Chapter 33PET in Thermoforming Applications
Over the past two decades PET (polyethylene terephthalte) gained rank among the top five of thermoplastic resins.1 In film and sheet selection, a variety of different material types are available:
- A‐PET
- PET‐G
- Multilayer film GAG (PET–G/A–PET/PET–G)
- C‐PET
In case of A‐PET, crystallization is minimized to allow for easier thermoforming and improved clarity. In case of crystallized PET or C‐PET, crystallization is enhanced for high temperature end use.
The overwhelming majority of PET volume (>90%) is used for bottles and containers. Packaging and film application volumes include most of the applications where PET has been substituted for polystyrene volume in recent years.
A‐PET resins and final articles have variety of desirable properties. A‐PET has very low haze levels (0.5%), which makes it desirable for any packaging application where the display or presentation of the packaged article in its container is required.
In addition, A‐PET is a tough material, as is shown by its high tensile elongation at break and high tensile modulus. The only two limitations to the use of A‐PET resins are the low Vicat heat distortion and high specific gravity. The low heat distortion eliminates its applications in some food service applications such as hot soup. The high specific gravity increases its cost per unit volume compared with polymers with lower specific gravities such as polystyrene and polypropylene.
33.1 EXTRUSION AND THERMOFORMING ...
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