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One Component Polyurethane of Fumed Silica

High-surface-area carbon blacks and fumed silica are more efficient on an equal-weight basis as reinforcing agent than other rheology-control additives. Carbon black is used to build viscosity, provide sag resistance, and increase the cohesive strength of automotive windshield adhesives. Coated precipitated calcium carbonates (PCCs) are used for rheology control of STP and polyurethane adhesives and sealants. Those PCCs with hydrophobic coatings (e.g., fatty acid or stearic acid) do yield shear-thinning rheology in polyurethane systems and have the added benefit of providing modest increases in adhesive strength. The increase of lap shear strength of a moisture-curing, one-component polyurethane adhesive consisting of a polyurethane prepolymer with NCO content < 2%, diisononylphthalate plasticizer, ground calcium carbonate filler, and organotin catalyst, with the addition of either a hydrophobic fumed silica or a coated PCC. On an equal-weight basis, treated fumed silica provides significantly more adhesive strength than the PCC in this system. Compounding the benefit of lower loading, fumed silica has a lower specific gravity than calcium carbonate and thus contributes far less to adhesive weight, which can benefit applications where adhesive weight is a concern (e.g., automotive lightweight). Pressure Sensitives: Fumed silica aggregates are commonly used to improve the processing and performance characteristics of films formed from natural rubber, polychloroprene, acrylates, and many other water-based latex emulsions. These submicron, high-specific-surface-area particles can decrease drying times, mitigate crack formation by modulating the capillary pressure, and enhance the mechanical properties of the final product. Pre-dispersed fumed metal oxides** provide an easy and effective "pour-in" means of incorporating these particles into the adhesive films. If you are looking for high quality, high purity and cost-effective Fumed Silica, or if you require the latest price of Fumed Silica, please feel free to email contact mis-asia.

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