Resins and Intermediates Selection Guide Silicone resins for high-performance d

Resins and Intermediates Selection Guide Silicone resins for high-performance decorative and protective coatings Silicon-based chemistry from the XIAMETER® brand helps you solve tough performance challenges and gain a competitive edge in the coatings marketplace. XIAMETER brand silicone resins and resin intermediates feature resistance to temperature extremes, moisture,corrosion, electrical discharge, and weathering. They are compatible with many organic resins, and many combinations of silicone resins can beformulated for specific applications and film properties. Product Choice The XIAMETER brand from Dow Corning offers a diverse line of silicone resins and intermediates for formulating high-performance decorative and protective coatings. Solvent-based, solventless liquid and solid flake options ranging in silicone content from 50 to 100 percent, by weight, are available. This variety allows formulators to fulfill a wide range of performance and regulatory requirements and to achieve the best combination of performance and economy for each application. Tables 2 through 6 provide general guidelines for the selection of appropriate resins and intermediates. Innovative Technology The use of silicones in coatings markets has evolved over the decades, allowing formulators to cre­ ate differentiated, high- performance product offerings. Hybrid resin systems include cold-blended interpenetrating resin networks and copolymerized “true” resin hybrids. Silicone resins and intermediates found utility in silicone alkyd maintenance paints (1950s), silicone polyester coil coatings (1970s) and most recently, silicone epoxy industrial and marine maintenance coatings (1990s). Gloss and color retention, along with corrosion, moisture, weather, and heat resistance are achieved via the incorporation of silicon-based materials into a wide array of paints, finishes, and coatings. The level of silicone modification is dictated by the severity of the application performance requirements (See Table 1) and can range from a minimum of 15 to 90 percent silicone incorporation into the organic resin. Higher levels of silicone resin (90 to 100 percent of resin binder) provide the highest level of thermal and ultra-violet radiation resistance, but benefit from the inclusion of small portions of organic resins to improve physical properties such as hardness (phenolics and melamines), air dry (acrylics), corrosion resistance (epoxies), and toughness (alkyds). Temperature and Hardness Silicone resin choice is heavily influenced by the environmental temperatures to which the end application will be exposed. Film hardness is another important consideration. Optimum coating performance is achieved by balancing these two parameters. Softer, more flexible resins are recommended for coating formulations intended for the highest temperature ranges. Rigid resins with excellent hot hardness are recommended for mid-range temperature applications. See Tables 1, 3, and 4 for temperature and resin hardness information. Pigments When formulating silicone or silicone modified organic binder systems, the performance requirements of the application determine pigment suitability. Standard pigments used with organic binder systems can be employed for those coatings intended for applications exposed to low or moderate temperatures (121 to 204°C [250 to 400°F]). For higher temperatures, only heat-stable inorganic pigments should be utilized. Consideration should also be given to coatings exposed to weather or chemical attack. Aluminum pastes and metal oxides, in particular iron and titanium, are useful. Hydroxyl reactivity on the surface of the pigment allows direct interaction of the pigment with the silicone binder. At elevated temperatures, thermally stable metalo-silicon ceramics are formed. Non-reactive pigments, such as carbon black, or graphite can be used to achieve color shading, but should be minimized in the formulation. Thinners The resins described in this selection guide can be thinned with aromatic hydrocarbon solvents and hydrocarbon blends. They can also be thinned with most ketones, esters, chlorinated solvents, glycol ethers, and butanol.In selected situations, volatile methylsiloxanes (VMS) can be used as a diluent to reduce viscosity without increasing volatile organic compound (VOC) content. (Note: Exempt status of VMS must be approved by the state in which VMS is used.) Catalysts The addition of metallic driers such as zinc or cobalt octoate will improve the rate of cure of XIAMETER® silicone resins. Suggested amounts are 0.1 to 0.2 percent metal based on the resin solids. Lead catalysts should not be used with these silicone resins. Containers with soldered seams may cause gelation. Curing Coatings formulated with silicone- based resins or intermediates generally require a bake or cure at elevated temperatures to achieve optimum film properties. This is especially true if the coating