Hydraulic O-Circle Difficulty related to extrusion process

The water absorption of dry polyamides is relatively high. In a saturated state, this type of polymer can be absorbed in water at ambient temperature from 3 to 8% by weight. Due to the supply, the polymer was studied to absorb about 1% by weight in water. It is very important to extrude the polymer before drying to avoid the formation of air bubbles or pores in the finished balloon catheter.

The molten polymer absorbs up to 4.5-10% by weight of its weight in water in a cooling bath at which it leaves the extruder die. The amount of absorbed water can be affected by a number of factors including the temperature at which the polymer is melted, the flow rate of the molten polymer in the die and the cooling bath, and the distance between the cooling water bath temperature. As a plasticizer, water can modify the mechanical properties of the tube and the finished balloon catheter.

The morphology of the cooled semicrystalline polymer depends on the cooling rate, particularly when the crystallization rate is very low (e.g., when PET is used). In addition, since the polymer has a low thermal conductivity, the cooling rate may be different on the outer surface of the tube than on the inner surface, especially when the tube wall is thick. In the case of semicrystalline polymers, it has been demonstrated that this difference in cooling rate can be caused by extrusion or injection molding that results in the formation of very thin layers in different forms on the surface of the tube. This phenomenon is known as skin effect. After the silicone seal is extruded, the ring is cooled by water. Because water can be easily absorbed by the hot polymer, the loop should be hot air through the cooling bath to minimize drying after its properties or the adverse effects of those finished balloons.