ABSTRACT
This chapter explains how polytetrafluoroethylene (PTFE) is made into a microporous membrane and discusses properties of expanded PTFE (ePTFE) relevant to pharmaceutical and biopharmaceutical applications. It describes the unique characteristics of ePTFE membranes and also discusses the benefits of these characteristics in pharmaceutical and biopharmaceutical applications. The microstructure of an ePTFE membrane is characterized by nodes that are interconnected by fibrils. Moisture vapor flows through an ePTFE membrane by either bulk gas flow or diffusion. Scanning electron micrograph show that ePTFE is a highly porous material with a pore structure resembling a complex mesh-like network rather than idealized right cylindrical pores. The fibrils in ePTFE membranes designed for filtration are smaller in diameter than those found in many other commonly used filtration media. Filters constructed of ePTFE membranes are well suited for most venting applications. A unique application of ePTFE membrane technology is currently being used in the pharmaceutical industry to facilitate lyophilization in a closed tray.
