Effect of halogenation on the shock properties of semicrystalline thermoplastics

The high-strain rate response of polymers is a subject that has gathered interest over recent years due to their increasing engineering importance, particularly in the transport industries. This work explores the effect of fluorination upon semicrystalline thermoplastics. Polyethylene, with its simple hydrocarbon chain, is considered; with increasing fluorination of the carbon backbone polyvinylidene difluoride, and then polytetrafluorethylene (PTFE) is also compared. All three show a nonlinear equation of state behavior, which may be related to partial crystallinity. PTFE is shown to have anomalous release speed, which reflects its transformation from phase II to phase III transition at 0.7 GPa. Strength effects show a different ordering of behavior between the three materials. The first results are accountable purely using van der Waals forces between the chains. However, strength effects show the effect of further attractive forces that indicate some tacticity in the material associated with the state behind the shock. (C) 2007 American Institute of Physics.