Which characteristic is a benefit of polyurethane as a lead insulator?

Choosing high tear strength as the characteristic that benefits polyurethane as a lead insulator highlights a key property that enhances the durability and reliability of the materials used in medical devices such as pacemaker leads. High tear strength indicates that the material can withstand significant mechanical stress without tearing, which is crucial for ensuring the integrity of the lead insulation during implantation and throughout its lifespan in the body. This reduces the risk of lead failure, which can be critical in pacing applications.

The other characteristics, while they may have their own relevance in different contexts, do not align as closely with the specific advantages that polyurethane offers as an insulating material for medical leads. For example, excellent thermal conductivity is generally not a desired property for insulating materials, which are meant to prevent heat transfer. Low biocompatibility is not a favorable characteristic for medical materials, as it implies a higher chance of adverse reactions in the body. Lastly, high thermal expansion would be disadvantageous for insulation materials, as it could lead to stress on the lead connections due to changing temperature conditions. Thus, these factors collectively underscore why high tear strength is the appropriate choice in the context of lead insulation.