1. Skin-Forming Time and Potlife
One of the most important parameters when working with silicones is the time during which the material retains its optimal working properties.
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One-part silicones (1K): They cure under the influence of atmospheric moisture, which means the crosslinking process proceeds from the outside in. Understanding the skin-forming time is crucial to properly shape the joint before the reaction begins. A great example of a universal industrial sealant is ELASTOSIL® N9111, ideal for the electronics and automotive industries.
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Two-part silicones (2K): Here, the key concept is potlife, or the working time after mixing the two components. Depending on the project, you may need a fast-curing material, like ELASTOSIL® RT 772 (which works well in mechanical engineering and small appliances), or one that remains flowable for a long time, e.g., ELASTOSIL® RT 607 (highly heat-resistant, flame retardant in accordance with the strict EN 45545-1:2020 railway standard).
2. Proper Mixing and Deaeration: Protecting Electronics
Silicones are indispensable for potting and encapsulating electronic components. However, even the best elastomer will not fulfill its insulating function if the preparation process is carried out improperly.
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Mixing: Achieving a perfectly homogeneous mass in 2K silicones is fundamental. The size and geometry of static mixers in pneumatic dispensers have a direct impact on the consistency of the mixture.
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Deaeration (working under a vacuum): Air trapped in the silicone mass leads to the formation of voids (bubbles), which drastically reduces dielectric properties. Crosslinking under a vacuum is absolutely necessary when protecting sensitive components from external factors, ensuring a transparent and defect-free coating.
3. Lack of Adhesion and the Phenomenon of Inhibition
Sometimes silicone cures on the surface but completely fails to adhere to the substrate. The most common cause of this phenomenon is inhibition, or "catalyst poisoning." This problem particularly affects addition-curing (platinum-catalyzed) silicones.
The presence of the slightest contamination or contact with substrates containing sulfur or amines can block the crosslinking process at the interface of the materials. To avoid this, we recommend:
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Rigorous control of substrate cleanliness.
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Systematically conducting tensile lap-shear strength tests.
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Using a primer (adhesion promoter). If a surface (e.g., acrylic or polyamide) does not show natural adhesion with the chosen silicone, a primer is the only way to achieve a durable bond.
4. Thermal Resistance and Processing of Silicone Resins
For applications requiring the highest thermal resistance – such as insulation of electrical coil windings in motors or composite materials – silicone resins are used (e.g., in the form of SILRES® MK FLAKES or SILRES® H 62C liquid). These resins achieve their target parameters only after curing at elevated temperatures, often using appropriate catalysts that ensure rapid crosslinking without by-products.
Similar principles apply to silicone fluids – choosing a variant with heat stabilizers significantly extends their service life and functionality in demanding mechanical engineering applications.
Optimizing the processing of silicone elastomers allows you to avoid costly mistakes, failures, and downtime on the production line. The key is always selecting the right product and application technology.
Are you looking for proven solutions and top-class industrial chemicals? A full range of professional Wacker products, tailored to your technological process, can be found in the silray.pl store offer.
Have a question? Write to us: info@silray.pl
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