Scratch evaluation on a high performance polymer (original) (raw)
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Wear, 2014
The scratch behaviour displayed by a series of polymers in constant penetration depth scratch tests conducted by a microscratch tester was examined in relation to their intrinsic rate-dependent mechanical properties. Scratch hardness, which is considered as a measure of the scratch performance, was assessed by using a recently proposed scratch model. The adequacy of the model to explain deformation recovery and pile-up characteristics of the material in the scratch test was questioned by comparing the predictions of the model with residual profile measurements. The study demonstrated that the scratch phenomenon is dominated by the yield stress of the material. Besides, scratch hardness was found to be independent of the loading conditions. Indentation hardness and scratch hardness are comparable if the testing conditions are similar.
Scratch resistance of high performance polymers
Tribology International, 2011
Scratch tests were carried out on various high performance polymers, including (1) polybenzimidazole (PBI), (2) polyparaphenylene (PPP), (3) polyetheretherketone (PEEK), and (4) polyimide (PI). The scratch damage features were characterized using laser confocal and scanning electron microscope. Scratch resistance at room temperature decreased in the same order as the materials are listed above. It was attempted to correlate the scratch depth with basic mechanical properties, such as Young's modulus, tensile strength, and scratch hardness. Also, the scratch coefficient of friction was considered as a possible measure to differentiate between the various materials tested.
Progress in Organic Coatings, 2003
Scratch durability of polymer surfaces and coatings is becoming critical for the increasing use of these materials in new applications, replacing other materials with harder surfaces. Scratch resistance of polymers has been the subject of numerous studies, which have led to specific definitions for plastic deformation characterization and fracture resistance during scratch testing. Viscoelastic and viscoplastic behavior during a scratch process have been related to dynamic mechanical properties that can be measured via dynamic nano-indentation testing. Yet, the understanding of the origin of the fracture process of a polymer during scratch remains approximate. Parameters like tip shape and size, scratch velocity and loading rate, applied strain and strain rates, have been considered critical parameters for the fracture process, but no correlation has been clearly established. The goal of this work is to define and analyze scratch parameters that relate to mechanical properties. The evolution of scratch resistance parameters as a function of temperature and strain rate, compared to the evolution of dynamic mechanical properties obtained from indentation and uniaxial tensile tests over a range of temperature for poly(methyl methacrylate) (PMMA) helped in identifying a correlation between the tensile stress-strain behavior and scratch fracture toughness. This correlation brings a new understanding of the origin of the fracture mechanisms during a scratch process. In particular, it is demonstrated that the characteristic strain applied by the indenter is a most relevant parameter to describe the fracture resistance during a scratch process, independently of the indenter geometry.
Improvement of Scratch and Wear Resistance of Polymers by Fillers Including Nanofillers
Nanomaterials (Basel, Switzerland), 2017
Polymers have lower resistance to scratching and wear than metals. Liquid lubricants work well for metals but not for polymers nor for polymer-based composites (PBCs). We review approaches for improvement of tribological properties of polymers based on inclusion of fillers. The fillers can be metallic or ceramic-with obvious consequences for electrical resistivity of the composites. Distinctions between effectiveness of micro- versus nano-particles are analyzed. For example, aluminum nanoparticles as filler are more effective for property improvement than microparticles at the same overall volumetric concentration. Prevention of local agglomeration of filler particles is discussed along with a technique to verify the prevention.
Tribological Measurements Of Polypropylene Nanocomposites By Scratch And Friction Tests
MWCNTs are used as extremely strong nano-reinforcements for nanocomposites due to their superior electrical, thermal, and mechanical properties to produce a new generation of reinforced plastics with better application properties. In this experimental study the tribological properties of iPP/MWCNT polymer nanocomposites with nanofiller concentrations in the range of 0.05-1%wt MWCNT with maleic anhydride amount respectively from 0 up to 7.5wt % are investigated by using three types of test methods.
