Page 14 - PERIODIC Magazine Issue 7
P. 14

              Transparent,       cyclable,

              low-energy food


              Researchers in the O’Hare group                 Open a packet of crisps or a bag of candy, and there it is:
              have developed a nanosheet-based                the shiny metallised film that keeps our snacks pleasantly

              barrier coating that provides an                crisp and fresh. Structurally, it is a polymer (often PET,
                                                              polyethylene terephthalate) film coated with a thin layer
              environmentally friendlier alternative          of a metal, usually aluminium. The glossy looks of such
              to the metallised films used in food            metallised films are a comforting reassurance that our
              packaging.  They explain how their              crisps and popcorn are protected from the oxygen and
                                                              moisture in the environment, thus extending their shelf
              new coating formulation is recyclable,          life.
              low-energy, non-toxic and highly                But these metallised films have a less shiny side to them;
              efficient at preventing oxygen and              their inability to be easily recycled and the high carbon
              water vapour from getting to your               footprint used in their production. Metallised films are
              snacks.                                         also non-transparent, which is a distinct disadvantage
                                                              when you want to show off the product inside your food
                                                              packaging and attract unsuspecting and hungry shoppers
                                                              on their way to check out.

                                                              So we decided to turn our attention to these current
                                                              environmental and practical concerns over non-
                                                              degradable plastics.

                                                              Our low-energy alternative barrier coating eliminates
                                                              the metallic layer from the polymer packaging film.  It is
                                                              therefore much easier to recycle, completely non-toxic
                                                              and mechanically stronger than metallised film.  It is also
                                                              transparent and has a lower carbon footprint.  It is even
                                                              Our barrier properties arise from a synthetic inorganic
                                                              material, a layered double hydroxide (LDH), which
                                                              is prepared by a reconstruction method that allows
                                                              the formation of high aspect ratio nanosheets. When
                                                              embedded in a PVA (polyvinyl alcohol) matrix and coated
                                                              onto a PET film, these nanosheets form what is essentially
                                                              a complex labyrinth that oxygen or water molecules need
                                                              to traverse in order to reach the food contained within
                                                              the packaging (a mechanism known as the “tortuous
          Supermarket shelves displaying snacks in traditional non-recyclable packaging
                                                              pathway”). And much like the average person when
                                                              they encounter a labyrinth: most of the molecules do
                                                              not enter or eventually just go back the way they came,
                                                              never reaching the crisps or popcorn we are protecting in
                                                              the middle of the LDH labyrinth.

            Periodic        The Magazine of the Department of Chemistry
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