Heat shrink-able thermoplastic tubing is used in a variety of industries and can be made from many types of plastic. The tubing is heated with internal pressure and then cooled while maintaining the pressure. Once cooled the diameter remains expanded. If the tubing is then heated at or above the temperature that it was expanded at, it will shrink back to its original diameter. The precise control of the process is important for a quality product. Shrink tubing is important for the production of catheters to provide a smooth consistent outer surface.
The generic industrial heat-shrink tubing is relatively easy to make from a cross-linked polymer or any material that gains strength when stretched. A rubber band is easy to stretch until it reaches its limit and then it gets much stiffer. Many polymer materials are in this category and called “FREE-EXPANDING”, because they can be expanded without any external diameter constraint during the process. Some other common polymer materials in this category are: Polyester, polyethylene, PVDF ( Kynar), etc.
Common flouropolymer Teflon-like materials are Polytetrafluoroethylene (PTFE) and Fluorinated ethylene propylene (FEP). While they all melt at higher temperatures they all act different when expanding and then recovering (shrinking) in a typical process. They are difficult to make because they lose strength when expanded and must be constrained during the expansion and heating process. If not they will simply blow up. This requires “CONSTRAINED EXPANSION
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EBD has a solution for both types of expansion. Our modular tooling allows for multiple of expanded tube sizes to be run on the same machine. Just let us know what you need!