However, not all of them are believed to be entirely harmless to health. The oxime silicones based on methyl ethyl ketoxime( MEKO) are considered to be carcinogenic. But now, with Pattex FUSIONXLT, Henkel has launched an oxime-free technology offering impressive user safety and an all-in-one solution that covers virtually every application, whether interior or exterior.

The silicone sealant product group can be divided into three systems: acetate silicones are characterised by their acidic crosslinking process, which means they release acetic acid upon curing and therefore give off a vinegary smell. Their strengths lie primarily in sanitary and kitchen applications.

However, they are unsuitable for some substrates due to their tendency to react with certain materials such as metal or concrete. Another sort, alkoxy systems, undergo neutral crosslinking and are extensively odourless. They are suitable for many substrates but cure relatively slowly, which can lead to sealant contamination.

Neutrally crosslinking oxime silicones based on methyl ethyl ketoxime( MEKO), although offering good adhesion and fast curing, release MEKO, the common name for 2-butanone oxime. This substance is suspected of being carcinogenic and there is an occupational exposure limit( OEL) on it in Germany.

However, Germany’ s BG Bau( employers’ liability insurance association for the construction industry) has determined in tests performed under realistic application conditions and involving several MEKO-releasing products, that during actual application this figure has invariably been exceeded by three to five times, even under good ventilation conditions. For this reason, BG Bau has determined that the‘ STOP’ principle needs to be applied in hazard assessment i. e. it recommends to first check whether MEKO-releasing products are at all necessary in the first place. If possible, they should be replaced by alternative sealant systems. Only if this is not

outstanding adhesion on virtually all substrates, whether concrete, glass, metal, wood or tiles

possible for technical reasons, says BG Bau, may the use of MEKO-releasing products be considered.

In such cases, the wearing of protective gloves and a protective respiratory mask is additionally required. The latter must also be worn post application until concentrations safely fall below the OEL. Depending on the ventilation and the type of room involved, this can take several days.

Because of this situation, Germany’ s Industrial Association for Sealants( IVD) has decided to substitute out MEKO-releasing products within the next two years. In addition, BG Bau recommends that the preventative measures described also be applied in the case of all other oxime silicones, as here too the suspicion of carcinogenic effects cannot be precluded.

Following extensive research, Henkel is already able to provide an innovative solution that can completely replace oximes while uniting all the advantages of a neutrally crosslinking sealant – Pattex FUSIONXLT Premium Neutral Silicone. This new silicone generation is able to ensure outstanding adhesion on virtually all substrates, whether concrete, glass, metal, wood or tiles.

Compliant with EN 15651, Pattex FUSIONXLT Premium Neutral Silicone is also suitable for glazing systems and sanitary applications. The flexible material exhibits very good compatibility on most standard commercial coating systems. It has a shelf life of 18 months and is certified for use in both clean rooms and HVAC systems.

A true all-rounder, it is easy to use and can be ideally smoothed. Fast curing and miminal shrinkage complete its application profile.

Compared to oxime silicones, the product does not give rise to critical emissions – making it ideal for interior applications without restriction. The formulation is also suitable for external applications due to its UV stability and high weather resistance.