Medical Device Link . Chlorine-Free Blends for Flexible Medical Tubing

Polyvinyl chloride (PVC)­based tubing and film are used in numerous medical products. The material is easy to formulate and process, is relatively inexpensive, and performs well in most applications. However, some concerns exist about PVC disposal and the chlorinated by-products of incineration, as evidenced by the list in Table I. In addition, there have been reports of the inadequacy of PVC for some drug-delivery applications because of PVC-drug interaction. Table I. Volatile chlorinated compounds (parts per billion) identified in a PVC incineration study. Typical requirements for tubing used in medical devices--such as the intravenous (IV) set shown in Figure 1--include clarity, flexibility, kink resistance, toughness, scratch resistance, ease of bonding with common solvents or adhesives, and suitability for gamma, EtO, or E-beam sterilization. While other thermoplastic polymers have been used to replace flexible PVC in medical tubing, none to date has been able to match the advantages provided by PVC. For example, polyurethane and silicone have been tried, but both are relatively expensive. Nevertheless, there are several commercial offerings of non-PVC medical tubing available on the market. Tubing made by one device company, for instance, employs a polybutadiene-based material that is translucent and kinks easily. Another tubing made by a different company features a three-layer construction, with the outer layer consisting of plasticized PVC and the inner layer of a polyolefin material. As yet, however, no substitute has been widely accepted as a chlorine-free replacement for PVC-based materials. Figure 1. An example of an intravenous set with the tubing bonded to a variety of IV components. In the present study, two chlorine-free thermoplastics were examined in an attempt to mimic the key properties of flexible PVC. The research involved blending two classes of polyolefinic resins in order to develop medical tubing that could improve tubing/drug compatibility and offer a product