Dynamic nanoindentation of some polyolefins

Abstract

Nanoindentation tests have been conducted on five different polyolefins, comprising a high density polyethylene, a low density polyethylene, a linear low density polyethylene, a polypropylene homopolymer and a polypropylene copolymer. The nanoindenter was fitted with a "Dynamic Stiffness Measurement" (DSM) facility that permits measurement of storage modulus and loss modulus at frequent intervals during an indentation test. The results were quite scattered, especially those for the loss modulus, and methods of processing the data to derive meaningful results were examined and are discussed. The storage modulus measurements were found to give the same stiffness ranking as the monotonic load-displacement data when comparing indentations on the same material. Some correlation was found between the storage modulus and fractional crystallinity. An averaging procedure was developed for the loss modulus values that appeared to give a consistent assessment of the dissipation properties of the different materials. Analysis of the monotonic component of the load-displacement data indicated that the nature of the deformation changed from mainly elastic/viscoelastic to mainly viscoelastic/plastic during the course of the indentation tests. POLYM. ENG. SCI., 46: 1160 -1172, 2006.

Surface detection errors cause overestimation of the modulus in nanoindentation on soft materials

“…Dynamic nanoindentation was used to distinguish small differences in the storage moduli of eight engineering polymers with different material densities (Odegard et al, 2005). Bouaita, et al tested several polyolefins using a dynamic stiffness measurement method where an AC signal is applied on top of the DC actuation of a standard nanoindentation test (Bouaita et al, 2006).…”

Study on the viscoelastic properties of the epoxy surface by means of nanodynamic mechanical analysis

“…This method has proven to be an effective method for nanoscale studies. [6][7][8][9][10][11][12][13] It is based on the dynamic model of depth-sensing indentation which utilizes the load-penetration depth curves to characterize hardness, toughness, Young's modulus, residual stress, yielding stress, and subsurface damage for both film and bulk materials. [14][15][16] The widely accepted scheme (Oliver and Pharr 15 ) was developed from Sneddon's 17 contact mechanics solution on a linearly elastic halfspace, and it works well for the elastic contact of tip and sample during the unloading period.…”

Time-dependent mechanical characterization of poly(2-hydroxyethyl methacrylate) hydrogels using nanoindentation and unconfined compression

“…20 Dynamic nanoindentation was used to distinguish small differences in the storage moduli of eight engineering polymers with different material densities in Odegard et al 21 In Bouaita et al several polyolefins were tested using dynamic stiffness measurement method where an alternating current (ac) signal is applied on top of the direct current (dc) actuation of a traditional nanoindentation test. 22 An alternative approach to spring-dashpot models is to characterize two independent material properties using different testing methods. In Huang and Lu, this approach was used to characterize polymers indented with both Berkovich and spherical tips to calculate the bulk and shear relaxation moduli.…”