I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I can
get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue or
wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.

"Royston Vasey" fired this volley in
. au:

I'm trying to seal a printed circuit board into a PVC part I've turned
out on my lathe. The problem I'm having is the that the epoxy goes
quite runny as it goes through its curing process and some of it runs
through small gaps ( 0.5mm) where I'd prefer it didn't.

....
Has anyone played around with this type of problem?


Yep. If you cannot seal the gaps (don't understand why you can't -- or
is it just too much trouble to do?), then you'll need to add a thixotrope
to the epoxy. Stirring will thin the material for pouring (thixotropic
== "shear thinning"). Remaining still will cause it to thicken; the
time-to-thicken and the degree of thickening are determined by the nature
of the thixotrope and how much you add.

LLoyd

On Mon, 15 Feb 2010 18:28:26 +0800, "Royston Vasey"
wrote:

I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I can
get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue or
wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.

You can also get 5 and 30 minute epoxy. Either should be more viscous
than a casting resin, which is intended to be low viscosity to allow
bubbles to escape as well as fill small details.

On Mon, 15 Feb 2010 18:28:26 +0800, "Royston Vasey" wrote:

I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I can
get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue or
wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.


Talcum powder or baby powder to thicken resin if strength isn't an issue, chopped fibers if it is,
all are available at any good boat store such as West Marine.
*****************
Thank You


To reply to this email please remove the AT
after the kgs in the reply to address as shown above.

Never ever under estimate the incompetent.

KG wrote:
On Mon, 15 Feb 2010 18:28:26 +0800, "Royston Vasey" wrote:

I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I can
get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue or
wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.


Talcum powder or baby powder to thicken resin if strength isn't an issue, chopped fibers if it is,
all are available at any good boat store such as West Marine.
*****************
Thank You


To reply to this email please remove the AT
after the kgs in the reply to address as shown above.

Never ever under estimate the incompetent.

Fumed silca is the preferred stuff.
West 406

--

Richard Lamb
http://www.home.earthlink.net/~cavelamb/

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in
. 3.70:

"Royston Vasey" fired this volley in
. au:

I'm trying to seal a printed circuit board into a PVC part I've
turned out on my lathe. The problem I'm having is the that the epoxy
goes quite runny as it goes through its curing process and some of it
runs through small gaps ( 0.5mm) where I'd prefer it didn't.

...
Has anyone played around with this type of problem?

Yep. If you cannot seal the gaps (don't understand why you can't --
or is it just too much trouble to do?), then you'll need to add a
thixotrope to the epoxy. Stirring will thin the material for pouring
(thixotropic == "shear thinning"). Remaining still will cause it to
thicken; the time-to-thicken and the degree of thickening are
determined by the nature of the thixotrope and how much you add.

We use Hysol (now part of Loctite) 1C epoxy, which has thixotrope mixed
in (http://www.tedpella.com/technote_html/891-60%20TN.pdf) when we don't
want it to flow. McMaster carries it, part #1813A221. It takes a while
to cure, but it's very strong.

Also, very few epoxies will stick well to PVC unless you clean the
surface with a good solvent to remove the oily monomers. They sell
special primers that worke very well, but the solvents are really nasty.

Doug White

"Royston Vasey" wrote in message
. au...
I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small
gaps ( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I
can get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue
or wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.

As Lloyd an others have suggested, straight epoxy is going to be a problem
if you need to overcome its tendency to run. In fact, it's inherently
anti-thixotropic -- just the opposite of what you want. Epoxy drools.

The two usual solutions are to add a thickener, which doesn't directly
address the problem but which slows down the running, or to add a
thixotrope. That's the better solution in most cases although you have to be
careful because the suppliers usually aren't very clear about what their
products actually do -- thicken it, or make it thixotropic. There are a
couple of other possibilities, like rotating the part slowly while it's
curing, or applying the epoxy in steps, to one plane at a time, and making
sure the plane to which you've applied it is held horizontal while it's
curing. I can't picture your application but it sounds as if these solutions
wouldn't work for you.

Not being up on the latest, I can't give any specific recommendations, but
I'd follow the suggestions of people who understand the difference between
these two properties.

--
Ed Huntress

On Feb 15, 5:28*am, "Royston Vasey" wrote:
I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) *where I'd prefer it didn't.
...
Has anyone played around with this type of problem?
thanks.

