Cross-linked coatings

Microwave or radio frequencies above 1 MHz that are appHed to a gas under low pressure produce high energy electrons, which can interact with organic substrates in the vapor and soHd state to produce a wide variety of reactive intermediate species cations, anions, excited states, radicals, and ion radicals. These intermediates can combine or react with other substrates to form cross-linked polymer surfaces and cross-linked coatings or films (22,23,29). 

The Hquid monomers are suitable for bulk polymerization processes. The reaction can be conducted in a mold (casting, reaction injection mol ding), continuously on a conveyor (block and panel foam production), or in an extmder (thermoplastic polyurethane elastomers and engineering thermoplastics). Also, spraying of the monomers onto the surface of suitable substrates provides insulation barriers or cross-linked coatings. 

The other broad class of refinish coatings is cross-linking coatings, caHed enamels in the trade. In the United States, most shops cure the enamels at room temperature in Europe, cure is commonly carried out at temperatures of 60—75°C. TraditionaHy, the vehicle was an oxidi2ing medium oH alkyd. 

Network Formation and Degradation in Urethane and Melamine-Formaldehyde Cross-Linked Coatings... 

The nse of organotin catalysts in secondary amine fnnctional polyaspartate-polyisocyanate cross-linked coatings has shown to improve the potlife of the formulation. 

In coating applications, urethane chemistry is used to cross-link coatings and also to prepare thermoplastic polyurethanes or isocyanate-terminated pre-polymers. 

Linear polymers such as polyamide imides and polyimides are sometimes used as varnishes however, they produce coatings that are not cross-linked. For some applications for which rework and repairs have to be made, cross-linked coatings have a disadvantage. Soluble polymer systems that can be repaired are to be preferred in such cases. 

In some instances such as in isocyanate cross-linked coatings, the amount of moisture present must be taken into account in formulating calculations. Cellulose esters are packaged with very low moisture content however, if exposed to the atmosphere, cellulose ester powder or flake will regain moisture. The amount gained is dependent upon the relative humidity and the cellulose ester type, as illustrated in Table III. To ensure a consistent composition, all cellulose esters should be stored in low relative humidity surroundings or kept in a closed container. 

Solvents used for paint removal are able to dissolve or considerably swell physically drying binders (e.g., vinyl chloride copolymers, cellulose nitrate, polyacrylates) and chemically cross-linked coatings (e.g., oil-based paints, dried alkyd resins, cross-linked polyester-melamine resins, cross-linked epoxy and isocyanate coatings) [14.237]. A combination of dichloromethane with low-boiling ketones or esters is particularly suitable. Small amounts of high-boiling solvents with a low volatility (e.g., tetrahydronaphthalene, solvent naphtha, methyl benzyl alcohol, or benzyl alcohol) are added to these mixtures to retard evaporation and increase the solvency. Modern paint removers do not contain chlorinated hydrocarbons, they are formulated on the basis of high boilers (e.g., dimethylformamide, dimethyl sulfoxide, propylene carbonate, and yV-methylpyrrolidone) in combination with alcohols and aromatics, or consist of aqueous, frequently alkaline or acidic systems. 

Plasma treatment of PDMS followed by adsorption of self-assembled silane monolayers has enabled us to controllably modify the surface energy of elastomer surfaces as described in the section on the Johnson, Kendall, and Roberts approach to deriving the surface free energy of solids. A similar treatment of silicon substrates has produced a useful, low—hysteresis model substrate for contact angle study. There are three types of PDMS contact angle substrates usually studied fluids baked or otherwise chemisorbed on solids such as glass or metals cross-linked coatings on flexible substrates, such as paper or plastic film PDMS elastomer surfaces. 

Basu, S.K., McCormick, A.V., Scriven, L.E. Stress generation by solvent absorption and wrinkling of a cross-linked coating atop a viscous or elastic base. Langmuir22(13), 5916-5924 (2006)... 

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