Scratch behavior and material property relationship in polymers

The scratch behaviors of a broad range of polymers are investigated to unde rstand how the material characteristics of a polymer affect the scratch res istance. A constant load scratch test and a progressive load scratch test a re chosen for the present study. A scratch model proposed by Hamilton and G oodman is applied to correlate the mechanics and material parameters during the scratch process. An attempt is made to correlate the scratch behavior and basic material properties, such as the Young's modulus, yield stress, a nd tensile strength. A correlation between the scratch behavior and materia l surface characteristics, such as the friction coefficient, scratch hardne ss, and elastic recovery, under the current scratch tests are also made. Sc ratch subsurface damage in polymers is studied using optical microscopy. It is shown that shear yielding is the main cause of the plastic flow scratch pattern, while tensile tear on the surface and shear-induced fracture on t he subsurface are the main damage mechanisms found in the fracture scratch pattern. The main causes for the susceptibility of thermoplastic polyolefin s to scratch damage are discussed. Approaches for making scratch-resistant polymers are also addressed. (C) 2000 John Wiley & Sons, Inc.