I use 5 minute epoxy to sculpt freehand shapes. A small jet of hot air
will make parts of it set up faster.

jsw

"Doug White" wrote in message
.. .
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in
. 3.70:

"Royston Vasey" fired this volley in
. au:

I'm trying to seal a printed circuit board into a PVC part I've
turned out on my lathe. The problem I'm having is the that the epoxy
goes quite runny as it goes through its curing process and some of it
runs through small gaps ( 0.5mm) where I'd prefer it didn't.

...
Has anyone played around with this type of problem?

Yep. If you cannot seal the gaps (don't understand why you can't --
or is it just too much trouble to do?), then you'll need to add a
thixotrope to the epoxy. Stirring will thin the material for pouring
(thixotropic == "shear thinning"). Remaining still will cause it to
thicken; the time-to-thicken and the degree of thickening are
determined by the nature of the thixotrope and how much you add.

We use Hysol (now part of Loctite) 1C epoxy, which has thixotrope mixed
in (http://www.tedpella.com/technote_html/891-60%20TN.pdf) when we don't
want it to flow. McMaster carries it, part #1813A221. It takes a while
to cure, but it's very strong.

Also, very few epoxies will stick well to PVC unless you clean the
surface with a good solvent to remove the oily monomers. They sell
special primers that worke very well, but the solvents are really nasty.

Doug White


thanks Doug & Lloyd - looks like an alternate epoxy maybe the answer.

"Ed Huntress" wrote in message
...

"Royston Vasey" wrote in message
. au...
I'm trying to seal a printed circuit board into a PVC part I've turned
out on my lathe. The problem I'm having is the that the epoxy goes quite
runny as it goes through its curing process and some of it runs through
small gaps ( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I
can get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue
or wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.

As Lloyd an others have suggested, straight epoxy is going to be a problem
if you need to overcome its tendency to run. In fact, it's inherently
anti-thixotropic -- just the opposite of what you want. Epoxy drools.

The two usual solutions are to add a thickener, which doesn't directly
address the problem but which slows down the running, or to add a
thixotrope. That's the better solution in most cases although you have to
be careful because the suppliers usually aren't very clear about what
their products actually do -- thicken it, or make it thixotropic. There
are a couple of other possibilities, like rotating the part slowly while
it's curing, or applying the epoxy in steps, to one plane at a time, and
making sure the plane to which you've applied it is held horizontal while
it's curing. I can't picture your application but it sounds as if these
solutions wouldn't work for you.

Not being up on the latest, I can't give any specific recommendations, but
I'd follow the suggestions of people who understand the difference between
these two properties.

--
Ed Huntress


I agree, sounds like an expoxy with a thixotrope is what is needed. It's not
really practical to do it in multiple steps.

"Jim Wilkins" wrote in message
...
On Feb 15, 5:28 am, "Royston Vasey" wrote:
I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small
gaps
( 0.5mm) where I'd prefer it didn't.
...
Has anyone played around with this type of problem?
thanks.

I use 5 minute epoxy to sculpt freehand shapes. A small jet of hot air
will make parts of it set up faster.

jsw

I'm off the hardware - I'm going to give some quick set expoxy a go before
looking at more expensive options. Cheers.

What's that Lassie? You say that Royston Vasey fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Mon, 15 Feb 2010 18:28:26 +0800:

I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.

Has anyone played around with this type of problem?

thanks.

If you have any marine stores in your area, look at what they have.
West system epoxy has several thickeners that you add in powder form.
Can be made as thick as peanut butter if you like.


--

Dan H.
northshore MA.

Royston Vasey wrote:
"Ed Huntress" wrote in message
...
"Royston Vasey" wrote in message
. au...
I'm trying to seal a printed circuit board into a PVC part I've turned
out on my lathe. The problem I'm having is the that the epoxy goes quite
runny as it goes through its curing process and some of it runs through
small gaps ( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I
can get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue
or wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.
As Lloyd an others have suggested, straight epoxy is going to be a problem
if you need to overcome its tendency to run. In fact, it's inherently
anti-thixotropic -- just the opposite of what you want. Epoxy drools.

