Water repellant silane

There are reactive softeners, some of which are N-methylol derivatives of long-chain fatty amides (10.241) while others are triazinyl compounds (10.242). The N-methylol compounds require baking with a latent acid catalyst to effect reaction, whereas dichloro-triazines require mildly alkaline fixation conditions. The N-methylol compounds are sometimes useful for combination with crease-resist, durable-press, soil-release and water-repellent finishes. In this context, the feasibility of using silane monomers such as methyltri-ethoxysilane (10.243), vinyltriethoxysilane (10.244), vinyl triace tylsilane (10.245) and epoxypropyltrimethoxysilane (10.246) in crosslinking reactions to give crease-resist properties and softness simultaneously has been investigated [492]. 

Water repellency is achieved by making the surface hydrophobic - ysv has to be reduced as much as possible if ysv - ySL is negative, 9 > 90° C - water repelling materials include waxes, petroleum residues and silicones for example, if =SiOH groups on glass or Si02 surfaces have reacted with silanes to form =SiO—Si—Alkyl... 

The mechanism of action by which silane and siloxanes reduce expansion has been attributed to water repellence and air entrainment. Phosphate addition or coatings may interfere with the dissolution of silica gel and the formation of gel. It is also possible that phosphate reduces the osmotic potential and the swelling pressure in the gel. The manner in which air entrainment reduced expansion was attributed to the accommodation of alkali-silica gel in the air void system. For example, it was found that air-entrained concrete with 4% air voids could reduce AAR expansion by 40% [23]. 

An alternative procedure used for large apparatus is to rinse it with a 5% solution of dichloromethyl silane in chloroform, then rinse several times with water before baking at 180°/2h (for glass) or drying in air (for plasticware). REPEL-SILANE (a solution of 2% w/v of dichloromethyl silane in 1,1,1-trichloroethane) is available commercially (LKB, Sweden). 

Exemplary water-repellent treatments for masonry surfaces include metal stearates, oils, waxes, acrylates (both polymers and monomers), silicones (solvent-based and emulsion), siliconates, silanes and, fluorochemicals. In contrast, to waterproofing coatings, water-repellent coatings, because they are permeable to water vapor, do not trap moisture and, therefore they can reduce spalling. In addition most water-repellent coatings do not alter the appearance of a porous masonry. 

Silanes. The use of silanes was exploited in the early 1970s. They are actually alkoxy silanes but are referred to in short as silanes. Silanes are not in themselves water-repellent but react with the moisture of the substrate to which they are applied, producing the active substance (Figure 6.14). 

Silanes exhibit hydrophilic and hydrophobic properties. The molecule has both a non-polar and a polar component. The non-polar organic alkyl group is the vehicle for the water-repellent action. The effectiveness, durability and stability of the waterproofing agent depends on the size and nature of this group (Huls, 1991). 

A frequent concern about the use of monomeric silanes is their volatility, which increases at high temperatures and also in windy conditions. In such cases, evaporation occurs after application before they are converted into the non-volatile water-repellent substance. Comprehensive and systematic investigations have shown that evaporation losses can be overcome by correct choice, to maximise the chances of success. Incorporation of catalysts accelerates the formation of active substances on the treated surface so that there is no appreciable loss from evaporation. 

However, when such insulation mats are exposed to moisture, the bonding strength is reduced, which can affect the quality of the insulation material. To prevent this problem, on the one hand, a hydrophobic agent is added to make the mineral wool more water repellent, and on the other hand silane is included in the binder mixture to enhance the bond between the inorganic fibers and the organic binder. 

Penetrating sealers have been recommended as a way of stopping chlorides getting into concrete. The chemistry of the process is that silanes, siloxysi-lanes and similar chemicals will penetrate the pores of the concrete and react with the water in the pores to from a hydrophobic (water repelling) layer that stops water getting in as a liquid (that may carry salt with it), but allows water vapour in and out of the concrete so that it will breath . 

Chem. Descrip. Phenyl trimethoxy silane CAS 2996-92-1 EINECS/ELINCS 221-066-9 Uses Surf, treatment, pigment/filler treatment in primers, water repellents, paints, inks, and adhesives reactive intermediate tor silicone resin synthesis and org. resin modification adhesion promoter Properties Low-vise, liq. sp.gr. 1.05 vise. 1.7 cSt flash pt. (CC) 29 C 100% act. 

Chem. Descrip. Alkyltrialkoxy silane with oleophobic additive Uses Water repellent tor concrete, brick, and nat. stone Features Resist, to automotive fluids, water intnision, chloride ion screening low VOC... 

Chem. Descrip. Methoxy-functional silane Uses Water repellent, penetrating sealer for cementitious substrates Features Good alkali resist., low volatility, exc. penetration, exc. water repellency, suitable for both dry and damp surfaces, reducible with solv. VOC compliant... 

GP-179 Silicone Resin GP-596 SWcone Resin Sol n. GP-667 Silicone Resh Sol n. GP-740 Silicone Resin Sol n. Silquest A-1106 Silquest A-2120 filler treatmerfl, paints Dow Coming Z-6124 Silane filler treatment, primets Dow Coming Z-6124 Silane filler treatment, water repellents Dow Coming Z-6124 Silane filler, ABS... 

Coal is also an essential ingredient in the production of specialist products such as (1) activated carbon, which is used in filters for water and air purification and in kidney dialysis machines, (2) carbon fiber, which is an extremely strong but light-weight reinforcement material used in construction, and (3) silicon metal, which is used to produce silicones and silanes that, in turn, are used to make lubricants, water repellents, resins, cosmetics, hair shampoos, and toothpastes. 

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