the seal?

How much dead band does the temperature controller have? [temp variation]

heaters in both jaws?

I'll guess that the leaks are at the ends?

you might try a thin piece of silicone rubber covered with some sticky back teflon tape over one jaw [adjust gap accordingly]

can you lower the temp & increase the dwell time?

Is the seal wrinkled ?