ORGANIC-INORGANIC SILOXANE HYBRIDS

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ORGANIC-INORGANIC SILOXANE HYBRIDS 

Reinforcement of polydimethylsiloxane through formation of inorganic-organic hybrid network.(Technical report): An article from: Polymer Engineering and Science

Chemistry

The excellent heat, ultraviolet light and chemical resistance properties of inorganic siloxane binders make them obvious choices for improving the properties of organic coatings.

Formulators have tried to utilize alkyl silicate and silicone resin chemistry for this purpose but success was limited by the peculiarities of their film forming mechanisms.

Significant progress has been made in the last 5 to 8 years with the patenting of a range of methods for modifying a variety of organic binders with inorganic siloxane to produce hybrids with unique combinations of properties. 

Formulators select the appropriate type and ratio of organic and inorganic siloxane constituents in an effort to achieve a balanced set of application and performance properties. 

Oxysilane and silicone resin precursors are selected for cure speed, degree of cross-linking, balanced film properties and compatibility with organic resin constituents. 

 

The types of silicon-based materials used are typically alkoxy or silanol functional silicone resin intermediates ranging in molecular weight from 600 to 1000 and various types of organofunctional oxysilanes. 

An important feature of the oxysilane and silicone resin precursors is their very low viscosity. This feature has enabled development of very high solids coatings that meet all current and likely future regulatory requirements for volatile organic content. 

Organic resin precursors are generally chosen for their principal performance feature. For example, an aromatic epoxy resin would be used for applications requiring chemical resistance and an acrylic resin would be chosen for use in a coating requiring good weatherability. 

 

It has been found that organic-inorganic siloxane hybrid binders containing 20-50% organic resin give optimum performance in terms of film formation, adhesion, mechanical properties and chemical, corrosion and weathering resistance. 

Handbook of Cosmetic Science and Technology, Third Edition

Lower levels of organic resin result in coating films that exhibit undesirable properties e.g., low impact resistance and flexibility and loss of adhesion on aging. Higher levels of organic modification detract from important polysiloxane characteristics like resistance to ultraviolet light and oxidation.

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