The two usual solutions are to add a thickener, which doesn't directly
address the problem but which slows down the running, or to add a
thixotrope. That's the better solution in most cases although you have to
be careful because the suppliers usually aren't very clear about what
their products actually do -- thicken it, or make it thixotropic. There
are a couple of other possibilities, like rotating the part slowly while
it's curing, or applying the epoxy in steps, to one plane at a time, and
making sure the plane to which you've applied it is held horizontal while
it's curing. I can't picture your application but it sounds as if these
solutions wouldn't work for you.

Not being up on the latest, I can't give any specific recommendations, but
I'd follow the suggestions of people who understand the difference between
these two properties.

--
Ed Huntress


I agree, sounds like an expoxy with a thixotrope is what is needed. It's not
really practical to do it in multiple steps.



Like I said... West 406. Fumed silica is the preferred agent.
Mix to consistency of mayonnaises to peanut butter and trowel it in.


--

Richard Lamb
http://www.home.earthlink.net/~cavelamb/


"The clock of life is wound but once, and no man has the power
to tell just when the hands will stop, at late or early hour...
Now is the only time you own. Live, love, toil with a will.
Place no faith in time. For the clock may soon be still."

On Mon, 15 Feb 2010 18:28:26 +0800, "Royston Vasey"
wrote:

I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I can
get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue or
wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.

I did that today. It's curing in my lab toaster oven right now.

In a word, make a plug that fits or use epoxy, RTV or hot glue to seal
gaps.

I'd made a tube by boring out and turning down ABS water pipe to a
wall thickness of about 1/32". My circuit board was about the size of
a stick of gum, about 5/8" x 2". It has two round cords, one from the
supply and one to the load. I wanted to make this module, the current
regulator, a bulge in the cord.

I turned a plug about 1/8" thick by appropriate dia to fit the tube
with a bop fit -- bop it with heel of hand to get it in. Damned near
airtight. Made that out of fiberglass rod because that's what I had
at hand. (Yes, I protected the ways with a cloth!) I drilled a .110"
dia hole to pass a cord, countersunk it, ran the cord thru it and
drizzled in some 5-minute epoxy to seal that up. When that had cured I
sparingly wiped some 5-minute epoxy on the edge of the plug and bopped
it in. The epoxy was very likely not necessary but what the hell, eh?
I mixed up some Scotchcast 235, a resin intended for encapsulating
electrical stuff. At elevated temperature (about 80C) this stuff is
about as runny as water. It fills nooks and crannies and releases air
bubbles readily. Doesn't stress elex by shrinking because it doesn't
cure brittle-hard like epoxy, it retains a bit of give. Poured it in,
put it in the oven. It'll be "done" tomorrow about lunchtime.

On Mon, 15 Feb 2010 08:36:43 -0600, cavelamb
wrote:

KG wrote:
On Mon, 15 Feb 2010 18:28:26 +0800, "Royston Vasey" wrote:

I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I can
get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue or
wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.


Talcum powder or baby powder to thicken resin if strength isn't an issue, chopped fibers if it is,
all are available at any good boat store such as West Marine.
*****************
Thank You


Fumed silca is the preferred stuff.
West 406

Good stuff. West calls it colloidal silica, or did at one time.

Don Foreman wrote:
On Mon, 15 Feb 2010 08:36:43 -0600, cavelamb
wrote:

KG wrote:
On Mon, 15 Feb 2010 18:28:26 +0800, "Royston Vasey" wrote:

I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I can
get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue or
wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.

Talcum powder or baby powder to thicken resin if strength isn't an issue, chopped fibers if it is,
all are available at any good boat store such as West Marine.
*****************
Thank You

Fumed silca is the preferred stuff.
West 406

Good stuff. West calls it colloidal silica, or did at one time.

That's the same stuff.
AKA Cab-O-Sil


Another source might be Aircraft Spruce and Specialty.
http://www.aircraftspruce.com/menus/cm/thickening.html


--

Richard Lamb
http://www.home.earthlink.net/~cavelamb/

Don Foreman wrote:
On Mon, 15 Feb 2010 18:28:26 +0800, "Royston Vasey"
wrote:

I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I can
get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue or
wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.

I did that today. It's curing in my lab toaster oven right now.

In a word, make a plug that fits or use epoxy, RTV or hot glue to seal
gaps.

I'd made a tube by boring out and turning down ABS water pipe to a
wall thickness of about 1/32". My circuit board was about the size of
a stick of gum, about 5/8" x 2". It has two round cords, one from the
supply and one to the load. I wanted to make this module, the current
regulator, a bulge in the cord.

