Scratch-and Abrasion-Resistant Coatings

Coatings are susceptible to damage caused by scratch and/or abrasion. Clearly, the consumer prefers to retain the aesthetic appearance of coated materials, and for this reason clear coats used on automobiles must have good scratch and abrasion resistance. An added problem is that scratches may also cause damage to the underlying substrate. 

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Botup, B., Eddmann, R and Mehnert, R. (2003) Silanes and inorganic particles the winning combination for scratch and abrasion resistant coatings. Eur. Coat.]., 6. 21-27. 

Schottner G., Rose K., Posset U. Scratch and abrasion resistant coatings on plastic lenses— state of the art, current development and perspectives. J. Sol-Gel Sci. Technol. 2003 27 71-79... 

Chem. Deserp. Aromatic urethane acrylate oligomer Uses Film-former for U V/EB coatings and inks, clear overprint varnishes and pigmented systems on wood, metal and rigid plastic substrates Features Fast cure pourable exc. scratch and abrasion resist, chars. ... 

PC sheet and injection molded parts may have a variety of coatings, including a range of hardcoats that enhance weathering, scratch, and abrasion resistance. 

Bauer F, Flyunt R, CzUial K, Buchmeiser MR, Langguth H, Mehnert R (2006) NanoMicro particle hybrid composites for scratch and abrasion resistant polyacrylate coatings. Macromol Mater Eng 291(5) 493 98... 

Silane coupling agents may also be directly used as coatings for a variety of applications (10,13,14). Coupling agents in coatings formulations can be used in either solvent- or water-borne systems, such as clear coats for automotive applications (13,15). Formulations can also be used to impart scratch and abrasion resistance to softer materials such as polycarbonate and poly(methyl methacrylate) (PMMA) (14). Applications of this type allow the use of materials whose bulk properties are desirable because the surface properties can be fine-tuned. 

Mechanical protection of substrates is one of the most important applications of sol-gel coatings [31,32], and in the literature most of the works are related to enhancing the scratch and abrasion resistance of underlying substrates. Therefore, the mechanical robustness of the coating is vital for its tribological behavior. 

One of the attractive features of the sol-gel process is that it enables the preparation of numerous types of new organic-inorganic materials with improved thermal, mechanical, optical and electrical properties, such as host oxide materials, which are either impossible or extremely difficult to synthesize by any other process. The numerous applications of these materials include scratch and abrasive-resistant hard coatings and special coatings for polymeric materials, metal and glass surfaces. Specifically for mild steeE and aluminum 2024 alloys - widespread uses of these ormosil materials have been reported. 

Poly(ether- -urethane)s and poly(ester-6-urethanes)s are designated as TPUs. Interestingly, nanoreinforcement is considered as a suitable tool for the property improvement of crosslinked polyurethanes. The interest in this development is due to the traditional application of crosslinked polyurethanes (coatings, varnishes, etc.) where the modification with nanoparticles may be very promising e.g., yielding scratch and abrasion resistance). Therefore, it is appropriate to have a look at the related works and adopt the results for thermoplastic grades. Note that the related teaching can be rather easily transferred from thermoset to thermoplastic polyurethanes. 

Surface hardness of coatings and molded objects is also measured by scratch and abrasion resistance. In one simple test for painted surfaces, the hardness can be quantified in terms of the pencil hardness (HB, 4H, etc.) that leaves an indentation. As a rule, polymer systems cannot approach the surface hardness of silica glass, which is itself a highly cross-linked structure. Some highly cross-linked laminates do have scratch resistance nearly like that of glass. 

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. 

VueguardL [Panelgrt hic] Coating treatment for plastic sheet and molded articles providing resistance to scratching and abrasion. 

For example, the abrasion-resistant coatings based on a silicone-silica hybrid (33) have provided a scratch- and mar-resistant finish for polycarbonate as well as metals. The chemistry involved is discussed by Vincent, Kimball and Boundy (3iL). The coating consists of polysiloxane and silane-modified submicron silica particles, microscopically dispersed in the solution. The coating is then cured at elevated temperatures. Currently, this type of abrasion resistant coating is marketed in the U.S. by Dow Corning and General Electric Company. 

Acrylated melamines have properties which make them suitable for use in OV curable coatings. Properties can be varied by adjusting the combined acrylamide content and the inclusion of other modifiers. Formulation viscosities are satisfactory for normal application methods, and films cure to a high degree of hardness at practical irradiation levels. Benefits demonstrated include improved tape and scratch adhesion, abrasion resistance, color, and Q-U-V durability. 

Many substrates, for example, many wood products, are provided with protective and decorative coatings of organic polymers, for example, radiation- or heat-curable polyacrylates, polyacrylate copolymers, polycarbonates or terephthalic resins, so as to improve gloss, dryness (no tack), and abrasion resistance and scratch resistance. 

While PVF and FEP have good resistance to abrasion, PMMA and PC are subject to scratching and abrasion from dust particles. Their resistance to such damage can be greatly improved by hard coating of polydimethylsiloxane. 

Scratch resistant AR coatings In order to improve the mechanical strength and more precisely the abrasion-resistance of the standard colloidal AR-coating, we have developed a hard AR-coating, so-called "Fluosil". This "Fluosil" (Fig.3) coating features four innovations to enhance adhesion and abrasion resistances by creating a real chemical bond between substrate and film. For this, we use ... 

Chem. Descrip. Micronized PTFE-modified polyethylene wax Uses Surf, modifier for a variety of baking and air-dry coating and ink applies., plastics, esp. for food-contact coatings provides exc. slip, water-repelling props. improves scratch/scuff/abrasion resist., antiblocking props. enhances meat release effective in polyesters, acrylics, epoxies, PU, alkyds, PVC... 

Chem. Descrip. Micronized modified polyethylene and PTFE Uses Lubricant, abrasion/scratch resist, aid for inks, paints/coatings incl. solvent- and water-based printing inks, lacquers and coatings applied on nonporous substrates, wood and leather finishes, coil and can coatings, industrial finishes, and low energy heat-set cover inks Features Provides abrasion, scratch and heat resist., smooth, silky feel, and surf, lubricity... 

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