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Polysulfide Sealants with Specialty Minerals Precipitated Calcium Carbonates and Other Minerals

Polysulfides are one of the older polymer technologies for the manufacture of high-performance sealants. Despite a decline in popularity, they continue to be used in many parts of the world.

Chemically, polysulfides are sulfur-containing liquid polymers. Conventional types are mercaptan terminated. Others are modified polysulfides (polythioethers). They are normally cured using manganese dioxide, lead oxide or a dichromate. Polysulfide sealants can be formulated as one- or two-component products.

Polysulfide sealants are mainly used for the manufacture of insulating glass windows. Because of their excellent resistance to jet fuel, they are also used for expansion joint sealants in airport construction and in various aerospace applications, including sealants for airplane fuel tanks and windshields. Electrically conductive sealants are often based on polysulfides.


SMI Precipitated Calcium Carbonates in Polysulfide Sealants
Specialty Minerals Inc.’s (SMI’s) ultrafine and nano precipitated calcium carbonates (PCCs) provide excellent rheological and physical properties when used as the main rheological additive and functional filler in polysulphide sealants. PCCs provide a good balance of viscosity, thixotropy, and sag and slump control, as well as polymer reinforcement.

Precipitated calcium carbonates grades recommended for polysulphide sealants are:

  • Calofort® SM and SV PCCS – high efficiency, 0.07 micron, stearic acid-coated nano PCCs made in SMI’s plant in Birmingham, U.K.
  • Ultra-Pflex® PCC – high-efficiency, 0.07 micron, stearic acid-coated nano PCC made in Adams. 
  • Thixo-Carb® 300 PCC –performs well in polysulfides by using a proprietary coating for best compatibility and dispersion. A 0.15 micron ultrafine PCC made in SMI’s plant in Adams, Massachusetts.
  • Thixo-Carb® HP PCC – provides excellent viscosity build and excellent sag resistance when very high shear-dispersion equipment is needed.  A 0.06 micron, high surface area PCC manufactured in Adams.

Click on one of the product names to download its technical data sheet.

To read more about the range of PCCs for sealants made by Specialty minerals, how they differ in properties, why PCCs are coated, and the effect of dispersion equipment on efficiency, click here. Click here to read more about how to choose the best PCC for a given application, including the effect of particle size and surface properties on that choice. An application selector chart of PCC/polymers can be viewed by clicking here.


Other SMI Minerals in Polysulfide Sealants
In addition to the rheological control agent, polysulfide sealants also contain some filler mineral such as ground calcium carbonate (GCC), to reduce cost, add non-thixotropic thickening and bring up solids level to desired specifications. 

In the U.S., Specialty Minerals manufactures high-quality GCCs (ground limestone) and ground dolomite (calcium magnesium carbonate) fillers that are useful in polysulfide sealants. Finer grades yield higher non-thixotropic viscosity build while coarser grades allow higher loadings and greater economy. These include the Vicron®, Marblewhite®, and Rivercal™ GCCs and the Dolocron® dolomites.

Coated GCCs are valuable when better filler dispersion or higher filler loadings are required. SMI coated GCC products are Hi-Pflex® 100 and Pfinyl® 402 stearic acid coated GCCs. Click here to learn more about SMI’s carbonate fillers for polysulfide sealants.

 

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