Tough formulations with excellent electrical properties.

Improving the fracture toughness of epoxy resins without decreasing the modulus or the glass transition temperature - no problem with Albidur®! Further property improvements can be obtained without increasing the viscosity of the resin, e.g. thermal stability and electrical properties.

Product overview
Improvements to properties
How it works

Product overview [back]

Technical data (no specification)

Albidur® EP 2240 and 2240 A differ in the silicone base: The elastomer particles in EP 2240 are based on a condensation curing silicone (C-Silicone base), while Albidur® EP 2240 A is based on an addition curing mechanism (A-Silicone base). This results in a different hydrophobicity of the particles which can be utilized to adjust to the polarity of formulations.

Improvements to properties [back]

With Albidur®, the impact strength of an epoxy resin formulation can be improved without decreasing modulus and glass transition temperature (Tg) and without significantly increasing the viscosity of the formulation.

Figure 1: Fracture toughness and energy depending on the silicone content

Figure 1 shows the fracture toughness and energy depending on the silicone content of the formulation (bisphenol A epoxy-based formulation, cured with anhydride), which reveals significant improvements. For best performance, we recommend 3 – 5 % silicone elastomer in the total formulation (without fillers), because this is usually sufficient for a significant improvement in fracture toughness without decreasing the modulus. (Please note: Albidur® contains 40 % silicone elastomer.)

Further advantages besides the low viscosity are the high thermal stability of the silicone elastomer (up to 200 °C) as well as the excellent electrical properties, as can be seen in Figure 2.

Figure 2:  Dielectric properties of a formulation based on  a cycloaliphatic epoxy resin with Albidur®

In addition, the shrinkage upon cure of a formulation modified with Albidur® can be influenced very favourably, as the silicone elastomer particles expand at increased temperatures during the curing and hence counterbalance the shrinkage.

How it works [back]

Albidur products consist of an epoxy resin in which silicone elastomer particles of a defined size (0.1 – 3 µm) are finely distributed. The silicone elastomer particles have an organic shell structure comprising reactive groups (Figure 3).

Figure 3:  Schematic representation of an Albidur® particle

These particles are able to chemically link into the epoxy matrix. If a mechanical load is applied to the cured resin, it can be dissipated uniformly in all directions when interfering with a rubber domain. If a tear has already occurred, it is prevented from propagating, because the elastomer particles stretch perpendicular to the direction of tear and are not torn out, as they are chemically bound into the matrix. Figure 4 shows the finely distributed silicone elastomer particles in the epoxy matrix.

Figure 4: Scanning electron microscope image of an epoxy resin modified with Albidur®

For further details, please contact our application specialists.