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The material selection platform
Adhesives Ingredients
The material selection platform
Adhesives Ingredients

Silicone Sealant – High Modulus

Adhesives Formulation

Applicable Type
Applicable Base Polymer

Applicable Base Polymer Properties

Silicone polymers display an exceptionally wide range of chemistries and physical properties. These polymers can be low viscosity liquids, crosslinkable elastomers, or hard solids. Applications for silicone sealants are extremely broad. Markets include construction, automotive, assembly, maintenance, electrical/electronic, aerospace, and consumer products. Silicone sealants often compete with other materials such as polyurethanes, polysulfides, and acrylics. However, in applications requiring long-term durability to harsh environments, silicones are generally specified.

Typical Formulation Ingredients

Ingredient
Parts by weight
Silanol polymer (20 Mcs) 
xxxxx 
Fumed silica (treated or untreated) 
xxxx 
Acetoxy crosslinker 
xxx 
Tin catalyst 
xxxxxxxx 

Typical Properties

Properties
Skin-over time, mins 
xxxx 
Tack free time, mins 
xxxxx 
Hardness, Shore A 
xxxxx 
Tensile strength, psi 
xxxxxxx 
Elongation, % 
xxxxxxx 
100% modulus, psi 
xxxxxx 
Tear strength, lb/in 
xxxxx 

Processing

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Resulting Properties

The table above provides a starting formulation for a basic high modulus room temperature vulcanizing (RTV) silicone sealants based on acetoxy crosslinker. This is an example of one of the oldest and most common RTV silicone sealants.
The reaction rate of the moisture cure RTV silicone sealants depends primarily on their formulation, relative humidity, and temperature. Generally the fastest tack-free times (0.25-0.75 hrs) and cure times (12-24 hrs) are provided by the acetoxy and octoate cure systems. Alkoxy and amine cure silicones exhibit much slower cure rates (2-3 hrs tack free time and 48-72 hours for full cure).

Tips and Tricks

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