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Choosing a Specialty Minerals Talc for Reinforced Plastics

From the broad range of talcs manufactured by Specialty Minerals Inc. (SMI), one will have the desired combination of particle size and brightness for your reinforced plastics application. How to begin?

Click here to read more about how flexural modulus (stiffness) is affected by filler aspect ratio, talc loading level, and talc particle size.

Formulating Reinforced Plastics with Talc for Flexural Modulus and Impact Strength
The goal is to achieve the desired stiffness/impact balance with the right economics. The variables include:

  • Particle size of talc
  • Talc loading
  • Impact modifier level
  • Rubber level, if in a thermoplastic olefin (TPO)

If you are looking to improve the flexural modulus or stiffness of an existing formulation, keep the particle size the same and increase the talc loading, if possible. 

If working with a new formulation, pick the size talc that is typical for that type of polymer and desired level of performance or start with your standard grade of talc. Check the flexural modulus and adjust the loading and particle size until the stiffness is where you would like it to be.

  • If the flexural modulus is not high enough, go progressively down in talc particle size until the compound is in the desired range of stiffness, then check the other properties, especially impact strength. 
  • If the stiffness is acceptable, but the impact strength falls short, go to an even smaller talc. If the smallest, 1 micron, talcs still do not allow you to meet your impact goal, then increase the impact modifier level.
  • If the stiffness is fine, but the impact is higher than needed, use a slightly larger talc or keep the particle size the same, while reducing the amount of impact modifier.
  • If working in a TPO, and the impact is high, some of the rubber can be removed, which will lower the impact level and reduce cost at the same time.
  • If the flexural modulus is too high, increase the particle size of the talc used and/or reduce the loading level.

 

Specialty Minerals Talcs for Reinforced Plastics
SMI has been producing talcs since the 1950s and has developed families of talcs of different particle sizes and brightnesses for use in plastics. Bright white talcs are mined and processed at our Barretts, Montana plant. Appearance-grade talcs, coated for even higher brightness, are also manufactured there. The highest brightness SMI talcs are produced in the Mount Vernon, Indiana plant, using carefully selected Chinese raw materials. Particle-size grades yielding the entire span of performance options are produced at both plants, from the ultrafine talcs–1 micron or less for highest plastics performance–up to 10 microns, for less demanding uses. SMI talcs are used in reinforced polyolefins such as polypropylene and TPOs, as well as in nylon, acrylonitrile-butadiene-styrene (ABS), polycarbonate and polybutylene phthalate (PBT), and other engineering resins.

This family property chart may help guide your choice of products for your particular reinforced plastics application:

 

 

You can read more about these families of talcs and individual products for plastic composites by clicking here or download the technical data sheets for the products by clicking here. To go directly to web pages with information on talcs for particular types of polymers and applications, click on one of the Learn More links below.

 

Learn more: