Nanoindentation of Isotactic Polypropylene: Correlations Between Hardness, Yield Stress, and Modulus on the Local and Global Scales

The correlations between the hardness, yield stress, and modulus of elasticity of isotactic polypropylene (iPP) were evaluated on the local and global scales. Nanoindentation and traditional macromechanical tests were incorporated for this purpose. Thus, local and global mechanical properties were measured at various temperatures and strain rates. A certain relation was found between the local and global mechanical properties. Moreover, Johnson's model (developed according to the expanding cavity model) was also evaluated at various temperatures and strain rates. The Johnson model was valid only for the yield stresses obtained by nanoindentation and compressive tests and also the elastic modulus obtained via nanoindentation. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 930-938, 2011