Fluorocarbon Polymers in Biomedical Engineering

Abstract

Fluorocarbon polymers are fully or partially fluorinated polyolefins that provide chemical inertness, thermal resistance, mechanical durability, and lubricity. These exceptional properties are because of the fluorine sheath that protects the carbon backbone from chemical attack resulting in a hydrophobic polymer with low surface energy. Most fluorocarbon polymers are semicrystalline owing to the spatial packing efficiency of the linear or helical polymer chains. In general, fluorocarbon polymers have low glass transition temperatures and high melting points resulting in a flexible polymer with exceptional toughness and resilience. Medical-grade fluorocarbon polymers are processed with minimal additives to ensure that no leachables are present in the medical device. While there is a wide range of fluoropolymers available, the use of these materials for biomedical applications is predominantly based on polytetrafluoroethylene (PTFE) in expanded form. PTFE is a completely fluorinated homopolymer which is highly nonreactive and nontoxic when implanted in biological tissues. PTFE can be manufactured in porous form in order to generate expanded PTFE (e-PTFE) with controlled internodal distances (INDs) or pore sizes. The expanded microstructure (as shown in Figure 1) provides unique mechanical properties and enables controlled tissue ingrowth as well as neovascularization in vivo.