I turned a plug about 1/8" thick by appropriate dia to fit the tube
with a bop fit -- bop it with heel of hand to get it in. Damned near
airtight. Made that out of fiberglass rod because that's what I had
at hand. (Yes, I protected the ways with a cloth!) I drilled a .110"
dia hole to pass a cord, countersunk it, ran the cord thru it and
drizzled in some 5-minute epoxy to seal that up. When that had cured I
sparingly wiped some 5-minute epoxy on the edge of the plug and bopped
it in. The epoxy was very likely not necessary but what the hell, eh?
I mixed up some Scotchcast 235, a resin intended for encapsulating
electrical stuff. At elevated temperature (about 80C) this stuff is
about as runny as water. It fills nooks and crannies and releases air
bubbles readily. Doesn't stress elex by shrinking because it doesn't
cure brittle-hard like epoxy, it retains a bit of give. Poured it in,
put it in the oven. It'll be "done" tomorrow about lunchtime.


Are you using the same resin? CW177/HY177

--

Richard Lamb
http://www.home.earthlink.net/~cavelamb/


"The clock of life is wound but once, and no man has the power
to tell just when the hands will stop, at late or early hour...
Now is the only time you own. Live, love, toil with a will.
Place no faith in time. For the clock may soon be still."

Don Foreman wrote:
On Mon, 15 Feb 2010 18:28:26 +0800, "Royston Vasey"
wrote:

I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I can
get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue or
wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.

I did that today. It's curing in my lab toaster oven right now.

In a word, make a plug that fits or use epoxy, RTV or hot glue to seal
gaps.

I'd made a tube by boring out and turning down ABS water pipe to a
wall thickness of about 1/32". My circuit board was about the size of
a stick of gum, about 5/8" x 2". It has two round cords, one from the
supply and one to the load. I wanted to make this module, the current
regulator, a bulge in the cord.

I turned a plug about 1/8" thick by appropriate dia to fit the tube
with a bop fit -- bop it with heel of hand to get it in. Damned near
airtight. Made that out of fiberglass rod because that's what I had
at hand. (Yes, I protected the ways with a cloth!) I drilled a .110"
dia hole to pass a cord, countersunk it, ran the cord thru it and
drizzled in some 5-minute epoxy to seal that up. When that had cured I
sparingly wiped some 5-minute epoxy on the edge of the plug and bopped
it in. The epoxy was very likely not necessary but what the hell, eh?
I mixed up some Scotchcast 235, a resin intended for encapsulating
electrical stuff. At elevated temperature (about 80C) this stuff is
about as runny as water. It fills nooks and crannies and releases air
bubbles readily. Doesn't stress elex by shrinking because it doesn't
cure brittle-hard like epoxy, it retains a bit of give. Poured it in,
put it in the oven. It'll be "done" tomorrow about lunchtime.



Are you using the same resin? CW177/HY177

--

Richard Lamb
http://www.home.earthlink.net/~cavelamb/

On Tue, 16 Feb 2010 00:02:47 -0600, cavelamb
wrote:

Don Foreman wrote:
On Mon, 15 Feb 2010 18:28:26 +0800, "Royston Vasey"
wrote:

I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.


I'm using CW177 resin & HY177 hardener in the 5:1 mix recommended.

The data sheet is he

http://www.meury.com.au/uploads/170666853166.pdf

I tried some rapid set epoxy (~90 seconds) but it turns to crap before I can
get it in where it needs to go.


It's not really practical to use anything else (like RTV, tape, hot glue or
wax etc) to seal the small gaps in the bottom of the assembly.

Has anyone played around with this type of problem?

thanks.

I did that today. It's curing in my lab toaster oven right now.

In a word, make a plug that fits or use epoxy, RTV or hot glue to seal
gaps.

I'd made a tube by boring out and turning down ABS water pipe to a
wall thickness of about 1/32". My circuit board was about the size of
a stick of gum, about 5/8" x 2". It has two round cords, one from the
supply and one to the load. I wanted to make this module, the current
regulator, a bulge in the cord.

