Mar and abrasion

Polysiloxanes are often used as mar additives. Polysiloxanes in their pure form are incompatible with most resins due to their low surface tension. This incompatibility may result in unwanted side effects, such as formation of craters. Normally, polysiloxanes are modified for applications in different resins and this eliminates the problem.  

Crosslinked polysiloxanes are made by a controlled hydrolysis and condensation of methyltrimethoxysi-lane. They form spherical particles of 0.5 to 12 xm in diameter depending on grade. The particles added to paints (and other materials) reduce coefficient of friction and thus improve abrasion resistance.  

Perfluoropolyether oils are added in small concentrations (0.1 to 0.5%) to thermoplastic polyurethanes to improve their mar and abrasion resistance.  

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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. 

Hardness can be defined as a measure of the resistance to abrasion, to deformation, or to penetration by a much harder body. In plastics the resistance to scratching, marring, and abrasion is related to the hardness. 

Features Exc. mar and abrasion resist., COE reduction, recoatabilily esp. for high temp, resist, systems... 

Chem. Descrip. Micronized HDPE homopoiymer CAS 9002-88-4 EiNECS/ELiNCS 200-815-3 Uses Additive wax for adhesives, inks, personai care, and rubber appiics. good performance in solv.-based coatings food pkg. adhesives, coatings, paper/paperboard, cellophane, rubber articles, textiles, lubricants Features Exc. mar and abrasion resist. exc. recoatability Regulatory FDA 21CFR 175.105,175.300,175.320,176.170,176.180,... 

These can be considered as reacting by both routes, since the unreacted acid in the alkyd may take part. Epoxy resin of molecular weight 900 n = 2) is used, since alkyd-epoxy resin compatibility is poor at higher molecular weights. Stoving is at temperatures of 150°C and above. Improvements over alkyd-melamine finishes occur in adhesion, flexibility, chemical and water resistance and mar and abrasion resistance. Uses are similar, particularly where finishing industrial and domestic equipment is concerned, since the excellent adhesion of the epoxy resin can allow the user to omit a primer. 

Up to 1% SI powders reduce machine torque and power demand and may improve gloss and resistance to marring and abrasion masterbatch gives improved internal lubricity, surface slip, abrasion resistance ... 

Urethane oils are generally similar to alkyd resins of comparable type and oil length but are quicker drying. They give films with superior mar and abrasion resistance and resistance to solvents and chemicals. On the other hand, films from uretliane oils discolour more rapidly than those from alkyd resins. Urethane oils find application in wood varnishes and quick-drying enamels. 

Waxes included in this group are either manufactured by free radical polymerization, or obtained by pol5mier degradation. Emulsifiable grades are obtained by oxidation. In addition to antiblocking, release, and slip properties, these waxes are known to improve mar and abrasion resistance. They are also used in coating for their flatting characteristics. 

Polyethylene waxes have been added to paints and varnishes as far back as 1950 to improve their mar and abrasion resistance. Figure 10.4 shows performance polyethylene wax in alkyd-based traffic paint. Less than 2% polyethylene wax improves resistance by a factor of five. Polyethylene waxes used in these older applications had molecular weights tfom 2,000 to 5,000 daltons. Later information shows that molecular weights of polyethylene-based additives used now are in a similar range (1,500 to 5,000 daltons). Up to 5 wt% solids are used now to improve mar and abrasion resistance of coatings. The additives act by... 

Paint films also may be required to resist acids and alkalis, solvents, staining, heat, impact, marring, and abrasion. Some coatings must be able to withstand flexing without cracking or flaking. Table 5 lists paints that have proven successful in withstanding mechanical and chemical action. 

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