Compressive properties of four fluoropolymers as a function of temperature and strain rate

Compared with other polymers, those containing fluorine present several advantages for load-bearing structural components including higher strength at elevated temperatures and higher toughness at lowered temperatures. Failure sensitive applications of fluorocarbon polymers include surgical implants, aerospace components, motor seals, and barriers for hazardous chemicals. Fluoropolymers are semi-crystalline in nature, with their linear chains forming complicated phases near room temperature and ambient pressure. The most widely used fluorocarbon polymer for engineering applications is Teflon (polytetrafluoroethylene, PTFE), due to its extremely low coefficient of friction, outstanding resistance to corrosion, and excellent electrical properties. Stress-strain measurements have been conducted on two homopolymers (Teflon and Kel-F 81) and two copolymers (Kel-F 800 and THV500) as a function of temperature (-100°C-100°C) and strain rate (0.001-2600 s"1). A split-Hopkinson pressure bar (SHPB) was used to achieve strain rates of about 2600 s^-1 in compression, while conventional testing machines were used for strain rates from 0. 001-1 s^-1. These polymers exhibit increasing yield stress with increasing rate and decreasing temperature. However, despite similarities in structure these polymers have glass a wide range of melting temperatures from 85-340 °C and similar variability in strain hardening behavior.