Wacker to unveil 2 new silane-terminated polymer grades

MUNICH, GERMANY: Wacker Chemie AG said that it will be unveiling two new silane-terminated polymers: GENIOSIL XM 20 and GENIOSIL XM 25. They can be used as binders in adhesives and sealants, where they can modify the mechanical properties, in particular, impacting modulus. This allows adhesives and sealants manufacturers to compound without the need of conventional plasticisers.

In plasticizer-free adhesives, the new grades additionally enhance the bonding properties. In low-modulus sealants, they ensure high elastic recovery. As a result, GENIOSIL XM opens up applications in the adhesives and sealants sector that had previously been inaccessible to silane-crosslinking polymers.

The new grades complement the portfolio of silane-terminated polyethers that the company markets under its GENIOSIL brand. As all silane-terminated polymers, GENIOSIL XM cures at room temperature under the influence of atmospheric humidity via silane crosslinking. In contrast to the other polymers, GENIOSIL XM 20 and GENIOSIL XM 25 only have one silane group at one of their chain ends, meaning they are cross-linkable only at that end.

GENIOSIL XM can be blended with other silane-terminated polymers in the desired ratio. On curing, the new polymers are firmly integrated into the resulting three-dimensional polymer network, reducing the crosslink density. This leads to a relatively wide-meshed network.

GENIOSIL XM thereby modifies the elasticity of the cured material, resulting in a low modulus system with high elastic recovery. When stretched, or compressed, it behaves like a soft spring. In formulations of silane-terminated polymers, the two new grades thus act as reactive plasticisers. Since they do not alter the mechanical strength of the cured material, they can replace conventional plasticisers. This affords manufacturers of sealants and adhesives the freedom to formulate plasticizer-free products.

The two GENIOSIL XM grades not only adhere to concrete, wood, aluminium and glass, but also to low-energy surfaces such as polyvinyl chloride (PVC), polystyrene (PS) and cured ethylene propylene diene monomer (EPDM) rubber without prior pretreatment of these substrates.

Adhesive specialist: GENIOSIL XM 20

GENIOSIL XM 20 is an alpha-silane-terminated polyether. This grade opens the door to plasticizer-free adhesives with extremely high elasticity. At the same time, these possess high ultimate strength and also adhere well to difficult substrates. Furthermore, the product can extend skin over time. This provides the user with sufficient adhesive tooling time. Typical applications include wood flooring adhesives and all-around adhesive sealants.

Sealant specialist: GENIOSIL XM 25

GENIOSIL XM 25, a gamma-silane-terminated polyether, allows the formulation of low-modulus sealants with exceptionally high elastic recovery. Should sealant manufacturers use this grade as a co-binder, low-modulus construction sealants that exceed ISO 11600 specifications are possible. Potential applications include sealants for expansion joints in buildings made of industrially prefabricated concrete parts and for connection joints between window frames and walls.

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