I turned a plug about 1/8" thick by appropriate dia to fit the tube
with a bop fit -- bop it with heel of hand to get it in. Damned near
airtight. Made that out of fiberglass rod because that's what I had
at hand. (Yes, I protected the ways with a cloth!) I drilled a .110"
dia hole to pass a cord, countersunk it, ran the cord thru it and
drizzled in some 5-minute epoxy to seal that up. When that had cured I
sparingly wiped some 5-minute epoxy on the edge of the plug and bopped
it in. The epoxy was very likely not necessary but what the hell, eh?
I mixed up some Scotchcast 235, a resin intended for encapsulating
electrical stuff. At elevated temperature (about 80C) this stuff is
about as runny as water. It fills nooks and crannies and releases air
bubbles readily. Doesn't stress elex by shrinking because it doesn't
cure brittle-hard like epoxy, it retains a bit of give. Poured it in,
put it in the oven. It'll be "done" tomorrow about lunchtime.



Are you using the same resin? CW177/HY177

No. As said (feel free to re-read) I used Scotchcast 235. Why?
Because that's what I have at hand, left over from projects a decade
ago. I'm amazed that the stuff still works.

On 2/16/2010 12:38 AM, Don Foreman wrote:
Doesn't stress elex by shrinking because it doesn't
cure brittle-hard like epoxy, it retains a bit of give.

Don has brought up something the OP may not be considering. If one whips
up one's own witch's brew of a potting compound, the desired
electrical/mechanical characteristics may not be there. As an example,
the device the OP posted bears a superficial resemblance to a
microphone. If you were trying to pot the high impedance buffer of a
capacitor microphone, the results may be disappointing. A board is
generally pretty difficult to unpot.

Kevin Gallimore

"axolotl" wrote in message
...
On 2/16/2010 12:38 AM, Don Foreman wrote:
Doesn't stress elex by shrinking because it doesn't
cure brittle-hard like epoxy, it retains a bit of give.

Don has brought up something the OP may not be considering. If one whips
up one's own witch's brew of a potting compound, the desired
electrical/mechanical characteristics may not be there. As an example, the
device the OP posted bears a superficial resemblance to a microphone. If
you were trying to pot the high impedance buffer of a capacitor
microphone, the results may be disappointing. A board is generally pretty
difficult to unpot.

Kevin Gallimore

Thanks Kevin, luckily conductivity of the epoxy isn't a major issue (well it
is if its toooo low but its not critical). Water absorption is however
important, the LC177 isnt too bad at this at 0.3% w/w.

Royston Vasey wrote:
I'm trying to seal a printed circuit board into a PVC part I've turned out
on my lathe. The problem I'm having is the that the epoxy goes quite runny
as it goes through its curing process and some of it runs through small gaps
( 0.5mm) where I'd prefer it didn't.
I do this for vacuum feed-throughs and use Huntington Mechanical Labs
Vacuum Epoxy. It is much thicker that many other epoxies so it stays
put better. It is hard stuff, so it can crack if the assembly is made
to flex. The Huntington stuff is apparently the same as Varian's famous
Torr Seal, but about 1/4 Varian's price. Huntington has a minimum order
that may make this unreasonable for a one-off home project.

A trick is to seal up the bottom of the assembly with 3M magic tape
before applying the epoxy. it sticks just well enough to keep the epoxy
from flowing out the bottom.

Jon

"Jon Elson" wrote in message
...
Royston Vasey wrote:
I'm trying to seal a printed circuit board into a PVC part I've turned
out on my lathe. The problem I'm having is the that the epoxy goes quite
runny as it goes through its curing process and some of it runs through
small gaps ( 0.5mm) where I'd prefer it didn't.
I do this for vacuum feed-throughs and use Huntington Mechanical Labs
Vacuum Epoxy. It is much thicker that many other epoxies so it stays put
better. It is hard stuff, so it can crack if the assembly is made to
flex. The Huntington stuff is apparently the same as Varian's famous
Torr Seal, but about 1/4 Varian's price. Huntington has a minimum order
that may make this unreasonable for a one-off home project.

A trick is to seal up the bottom of the assembly with 3M magic tape before
applying the epoxy. it sticks just well enough to keep the epoxy from
flowing out the bottom.

Jon


Thanks Jon, yeah the magic tape works well, I've done that before. Heat
shrink tubing is useful as well - cut it off when the epoxy has hardened.

I've ended up using some hot glue to seal the base - its a bit messy but
do-able.