Study of elastic properties of polymers from microhardness tests

Abstract

A numerical method of identification to derive the elastic properties of polymers from indentation experiments has been developed. Five different polymers were tested: amorphous and semi-crystalline polyethylene terephthalate (PET), semi-crystalline polyvinylidene fluoride (PVF2), a copolymer of polyvinylidene fluoride and trifluorethylene, P(VF2/F3E) 60/40, and high pressure crystallised polyethylene (PE). The elastic properties of the polymers are calculated by two methods. On the basis of finite element solution, a simple function relating the load to the indentation depth and elastic modulus is first obtained. The elastic properties are then derived from the load-indentation depth and elastic modulus is first obtained. The elastic properties are then derived from the load indentation depth experimental data (loading curve). A second method to determine the elastic properties is based on using the experimental data of the unloading curve. Elastic properties obtained from loading and unloading curves are in good agreement.