Thickening

This video shows some of the properties of a dilatant compound (Shear Thickening Fluid) including its ability to stretch, flow, and tear. The simple explanation: This substance displays four different properties on four different time scales. At very long timescales, it behaves like a liquid spreading out onto a flat surface. At moderate timescales, the substance stretches like a plastic solid. At short timescales, it bounces like an elastic solid. And, at very short timescales (the impact of a high-speed projectile), the substance simply shatters. This substance is a dilatant compound, which means it becomes solid under the influence of pressure. If you've ever played with Oobleck or Smart Mass Putty, you've experienced the same properties. The complicated explanation: Some of the behaviors listed above are an example of a dilatant compound, where the viscosity (ie the resistance to flow) increases faster than the strain rate. Although not common, some materials do exhibit dilatant behavior (concentrated aqueous corn starch suspensions -- read: Oobleck). However on its own, this is not enough to explain the behavior of this substance. In fact there are two mechanisms (and hence two characteristic time scales) at work. The high molecular weight of the primary ingredient PDMS (Poly Dimethyl Siloxane) has a characteristic polymeric relaxation time, defined by the time that a random walk allows the chain to relax from a stretched state through thermal vibrations. However due <b>...</b>