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Reactive Silicones

Mono terminal and Bi terminal reactive silicones

Used as Filler dispersants

Reactive Silicones

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.

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6 products
Compare Products
6 products

Product Selector Guide

Mono Terminal

Product Structural formula Molecular weight Specific gravity Viscosity


1,000 0.96 10 - 25
FM-0421 5,000 0.97 60 - 80
FM-0425 10,000 0.97 140 - 180
FM-DA11 Diol

1,000 0.97 50 - 70
FM-DA21 5,000 0.97 80 - 160
FM-DA26 15,000 0.97 300 - 700
FM-0711 Methacryloxy

1,000 0.96 7 - 13
FM-0721 5,000 0.97 54 - 79
FM-0725 10,000 0.97 150 - 260
TM-0701T Methacryloxy

423 0.91 2.9 - 6.1


Bi Terminal

Product Structural formula Molecular weight Specific gravity Viscosity


1,000 0.95 11 - 15
FM-3321 5,000 0.97 90 - 150
FM-3325 10,000 0.97 200 - 400
FM-4411 Hydroxy

1,000 0.97 30 - 40
FM-4421 5,000 0.98 100 - 125
FM-4425 15,000 0.97 250 - 400
FM-7711 Methacryloxy

1,000 0.98 14 - 20
FM-7721 5,000 0.98 30 - 100
FM-7725 10,000 0.97 80 - 180


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Mono and Bi Terminals

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.


Why do we need the Reactive functional groups?

Not reactive silicones (ie Silicone oil) are not grafted or blocked in place with their functional groups, leading to extensive bleed out. This is a result of plain mixing and zero copolymerization happening between the resin and the Silicone. Mixing doesn't bind anything into place so bleeding can occur very easily.

Filler Dispersion

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:

  1. Reactive silicones can lower the viscosity while keeping the same thermal conductivity and filler ratio
  2. Reactive silicones can increase thermal conductivity by allowing an increase in filler content.

Test sample composition

  • Binder: Straight silicone oil
  • Filler: Alumina (65.0vol%)
  • Dispersant: Blank(No Dispersant), HDTMS** or Silaplane® (FM-series)

Rheometer and thermal conductivity* measurement

*Compliant with JIS H7903, ASTM D 5470-1 standards

** Hexadecyltrimethoxysilane

Products for Filler Dispersion Applications

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.