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Answer to Activity 2
Composites in Everyday Use
Observations:
Step 1.
Beginning with a complete fruit juice container, pierce the straw through the hole provided and note the materials used. Your first observation should be that the hole is covered by a foil of aluminium which is able to seal the container but provide an easy access point for the straw.
Fig 1. The Fruit Juice Container (Poppa)
Step 2.
Cut the box in half using a pair of scissors. You will observe that the aluminium foil layer is continuous within the box.
Fig 2. The Fruit Juice Container cut in half
Discussion.
The schematic diagram below indicates the layers found in this composite material. It will not have been possible for students to identify the polyethylene materials but confirmation can be found on the web pages of the manufacturers.
Fig 3. The Fruit Juice Container (Poppa) is manufactured
from a composite material as outlined in the schematic diagram.
The printed design is the visible pattern on the exterior.
Conclusion:
The packaging material is composed of a laminate of paper making up 75% of the material to provide strength and stiffness. Polyethylene that comprises 20% of the material seals the package liquid tight and provides a barrier to microorganisms. Finally, aluminium foil makes up 5% of the package and keeps out air, oxygen, light, and off-flavours which are the things that can cause food to deteriorate. This combination of material varies to suit each separate product category, but in each case the only material to touch the contents of the package is food-grade polyethylene.
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