Improved fracture toughness without any decrease in the modulus

The fracture toughness or formulations based on epoxy resins or polyurethanes can be improved significantly using Albidur® - without any losses in the modulus or the glass transition temperature. Further important properties can be adjusted precisely with Albidur®.  

Product overview
Improvements to properties
How it works

Product overview [back]

Technical data (no specification)

Technical data (no specification)

Technical data (no specification)

Improvements to properties [back]

The impact strength of an epoxy resin formulation can be improved in such a way that losses in modulus and glass transition temperature are avoided without significantly increasing the viscosity of the mixture using products of the Albidur® series.

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

Figure 1 shows the dependence of fracture toughness and energy on the silicone content of the formulation (bisphenol A epoxy-based formulation, cured with anhydride), which reveals significant improvements.

The optimal performance is achieved at 3 – 5 % silicone elastomer in the total formulation (without fillers), where a discernible improvement in the fracture toughness can be achieved without compromising the modulus. (Please note: Albidur® contains 40 % silicone elastomer.)

Besides the low viscosity, further advantages are the high thermal stability of the silicone elastomer (up to 200 °C) as well as the improvement in surface smoothness, which is achieved by silicone elastomer particles on the surface. This enables coatings with a significantly lower coefficient of friction which can be useful e. g. in piping designs.

Albidur® PU 5640 is especially used in polyurethane formulations in order to adjust the adhesion of the coating surface. The silicone elastomer particles create reduced adhesion of the coating surface, which can be very desirable for coatings with release properties. UV and ozone resistance are also significantly improved.

How it works [back]

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.

Albidur® products consist of a reactive 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 2).

Figure 2:  Schematic representation of an Albidur® particle

These particles are able to bond to the resin matrix. If a mechanical load is applied to the cured resin system, it can be dissipated uniformly in all directions when encountering a rubber domain. If a tear has already occurred, it is prevented from further tearing: The elastomer particles stretch vertically to the direction of tear and are not torn out, as they are chemically bonded with the matrix.

Figure 3 shows the finely distributed silicone elastomer particles in the epoxy matrix.

Figure 3:  Scanning electron microscope image of an epoxy resin modified with Albidur®

For further details, please contact our application specialists.