GCM 746 Lecture Notes - Lecture 9: Shrink Wrap, Food Packaging, Thermoforming
22 May 2020
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Document Summary
Of the 78 million metric tons of plastic packaging produced globally each year, a mere 14 percent is recycled. Lightweight and floatable, plastic that escapes collection flows into our oceans: 9 million tons annually. More than 30 different plastics are currently used in packaging. Food wastes: plastic protects food over long journeys, guarding it against pressure, humidity, light, and the bacteria that accelerate rot. E. g. , shrink-wrap a cucumber in polyethylene and its shelf life stretches from three days to 14. Plastics and natural materials such as rubber or cellulose are composed of very large molecules called polymers. Polymers are constructed from relatively small molecular fragments known as monomers that are joined. Occur in nature and can be extracted. Include the large group known as plastics used in the packaging industry. Contain polymers that cross-link (three-dimensional structure) together during the curing process to form an irreversible chemical bond. Always remain in a permanent solid state (when heat is applied)
