Innovation on silicon molecular structure

There are three main classes of silicon compounds 
The silicones or silanes used in the hydrophobisation of construction or construction materials can be subdivided into three classes.

• Monomeric alkyl alkoxy silanes
• Oligomeric alkyl alkoxy siloxanes
• Polymeric siloxanes


All three types form a 3-dimensional resin like network after application and curing.  Their chemical stability to the silicate components of building materials produces a stable and durable bond to most mineral substrates. At the same time, the alkyl groups orient themselves towards the exterior (air) side and protect the surface, acting rather like microscopic umbrellas to protect against the penetration of humidity.


Molecular structure determines key properties
The mode of action or the site of attachment of the siloxanes depends on their chemical structure.
While polysiloxanes create a film at the surface of the substrate, low molecular weight silanes and oligomeric siloxanes penetrate into the available pores. i.e. these low molecular weight products are subject to capillary absorption.  Embedded in the pores of the building material, they reduce the capillary absorption of water, the well known “suction” effect of all capillaries.  Therefore, they have almost no influence on the surface of the substrate, and its appearance remains visually unchanged.


The polysiloxanes on the other hand, form a surface film which leads to a visual change producing a dark, wet looking surface.  Beading effects, which are commonly used to demonstrate the effectiveness of a hydrophobic treatment are more pronounced on a polysiloxane treated surface than for the two other product classes.  This is not, however, an indication of effectiveness.  On the contrary, no film forming polysiloxane is allowed or approved for use by certain European and US building agencies.


Silanes and polysiloxanes have been traditionally used as hydrophobing agents, but more recently oligomeric siloxanes have gained grounds. They represent an excellent way to combine certain properties of the other two classes, such as high effectiveness and good penetration, durable bonding, and minimal visual change to the surface along with its good water vapor permeability typical of silicones.


Innovation on silicon molecular structure
The ability to develop newer class of silicon emulsions is very much possible with technologies that improve both hydrophobic and oleophobic characteristics by producing silicon hybrids with multiple functionalities.  In addition to the standard characteristics that regular Silanes and Polysiloxanes has to offer, new hybrid silicon are developed by IMRAE to improve properties of concrete with greater effect on reactivity “in-situ” with other molecular structures formed during the continuous hydration of cement. This unique feature further enhances both its physical and chemical characteristics that further prolong the performance life of concrete.


References:
(1) Salvatore Re, Stain Prtoection…Paper at “Coatings for Masonry and Concrete”, Brussels
2003; published by the PRA, Hampton, UK.
(2) E. Garci, Silicon Resin Emulsions, Paper at “Silicons for Coating”, Brussels 1996, published
by the PRA, Hampton, UK.