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Seal the Right Way: Acetoxy vs. Neutral Silicone sealants?

Seal the Right Way: Acetoxy vs. Neutral Siliconee sealants?

Silicone Sealants Uses In Construction

Silicone sealants are versatile prodcuts have many uses in construction industry, the first is general joint sealing which is mainly to seal gaps between construction elements and prevent passage of air, water, etc., Enhance the visual appearance of the construction, and permitting limited movement of the substrates & accommodate theses movement in joints.

The second is Structural sealant glazing (SSG) where a sealant provides structural support and attachment of glazing and other components to a window, curtain wall, or other framing system in addition to function as a barrier against the passage of air and water through a building envelope.

We will focus today on the first use of silicone sealants and explain the differences between neutral & acetoxy sealants

Silicone sealants Properties

Silicone sealants compared with other joint sealants materials boast remarkable advantages, including exceptional elasticity and joint movement capabilities, high UV and weather resistance, excellent adhesion on non-porous substrates, heat stability across a wide temperature range, good chemical resistance, mould resistance and availability in a transparent color.

On the other hand, they have limitations such as being non-paintable, prone to dirt pickup, and limited tear propagation resistance.

What are Silicone Sealant Types?

Polydimethylsiloxane is the basic raw material of siliconee sealant, The cross-linking agent is a multifunctional silane compound, which can chemically react with Polydimethylsiloxane to change it from a chain molecule into a network cross-linked system.

Various crosslinking agents can be used and release various small molecules during curing. According to the types of small molecules released, architectural siliconee sealants can be mainly divided into deacetate type (acetic acid), deketoxime type(oxime), dealcoholization type(alkoxy).

Polysilicoane + cross linker (acetoxy, alkoxy, oxime) = siliconee +by products (acetoxy: acetic acid, alkoxy: Ethanol, oxime: MEK)

One component Silicone sealants cure due to the presence of air humidity and are divided into categories according to the chemicals that are released in the curing process, and most popular silicone sealants are neutral(alkoxy) and acetoxy.

  • Neutral (alkoxy) silicone sealants
  • Acetoxy silicone sealants

So, what is the difference between these two types?

Acetoxy siliconees such as U-fix Silicone A release acetic acid, which is similar to strong vinegar smell during the curing process.

Acetoxy sealants have the advantage of drying much faster than neutral cure siliconee. And some acetoxy siliconee usually becomes tack-free within minutes, although it is important to note that it will not be fully cured for up to 24 hours.

Acetoxy siliconees fit well in sealing sanitary rooms, where the most commonly used materials are ceramic tiles, glass, and anodized aluminum, and they even provide cost-effective advantages compared to neutral silicone sealants.

Acetoxy siliconees are considerably clearer than neutral siliconees sealing glass-to-glass connections, such as glass partition walls.

acetoxy siliconee sealants are more affordable than natural cure caulking materials.

aforementioned odor caused by acetoxy siliconee is not exactly pleasant.

  • Acetoxy-curing siliconee sealant is incompatible with corrosion sensitive metals/uncovered metals and alloys such as lead, zinc, copper, brass and ferrous metals because the acetic acid evaporates during the curing process and may cause corrosion. And Neutral siliconees shall be used instead.
  • With alkaline substrates such as mortar and concrete and porous substrate such as cement-based products (such as concrete, plastered surfaces, construction blocks, etc), stones, marble, granite etc. it is not recommended to use acetoxy siliconees with. as high concentration of acetic acid released from acetoxy siliconee is highly corrosive, and can also cause discoloration when used on natural stone.
  • Not recommended to be used on bituminous substrates.


Neutral Silicone Sealants Such as U-Fix silicone N release compounds that have a specific sweet aroma or are mainly odourless during the curing process.

Perfect for caulking materials that would otherwise be affected by acetoxy sealant (I.e. concrete, stones, brass, copper, mirrors, bituminous materials and any space that is close to sensitive electronics.)

Connections between metal surfaces, window sills, ventilation appliances, concrete façade joints, and masonry are just a few examples where neutral siliconee works properly but acetoxy siliconee does not.


It is also excellent for exterior applications because it is more weather resistance than its acetoxy alternative.