Methods for studying the mechanical and tribological properties of hard and soft coatings with a nano-indenter

Abstract

This study illustrates the capabilities of a nanoindentation/nanoscratch tester to assess mechanical and tribological properties of coating films. Properties such as hardness, elastic modulus, mar and scratch resistance, and critical force for cracking can be accurately measured. Operation of the Nano-Indenter is described in detail. A scanning probe microscope (SPM) is shown to be a valuable supplement to the Nano-Indenter. Well-characterized thermoset acrylic clearcoats and thermoplastic latex films were studied. For the first time, operating parameters are described for measurement of relatively soft coatings, such as films cast from a latex with a glass transition temperature (T g ) of 8°C. Thus, the method is made available for study of most types of coatings. The method can easily discriminate between coatings with different T g s and crosslink densities. Once operating parameters are established, it takes about 10 minutes for an indentation test and 10 minutes for a scratch test with the Nano-Indenter, and with further automation this time could be reduced. Each indentation test accurately measures hardness and elastic modulus as a function of depth within the coating, and each scratch test provides additional insight into the material's behavior. The method is sensitive to small changes in polymer composition and formulation, and results are highly reproducible.

Investigation of the effect of precoalescence or postcoalescence crosslinking on film formation, properties, and latex morphology

“…Its operation was described in detail in a previous paper by Shen et al 17 In the present study, a Berkovich diamond tip with an angle of 142.4°was used for the indentation experiments. The tests were performed by applying Z-direction force (loading) at a constantly increasing rate for 15 s, holding at maximum force for 30 s, and decreasing the force to zero (unloading) during 15 s. The holding time was 30 s. The temperature was 26-28°C.…”

Effect of polysiloxane additives on the scratch resistance of an acrylic melamine automotive clearcoat

“…Modifying the viscoelastic properties of clearcoats aims to create plastic scratches. [7][8][9][10][11][12][13] Improving the scratch resistance of a clearcoat would require changes in its chemical structure, which is not easily achievable and may create other difficulties such as adverse effects on other properties and/or the price. Consequently, attempts to improve scratch resistance of a clearcoat by the incorporation of additives to restrict large variations in other properties of a clearcoat, as well as making it economically viable, provide an attractive alternative.…”

“…The utilized load of each additive, as well as its compatibility with polymeric chains of the clearcoat, also affects its surface migration capability. [12][13][14][15][16][17][18] In the current study, attempts were made to investigate the effects of modification type, as well as utilized loads of each polysiloxane additive on the scratch resistance of an acrylic melamine automotive clearcoat. Attempts were also made to clarify, as much as possible, the mechanism by which each additive tended to improve the scratch resistance of the clearcoat.…”

Analysis of the practical force accuracy of electromagnet-based nanoindenters

“…The nanoindenter has become a main measurement tool in recent years in the micro/nano-mechanics and materials field owing to its capability for high resolution force measurements [1][2][3][4]. There are several types of nanoindenters, for example, MTS Nano Indenter Ò (incorporated into Agilent in 2008), Hysitron TriboIndenter Ò , CSM Nano Hardness Tester Ò , MML NanoTest Ò and CSIRO UMIS Ò .…”