Polyethylene – the material from which Tupperware is made – has changed the way people stored and transported food forever. Tupperware consisted of lightweight, tough containers with lids that had air-sealing properties. When you pushed down the lid you would expel the air, creating a small vacuum in the container, and the removal of air kept food fresh for longer. This was a difficult concept to communicate effectively on packaging, and so gave rise to the home demonstration and the christening of the ‘burp’, the sound of the air being drawn into the container. Imagine, the sound of a material leading a marketing campaign.
Polyethylenes are the most widely used plastics worldwide, and one of the hardest to summarize, simply because they have so many different varieties. Some are soft and waxy while others are stiff; some are strong with high impact strengths while others are easily breakable. However, the typical characteristics that designers should know about are: good chemical resistance (think of the engine oil bottles you buy from the garage); they are tough, which is why children’s toys are often made from polyethylene; they have low friction and low water absorption; they are cheap and very easy to process. These last qualities mean polyethylenes have been used to make everything from the original Hula-Hoop and Frisbee to another type of American icon, Tupperware.
Image: Polyethylene traffic cone
Key features
•Versatile processing
•Waxy surface
•Low friction
•Excellent chemical resistance
•Springy toughness
•Easy to colour match
•Recyclable
Sources
Widely available from multiple global suppliers.
Cost
Rotational moulding HDPE is only slightly more expensive than bottle grade PET.
Sustainability issues
PE is one of the most widely recycled plastics. The nature of thermoplastics – materials that soften when reheated – means that all of the materials featured here are recyclable. As with any issue concerning the environment there are many factors to consider, one of which is the ability of single materials to be separated from each other. HDPE is identified by the number 2 in the recycling symbol and LDPE by the number 4.
Production
As with many commodity thermoplastics, PE can be formed using a number of methods. The most common are probably rotational moulding and blow moulding.
A number of large-scale children’s toys are made from HDPE. Other products include chemical drums, household and kitchenware, cable insulation, carrier bags, car fuel tanks, furniture and the iconic Tupperware.
Derivatives
–PET (Polyethylene terephthalate) commonly know as polyester
–LDPE (low-density polyethylene)
–HDPE (high-density polyethylene)
–MDPE (medium-density polyethylene)
–ULDPE (ultra low-density polyethylene)
–LLDPE (linear low-density polyethylene)
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–Low cost –Easy to process –Versatile –Tough –Recyclable |
–Not readily biodegradable |