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dgankey
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Join Date: Jul 2007
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Why epoxy did not stick to plastic housing?

10/05/2008 10:41 PM

Lord Epoxy EP-20 resin + Lord No. 66 Hardener (ratio is 1:1)

this Epoxy did not sitck to plastic housing.

the plastic housing material is PA6 - Nylon6, 33% Glass Filled (Heat Stabilized).

Because MOLD RELEASE ???? Cause the cure process e.g. temperature or cure time???

tks in advance

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dgankey
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#1

Re: Why epoxy did not stick to plastic housing?

10/06/2008 3:01 AM

NO response! it's urgent....Help!

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Del the cat
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#2

Re: Why epoxy did not stick to plastic housing?

10/06/2008 3:02 AM

The mold release is one possibility, but Nylon is inherantly self lubricting and thus not a good surface to try to stick to.
Maybe try sand basrting.wire brushing it first.

It's hard to comment without seeing the complete design, but it sounds like bad design to me.

If you are going to the trouble of having a part molded then it would seem to be sensible to design in a mechanical fixing/retaining arrangement of some sort.

Del

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Kris
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#3
In reply to #2

Re: Why epoxy did not stick to plastic housing?

10/06/2008 4:16 AM

I'm going to have to give you a GA for that Del. Surface treatment or mechanical seems the best options if having to use Nylon. Down the bottom of this link is some stuff called Hinge Glue, which claims to micro-etch the surface before bonding ;

http://www.helihobby.com/html/adhisves_and_lubes.html

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Del the cat
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#4
In reply to #3

Re: Why epoxy did not stick to plastic housing?

10/06/2008 4:29 AM

I'm going to have to give you a GA for that Del..

well go on then you tight git

Del

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Kris
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#6
In reply to #4

Re: Why epoxy did not stick to plastic housing?

10/06/2008 6:58 AM

I didn't say where and when ! Transferable letter of credit by the usual means.

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dadw5boys
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#7
In reply to #2

Re: Why epoxy did not stick to plastic housing?

10/06/2008 11:03 PM

Or at least ETCH .

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Bricktop
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#5

Re: Why epoxy did not stick to plastic housing?

10/06/2008 6:51 AM

Regular epoxy does not bond well to plastic. There are special epoxies made for plastic.

http://www.amazon.com/Loctite-Plastic-Epoxy/dp/B000LF5XYW

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dadw5boys
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#8

Re: Why epoxy did not stick to plastic housing?

10/06/2008 11:06 PM

the plastic is super slick you have to give it something to anchor too.

etch will remove the gloss and rough up the surface to allow bonding.

sand blasting would allow a rough surface to bond too.

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plaasteek
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#9

Re: Why epoxy did not stick to plastic housing?

10/06/2008 11:59 PM

The problem you're facing is the surface energy of the PA6 not sufficient enough for the adhesive to work properly.

You can:

1. plastic weld the parts.

2. plasma treat the PA to get the correct surface energy that the adhesive will work with.

3. "dissolving some scraps of nylon in the formic acid to make a syrup or paste, then laying it in the corners. Use concentrated formic acid. 90% concentrated should do. Be careful it is corrosive and has noxious fumes."

4. contact an adhesive company such as Loctite.

www.henkel.com/cps/rde/xchg/SID-0AC8330A-5E6A7911/henkel_com/hs.xsl/12165_COE_HTML.htm

Books have been written on this subject so you are not alone.

http://www.springerlink.com/content/w8q3591kvw57176n/

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hazman
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#13
In reply to #9

Re: Why epoxy did not stick to plastic housing?

10/07/2008 7:10 AM

Probably not mould release - plastic surfaces are generally too slick to give adhesion unless roughed up or Sparked (elect discharge). If this is a patch up job and appearance not important you can perhaps get a mechanical effect by perforating it then wiring it together then scuff the surface and apply a coat of epoxy which should stick to the stitching and so get a grip and also give a seal. Suggest also using surfacing tissue (light weight glass fibre) embedded in the resin to give added strength and continuity,

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imintowater
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#10

Re: Why epoxy did not stick to plastic housing?

10/07/2008 12:23 AM

Scuff the mating surface with a coarse grade sandpaper, that particular action will allow some adhesion. The epoxy fluid will not so much permeate the surface, but it will allow the epoxy to attach itself to the resulting abrasion-related imperfections in the mating surface.
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dgankey
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#11

Re: Why epoxy did not stick to plastic housing?

10/07/2008 1:53 AM

Thank you.

This design is not good I agree so. We put the epoxy into the housing in order to prevent the leaking issue happen.

If there is gap between the wall of plastic housing and epoxy, it surely will leak...

New design will add plastisol first before we put the epoxy into the housing..It is not applicable to ETCH the housing surface. I am not sure the diesel oil will erode the plastisol ....?? Anybody know???

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Del the cat
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#12
In reply to #11

Re: Why epoxy did not stick to plastic housing?

10/07/2008 2:35 AM

Ha!
A classic case of asking the wrong question!


We put the epoxy into the housing in order to prevent the leaking issue happen.

How to seal against leaks is an entirely different question...
I'm out.
Del

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welderman
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#14

Re: Why epoxy did not stick to plastic housing?

10/07/2008 9:19 AM

Nylon is a thermoplastic. In general, it is difficult to obtain good adhesion of epoxy adhesives to thermoset plastics without surface preparation described in previous comments. Another option may be to switch to a thermoset plastic part, like epoxy, phenolic, etc. In general, epoxy adhesives adhere well to thermoset plastics.
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V.Daniel
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#15

Re: Why epoxy did not stick to plastic housing?

10/07/2008 10:22 AM

Try applying dissolved resorcinol on the bonding surface prior to the epoxy.
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Users who posted comments:

Bricktop (1); dadw5boys (2); Del the cat (3); dgankey (2); hazman (1); imintowater (1); Kris (2); plaasteek (1); V.Daniel (1); welderman (1)

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