varying the ratio on JB Weld or other epoxy
 

I want something like epoxy but that will not dry hard and brittle. Tried
the standard 50/50 mix with JB Weld on a piece of cardboard and it cracks
when bent, but I understand that this is way it was designed.

On another test piece I put 75% hardner and 25% "steel", then next to (not
touching it) did a spot of 75% steel and 25% hardner. 17 hours later
neither one seems cured.

The 75% steel spot did the best, it is tack free and flexible, feels sort of
rubbery. This is almost exactly what I need if it stays like this over the
long term.

The 75% hardener spot feels tacky and has not "skinned" yet.


I know that it's a chemical vulcanization so I expect the cure time on both
to be longer than a 50/50 mix. Am I wrong for expecting it to cure at all?

I'm generally curious about the possibility of varying the ratio on 2-part
epoxy's, but also am specifically looking for something that dries softer/
more flexible than jb weld but harder than latex or silicone caulk. Doesn't
have to be extremely durable, just maintain cohesion and at least moderate
adhesion. Also would be nice to have the following:

- post cure service temp of -40c to 110c
- curing process should not corrode soft metals like copper or solder (like
an acetate or ammonia curing silcone RTV)
- not trap small particles after curing. Example - sprinkle some graphite
dust on white cured caulk and it will get stuck in the silicone
- not "set up" quickly. I need about 30 min. to smear it around.

Purpose is sort of a special electronics project. It will cover and protect
some silver based conductive paint on a circuit board. I know it helps to
know the application but that's about the best I can explain it. Appreciate
any help.

varying the ratio on JB Weld or other epoxy
 

In article , says...


I want something like epoxy but that will not dry hard and brittle. Tried
the standard 50/50 mix with JB Weld on a piece of cardboard and it cracks
when bent, but I understand that this is way it was designed.

On another test piece I put 75% hardner and 25% "steel", then next to (not
touching it) did a spot of 75% steel and 25% hardner. 17 hours later
neither one seems cured.

The 75% steel spot did the best, it is tack free and flexible, feels sort of
rubbery. This is almost exactly what I need if it stays like this over the
long term.


Devcon makes a product line called Flexane that cures into rubber. They have
various durometer ratings, and also sell an additive to vary the durometer
(hardness) rating. I believe McMaster Carr carries it.

http://www.devcon.com/products/produ...ndid=1&catid=3

--
Dennis

varying the ratio on JB Weld or other epoxy
 

In article ,
"campbell_09" wrote:

I want something like epoxy but that will not dry hard and brittle. Tried
the standard 50/50 mix with JB Weld on a piece of cardboard and it cracks
when bent, but I understand that this is way it was designed.

On another test piece I put 75% hardner and 25% "steel", then next to (not
touching it) did a spot of 75% steel and 25% hardner. 17 hours later
neither one seems cured.

The 75% steel spot did the best, it is tack free and flexible, feels sort of
rubbery. This is almost exactly what I need if it stays like this over the
long term.

The 75% hardener spot feels tacky and has not "skinned" yet.


I know that it's a chemical vulcanization so I expect the cure time on both
to be longer than a 50/50 mix. Am I wrong for expecting it to cure at all?

I'm generally curious about the possibility of varying the ratio on 2-part
epoxy's, but also am specifically looking for something that dries softer/
more flexible than jb weld but harder than latex or silicone caulk. Doesn't
have to be extremely durable, just maintain cohesion and at least moderate
adhesion. Also would be nice to have the following:

- post cure service temp of -40c to 110c
- curing process should not corrode soft metals like copper or solder (like
an acetate or ammonia curing silcone RTV)
- not trap small particles after curing. Example - sprinkle some graphite
dust on white cured caulk and it will get stuck in the silicone
- not "set up" quickly. I need about 30 min. to smear it around.

Purpose is sort of a special electronics project. It will cover and protect
some silver based conductive paint on a circuit board. I know it helps to
know the application but that's about the best I can explain it. Appreciate
any help.

1. I don't think most epoxies tolerate a lot of variation in the
prescribed mix ratio. I wouldn't expect your experiment to work out well.

2. Hysol has a good assortment of industrial epoxies; one of them might
have the properties you seek. Not available at your local hardware store.

3. For your application, why not use conformal coating? It's usually
dipped in production applications, but you can buy a DIY spray can, too.

varying the ratio on JB Weld or other epoxy
 

"Smitty Two" wrote in message
...
In article ,
"campbell_09" wrote:

I want something like epoxy but that will not dry hard and brittle.
Tried
the standard 50/50 mix with JB Weld on a piece of cardboard and it cracks
when bent, but I understand that this is way it was designed.

On another test piece I put 75% hardner and 25% "steel", then next to
(not
touching it) did a spot of 75% steel and 25% hardner. 17 hours later
neither one seems cured.

The 75% steel spot did the best, it is tack free and flexible, feels sort
of
rubbery. This is almost exactly what I need if it stays like this over
the
long term.

The 75% hardener spot feels tacky and has not "skinned" yet.


I know that it's a chemical vulcanization so I expect the cure time on
both
to be longer than a 50/50 mix. Am I wrong for expecting it to cure at
all?

