Specialty Chemicals, Adhesives & Plastics
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Reactive Silicones grant permanent silicone properties to organic materials and other polymers. They harness the excellent heat resistance, flexibility, and mold release properties of Silicones and impart them to Organic materials while also maintaining abrasion resistance, water repellency, and good oxygen permeability.
They enhance the oxygen permeability of contact lenses, water repellency is added to functional paints, and artificial leathers are made to slide more by diminishing abrasion resistance. Reactive silicones have a very narrow molecular weight distribution, enabling uniform reactivity and very low volatiles such as cyclic siloxanes.
Reactive Silicones (Polydimethylsiloxanes), depending on their functional group, can react with a variety of organic compounds. Amino reactive groups react with Amide, Imide and Epoxies. Hydroxy reactive groups react with Urethanes and Esters. Finally Methacryloxy reactive groups are compatible with Acrylic resins.
Reactive Polydimethylsiloxanes have two main grades. Mono and Bi terminals, meaning they have a reactive site in one or both ends of the chain. Monoterminal silicones are used for grafting polymers while bi terminal types are used for block polymers.
Mono terminal Polydimethylsiloxanes are grafted onto the resin, modifying the surface properties while biterminal Polydimethylsiloxanes are integrated into the block polymer, modifying the physical properties. Their narrow molecular weight distribution ensures uniform reactivity and low volatiles and impurities.
The main application of the mono terminal Silaplane, which has a linear chain resin, is the ability to make the inorganic filler easier to blend into the silicone binder resin. In other words, it facilitates filler dispersion.
It improves the flowability of the highly filled filler dispersions and facilitates their handling. It is a perfect fit for applications that would benefit from the introduction of higher filler content, such as Thermal Interface Materials.
The product's narrow molecular weight distribution ensures uniform reactivity, low impurities and also low volatiles. With this variability, we can fine tune the silicone and compatibility buttons and have a product that perfectly fits the best of both worlds.
The silicone functional group of our Reactive PDMS (Polydimethylsiloxane) has a very high affinity to bind on the silicone binding resin. This improves the wettability between the resin and the filler. Additionally, the repulsive force that is created between the fillers, stabilizes the dispersion. This is a result of the silicone repulsion and the osmotic pressure effect.
The material turns from a highly viscous fluid that is in an aggregated state to a low viscosity one in a dispersion state that flows easier while also retaining higher filler content than it otherwise could. This results in higher flowability compared to other common silane dispersants.
In practical terms this means two things:
Test sample composition
Rheometer and thermal conductivity* measurement
*Compliant with JIS H7903, ASTM D 5470-1 standards
Filler dispersion applications can benefit from the grafting properties of Mono terminal PDMS and the repulsive force that is created between the fillers. That's why we suggest them for this type of application. Hydroxy and Diol Hydroxy functional groups lend themselves better as a filler dispersant and have been used successfully on TIM applications.
Silaplane molecular weight distribution is very narrow (~1.03-1.4 Mw/Mn compared to the 1.8 or general reactive silicones) and you have a choice between compatibility and acquired silicone properties to fine tune your end product.