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hard and stiff material that is moldable

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gao7857

Mechanical
Aug 16, 2010
37
Hi there,

I am looking for a strong and hard polymer that is moldable. The material is expect to be able to cut into (with some pressure) soft polymer such as nylon. It need to have high strength and stiffness to avoid brittleness break.
I was thinking of PPS, PEEK and fiber reinforced nylon. Any comments, suggestions are appreciated.

Gao
 
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Nylon is not normally considered a soft polymer, byt anything you listed could cut into unfilled nylon. Can you be a lot more specific about materials to be cut and environment and designs.

Regards
Pat
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Thanks Pat.
We are currently using unfilled nylon in our product where strength and elongation are two critical factors. To re-design the product we want to keep the nylon portion to keep the mechanical properties. We need another part that can bite into nylon and hold it at some strength (higher strength than the nylon part). For the hard material, the strength (tensile, flexural, and impact)and hardness are the main thoughts right now. Since it need to hold the nylon part, we hope it will not break brittlely as hard material sometimes does. (seems like steel could work, but we want to use polymers) And after all, the hard polymer need to be able be molded without too much trouble.

Gao
 
What temperature, what humidity, how long, how many applications of load are a few of the non stated aspects that cause me to feel very nervous about a recommendation.

Also there are quite a few types of nylon with quite a few grades of each type. Moisture content of the nylon makes a huge difference. This moisture is normally absorbed from the air.

Regards
Pat
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There is no special requirements for the environments (T, RH, life). The nylon is PA66 and we understand there is humidity issue with PA66, and we are ok with it. If I could summary our need, the hard polymer is expect to work in the same environment (23C, 50% RH) of the PA66 counterpart and have a life that is no shorter than PA66 (which is 3~5 years).
In product operation, the load (shear+tensile) will be applied to the parts for the bite and, when the hard part bite into the PA66, it become static load that the part will keep holding. The application load will involve the geometry of the part, which based on experience, is a combination of tensile, shear and flextural, with tensile strength be the most criticle one. There is no other type of load applications.

Thanks, -Gao
 
OK

Even acetal homopolymer might do the job at std ambient indoors.

Creep may be an issue, but if the clamp force is maintained, the cutting 9I presume for grip) will get deeper with time. The sharp edge will also dull with time under load, simply from creep.

Regards
Pat
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Thanks a lot Pat!
When you say the cutting will get deeper with time, does that because the creeping of the softer nylon?

Could you comment on the cutting performance of acetal homopolymer, unfilled PPS, filled PA66 (30%) and unfilled PEEK? What are the parameters that determines a better cutting? hardness? modulus? brittleness? Thanks, -Gao
 
Hardness in my opinion. After all a hardness test measures indentation under pressure.

Both parts will creep, but for non cross-linked thermoplastics, the softer one will tend to creep more.

From memory, acetal is about the same performance as 15% GF nylon 6.6 conditioned to std temperature and humidity.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
 
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