I'm generally curious about the possibility of varying the ratio on
2-part
epoxy's, but also am specifically looking for something that dries
softer/
more flexible than jb weld but harder than latex or silicone caulk.
Doesn't
have to be extremely durable, just maintain cohesion and at least
moderate
adhesion. Also would be nice to have the following:

- post cure service temp of -40c to 110c
- curing process should not corrode soft metals like copper or solder
(like
an acetate or ammonia curing silcone RTV)
- not trap small particles after curing. Example - sprinkle some
graphite
dust on white cured caulk and it will get stuck in the silicone
- not "set up" quickly. I need about 30 min. to smear it around.

Purpose is sort of a special electronics project. It will cover and
protect
some silver based conductive paint on a circuit board. I know it helps
to
know the application but that's about the best I can explain it.
Appreciate
any help.

1. I don't think most epoxies tolerate a lot of variation in the
prescribed mix ratio. I wouldn't expect your experiment to work out well.

2. Hysol has a good assortment of industrial epoxies; one of them might
have the properties you seek. Not available at your local hardware store.

3. For your application, why not use conformal coating? It's usually
dipped in production applications, but you can buy a DIY spray can, too.


Thanks, I'll look at the conformal coatings. The ones I found have acetate
though, but they are made for electronics. I thought acetate was corrosive
to most metals used in electronics though. Maybe I have something to learn.
I sent an email to the company about this product, will see what they say.

varying the ratio on JB Weld or other epoxy
 

"campbell_09" wrote in message
...

"Smitty Two" wrote in message
...
In article ,
"campbell_09" wrote:

I want something like epoxy but that will not dry hard and brittle.
Tried
the standard 50/50 mix with JB Weld on a piece of cardboard and it
cracks
when bent, but I understand that this is way it was designed.

On another test piece I put 75% hardner and 25% "steel", then next to
(not
touching it) did a spot of 75% steel and 25% hardner. 17 hours later
neither one seems cured.

The 75% steel spot did the best, it is tack free and flexible, feels
sort of
rubbery. This is almost exactly what I need if it stays like this over
the
long term.

The 75% hardener spot feels tacky and has not "skinned" yet.


I know that it's a chemical vulcanization so I expect the cure time on
both
to be longer than a 50/50 mix. Am I wrong for expecting it to cure at
all?

I'm generally curious about the possibility of varying the ratio on
2-part
epoxy's, but also am specifically looking for something that dries
softer/
more flexible than jb weld but harder than latex or silicone caulk.
Doesn't
have to be extremely durable, just maintain cohesion and at least
moderate
adhesion. Also would be nice to have the following:

- post cure service temp of -40c to 110c
- curing process should not corrode soft metals like copper or solder
(like
an acetate or ammonia curing silcone RTV)
- not trap small particles after curing. Example - sprinkle some
graphite
dust on white cured caulk and it will get stuck in the silicone
- not "set up" quickly. I need about 30 min. to smear it around.

Purpose is sort of a special electronics project. It will cover and
protect
some silver based conductive paint on a circuit board. I know it helps
to
know the application but that's about the best I can explain it.
Appreciate
any help.

1. I don't think most epoxies tolerate a lot of variation in the
prescribed mix ratio. I wouldn't expect your experiment to work out well.

2. Hysol has a good assortment of industrial epoxies; one of them might
have the properties you seek. Not available at your local hardware store.

3. For your application, why not use conformal coating? It's usually
dipped in production applications, but you can buy a DIY spray can, too.


Thanks, I'll look at the conformal coatings. The ones I found have
acetate though, but they are made for electronics. I thought acetate was
corrosive to most metals used in electronics though. Maybe I have
something to learn. I sent an email to the company about this product,
will see what they say.

link

http://www.techspray.com/newinfo/2102.pdf

varying the ratio on JB Weld or other epoxy
 

If you don't mix epoxies in the ratio specified, they will not cure
properly and excess of one material will slowly degrade. There are a
variety of epoxies designed to be rigid and flexible and you should try
to find one of these. Also, you can modify somewhat yourself with inert
additives. I've used carbon black, sand and fibrous additives to help
match intended use.

varying the ratio on JB Weld or other epoxy
 

On Jun 30, 12:54*am, Smitty Two wrote:
In article ,





*"campbell_09" wrote:
I want something like epoxy but that will not dry hard and brittle. *Tried
the standard 50/50 mix with JB Weld on a piece of cardboard and it cracks
when bent, but I understand that this is way it was designed.

On another test piece I put 75% hardner and 25% "steel", then next to (not
touching it) did *a spot of 75% steel and 25% hardner. *17 hours later
neither one seems cured.



1. I don't think most epoxies tolerate a lot of variation in the
prescribed mix ratio. I wouldn't expect your experiment to work out well.



Agreed.

The prescribed epoxy mix ratio gives optimum strength and adhesive
power. Fiddling with the mix degrades the final product. They will
tolerate some deviation but too much moves you from hard to "cheesy"
to sticky, unusable mess. If you want flexibility, start with a
flexible resin, i.e. silicones or urethanes. There are non-curing
materials that set by water or solvent loss that might be useful
(acrylates, PVC)

Regards
-J