Since PETG plastic film is an adaptation of PET, it is important to understand the origins of polyester plastic first.
In 1941, British scientists John Whinfield and James Dickson created polyethylene terephthalate (polyester) by combining phthalic acid polymers with glycol-based synthetic fibers. By using the process of esterification to heat glycols with terephthalic acid, long-chain molecules of PET is created; it becomes a functional substrate when it is turned into fibers with high melting points and low dissolvability.
At first, PET plastic film became most popular within the Textile industry. By 1952, it was being used as a substrate for food packaging.
While it is one of the most widely used plastic film substrates in the performance plastics industry today, a disadvantage to be aware of is its ability to be susceptible to crystalizing in high temperatures. Once it reaches a certain temperature, PET tends to become opaque and weakens its structure.
The creation of PETG is beneficial due to its ability to stop the crystallization of PET by replacing the ethylene glycol molecules with a larger monomer, Cyclohexanedimethanol. With this change in the molecular chain, PETG molecules don’t collect together as easily (as PET). By lowering the melting points, this hinders crystallization, thus increasing heat resistance.
With this benefit, PETG is an ideal substrate for thermoforming, 3D printing, and other applications that may require high temperatures.