Rubber to Metal bonding 3

[Elastomatt]

Hi Everyone and Anyone,

Need some more advice, currently reviewing the process of rubber to metal bonding. Got the general idea but wondered if anyone knows of a good resource on the subject.

Product needs to be well bonded and samples I have received have been inconsistent (good bond, bad bond on same piece).

Items are compression moulded with an EPDM to various metals.

I believe the issue is primarily with the thickness of the undercoat, as the failures appear to be between the topcoat and the undercoat.

Any advice is welcome

 

[btrueblood]

We've never seen a bond failure of the type you describe (failure in adhesive primer layers). Our vendors typically all use bonding primers from Lord Industries, if that is any help.

It can be quite difficult to distinguish between cured primer layer and adjacent rubber, especially if peel stresses are being applied along the bond line.

In general, picking the right primer for substrate and rubber, good hygiene in primer prep and application, and development of proper mold pressure all play a part in adhesive bond success.

Good luck.

 

[GrahamBennett]

As btrueblood says, talk to Lord Industries. They are the leaders in the field of bonding agents.

 

[Elastomatt]

According to our records we dealt with Lord several years ago, no clear reason given for the change.

I will speak with TEchnical/Purchasing to see if we can get them in.

Thanks again!!

 

[utkk]

Cleaning metal surface and oil film on rubber surface

http://rubber-engineering.blogspot.com

 

[Amustafat]

Bond EPDM with metal has always been a problem, you better contact Lord for an special adhesive or process parameters to control.

 

[loughnane]

Is the geometry such that you can't do an insert-compression mold? That would be ideal.

Chris Loughnane - Product Design

http://www.pdnotebook.com

http://www.twitter.com/_chrisloughnane

 

[Snarted]

I know Columbia Engineered Rubber has some proprietary EPDM compounds, and they also do rubber to metal bonding. They may be worth checking into. Here is their

http://www.columbiaerd.com/rubbertometal.html

rubber to metal page

 

[Elastomatt]

Thanks, Snarted.

I will take a look.

 

[Compositepro]

I have no idea if this applies to your problem, but many bonding primers are relatively brittle, so keeping the primer thickness to a minimum is critical.

With aerospace adhesive bonding the primer must be kept below 0.0002" or the bond strength rapidly declines.

 

[btrueblood]

Matt,

Did you ever get any resolution of this problem?

We are now experiencing a similar type of bonding failure between a peroxide-cured epdm and a primered brass substrate.

Wondered if you had any success with Lord Chemicals, and did they suggest any changes to the primer type?

 

[Elastomatt]

BTB,

We resolved the issue by moving the metal preparation to a sub-contractor. We set out sepcific instructions relating to the primer thickensss and monitoring of. I found that our process was applying inconsitent thickness of primer.
We have worked with Lord who checked some samples for us to help identify the failure type. We found that we had excess and insufficent primer along the strips. Since moving the process our defect rate has fallen to around 1% and bond failure has been eradicated.

Thanks to all for their contributions.

 

[btrueblood]

Glad to hear it, Matt. BTW, we (think we have) got our problem fixed too, figured out some tolerance stack issues were creating a nice seal along one edge of our parts, preventing proper air purge.