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Acrylic Plastisol Sealants with Specialty Minerals Precipitated Calcium Carbonates and Other Minerals

Acrylic plastisols are dispersions of an acrylic polymer (usually based on methyl methacrylate) in a plasticizer, which are heat cured. They are growing in popularity as halogen-free replacements for polyvinyl chloride (PVC) plastisol sealants. An added benefit to end users is the ability to use the same manufacturing and application equipment for acrylic plastisols as for the PVC plastisols they replace.

The primary use for acrylic plastisols is for auto body sealants in automobile, truck, and bus original equipment manufacturer (OEM) production. They serve as gap-filling seam sealers and as body sound deadening and underbody corrosion protection coatings.


Specialty Minerals Precipitated Calcium Carbonates for Acrylic Plastisol Sealants
As in PVC plastisols, precipitated calcium carbonates (PCCs) are outstanding as thixotropic functional fillers. PCCs are true rheological additives, building thixotropic viscosity and providing excellent control of sag, slump, and extrusion rates. A rheological additive-plus-filler package consisting of fumed silica and ground calcium carbonate (GCC) can be replaced with a combination of PCC and GCC. This reduces costs while providing needed rheology and stability. The rheological profile and extrusion rate can be adjusted as desired by altering the PCC to GCC ratio. More PCC gives lower extrusion rates/higher extrusion times and more GCC gives higher extrusion rates/lower extrusion times.

Specialty Minerals Inc. (SMI) manufactures ultrafine and nano PCCs in the U.S. and U.K. For acrylic plastisols, we recommend the following PCC products:

  • Calofort® SV PCC – a nano PCC with outstanding efficiency. It is a 0.07 micron (70 nanometer) stearic acid-coated grade PCC manufactured in SMI’s Birmingham, U.K. plant.
  • Ultra-Pflex® PCC – a nano, 0.07 micron stearic acid-coated PCC with excellent performance and uniformity manufactured in SMI’s Adams, Massachusetts plant.
  • Calofort® SM PCC – another coated nano-particle PCC with a 0.07 micron median particle size, with excellent dispersibility, but lower rheological efficiency than Calofort® SV PCC. Chosen for lower viscosity formulations require high sag resistance or where high levels of PCC are desired. It is manufactured in Birmingham.

Click on a product’s name to download the technical data sheet for that product.

For more information on Specialty Minerals' line of PCCs for sealants, their ability to build rheological structure, the effect of dispersion equipment on efficiency and stability, and the role of their coatings, click here. Click here for more information on choosing a grade for a particular application, taking factors such as particle size, hydrophobicity, and surface moisture into account. An SMI PCC/sealant polymer application selector chart can be viewed by clicking here.


Other SMI Minerals for Acrylic Plastisol Sealants
Two other minerals from Specialty Minerals are often used in plastisol applications: barites for sound deadening and ground limestones/dolomites for filling.

Barites, sometimes called barytes, absorb sound and thus are excellent in sound-deadening coatings used in automobile trunks and on other parts of automobiles to maintain quiet interiors. SMI Baricron™ barites are a family of high-brightness products ranging in size from 1.5 to 8 microns. Click here to download the data sheet and click here to read more about SMI barites products.

Ground limestones (calcium carbonates) and dolomites (calcium magnesium carbonates) are the mineral fillers typically used in plastisols to bring solids to the desired level. These fillers reduce costs and add mildly thixotropic viscosity. SMI manufactures GCCs in a range of sizes for all applications at Adams, Massachusetts and Lucerne Valley, California. SMI’s products suitable for acrylic plastisols include the Vicron®, Marblewhite®, and Rivercal™ GCC families. Click here to learn more about these SMI carbonates.

 


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