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Fixed PTFENo CoolVert. CoolHoriz. Cool
Inspired by Dr Kazuo Hishinuma's standard text, published by DesTech, Heat Sealing. Technology and Engineering for Packaging, Principles and Applications. For the Induction Heat Seal app see HSC-I

© Copyright 2013 Abbott Apps
Heat Seal Calculator

This is a brief summary of the app. For more details read the User's Manual.

You have two heat seal jaws at temperatures TJaws1 and TJaws2. You have two heat seal layers HS1 and HS2 of polymers of your choice, with thicknesses of your choice. Between the first jaw and HS1 you have a maximum of two layers, T1, T2 again with your chosen polymer and thicknesses. Either/both can be zero thickness. The same thing applies between HS2 and the second jaw, with B1 being next to the second jaw (so that B1 mirrors T1 and B2 mirrors T2).

When you click the Calculate button (these thermal diffusion calculations take a little time so you can't get instant feedback by moving the sliders) you get a graph showing the temperature versus time at the point where H1 and H2 meet. The timescale for the graph is governed by t-Heat, which is your heating time. Moving the mouse over the graph gives you a readout of time and temperature

As we are taught by Hishinuma, it is vital to know TSeal and TBad. These are shown on the graph. The temperature should rise to a little above TSeal in the timescale of your process window, but should not have a chance to rise to TBad if you extend your process time for some reason.

The diagram on the left shows the temperature distribution top to bottom from jaw to jaw (silver), with clear jumps at the boundaries between polymers (marked with horizontal dashed lines) because of their different thermal properties. The diagram is colour-coded through time - violet is short time and red is long time. Moving the mouse gives you distance and temperature and if the mouse is over a line it indicates the time as well.

The choice of polymers dictates their thermal conductivities, heat capacities, densities and MPts. Where a polymer is followed by, say :105 that means that the effective melt temperature is 105°C (221°F). The polymers are further distinguished with a designation of N for Narrow melting range and W for Wide melting range. Modern heatseal polymers tend to be a wide melting range which makes the set-up less critical.

For those interested in what happens when the jaws are opened, there is a cooling option. As explained in the manual, the cooling depends on the orientation so you need to choose if the sealed device is vertical or horizontal. Cooling is relatively slow, so set a much larger time-scale, t-Cool, than used for heating.

For those who have PTFE stuck to the jaws, the Fixed PTFE option should be selected. It assumes that the PTFE is at jaws temperature at the start of the process, and also that the cooling involves just the non-PTFE layers.