A bag of potato chips shouldn’t be too easy to open

Friday, 11 May, 2012

All good design is a trade off. A bag of potato chips may be mildly difficult to open but the sealing process prevents it from opening sooner than intended.

Variations in atmospheric pressure, say as the chips are transported from a sea level to an area of high altitude, may be enough to cause the packets to open, something that most certainly necessitates a strong seal.

In a heat seal, you are attempting to melt the adhesive polymer and get it to flow into the other layer. Upon cooling, the two layers are now entangled and show adhesion. The strength of a heat-seal depends on three and only three variables: time, temperature and pressure. Increasing any of this will increase the strength of the bond, but most manufacturing engineers are really only open to increasing pressure. Increasing sealing time slows the entire process, and increase the sealing temperature also slows the process since it takes longer to heat the adhesives to the higher temperature, that adds to the time as well. The best option was to develop an adhesive that sealed at a lower temperature, something that was successfully accomplished, or so I’m led to believe from all the complaints that colleagues pile on me now that they know I’m that guy.

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