Scratch hardness as a quasi-intrinsic parameter to measure the scratch resistance of polymers
Wear
In this work four different polymers (acrylonitrile-butadiene-styrene, high-impact polystyrene, rubber-toughened polybutylene terephthalate, linear low-density polyethylene) were characterized in terms of their bulk (modulus and yield stress) and surface (scratch hardness) mechanical properties. The intrinsic time-dependence of the materials was addressed by performing DMA and compression tests at varying testing speed/frequency, exploiting timetemperature superposition and Eyring's model to obtain data at strain rates compatible with scratch experiments. The latter were performed by applying different loading histories (constant depth or load) and indenters. Scratch hardness was determined using Pelletier's model; it was demonstrated that such a parameter provides a reliable and almost intrinsic (i.e. loading history independent) evaluation of scratch resistance, seen as the resistance the material opposes to indenter penetration. Its relation with other aspects of the scratch phenomenon (in particular deformation recovery) was also explored, accounting for the specific deformation regime imposed by the indenter (transitioning from elastic to predominantly plastic).
Employing coatings is one of the most effective methods to reduce friction and protect contacting surfaces from wear. The deposition of protective coatings from thermosetting polymer powders has witnessed a rapid growth as an ecological, economic and energy efficient technology. During the last few decades, many new deposition techniques have been developed, and more and more tribological coatings have been made available. In this context, our present investigation tried, firstly to analyze the friction and wear behavior of electrostatically sprayed polyester powder coatings deposited on an aluminum substrate and secondly to focus on the response of these thermosetting coatings to micromechanical deformation under scratch test loading. The effect of graphite and hexagonal boron nitride (hBN) solid lubricant fillers on the friction and wear behavior of polyester composite coatings was evaluated using a reciprocating tribometer under dry friction condition. The experimental findings show that the additions of graphite or hBN are effective in enhancing the wear life of polyester powder coatings. Meanwhile, under the same sliding conditions, the wear results revealed that the polyester coating filled with only 10 wt.% of graphite has a higher anti-wear ability compared to the polyester coating filled with the same weight fraction of hBN. Thus, the two reinforcing polyester matrix fillers play an important role in reducing the plastic deformation of the coatings and enhance the formation of thick third body between the sliding parts as the fraction of solid lubricant increases from 0 wt.% to 10 wt.%. From the scratch analyses, we deduced that coatings scratch behavior is severely affected by the kind and amount of fillers inside the polyester matrix. In fact, the best friction characteristic and scratch resistance are observed in the case of polyester coatings filled with very low amount of hBN (5 wt.%).
Mechanical and Tribological Properties of Polymers and Polymer-Based Composites
Chemistry and Chemical Technology, 2020
A definition of rigidity of polymers and polymer-based composites (PBCs) by an equation is formulated. We also discuss tribological properties of polymers and PBCs including frictions (static, sliding and rolling) and wear. We discuss connections between viscoelastic recovery in scratch resistance testing with brittleness B, as well as Charpy and Izod impact strengths relations with B. Flexibility Y is related to a dynamic friction. A thermophysical property, namely linear thermal expansivity, is also related to the brittleness B. A discussion of equipment needed to measure a variety of properties is included.
Journal of Tribology, 2004
An experimental and numerical study of the scratch test on polymers near their surface is presented. The elastoplastic response of three polymers is compared during scratch tests at large deformations: polycarbonate, a thermosetting polymer and a sol-gel hard coating composed of a hybrid matrix (thermosetting polymer-mineral) reinforced with oxide nanoparticles. The experiments were performed using a nanoindenter with a conical diamond tip having an included angle of 30 deg and a spherical radius of 600 nm. The observations obtained revealed that thermosetting polymers have a larger elastic recovery and a higher hardness than polycarbonate. The origin of this difference in scratch resistance was investigated with numerical modelling of the scratch test in three dimensions. Starting from results obtained by Bucaille (J. Mat. Sci., 37, pp. 3999–4011, 2002) using an inverse analysis of the indentation test, the mechanical behavior of polymers is modeled with Young’s modulus for the ela...