Choosing a Talc Product for a Reinforced Plastics Application
Aspect ratio, particle size, and loading levels, and their effect on flexural modulus and impact strength, can be used to understand how to choose the best talc product for an application. SMI manufactures families of ultrafine, fine, and medium-sized talc products for plastics in the United States.
Choosing a Specialty Minerals Talc for Reinforced Plastics
From the broad range of talc products manufactured by Specialty Minerals Inc. (SMI), one will have the desired combination of particle size and brightness for your reinforced plastics application. But how does one determine the optimum product?
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 using a thermoplastic olefin (TPO)
If you are looking to improve the flexural modulus or stiffness of an existing reinforced 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 particle size talc product still does 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 particle size talc product 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.