is to be exposed to extreme temperatures or to thermal cycling and shock. With silicone-based coatings, there is a greater danger of under-curing than over-curing. Under-cured films are relatively soft and have poor adhesion. Curing cycles are primarily determined by the silicone content of the resin vehicle. The typical cure for a coating based on a 100 percent silicone resin is 30 minutes at 232°C (450°F). A satisfactory cure time for a 50 to 80 percent silicone resin is 15 to 30 minutes at 218°C (425°F). For blends or copolymers of silicone and organic resins in which silicone is not the primary component, follow the cure recommendation for the primary resin. Corrosion Resistance Properly cured, XIAMETER silicone resins have good resistance to water and most dilute acids. The degree of corrosion resistance is dependent on several variables such as type of silicone resin, cure conditions, film thickness, pigmentation, if used, and the application environments. Intercompatibility of Silicone Resins In general, XIAMETER silicone resins have good intercompatibility. Resins with a phenyl/methyl ratio lower than 1.0/1 tend to be less compatible. Laboratory testing of resin mixtures should be done before commercial use. XIAMETER® Resin Properties Relative Hardness (0 - Soft) 55 60 65 70 75 80 3 2.5 2 1.5 1 0.5 0 Organic Compatibility (0 - Low) RSN- 6018 RSN- 0217 RSN- 0220 RSN- 0233 RSN- 0249 RSN- 0804 RSN- 0806 RSN- 0840 RSN- 0808 RSN- 0805 RSN- 0431 RSN- 0409 RSN- 0255 (Bubble Size Denotes Percent Non-Volatile Content) All products are XIAMETER® brand. 1 1000 hours, minimum. 2 15-50 percent silicone. 3 51-90 percent silicone. Performance Temperature Range 1 Resin Type Pigment 121-204°C (250-400°F) Silicone-modified organic 2 All pigments 204-316°C (400-600°F) Silicone-modified organic 2 Aluminum Organic-modified silicone 3 Colored 316-427°C (600-800°F) Organic-modified silicone 3 Black, aluminum Silicone Colored 427-538°C (800-1000°F) Silicone Black, aluminum 538-760°C (1000-1400°F) Silicone Ceramic Table 1. Using Resins for Cost-Effective High-Temperature Performance 121°C (250°F) 760°C (1400°F) Flake Resins Resin Intermediates XIAMETER brand Product RSN-0217 Flake Resin RSN-0220 Flake Resin RSN-0233 Flake Resin RSN-0249 Flake Resin RSN-0255 Flake Resin RSN-6018 Intermediate RSN-3037 Intermediate RSN-3074 Intermediate RSN-5314 Intermediate Characteristics Physical Form Solid flake Solid flake Solid flake Solid flake Solid flake Solid flake Liquid Liquid Liquid Functionality Silanol Silanol Silanol Silanol Silanol Silanol Methoxy Methoxy Methoxy Silicon Dioxide Content 1 47 52 52 63 62 51 65 54 46 Silanol Content 1 6 6 5 5 56 6 15-18 7 15-18 7 35 7 Degree of Crosslinking, percent 2 75 70 71 71 74 75 58 67 68 Phenyl/Methyl Ratio n/a 2.0/1 1.3/1 0.6/1 0.84 2.7/1 8 0.5/1 1.0/1 3.3/1 Molecular Weight3 1500 - 2500 2000 - 4000 2000 - 4000 2000 - 4000 2500 - 4500 1500 - 2500 800 - 1300 1000 - 1500 Monomer blend Typical Properties Resin Solids, percent by weight 4 99 99 99 99 >98 99 100 (actives) 100 (actives) 100 (actives) by volume - - - - - - - - - Solvent - - - - - - - - - Specific Gravity 1.34 1.33 1.32 1.30 1.22 1.31 1.07 1.16 1.04 VOC 5, g/L (lb/gal) - - - - - - - - - Viscosity (centipoise) - - - - - - 14 120 1.87 Flash Point, closed cup, °C (°F) 138 (280) 138 (280) 138 (280) 138 (280) 138 (280) 138 (280) 138 (280) 138 (280) 28 (83) Glass Transition Temperature (Tg) °C (°F) 65 (149) 49 (120) 47 (117) 41 (106) 56 (133) - - - - 1 Percent by weight. 2 Silica (SiO 2) – 100% crosslinked; dimethyl silicone fluids [(CH 3)2SiO] x – 50% crosslinked. 3 Weight average. 4 1.5 g, 3 hr at 135°C (275°F). 5 Volatile Organic Compound, EPA Reference Method 24. 6 Hydroxyl content. 7 Methoxy content. 8 Propyl. Table 2. Characteristics and Typical Properties Specification Writers: Please contact your local sales office before writing specifications on this product. Liquid XIAMETER brand Product RSN-0409 HS Resin RSN-0431 HS Resin RSN-0804 Resin RSN-0805 Resin RSN-0806 Resin RSN-0808 Resin RSN-0840 Resin Characteristics Physical Form Solvent solution Solvent solution Solvent solution Solvent solution Solvent solution Solvent solution Solvent solution Functionality Silanol Silanol Silanol Silanol Silanol Silanol Silanol Silicon Dioxide Content 1 52 52 64 52 52 57 52 Silanol Content1 1 3 3 1 1 1 3 Degree of Crosslinking, percent 2 60 66 68 60 66 63 66 Phenyl/Methyl Ratio 1.1/1 1.2/1 0.4/1 1.1/1 1.2/1 0.7/1 1.2/1 Molecular Weight3 2000 - 7000 2000 - 7000 2000 - 7000 200,000 - 300,000 200,000 - 300,000 200,000 - 300,000 2000 - 7000 Typical Properties Resin Solids, percent by weight 4 80 80 60 50 50 50 60 by volume 74 74 51 42 41 42 51 Solvent Xylene Toluene Toluene Xylene Toluene/Xylene Xylene Toluene Specific Gravity 1.12 1.14 1.07 1.01 1.02 1.01 1.06 VOC 5, g/L (lb/gal) 228 (1.9) uploads/Management/ resin-selection-guide.pdf

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• Publié le Dec 04, 2022
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