Medical Tubing
Medical tubing is sterilized plastic tubing that is used to convey fluids or gases in a variety of medical applications. With strict requirements regarding cleanliness and non-toxicity from the medical industry, medical tubing can only be made from a limited variety of materials including HDPE, HIPS, polypropylene, polyethylene, polycarbonate, nylon, LDPE and polyurethane. However, the most common materials for medical tubing are PVC, silicon and latex. Typical applications for medical tubing include surgical tubes, catheters, swab sticks, ampoules, X-ray contrast tubing, IV connectors, culture tubes and artificial inseminators. Since medical tubing is made from FDA approved materials it can also be used in industries such as food processing, food and beverage, pharmaceutical and chemical processing. Even though medical tubing is typically more expensive than other types of plastic tubing, the use of medical tubing provides numerous benefits, even outside of the medical industry. Some of the advantages include the ability to be put on a reel, extremely small diameters, multiple fluid paths and provides a clean room atmosphere for any application. Most medical tubing manufacturers produce multilayered tubes with reinforcements made with multiple layers of many different materials.
Medical tubing is manufactured using the extruded tubing process. This process is the same as a regular extrusion process except for the die. To be extruded, thermoplastic pellets are fed into a hopper placed atop a closed extruding channel. Gravity feeds the raw plastic material down into the extruding channel; running through the length of the channel is a screw conveyor which moves the raw plastic along towards the opposite end, shearing and heating the plastic through friction. Electric heaters built into the extruding channel often help the screw conveyor to melt, or "plasticize" the plastic pellets, so that the plastic is completely molten by the time it comes to the end of the channel. On the end of the conveyor channel a die is secured which forms the molten plastic into a specific profile as it is pushed, or "extruded" through by the screw conveyor. For the extruded tubing process, a pin or mandrel must be placed inside of the die and a positive pressure is applied to the internal cavities through the pin. This creates the hollow inside of the tubing. The newly formed medical tubing is instantly cooled with cold water, pulled through by a series of conveyors and cut to length. For multilayer tubes, the medical tubing is braided over after extrusion with either a wire or a polymer. Next, an outer jacket is extruded over the braided materials. Lastly, the tube is drawn through a hot die in order to fuse together the multiple layers of material.