High Rate Deformation of Amorphous Polymers and Their Blends

The purpose of this study was to measure and be able to quantitatively approximate the effect of strain rate and composition on the yield stress of a blend of two thermoset polymers. In this case, one of the constituants was a glassy state thermoset polymer (Derakane 8084 Vinyl Ester) and the other one was a near rubbery state thermoset at room temperature (Crestomer 1080 Urethane Acrylate). The results of stress vs. strain tests conducted on both an Instron hydraulic testing machine and a split-Hopkinson bar indicated that the yield stress was highly dependent on strain rate, and the sensitivity of the yield stress to strain rate increased as the amount of Crestomer 1080 was increased. Of particular note was the change in behavior of the 100% Crestomer material from that of a rubber at low strain rates (−.00065/s) to that of an elastic-plastic behavior at very high (−2000/s) strain rates. A predictive equation was developed to estimate the compressive yield stress of a polymer blend at a given rate. This model utilized the yield stress of the two pure constituents and a weighting criteria based on the glass transition temperature (Tg) of the blend which was measured experimentally using a DMTA. It is believed that a plot of this kind can be used to quantify to what degree each component controls the deformation process, and at what composition the transfer of dominance between components occurs.