22 Jun 2004 01:40:17
Fred Agnir
Bonding Delrin

I had a project several years ago where I had to bond two parts that were
threaded together. The requirement was that they couldn't un-thread at less
than X torque. The parts were Polyamide and Acetal. That's Nylon and Delrin.
So that's tip #1, if you're going to ask the technical support folks, they
might only know "Acetal."

Acetal is naturally a lubricant and has a very slick surface. Adhesives like
Cyanoacrylates and Epoxy work best as mechanical bonding. They need to bite
and seep into the substrate. Nylon is the natural sponge of the plastics
industry, so CA and Epoxy work very well with it. Wood and plastic foams
(urethane foam, styrofoam) are perfect for Epoxy. Acetal is one of the worst
for these two. There are no pores to get into. There *is* some surface
micro-bonding, but the bond can easily be broken. Add to that, both CA and
Epoxy are brittle. Epoxy moreso, I believe. So, there are two things to
contend with: the brittleness of the adhesive and the low bond strength in
shear. So, in other words, Epoxy by itself might be the worst adhesive for
Delrin/Acetal.

For my case, the thing that made the bond about 10 or 15 times stronger was
a primer on the acetal. The primer changes the molecular structure of the
surface of the acetal, giving a tooth for the CA to bond. Additionally, by
going to glass-filled acetal, that doubled the strength. The glass fibers
themselves provided more tooth for the CA. So, in the end, I had a bond that
was some 30 times stronger than just CA alone. BTW, my CA bond was stronger
than the Epoxy bond alone. Epoxy was no good for high volume production
anyway. Glass-filled Acetal looks different and is brutal on tools. YMMV.

The primer must be applied and allowed to flash off. There is a certain time
between application of the primer and the application of the CA. That is,
you couldn't batch dunk the parts, and assemble them sometime the next day.
And you couldn't add the CA while the parts were still wet. Nasty chemical
reaction. Also, putting the primer on the Nylon part gave exactly the
opposite effect (less bonding).

Things that had little effect or even worse effect: surface roughening,
flame treating, Corona disharge treating. I think a lot of people think that
every substrate you just simply sand. Not true. Sometimes, surface
roughening is worse, not better.

That being said, my project worked under a dynamic load, but the parts were
also threaded. So, it wasn't straight shear. So, I'd suggest putting as many
bonding methods as realistic to "distribute the load." Threading and keying
would be my suggestions. I also believe that using a more flexible adhesive
like a urethane adhesive along with the primer might work out better, even
though the shear strength of the urethane isn't anywhere near as strong. The
flexibility might take the strength requirement out of the equation. But,
maybe someone else may have already tried this. There is also a new adhesive
for Polypropylene and other olefins that has a higher shear strength than
the urethane adhesive when used on Acetal, and more flexibility than the
epoxy. IIRC, it's a heat activated adhesive.

Much of what I've just written is out there and available. What isn't
available is the engineering study of the actual process as it pertained to
my parts. A Design of Experiments to determine the best process, amount,
time, application method, all of that. And it had to be repeatable and
robust. There's also a whole study on dynamic loads and isolating (and
protecting) what might fail. And then theres a study on industrial joint
design.

Oh, there's more, but that's enough.

