The use of plastics in manufacture is of great industrial importance to-day. In order to make the best economic use of plastics, their mechanical properties must be properly determined .
In this paper some analysis of elastic and viscous properties of linear viscoeleastic bodies are made. A simulant of a solid propellant rocket fuel is subjected to this study. Gottenberg(2) made some experiments to find the relaxation function which represent the mechanical behaviour of this simulant of a solid propellant rocket fuel. A procedure is proposed here to find the mechanical constant of each element contained in a mathematical model for a linear viscoelastic material using experimental data. This model consisting of some suitable combination of springs, and viscous dashpots. The mechanical functions entering the constitutive relations of the theory of viscoelasticity are determined by experimental and theoritical means. Some experiments are made to find the mechanical behaviour of an available
viscoelastic material (PVC).