ACETAL-POLYAMIDE JOIN

[GKINO13]

I WANT TO JOIN A PART MADE OF ACETAL (POM) WITH A PART MADE OF POLYAMIDE. THIS JOIN MUST BE CAPABLE TO HOLD ABOUT 8KG LOAD WHILE THE JOINING AREA IS ONLY A FEW SQUARE MILLIMETERS .ANY SUGGESTIONS?

 

[CoryPad]

If one assumes that Earth's gravity interacts with the objects mass, then F = ma = 8 kg [·] 10 m s^-2 = 80 N. If one assumes that "A FEW SQUARE MILLIMETERS" is A = 3 mm², and one assumes that this is a butt joint that must resist tension, then [σ] = F/A = (80 N)/(3 mm²) = 27 MPa. Now you need to find a welding method, adhesive, or mechanical fastener than can withstand 80 N or 27 MPa. How about an epoxy-based adhesive? Try contacting 3M, Loctite, and Devcon.

Regards,

Cory

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[GKINO13]

YOUR THEORY IS CORRECT AND I ALREADY KNOW ALL THAT. THE THING I AM ASKING IS WHICH ADHESIVE CAN JOIN THOSE MATERIALS.I HAVE ALREADY CONTACTED LOCTITE AND THEY RESPOND THAT A CYANACRYLATE ADHESIVE WOULD BE APPROPRIATE.THE FACT IS THAT IN OTHER PEOPLE'S OPINION THIS IS NOT GOING TO WORK!
ANY EXPIERIENCE IN THIS SUBJECT WOULD BE VERY HELPFULL!
THANKS.

 

[vpl]

GKIN013

As a general comment, use of the lower case and spacing between sentences/words would make your question easier to read.

As a specific comment, you stated that you contracted a manufacturer that gave you a recommendation but some unspecified "other people" told the manufacturer's recommendation would not work. Did they say why it wouldn't work? What is your criteria for deciding who to believe? If I said the manufacturer was right, does that hold more or less weight than the people who said it wouldn't? How would you know if I had any idea of what I was talking about? If someone else responds and says to use something different, how would you know that they know what they're talking about?

I'd recommend that you go back to the manufacturer and ask them about why they made their recommendation. Share with them the information you have as to why others feel it wouldn't work. Make an informed decision based on repeatable information, not on what somebody on the Internet told you.

Patricia Lougheed

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[CoryPad]

Cyanoacrylates are suitable for higher surface energy materials like metals. For low surface energy materials like polymers, especially POM, you need an adhesive with better bonding - like an epoxy. Loctite does tend to promote cyanoacrylate adhesives instead of other options. I would contact another source - in addition to 3M and Devcon, try Huntsman, Lord, and Sika.

Regards,

Cory

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[unclesyd]

I would contact either Reltek or Masterbond with you specific materials and conditions.

http://www.reltekllc.com/adhesives-for-delrin.htm

http://www.masterbond.com/sg/masterbond_substrat.html

 

[GKINO13]

Thanks Cory, you to unclesyd.
Dear vpl thanks for your general comment i'll try to adjust. As far your specific comment i would like to say that many times manufacturers that don't have a product for the purpose you need it usually recommends the one closest to that even if it is not suitable.In that case the most safe way is by practical knowledge, two parts a little adhesive and test.That is what i was looking for. Some experience.
I would like to say that i tried the cyanoacrilate along with primer and i failed.i tried also epoxy and was a disaster. If someone had better luck it would be helpful for the future.

 

[CoryPad]

Why was the epoxy a disaster? Did it not bond at all to the other parts? If so, you may need to improve the surface conditions (cleanliness, roughness). You need to find out exactly what is in the PA and POM parts - if they have any lubricants, release agents, etc. that can prevent bonding.

You may want to consider welding. Even simple hot plate welding - heat a piece of steel, touch the parts to it, then press the parts together. More sophisticated methods are available also, like ultrasonic welding.

Regards,

Cory

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[MintJulep]

Many Poly-whatever plastics are notoriously difficult to bond. Correct selection of an adhesive is critical - get the adhesive manufacturer involved. Correct surface preparation is critical. Correct surface preparation will likely be more than a simple surface roughening and cleaning. Many Poly-whatever plastics have inactive surfaces. Etching with a witches' brew of acid, flame treatment or exposure to plasma or a corona discharge may be needed to activate the surface prior to bonding.