Fred




22 Jun 2004 02:20:34
dalecue
Re: Bonding Delrin


Fred Agnir wrote in message <56MBc.69142$2i5.18135@attbi_s52 >...
>I had a project several years ago where I had to bond two parts that were
>threaded together. The requirement was that they couldn't un-thread at less
>than X torque. The parts were Polyamide and Acetal. That's Nylon and
Delrin.
>So that's tip #1, if you're going to ask the technical support folks, they
>might only know "Acetal."
>
>Acetal is naturally a lubricant and has a very slick surface. Adhesives
like
>Cyanoacrylates and Epoxy work best as mechanical bonding. They need to bite
>and seep into the substrate. Nylon is the natural sponge of the plastics
>industry, so CA and Epoxy work very well with it. Wood and plastic foams
>(urethane foam, styrofoam) are perfect for Epoxy. Acetal is one of the
worst
>for these two. There are no pores to get into. There *is* some surface
>micro-bonding, but the bond can easily be broken. Add to that, both CA and
>Epoxy are brittle. Epoxy moreso, I believe. So, there are two things to
>contend with: the brittleness of the adhesive and the low bond strength in
>shear. So, in other words, Epoxy by itself might be the worst adhesive for
>Delrin/Acetal.
>
>For my case, the thing that made the bond about 10 or 15 times stronger was
>a primer on the acetal. The primer changes the molecular structure of the
>surface of the acetal, giving a tooth for the CA to bond. Additionally, by
>going to glass-filled acetal, that doubled the strength. The glass fibers
>themselves provided more tooth for the CA. So, in the end, I had a bond
that
>was some 30 times stronger than just CA alone. BTW, my CA bond was stronger
>than the Epoxy bond alone. Epoxy was no good for high volume production
>anyway. Glass-filled Acetal looks different and is brutal on tools. YMMV.
>
>The primer must be applied and allowed to flash off. There is a certain
time
>between application of the primer and the application of the CA. That is,
>you couldn't batch dunk the parts, and assemble them sometime the next day.
>And you couldn't add the CA while the parts were still wet. Nasty chemical
>reaction. Also, putting the primer on the Nylon part gave exactly the
>opposite effect (less bonding).
>
>Things that had little effect or even worse effect: surface roughening,
>flame treating, Corona disharge treating. I think a lot of people think
that
>every substrate you just simply sand. Not true. Sometimes, surface
>roughening is worse, not better.
>
>That being said, my project worked under a dynamic load, but the parts were
>also threaded. So, it wasn't straight shear. So, I'd suggest putting as
many
>bonding methods as realistic to "distribute the load." Threading and keying
>would be my suggestions. I also believe that using a more flexible adhesive
>like a urethane adhesive along with the primer might work out better, even
>though the shear strength of the urethane isn't anywhere near as strong.
The
>flexibility might take the strength requirement out of the equation. But,
>maybe someone else may have already tried this. There is also a new
adhesive
>for Polypropylene and other olefins that has a higher shear strength than
>the urethane adhesive when used on Acetal, and more flexibility than the
>epoxy. IIRC, it's a heat activated adhesive.
>
>Much of what I've just written is out there and available. What isn't
>available is the engineering study of the actual process as it pertained to
>my parts. A Design of Experiments to determine the best process, amount,
>time, application method, all of that. And it had to be repeatable and
>robust. There's also a whole study on dynamic loads and isolating (and
>protecting) what might fail. And then theres a study on industrial joint
>design.
>
>Oh, there's more, but that's enough.
>
>Fred

good info
cupla queries

1. any hints as to what this primer was
2. would it also help with epoxy?

thanks
Dale
>
>




22 Jun 2004 10:41:08
Jimbo Ct
Re: Bonding Delrin

Fred A saz: >Things that had little effect or even worse effect: surface
roughening,
>flame treating, Corona disharge

I had that once, now I only drink American beer.

Nice story Fred but why bother??? Some may appreciate it but I am sure you'll
get at least 1 "I already knew that" and a boat load of crap for the other know
it alls.

Jim <---Sharing info here has no reward :-)

PS Thanks for sharing, even if I have zero use for it, it's always fun to read
an educated post.



22 Jun 2004 07:20:12
Fred Agnir
Re: Bonding Delrin

"dalecue" wrote:

>
> good info
> cupla queries
>
> 1. any hints as to what this primer was
> 2. would it also help with epoxy?
>

Standard primer from Loctite: Prism 770. It's a solvent-based product
(heptane). I'm sure there are other products that have the same stuff
in it.

