Tecobax~(TM) - A New Class of Non-softening Thermoplastic Polyurethanes for Medical Applications

摘要

Thermoplastic polyurethanes (TPUs) are a class of thermoplastic elastomers (TPEs) that are used in a variety of medical applications (1). Their characteristics including low temperature flexibility, excellent abrasion resistance, high tensile strength, good processing characteristics, and biocompatibility make them particularly attractive for medical applications by the device design engineers. In general current medical grade TPUs have the unique property of undergoing a reduction in flex modulus when placed in the body (2). This characteristic is referred to as "softening." A new class of TPUs has been developed that retains many of the characteristics found attractive by designers but now offers the non-softening characteristic, broadening the design space for TPUs in medical devices. A non-softening TPU may be an attractive material for use in percutaneous interventional catheters where retention of stiffness is desired to enhance trackability and torqueability. Three grades of non-softening TPUs, covering low to mid durometers have been introduced into the market: Tecobax~(TM) 25D, 40D, and 45D. The performance characteristics of these TPUs were measured and compared to other softening TPUs as well as non-softening TPEs. These materials maintain many of the typical TPU characteristics which make them widely used. For example, the 25D, 40D and 45D durometers have excellent tensile strengths and abrasion resistance. Softening characteristics were tested by comparing flexural modulus values at ambient conditions (22°C, 50% RH) to body conditions (100% RH, 37°C). The degree to which these new materials soften, especially in the harder grades, is significantly less than other TPUs but is comparable to non-softening TPEs. Torqueability at body conditions is also comparable to common non-softening TPEs. These materials also offer other unique characteristics which are of particular interest to the medical device community. For example, these materials have a high Vicat softening temperature; the 40D and 45D are above 100°C, resulting in compatibility with steam sterilization. In addition, these materials produce excellent quality extrusion components using standard extrusion equipment. Other unique characteristics and potential medical applications will be discussed.