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Specialty Minerals Precipitated and Ground Calcium Carbonates in Rigid / Unplasticized PVC

Role of Calcium Carbonate Particle Size and Distribution in Rigid PVC
Particle size distribution is the most important functional filler property because it will determine the role the mineral can play. Calcium carbonates with an average particle size greater than 1 micron tend to function as fillers. The purpose of a filler is to extend the more expensive compound, thus lowering its cost per unit volume. Sub-micron calcium carbonates are used as functional additives, which enhance value because of their beneficial effect on the compound’s performance. Though they cost more on a volumetric basis than the PVC compound, they will lower cost if they replace a more expensive ingredient in the compound.

The most valuable function of ultrafine and sub-micron precipitated calcium carbonate (PCC) is its ability to act as an impact modifier. The smaller the particle size of the calcium carbonate, the stronger this effect. Specialty Minerals Inc. (SMI) produces PCC products with average particle sizes as low as 0.07 microns (70 nanometers).

Click here to download the SMI brochure “Fillers in PVC—A Review of the Basics.”


Specialty Minerals Nano Ultrafine Precipitated Calcium Carbonates
Our PCC for polymer applications is surface treated to enhance filler dispersion and minimize interactions with other polymer additives. SMI’s product line spans nano-sized products to those over 1 micron in average particle size. The choice is dictated by performance and cost considerations for each specific application. The following product selector chart will help guide your initial formulation development.

Click on a product name on the chart to download the technical data sheet for the product. Click here to download a brochure on Tuffgard® PCC in rigid PVC.

Tuffgard® and Ultra-Pflex® are PCC products with particle sizes of 0.35 and 0.07 microns and are manufactured in the United States. Calofort® S is a 0.07 micron, stearic acid-coated nano or ultrafine PCC and is manufactured in Birmingham, U.K. All of these products permit the removal of impact modifier from the formulation without any loss in impact performance. When switching to Tuffgard® PCC in a typical rigid formulation containing 5 phr (parts per hundred parts per resin) of impact modifier, two parts of impact modifier can be removed. We also recommend that formulators check fusion time and adjust lubricants if necessary. Ultra-Pflex® and Calofort® S PCC's provide the best impact performance and surface gloss. Experimental work may be required to optimize the Ultra-Pflex® or Calofort® S PCCs loading level. Any rigid PVC formulation, which contains a significant level of impact modifier, should benefit by switching to Tuffgard®, Ultra-Pflex®, or Calofort® S PCC. Formulation costs can be decreased while performance is increased.

Download the SMI publication “The Effect of Calcium Carbonate Size and Loading Level on the Impact Performance of Rigid PVC Compounds Containing Varying Amounts of Acrylic Impact Modifier” by clicking here or download the publication “Adding Value to PVC Formulations with Ester Lubricants and Fine Calcium Carbonate“ by clicking here.


Specialty Minerals Fine Precipitated Calcium Carbonates
Super-Pflex® MS and Super-Pflex® 100 are U.S.-produced fine PCC products. Super-Pflex® MS PCC is a “drop-in” for 1 micron, ground limestone products. It offers slight improvements in performance and should not require any formulation adjustments. Super-Pflex® 100 is a 0.7 micron PCC product that offers advantages over 1 micron ground products. Higher loading levels or improved impact performance are possible. There may also be a slight improvement in surface finish. When switching to Super-Pflex® 100 PCC, especially if increasing the carbonate loading level, the formulator may find it necessary to reduce the level of external lubricant in the mix in order to prevent a lengthening of the fusion time.


Specialty Minerals Ground Calcium Carbonates
SMI’s surface-treated ground calcium carbonates (GCCs) are high-quality general purpose functional fillers designed to be free flowing and easily dispersed in a variety of plastics applications, including DWV piping, potable water piping, flexible PVC wire and cable coverings, and calendared sheet and PVC plastisols. The surface treatment reduces plasticizer absorption in flexible PVC formulations for increased plasticizer efficiency.

Hi-Pflex® 100, Pfinyl® 402 and Super-Fil® are dry ground limestone products. Hi-Pflex® 100 GCC has an average particle size of about 3.5 microns and Super-Fil® GCC at about 2 microns.  Pfinyl® GCC is larger, of about 5.5 microns. They are used as fillers. To determine the most economical formulation, one needs to first determine the highest possible filler loading for each carbonate product and then compare the costs of the respective formulations. It is always more cost-effective to increase impact performance by choosing a finer filler than by adding impact modifier.

 

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