Because of how epoxy is supposed to work, treating the surface of
Delrin with the primer should improve the shear strength. Loctite
doesn't agree, but from what I know of what the primer does, it should
improve it. But, an improvement of a crappy bond is just a little less
of a crappy bond. So, that might be why Loctite doesn't agree.

That being said, CA will actually perform better. Much better.
Depending on your joint design and whether or not you can work the CA
efficiently, of course. As I said earlier, I suggest threading
incorporated with a primer and CA. I had great results with several of
the Loctite Prism 400 series products with the primer.

Fred


22 Jun 2004 07:43:00
Edwin Reyes
Re: Bonding Delrin

jimboct@aol.comnojunk (Jimbo Ct) wrote in message news:<20040622064108.25561.00000457@mb-m29.aol.com >...
> Fred A saz: >Things that had little effect or even worse effect: surface
> roughening,
> >flame treating, Corona disharge
>
> I had that once, now I only drink American beer.
LOL, sure felt like those jelly beans are jumping their way out ey?
>
> Nice story Fred but why bother??? Some may appreciate it but I am sure you'll
> get at least 1 "I already knew that" and a boat load of crap for the other know
> it alls.
>
> Jim <---Sharing info here has no reward :-)
>
> PS Thanks for sharing, even if I have zero use for it, it's always fun to read
> an educated post.

Hold on a minute, I'm still reading and researching every line of that post.
Thanks Fred.

Edwin Reyes


22 Jun 2004 12:09:52
Sherm Adamson
Re: Bonding Delrin

Fred, Great info! Frankly, I doubt that I'll start using Delrin in my cues,
even if I can achieve a good bond, but I've used ton's of it for jigs and
fixtures. There are times where a good bond would invaluable there.

--
just more hot air! 8^)

Sherm
aka "cuesmith" in yahoo
Sherm Custom Billiard Cues by,
Sherman Adamson
3352 Nine Mile Rd., Cincinnati Ohio 45255
Shop (513)553-2172, Cell (513)509-9152
http://www.shermcue.com Over 20 years experience
almost a decade in "The American Cuemakers Association"

Sending unsolicited commercial email (spam) to this account incurs a fee of
$500 per message, and acknowledges the legality of this contract.
"Fred Agnir" <ohagnir1@PASScomcast.net > wrote in message
news:56MBc.69142$2i5.18135@attbi_s52...
> I had a project several years ago where I had to bond two parts that were
> threaded together. The requirement was that they couldn't un-thread at
less
> than X torque. The parts were Polyamide and Acetal. That's Nylon and
Delrin.
> So that's tip #1, if you're going to ask the technical support folks, they
> might only know "Acetal."
>
> Acetal is naturally a lubricant and has a very slick surface. Adhesives
like
> Cyanoacrylates and Epoxy work best as mechanical bonding. They need to
bite
> and seep into the substrate. Nylon is the natural sponge of the plastics
> industry, so CA and Epoxy work very well with it. Wood and plastic foams
> (urethane foam, styrofoam) are perfect for Epoxy. Acetal is one of the
worst
> for these two. There are no pores to get into. There *is* some surface
> micro-bonding, but the bond can easily be broken. Add to that, both CA
and
> Epoxy are brittle. Epoxy moreso, I believe. So, there are two things to
> contend with: the brittleness of the adhesive and the low bond strength in
> shear. So, in other words, Epoxy by itself might be the worst adhesive for
> Delrin/Acetal.
>
> For my case, the thing that made the bond about 10 or 15 times stronger
was
> a primer on the acetal. The primer changes the molecular structure of the
> surface of the acetal, giving a tooth for the CA to bond. Additionally, by
> going to glass-filled acetal, that doubled the strength. The glass fibers
> themselves provided more tooth for the CA. So, in the end, I had a bond
that
> was some 30 times stronger than just CA alone. BTW, my CA bond was
stronger
> than the Epoxy bond alone. Epoxy was no good for high volume production
> anyway. Glass-filled Acetal looks different and is brutal on tools. YMMV.
>
> The primer must be applied and allowed to flash off. There is a certain
time
> between application of the primer and the application of the CA. That is,
> you couldn't batch dunk the parts, and assemble them sometime the next
day.
> And you couldn't add the CA while the parts were still wet. Nasty chemical
> reaction. Also, putting the primer on the Nylon part gave exactly the
> opposite effect (less bonding).
>
> Things that had little effect or even worse effect: surface roughening,
> flame treating, Corona disharge treating. I think a lot of people think
that
> every substrate you just simply sand. Not true. Sometimes, surface
> roughening is worse, not better.
>
> That being said, my project worked under a dynamic load, but the parts
were
> also threaded. So, it wasn't straight shear. So, I'd suggest putting as
many
> bonding methods as realistic to "distribute the load." Threading and
keying
> would be my suggestions. I also believe that using a more flexible
adhesive
> like a urethane adhesive along with the primer might work out better, even
> though the shear strength of the urethane isn't anywhere near as strong.
The
> flexibility might take the strength requirement out of the equation. But,
> maybe someone else may have already tried this. There is also a new
adhesive
> for Polypropylene and other olefins that has a higher shear strength than
> the urethane adhesive when used on Acetal, and more flexibility than the
> epoxy. IIRC, it's a heat activated adhesive.
>
> Much of what I've just written is out there and available. What isn't
> available is the engineering study of the actual process as it pertained
to
> my parts. A Design of Experiments to determine the best process, amount,
> time, application method, all of that. And it had to be repeatable and
> robust. There's also a whole study on dynamic loads and isolating (and
> protecting) what might fail. And then theres a study on industrial joint
> design.
>
> Oh, there's more, but that's enough.
>
> Fred
>
>




