Normal epoxy or polyester resins for potting?

[Emil Johnsen]

I'v googled this but didn't come up with any useful information.

Can normal (intended for use with fiberglass) epoxy or polyester resins be
used for potting electronics?


--
Emil Johnsen

 

[Adam Aglionby]

"Emil Johnsen" <nospam.emil.johnsen@student.uib.no> wrote in message
news:cjqtaf$2ds6$1@toralf.uib.no...

I'v googled this but didn't come up with any useful information.

Can normal (intended for use with fiberglass) epoxy or polyester resins be
used for potting electronics?

Epoxys are more usually used with carbon fibre they are several multiples of
cost above polyester resins which are commonly used with glassfibre.

Think potting compounds are generally epoxy to keep exothermic effects down,
heat when curing, and shrinkage.

Polyesters get hot whilst curing and in castings are built up to save the
thing cracking or in extreme cases self igniting, er ,guess who put too much
catalyst in ;-) Polys are not, without additives , very flexible and also
shrink by up to 3 or 4 % .

Heat also finds every dry joint in your board ...

Adam

--
Emil Johnsen

 

[Adam Aglionby]

"Emil Johnsen" <nospam.emil.johnsen@student.uib.no> wrote in message
news:cjqtaf$2ds6$1@toralf.uib.no...

I'v googled this but didn't come up with any useful information.

Can normal (intended for use with fiberglass) epoxy or polyester resins be
used for potting electronics?


--
Emil Johnsen

Having said all above have potted a few things with poly resins, dont make a
3" deep block of the stuff in one pour, if it needs to be deep do it in a
few stages.

Use a filler, it helps extend, bulk out the resin , and mitigate shrinkage
and heat, aluminium powder or `micro balloons`, both commonly available from
glass fibre suppliers. look for boat building suppliers rather athn a DIY
store, the differnce in cost is fairly dramatic.

HTH
Adam

 

[Emil Johnsen]

Polyesters get hot whilst curing and in castings are built up to save the
thing cracking or in extreme cases self igniting, er ,guess who put too
much
catalyst in ;-) Polys are not, without additives , very flexible and
also
shrink by up to 3 or 4 % .

Heat also finds every dry joint in your board ...

I think that using less catalyst will help avoid the heat problem. It will
take longer to cure, but end result will be the same. Atleast that is my
limited experience from messing up the resin/catalyst ratio when making
fiberglass parts with polyester.

I'm concerned about effects from the resin being hard as most potting
compounds are flexible. Will this be a problem?

I was also concerned about chemical compatibility, ie. the resin disolving
plastics used in IC packages or other components, but I guess this can not
be a problem since you have used polyester.

Any long term problems?

Anyone else who has tried polyester resin for potting?


--
Emil Johnsen

 

[bob hoffman]

"Emil Johnsen" <nospam.emil.johnsen@student.uib.no> wrote in
news:cjqtaf$2ds6$1@toralf.uib.no:

I'v googled this but didn't come up with any useful information.

Can normal (intended for use with fiberglass) epoxy or polyester
resins be used for potting electronics?


--
Emil Johnsen

I have used Devcon 5 minute to pot connectors and several small modules.
It doesn't seem to degrade plastics. The stuff is clear and doesn't
contain any fillers.

 

[Adam Aglionby]

"Emil Johnsen" <nospam.emil.johnsen@student.uib.no> wrote in message
news:cjsthg$11g5$1@toralf.uib.no...

Polyesters get hot whilst curing and in castings are built up to save
the
thing cracking or in extreme cases self igniting, er ,guess who put too
much
catalyst in ;-) Polys are not, without additives , very flexible and
also
shrink by up to 3 or 4 % .

Heat also finds every dry joint in your board ...

I think that using less catalyst will help avoid the heat problem. It will
take longer to cure, but end result will be the same. Atleast that is my
limited experience from messing up the resin/catalyst ratio when making
fiberglass parts with polyester.

Should have siad hardner, strictly speaking catalyst is a differnt coponent
that is pre added.Adding less hardner will lower exotherm and slow
hardening.But in large pours thing still gets hot.

I'm concerned about effects from the resin being hard as most potting
compounds are flexible. Will this be a problem?

Think its only a problem if compnents are likely to get hot and try and
expand, power transistors,voltage regulators etc.

I was also concerned about chemical compatibility, ie. the resin disolving
plastics used in IC packages or other components, but I guess this can not
be a problem since you have used polyester.

My experince is it hasn`t been a problem, your mileage may vary.

Any long term problems?

Polyesters are actually organic and some actually degrade under water over
time.

HTH
Adam

Anyone else who has tried polyester resin for potting?


--
Emil Johnsen