Viscoelastic properties of silly putty® with hollow glass microspheres

• A detailed rheological characterisation of Silly Putty has been undertaken. • An eight element Maxwell model adequately models Silly Putty. • Hollow glass microspheres in Silly Putty improves impact energy absorption/mass. The rheological properties of Silly Putty were measured and shown to be strongly dependent on the shear rate. Silly Putty has a wide range of relaxation time dominated by the shorter molecular weight chains which determine an average relaxation time. For small strains and stresses, Silly Putty behaves like a viscoelastic solid. A continuous relaxation time spectrum was extracted from the modulus data, and it was shown that an eight element Maxwell model could reasonably model the Silly Putty. The addition of hollow glass microsphere to the Silly Putty in varying proportions modified the viscous behaviour at low shear rates where the interaction of boron with the glass surfaces resulting in the mixtures showing lower viscosities. Impact testing with a drop tower indicated that hollow glass microspheres and Silly Putty mixtures provided improved energy absorption per unit mass with the energy absorbed per unit mass rising from 0.2 to 0.23 Joules/gram when the hollow glass microspheres exceeded a 20- vol%.