22 Jun 2004 23:47:47
Fred Agnir
Re: Bonding Delrin


"Sherm Adamson" <shermcue@adelphia.net > wrote

> Fred, Great info! Frankly, I doubt that I'll start using Delrin in my
cues,
> even if I can achieve a good bond, but I've used ton's of it for jigs and
> fixtures. There are times where a good bond would invaluable there.

For static loads, the Prism 770 and Loctite 400 series is great. Of course,
so is countersinking and using flat-head screws.

Fred <~~~ and don't get me started on that double-sided tape




24 Jun 2004 23:22:48
b
Re: Bonding Delrin

this being a billiard forum, i guess the relevence of your post is in
regards to delrin used in the butt. delrin doesn't get used anywhere
else because it "feels" kinda,,,well,,,,,dead.

why not just do the sure thing and, after the delrin butt has been
screwed onto the threaded core,,,simply lock it in by drilling in a
tiny dowel-like "key" in between the delrin collar and the core.


25 Jun 2004 12:25:55
William Lee
Re: Bonding Delrin

Well that would be something to keep it from turning.
Most cuemakers that used Delrin as a butt cap held it in plsce with glue and
the weight bolt.
However, aside from the fact that adhesives don't stick to it very well
neither does the finish.
It is just not a very good cue material.

William Lee


"b" <bruin70@mail.com > wrote in message
news:95513a07.0406242222.2778204b@posting.google.com...
> this being a billiard forum, i guess the relevence of your post is in
> regards to delrin used in the butt. delrin doesn't get used anywhere
> else because it "feels" kinda,,,well,,,,,dead.
>
> why not just do the sure thing and, after the delrin butt has been
> screwed onto the threaded core,,,simply lock it in by drilling in a
> tiny dowel-like "key" in between the delrin collar and the core.




25 Jun 2004 14:59:20
Roger Orsulak
Re: Bonding Delrin

Well bless my hemi-acetal, Fred! Thanks for the info.

Roger

"Fred Agnir" <ohagnir1@PASScomcast.net > wrote in message
news:56MBc.69142$2i5.18135@attbi_s52...
> I had a project several years ago where I had to bond two parts that were

< threaded together. snip good delrin stuff >

> Oh, there's more, but that's enough.
>
> Fred
>
>