Device designers have to investigate application parameters while also dealing with the product’s regulatory and compliance requirements to choose the right tubing. Here is the process for selecting the right tubing product and supplier for a given application.
Alex Kakad, for NewAge Industries
When selecting a tubing material for your medical device application, the most important considerations are the key physical parameters of temperature range, pressure capabilities and chemical resistance to fluids that the application will see. However, other important physical attributes of the tubing may be durometer, or softness of the material, as well as bend radius, which will dictate the kink resistance of the product in application use. Lastly, cost is always a consideration when specifying a tubing product for use in an application.
In addition to the physical performance characteristics of a given material, another important factor is choosing a tubing supplier that has current data and validation information to back up claims made around their product, meets the quality and compliance standards set by the governing bodies involved with the application and has the breadth of product offerings to meet all the tubing needs for the application.
There is a wide range of materials that can be used for fluid transfer in medical device applications.
PVC tubing has a long history of use in the medical industry. It’s a flexible, durable and relatively inexpensive product that resists a variety of chemicals. PVC is also lightweight and offers excellent abrasion and corrosion resistance. Depending on its formulation, PVC can also offer compliance with FDA, USP, NSF and other standards needed for compliance in certain medical device applications.
Depending on specific application requirements, PVC may not have the purity needed. If leachables or extractables from the tubing are a critical element of the design, PVC may not be the best option. For industries where high purity tubing is critical to typical applications, other materials such as silicones or TPEs are more typically seen.
Silicone is an extremely pure material that processes into very flexible, soft tubing, making it less prone to kinking than other materials. It handles a wide range of temperatures – from as low as -100°F up to 500°F – and many products meet regulatory compliances related to the FDA, NSF and USP. Silicone is non-toxic, naturally translucent and free of substances of concern such as BPA, latex and phthalates. The tubing is also odorless and tasteless and can withstand repeated sterilization. Certain formulations of silicone also perform very well when used in a peristaltic pump.
Silicone tubing is typically broken into two main categories, peroxide cured silicone and platinum cured silicone. Both are widely used in medical device applications and offer a high level of purity compared to other material types. However, peroxide cured silicone does have low levels of benzylic acid as a byproduct of its processing. If the highest level of purity is required, platinum cured silicone is typically the best option.
TPE (or thermoplastic elastomer) tubing products are another good option if a high purity, flexible tube is required. A unique advantage to TPE tubing is that it can be welded or sealed to itself using a heat sealer for use in sterile applications. Many versions of this material also meet USP Class VI standards as well as FDA and NSF requirements.
Combining properties of plastic and rubber, phthalate-free polyurethane tubing offers more resistance to pressure and vacuum than corresponding sizes of PVC or rubber. It provides abrasion and tear resistance, high tensile and elongation values and virtually unlimited flexural abilities. Polyurethane offers good chemical resistance, and like silicone, its raw materials conform to FDA standards.
Another set of tubing products historically used in the medical device industry are fluoropolymers including FEP, PFA and PTFE. These products have a very high level of purity but are not as flexible or kink resistant compared to the other materials discussed in this article. Fluoropolymer tubing products do have a set of very unique properties including extremely high tensile strength and burst pressure, a wide range of chemical resistance, and a high spectrum of continuous operating temperatures (up to 500°F).
Choosing the right tubing for an application can be a daunting task as there are almost limitless options available, but very few candidates will meet all the requirements. In order to determine the most suitable tubing solution for an application, the best idea is to discuss your needs with a supplier that has a wide breadth of product offerings, an understanding of regulatory and compliance requirements, and a knowledgeable staff that can help recommend the most suitable tubing product to meet your individual application needs.
Alex Kakad until recently was a product manager at NewAge Industries (Southampton, Pa.).
The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of Medical Tubing + Extrusion or its employees.