Viscoelastic Behavior of Polymer Films During Scratch Test: a Quantitative Analysis

Abstract

Dynamic properties of polymer surfaces affect their ability to withstand abrasive actions. Kinetic conditions, like velocity, penetration depth and shape of the abrasive particles, change the abrasion mechanisms and the morphology of the abraded surface. Using the scratch technique, along with profilometry measurement across the scratches, we have been able to completely characterize the residual scratch morphology. Pile-up deformation and visco-plastic relaxation are key phenomena that characterize the importance of ductility in the scratch resistance of polymer surfaces. Cross profilometry aids in studying the relaxation of the scratch morphology for different time and temperature history after the scratch is made. The effect of scratch velocity, penetration depth and indenter geometry on the contact pressure and friction coefficient estimated during a scratch test can also be analyzed. Following Eyring's law, a good correlation, was found between normal indentation and scratch testing in the evolution of the contact pressure with the applied strain rate. This work results in a better understanding of the stresses and the strains applied by an abrasive particle, and especially relates the dynamic mechanical properties of viscous materials, like stress exponent, to their scratch behavior. The method presented can provide for the measurement of dynamic properties of polymer surfaces or thin films under a very large range of strain rates.

Mechanical, thermomechanical, and thermal properties of polystyrene crosslinked with a multifunctional zirconium oxo cluster

“…Moreover, the scratch resistance of selected polymers (PS, 0.43 and 0.87 mol % Zr6 ) was tested for deeper insights to materials behavior. The definition of scratch resistance varies for certain applications, and materials can show different scratch behavior although the hardness is the same 77. Such behavior was observed in the cluster doped samples (Fig.…”

An integrated approach towards the study of scratch damage of polymer

“…[28][29][30][31] Scanning probe microscopy instruments, such as the atomic force microscope, [32][33][34] have also been adopted and improvised by researchers to perform scratch tests at a nanometer scale. For evaluating the scratch surface and subsurface, researchers have used equipment like the optical microscope (OM), 18,24,26 atomic force microscope, 24,26,32,[35][36][37][38] scanning electron microscope, 14,15,26,39,40 X-ray photoelectron spectroscope, 41 laser confocal microscope, 18 Raman spectroscope, 28 white-light interferometer, 20,24 profilometer, 14,15,42 tribometer, 43 ellipsometer, 28 and scanner. 17,44,45 A review of the scratch test devices available for macroscopic testing 46 readily reveals that the ranges of normal loads and scratch rates for most devices are rather limited, while some of them may only be good for the evaluation of marred surfaces and, thus, insufficient for the scratch studies.…”

Probing Macromolecular Dynamics and the Influence of Finite Size Effects

“…In a similar study on polycarbonate, Jardret et al have observed distinctly different pile-up formations on nanoscratch samples of identical hardness. The difference in pileup height is attributed to the strain, with increased rim heights for larger strains, i.e larger tanβ [114]. With a 2D finite element approach, Ramond-Angélélis has modeled piled-up rim formation in viscoelastic-perfectly plastic materials as a function of the rheological factor X.…”