Medical composites formed into tubes are ideal for replacing traditional stainless, aluminum, and other thermoplastics such as PEEK and liquid-crystal polymers. One composite in particular, PolyMed, also works well in applications that call for thin-walled tubes, single as well as multilumen cannula. These tubes carry a USP Class VI rating and comply with ISO-10993.

Composites tubes offer dielectric insulation, radiolucence (transparent to X-rays), high strength-to-weight ratios, and corrosion resistance. They are also sterilized by conventional methods.

Performance characteristics of the composite are superior to those of thermoplastic materials and competitive metals. The material is also produced for structural tasks so it could replace metallic extrusions. PolyMed tubing has been used in laparoscopic procedures and external orthopedic components.

Composites from our company are manufactured with continuous fibers, which makes them stronger than injection molded or extruded thermoplastics, even those filled with fibers. Most PolyMed tubes are used to shield metals to prevent capacitance coupling. This electrical phenomena is useful for cauterizing wounds and bonding tissue after surgery. The drawback of such tools is that without the sheathing, any flesh the metal tips touch gets burned.

The tubes are available in three versions: braided, circumferentially wound (CW), or unidirectional (UD). The latter two refer to the geometry option of the braided fiber. Braiding interweaves or interlocks fibers into a circular shape, although other shapes are possible. Interweaving also provides a micro-structure similar to that of a bridge truss. The manufacturing process also uses an electrical-grade continuous fiberglass material encapsulated within a thermoset resin matrix. Braiding is one way to manufacturer thin walls, down to 0.23-mm thick when needed. In other applications, secondary unidirectional fibers can be added to increase tensile strength.

The strength of a composite tube comes from how it's made. For example, metals are isotropic. That is, their mechanic properties are the same in the x, y, and z directions. But composites are anisotropic — their mechanical properties differ in each direction. So varying the angle of the fiber path, by the aforementioned processes, allows significantly altering a tube's physical properties in a predictable manner.

Adaptations for the three designs are used in the tools for many minimally invasive surgical procedures. Tube diameters range from 1 to 20 mm, and walls can be as thin as 0.008 in. All methods that form tubes can produce single or multilumen designs.