Co-Polyester (PETG, VIVAK)

Forming Temperature

• 325°F -350°F - Upper Limit on Cast = 335°

Description

• Clear

Shrinkage

• Minimal – 1%

Self Adhesive

• Moderate, not dependable under stress.

Considerations ~

• All ovens vary in performance. It is recommended that the fabricator establishes a Heating/Time Schedule specific to the thickness and sizes of material being used in their ovens. Always record your successes and failures for future reference.
• This thermoplastic material is used in Prosthetic applications when low cost rigidity is required. Commonly used as initial or temporary check socket material for prosthetic sockets. All sockets using this material must be reinforced prior to dispensing and should be identified as having a very limited life expectancy when under repetitive loads. Formed seams are not dependable and should be sealed and or mechanically reinforce before being dispensed.
• A thin bubble formed PETG interface is sometimes laminated over to enhance vacuum assisted socket suspension systems. The theory is that co-polyester offers a smoother interface surface and is less gas permeable than the common laminations being used.
• Caution must be taken to not overheat this material as it will become very brittle.
• This material processes optimally on a suspended woven Teflon cloth material which allows the material to heat more evenly from all sides. This will increase the window of time the fabricator has before the material begins to break down (bubbles out) as it often does when using a “cookie sheet” / a closed Teflon cover.
• While not common, most protective films on PETG can be left on while processing. The film will act as a separator once the material has cooled. Trimming edges of the film will allow for a good forming seal on the bare material being formed. Make sure to ask your supplier if the film provided is compatible with this processing technique.
• Holes drilled in this material should have their edges relieved or slightly countersunk to try to prevent the hole from cracking at an attachment point.
• Co-Polyester that has begun to degrade (“bubble out”) should never be used for any check socket application. Catastrophic failure could create an injury that was preventable