Measurements of the viscoelastic moduli of an acrylate polymer in bulk and film form using a contact method

This paper describes a new method for the measurement of the viscoelastic properties of polymers using a contact mechanics approach. The latter is based on the determination of the tangential response of a macroscopic contact between a polymer specimen and a rigid sphere under small amplitude cyclic micro-motions. Using an acrylate polymer, it was found possible to achieve contact conditions where the tangential behaviour of the contact is strictly linear. Under such conditions, the measurement of the contact stiffness allowed to determine the viscoelastic moduli of the bulk polymer through the glass transition zone. In addition, it was also found to be possible to measure the damping properties of thin films (30 μm) using the same method. The results indicated a shift of the glass transition temperature of the films as compared to bulk specimens. This result was interpreted as an indication of the sensitivity of the glass transition of amorphous polymers to the hydrostatic pressure.