This is a simple but very effective application of polyester heat shrink tubing for masking areas during coating operations. One manufacturer requires a white coating over a clear balloon, but the neck must remain uncoated so that a UV curable adhesive can be used to bond it to the catheter. A piece of heat shrink tubing is applied to the neck, then the balloon is dipped in the coating. After it dries, the heat shrink is peeled away, leaving the neck uncoated. The key to this application is the thinness of the polyester tubing. A thicker shrink tubing would leave a thick edge of coating material on the balloon, unlike the ultra-thin wall polyester tubing.
Another manufacturer applies a slippery coating to a length of wire that has a fine spring coil at the end. Polyester heat shrink tubing is used to mask the spring to keep it from being coated during the dipping process. The low shrink temperature permits the masking operation without heat distortion, and the tight shrink fit prevents the coating from flowing into the spring. Afterwards, the polyester tubing is easily peeled away.
The key properties of polyester heat shrink tubing in masking applications are:
Very thin wall to prevent thick build up at edge Low shrink temperature allows application without heat distortion Easily removed Tight shrink fit on substrate
Removal of polyester heat shrink tubing:
Heat shrink tube is easily removed by pulling or peeling and the mandrel is pulled out of the catheter tube. The heat shrink tubing does not stick to most materials. If necessary, the tip may easily be trimmed using a razor blade. Observe the ultra, smooth glass-like surface finish of the taper produced using this process.