HDK® as a Reinforcing Filler
The reinforcing filler HDK® imparts the requisite mechanical properties to natural and synthetic rubbers and silicone elastomers. Hydrophobic HDK® grades can be used to produce combinations of high filler loading or tear strength with good processability.
Tailored Elasticity
For optimum results, the fillers used in natural and synthetic rubber and silicone elastomers must meet specifications. That is the only way to achieve products with precisely defined mechanical properties, such as tensile strength, elongation at break and tear strength (notch impact strength/Shore hardness). The reinforcing filler HDK® is a preferred auxiliary for achieving the desired system property.
Optimum Reinforcement
HDK® owes its outstanding reinforcing effect to its high specific surface area. The numerous interactions between the polymer chains of the elastomer network and the special particle structure of HDK® dissipates mechanical stresses and forces within the elastomer network – and so restricts the entropy space for polymer chains. This process increases the elastomers’ strength, elongation at break and load-bearing capacity.
High Sag Resistance
HDK® may be added to nonpolar silicone rubber to act both as reinforcing filler and rheological additive. The marked thickening action of hydrophilic HDK® provides the requisite degree of sag resistance, with the result that low-viscosity systems do not run down vertical surfaces.
Good Processability
In silicone elastomers, hydrophilic HDK® provides a high reinforcing effect – but at the same time results in a high viscosity, thereby limiting processability. One solution here is to use processing auxiliaries and low-molecular plasticizers. They block the interaction between the HDK® particles by adsorption and thus lower the viscosity. The system benefits from smooth running and perfect processing.