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Adhesives Functionalities Enabling Smart Food Packaging

Posted on 10/3/2016 11:05:57 AM By Deb Bhattacharjee
  

In food packaging applications, a variety of substrates including aluminum foil and plastics are utilized, each contributing to unique performance requirements1.  A typical structure of multi layer package is illustrated below:


                             click to enlarge

For example, aluminum foil delivers the rigidity, temperature resistance and protective/barrier properties to oxygen, humidity, odor, grease.  PET offers strength, transparency and printability while polyethylene is used for its elasticity, flexibility, and ease of processing sealing requirements.  However, several substrates have widely different surface energies and that is where adhesives play a critical role in uniting or bonding such layers.  Interestingly, in general, adhesives represent only about 1 weight % of the total package, yet delivers such an important functionality to combine all benefits of different layers.

Adhesives are used primarily to bond surfaces with dissimilar surface energies.  In order to achieve the optimum adhesion, an adhesive must thoroughly “wet out” the surface to be bonded.  To wet out a surface the adhesive must flow and cover the surface, allowing maximum contact area between the adhesive and the surface. The table below lists typical surface energies of commonly used substrates2.  Several delivery techniques (water, solvent or 100% solids) should be considered and compared for the best balance of productivity and performance. 


                            click to enlarge


However, are there other properties you would like an adhesive to impart for its differentiated performance?

Several advanced technologies which deliver additional functionalities besides adhesion have been developed, and these make adhesives more versatile and critical for success in its end use application.  These include:

  • Antibacterial properties
  • Barrier to oxygen
  • Barrier to moisture
  • Barrier to low molecular weight “migrating” species
  • Odor control
  • Barrier to grease/fat
  • Others?

This can be accomplished by chemically modifying adhesive polymer backbone or blending with additives which could either physically adsorb/absorb or chemically react with the desired species.

In subsequent issues, we will take a deeper look in these performance attributes.


References:

  1. “Food Packaging - Roles, Materials and Environmental concerns”, Kenneth Marsh and Betty Bugusu, Journal of Food Science, April 2007, 72 (3), R39-R55
  2. “Surface Energy Classification”, Literature from Nova Films & Foils Inc.