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Specialty Minerals Products for Automotive Reinforced Polyolefins

The list of automotive applications for polymers grows steadily because of continued efforts to reduce cost and weight and improve auto recycle ability. Reinforced polymers play a key role in exterior auto components such as bumpers, interior parts for dashboards and controls, and under-the-hood elements. Typical resin systems for these automotive applications are polypropylene and thermoplastic olefins (TPOs) which are polypropylenes modified with rubber to improve impact strength. But as these plastics increasingly replace metals, greater demands for strength and rigidity are placed on them. Functional mineral fillers play a critical role in meeting these demands while minimizing costs.


Minerals Improving Reinforced Polyolefins
A variety of functional minerals enhance the properties of the polymer composites used in automotive applications. Talcs are commonly included because they improve flexural modulus, also known as stiffness, maintain or improve impact strength, increase heat stability, reduce the coefficient of thermal expansion (CTE) and the heat deflection temperature, provide excellent surface finish, and contribute economy to this cost-conscious market. The nucleation-promoting effect of talc and its thermal transfer properties reduce cycle times thereby increasing production rates.

Bright appearance-grade talcs are required for light and bright colored parts, while standard-brightness talcs are acceptable in darker components. While the color demands for under the-hood components are not high—they are often black—they must have excellent physical properties to withstand the high temperature and harsh chemical environment under the hood. The inertness of talc is a plus in these end uses.

Fine ground calcium carbonates (GCCs), especially those that are surface coated, can increase impact strength while reducing costs. With calcium carbonates, the finer the product, the better the impact improvement. Barytes, also called barites, provide sound deadening.


Specialty Minerals Products for Reinforced Polypropylenes and Thermoplastic Olefins
Specialty Minerals Inc. (SMI) manufactures a range of talc products with different brightnesses and particle sizes from ultrafine, 0.8 micron, to 10 microns. We produce our highest-brightness products, the FlexTalc® talcs, from Chinese talc ores, in Mount Vernon, Indiana. These talcs provide an excellent impact/stiffness balance and the best color in polypropylene and TPO exterior/interior applications. For less critical color and under-the-hood polyolefin applications, bright appearance MicroTuff® talc grades and standard-brightness Ultratalc® talc grades with excellent performance are mined and processed in Barretts, Montana.

The finest 0.8 and 1 micron products give the highest flexural modulus increase, while maintaining or even improving the impact strength of the compound.  Slightly larger particled products, 2 to 3 microns, will boost stiffness but will not have as positive an effect on impact strength.

The effectiveness of ultrafine and fine SMI talcs can be seen on these webpages:

  • Click here to view the performance of FlexTalc® 610 talc, a 1 micron product, in an automotive TPO compound.
  • Click here to view the performance of MicroTuff® AG 609 and AG191 talc, 0.8 and 1.9 micron appearance grade Montana talcs, in an under-the-hood TPO composition.

An introduction to the fundamentals of reinforcing polyolefins with talcs, including guidelines for choosing the best grade of talc for a particular component, can be read by clicking here.

For less demanding applications where economy is a must, SMI manufactures ground calcium carbonate fillers that have median particle sizes ranging from 2 to 10 microns. The SMI Vicron® GCC products and their coated analogs, Hi-Pflex® 100 GCC and Pfinyl® 402 GCC, are economical filler/extenders that add to a composite’s toughness and dimensional stability. The coated analogs will provide better impact strength because the coating provides better dispersion in the composite. These products are produced in Adams, Massachusetts and Lucerne Valley, California. The Rivercal™ 8100 GCC series from SMI’s Mt. Vernon, Indiana plant offers good impact with attractive economics.

To view the results of a comparison of coated and uncoated GCCs in a polypropylene homopolymer composition, click here.

This selector chart can help guide you to the choice of the best SMI products for your automotive application. Click on a product name to download its technical data sheet.

 

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