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High stiffness plastic (unfilled) for injection molding

High stiffness plastic (unfilled) for injection molding

High stiffness plastic (unfilled) for injection molding

(OP)
Hi There,

I am looking for a high stiffness material that can be injection molded. Actually I try to use fibers to bring up the plastic strength several folds to close to that of soft metal, but a small component of this product cannot be reinforced by fibers. This component need to hold the compression type load without deformation so does not need any flexibility. So I am thinking a very stiff plastic may work. Injection moldable, very stiff. I need injection molding to produce some fine geometries. But I do not need the modulus be close to the metals.

I did a search and noticed LCP could be my best choice (15GPa) at a relatively expensive cost ($10/lb). There are others that are much cheaper but the modulus are also much lower. (2.7GPa (PET, POM) - 3.8GPa (SAN, AMMA)). I also found webpage of PrimoSpire self-reinforced polyphenylene (SRP) that claims 5.5GPa.

I never worked with LCP or SRP however. Any comments or suggestions?

Thanks in advance.
Gao

RE: High stiffness plastic (unfilled) for injection molding

Why don't you want to use fillers? That's by far the most inexpensive way to get there. I would suggest very high aspect ratio phlogopite mica. It's better than fibers in that you get reinforcement in all directions without warpage.

Chris DeArmitt PhD
President - Phantom Plastics LLC

Trusted adviser to leading companies around the world
www.phantomplastics.com

RE: High stiffness plastic (unfilled) for injection molding

LCP certainly is a top choice when you want higher strength and stiffness in a polymer. You seem to use strength and stiffness interchangeably. They are two distinct properties. Make sure you know what you need.

RE: High stiffness plastic (unfilled) for injection molding

(OP)
Chris,
What particle size and aspect ratio can phlogopite mica be?The small component is less than 1 cm and the small texture is about 1mm. For the large component we currently trying very long fibers that can can throughout the part dimension.

Cory, Thanks for reminding. I do need different properties for these two components. High strength for the large component and high stiffness for the small component. I do have some puzzle on the stiffness. The small component will receive compression load that will cause partially shearing and partially bending in the part, and the component should not deform much or break. I currently look at the flex modulus as it is popular property, but it probably not the best item to search for.

RE: High stiffness plastic (unfilled) for injection molding

The phlogopite grade I have in mind has an aspect ratio over 100:1 and the particle are around 40 microns in diameter. Sounds small enough for your parts.

Chris DeArmitt PhD
President - Phantom Plastics LLC

Trusted adviser to leading companies around the world
www.phantomplastics.com

RE: High stiffness plastic (unfilled) for injection molding

(OP)
Chris,
That sounds promising. Do you happen to know a compounder of a supplier that compound phlogopite into the plastic? Or a commercial plastic grade that is filled with phlogopite.
Thank you!
Gao

RE: High stiffness plastic (unfilled) for injection molding

There are lots of grades of lower performing micas. That particular very high aspect ratio one is called MicaFort PW80. Any of the compounders should be able to source it and add it to the polymer you choose (RTP, A Schulman, PolyOne, Teknor Apex, Modern Dispersions, etc..)

Chris DeArmitt PhD
President - Phantom Plastics LLC

Trusted adviser to leading companies around the world
www.phantomplastics.com

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