Mar resistance

New product introductions are generally heavily supported by the technical service function. Many customers using chemical feedstocks to produce multicomponent products for the consumer market require extensive on-line evaluations of new raw materials prior to their acceptance for use. An example of this would be the use of a new engineering polymer for the fabrication of exterior automobile stmctural panels. Full-scale fabrication of the part foUowed by a detailed study of parameters, such as impact strength, colorant behavior, paint receptivity, exterior photodurabiHty, mar resistance, and others, would be required prior to making a raw materials change of this nature. 

Currently, these tests are of no practical value to the designer and the only approach to the problem of scratch, mar, and abrasion resistance is to simulate actual performance needs. For optical purposes, a cast sheet in the allyl family of plastics known as CR39 has been used as a standard of comparison in evaluating scratch and mar resistance of a material. The CR39 is used for eye lenses and other optical products where the advantages of plastics are a consideration. Coatings have been developed for polycarbonate, acrylics, and other plastics that dramatically improve the scratch and mar resistance of these materials. 

Although hardness is a somewhat nebulous term, it can be defined in terms of the tensile modulus of elasticity. From a more practical side, it is usually characterized by a combination of three measurable parameters (1) scratch resistance (2) abrasion or mar resistance and (3) indentation under load. To measure scratch resistance or hardness, an approach is where a specimen is moved laterally under a loaded diamond point. The hardness value is expressed as the load divided by the width of the scratch. In other tests, especially in the paint industry, the surface is scratched with lead pencils of different hardnesses. The hardness of the surface is defined by the pencil hardness that first causes a visible scratch. Other tests include a sand-blast spray evaluation. 

Figure 8.17 shows how we can test the mar resistance of polymers. In this test, we rain abrasive grit down on an angled polymer sample at a known rate for a given period of time. We compare samples that have undergone testing under identical conditions to prepare a comparative ranking of mar resistance. 

Figure 8.17 Schematic illustration of apparatus used to evaluate the mar resistance of polymer surfaces...

Other possible applications are clear coats in automotive interiors (dashboard instrument screen-printed and top coats for gloss control, interior vinyl clear coat with excellent mar resistance and low gloss, wood grain printing and top coats for interior laminates), on alloy wheels and wheel covers and under the hood parts, and UV curable paint over physical vapor deposition (PVD) surfaces of various parts. Other examples are ... 

Evaluations of furniture polish application properties, gloss, uniformity, film clarity, smear and mar resistance, film healing, buffability, cleaning, water spotting, gloss retention, and dust attraction are all described in ASTM D3751-79. Federal Specification P-P553B (1977) indudes some standard test methods for the evaluation of liquid furniture polishes. 

The commercialization of isophthalic acid by Chevron in 1956(11) led to the introduction of di-2-ethylhexyl isophthalate (DOIP). This plasticizer showed improved lacquer mar resistance in flexible PVC(12). This need was limited, however. Because of its premium price, DOIP has not gained acceptance as a general purpose plasticizer. 

Abstract Mar resistance and surface structure (appearance) are two of the most important physical properties to characterize the mechanical and optical quality of a coating system. In this paper the relevant measuring techniques are discussed using typical examples reflecting the current status of application in the automotive and coatings industry. Especially the techniques to determine the mar resistance were recently improved (single... 

Characterizing Physical Properties of Coating Surfaces - Mar Resistance and Surface Structure... 

In this paper the recently developed techniques to characterize the mar resistance of coating systems were presented. The techniques base on methods that create a single scratch onto a surface. Characteristic values like the critical load as a measure for the transition from plastic behaviour to brittle fracture can be determined and used to rank different clearcoat systems and to compare these results with other physical properties. In the field of mar resistance the cross-linking density of the... 

Figure 6. The X-ray spectra firom 1.0 MeV proton bombardment of a) furnace black, b) mar resistant, and c) and d) two samples of the extra clean super smooth semiconductive compound. Note the improvement and the inhomogeneity of the remaining silicon and calcium.

Trifunctional (meth)acrylate fluorine-containing cyclic and acyclic silane compounds have been prepared that form photocurable resin compositions. Coatings from these resins are anti-fouling and resist organic stains from oil mist and fingerprints without detracting from surface mar resistance. 

Good impact resistance, abrasion resistance, mar resistance and chemical resistance are other key benefits. 

Floor selection criteria should include chemical resistance, stain resistance, scuff and marring resistance, ability to radius cove, durability, esthetics, and ease of maintenance and repair. Table 3 lists several floor compositions and selection criteria. Special areas may require static dissipative or conductive flooring in order to minimize explosion potential with flammable material. 

At first, characteristics of activated carbons basing on porous structure and specific surface, content of ash, water adsorption and mar resistance has been determined. The volume of pores (radius of capillaries from below 1.5 to 10 nm) and the specific surface of carbons have been determined by means of dynamic adsorption and desorption of benzene vapour on the sorptive porometer DHL-3 [30]. Pores of greater radius have been determined by means of method of mercury forcing (under pressure) in carbon sample on the porometer of Carlo Erba [31 ]. 

Use In plastics and metal powder lubricants, varnishes, lacquers, defoamers, and mar-resistant antiblock paints. 

Margard sheet [GE Plastics] Extraded polycarbonate glazing grade sheet uv stabilized, coated on both faces with mar-resistant silicone coating. 

Tego Glide. [Tego] Siloxane cq ly-mers mar resistant and flow additive for water and solvent-based paints, printing inks deaerator for epoxy resins. 

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