Viscoelastic properties of silly putty with hollow glass microspheres

Abstract: Silly Putty (SP) or Molykote 3179 is listed as a dilatant viscous liquid by Du Pont (2018), although most users perceive it as a squeezy type solid. It exhibits elastic behavior on short time scales and viscous behavior on long time scales, meaning it behaves as a viscoelastic fluid. While SP was claimed to have been discovered in 1943 and patented in 1948, this claim is still disputed in historical circles. There is little information on its rheological properties, despite its extensive use as a toy and model fluid in undergraduate laboratories to study viscoelastic behavior., The properties of SP were measured using a Kinexus Pro rheometer. SP showed shear thinning behavior, as measured through oscillation tests, and a relaxation time of around 0.3 s at 25C. The elastic and viscous modulus curves with frequency suggest that SP, as a polymer, has a narrow range of molecular weight., The use of hollow glass microspheres (HGM) can reduce the density of the SP material, making it suitable for use as a lightweight shock absorber, but little is known about how such a mixture will perform under impacts. SP-HGM mixtures with up to 40% by volume of HGM reduce the density of the mixture. Dynamic impact testing showed that the HGM-SP material absorbs impact effectively. It was found that above a 25% by volume of HGM, there was a distinct increase in the ability of the mixture to absorb energy, as measured by the energy absorbed per unit mass. Overall, SP-HGM mixtures with more than 25% HGM by volume led to a 15% increase in energy absorption capacity while providing a lighter-weight material for impact protection. Keywords: rheology, viscoelastic fluids, silly putty, viscosity, hollow glass microspheres, energy absorption