Temperature-Dependent Impact Properties of ABS Polymer

Polymeric materials are composed of chains of molecules known as monomers which are held together by secondary bonds. Amorphous polymers have a glass transition temperature above which their behavior transitions from glassy to viscoelastic, meaning they act like both a viscous liquid and an elastic solid. This concept may seem familiar to anyone who has used Silly Putty®; bouncing a ball of Silly Putty causes the material to behave elastically whereas it will flow into a puddle if left on a table overnight. Time temperature superposition (TTS) describes the dependence of viscoelastic mechanical properties on time and temperature. Repeating the Silly Putty experiment at a different temperature will change how long it takes to reach the same end mechanical property. The Williams-Landel-Ferry (WLF) equation empirically defines the relationship between a temperature shift and a shift in the timescale for a specific material property. It has been widely used for materials undergoing low rates of strain (e.g. creep, stress relaxation), but it applies to any property of viscoelastic behavior. This paper examines modeling the temperature-dependent impact behavior of polymers based on the WLF equation. Although polymers experience viscoelastic behavior for an incredibly short time prior to fracture, the strong temperature dependence and past literature suggest the validity of the WLF equation to higher rates of strain as demonstrated herein for the energy absorption of acrylonitrile-butadiene-styrene (ABS) undergoing high-velocity multiaxial impact tests.