Cheap potting compounds? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: February 05, 2015, 03:38:45 pm
content: Low voltage none critical application, is there a cheap potting compound available, preferably one that sets hard, but very viscous gel a possibility? The commercial stuff looks very expensive... Could I get away with fibreglass resin? Thanks.

author: peter.mcnair
author_rank: Contributor
timestamp: February 05, 2015, 03:45:39 pm
content: Candle wax.

author: Chris Wilson
author_rank: Super Contributor
timestamp: February 05, 2015, 03:52:04 pm
content: Quote from: peter.mcnair on February 05, 2015, 03:45:39 pmHmmmm:https://www.google.com/search?as_q=fork+handles+sketch&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=&as_occt=any&safe=images&tbs=&as_filetype=&as_rights=&gws_rd=ssl

author: SeanB
author_rank: Super Contributor
timestamp: February 05, 2015, 03:59:59 pm
content: Beeswax is better, as it is non crystalline. Otherwise you can just use 2 part epoxy resin for small jobs, or if it is large just encapsulate the major part in acetoxy free silicone ( for compliance) and then fill the rest of the box with fibreglass resin. Choose a gelcoat resin for clear, or add fine silica sand to bulk it up for a harder resin. For a very opaque resin get talcum powder from your resin supplier, it is used as a filler.For cheap ready mixed resin and powder use auto body filler and catalyst. Cheap, sets hard and is machinable as well as easy to use, though you will need throw away spatulas and a plastic painters sheet to do everything on.

author: PeterFW
author_rank: Frequent Contributor
timestamp: February 05, 2015, 04:03:23 pm
content: Quote from: Chris Wilson on February 05, 2015, 03:38:45 pmDepending on the type, this stuff gets very hot while curing, some parts might not like that.I used one of these two barrel syringes with a static mixer once to pot a circuit, afaik it is still running.And it shrinks ever so slightly, some SMD components might not like that.

author: wraper
author_rank: Unknown
timestamp: February 05, 2015, 04:08:02 pm
content: Should be cautious with hard stuff. If it significantly shrinks while setting or have thermal expansion coefficient significantly different than PCB it can just tear off the parts from the PCB.

author: macboy
author_rank: Super Contributor
timestamp: February 05, 2015, 06:17:40 pm
content: Quote from: wraper on February 05, 2015, 04:08:02 pmI think this is why SeanB suggested a layer of compliant silicone first, then a hardening resin to fill the bulk.

author: PeterFW
author_rank: Frequent Contributor
timestamp: February 05, 2015, 06:30:23 pm
content: Quote from: macboy on February 05, 2015, 06:17:40 pmYou could use a hardware store non-acidic caulking for that, in the same isle you get the 2 part syringe epoxy.Greetings,Peter

author: SeanB
author_rank: Super Contributor
timestamp: February 05, 2015, 06:46:45 pm
content: Caulk tends to shrink, and most of those I have met are water based, not something you want to put next to conductors. No matter how long you let it dry unless you cook it to rock hard it will contain moisture. I have to redo some I used to fill some drywall repair as it has cracked during curing, but it is not serious there. On a PCB it will be bad.

author: marshallh
author_rank: Unknown
timestamp: February 05, 2015, 06:55:26 pm
content: Silicone caulk has absolutely no business outside the bathroom, and maybe PCBs... that stuff is the bane of my life

author: Falcon69
author_rank: Super Contributor
timestamp: February 05, 2015, 07:10:03 pm
content: I've been using thishttps://www.creativewholesale.com/ProductDetail/tabid/174/ProductID/255/Default.aspxit works great, didn't seem to shrink at all, and does not get hot. Crystal clear when dry. It takes about a day for it to cure.You don't have to buy a full gallon either, they sell in smaller quantities, really easy to use, a simply equal two part mix. You just have to be careful of air bubbles. Don't mix it too fast.You can see the switches I've done on my Sitewww.x2df.comI'll post a pic here too so you can see them. I'm not sure of your application, but I had to make a mold for the switches using silicon.

author: PeterFW
author_rank: Frequent Contributor
timestamp: February 06, 2015, 01:44:14 pm
content: Quote from: SeanB on February 05, 2015, 06:46:45 pmI thought non acidic silicone should not have anny significant water content, im curious but could not find anny information on that besides a patent with too many fancy words for me to understand. Do you have anny additional information?Greetings,Peter

author: SeanB
author_rank: Super Contributor
timestamp: February 06, 2015, 03:30:13 pm
content: Caulks tend to be different here to silicones. The typical caulk is an acrylic based item, which is water cleanable. then you get the silicones with assorted cures and finally the urethanes with a cyanamid cure. The urethanes do shrink very little, and they tend to be compatible with copper surfaces as well, but are expensive and hard to clean up. They do make an excellent encapsulant though, at about 6 times the cost of silicones. they also take a day per millimeter to cure, so if you want to overcoat them with a hard epoxy you will need to leave the job for a week or two to cure, otherwise it will never cure once oxygen is excluded from it by the outer shell. It is slightly conductive until well cured though, like most single component sealers.

author: rdl
author_rank: Super Contributor
timestamp: February 06, 2015, 03:34:34 pm
content: Yeah, I figured that was in reference to the lower cost, consumer grade caulk that you get at places like Home Depot. Most of those are water based, and some of them may not actually contain much silicone at all.I was a formulator at one of the big paint companies for a long time. Years ago the guys in their consumer division came up with what they thought was a great formula for a water-base clear wood finish. They sold it in two versions. One used 100% acrylic for the resin part, the other was 90% (the same) acrylic, with 10% polyurethane. This was so they could print labels with 2 inch tall letters that advertised "Polyurethane" (and charge a considerably higher price). The actual performance of the two versions was nearly identical.Quote from: PeterFW on February 06, 2015, 01:44:14 pm

author: PeterFW
author_rank: Frequent Contributor
timestamp: February 06, 2015, 03:49:30 pm
content: Quote from: SeanB on February 06, 2015, 03:30:13 pmAhhhh... i think i identified the problem. Until today i thought "caulk" was generic english term for anny kind of gap brideing sealant.I will update my vocabulary accordinglyGreetings,Peter

author: robrenz
author_rank: Super Contributor
timestamp: February 06, 2015, 04:54:04 pm
content: I know you are in England but this stuff is outstanding and is extremely cheap compared to the electronic branded stuff. His site is extremely informative on all epoxies.http://www.ebay.com/itm/EPOXY-RESIN-CIRCUIT-BOARD-POTTING-COMPOUND-WATERPROOF-MASKING-SEALANT-96-OZ-KIT-/310368256789?pt=LH_DefaultDomain_0&hash=item484363c315

author: Zero999
author_rank: Super Contributor
timestamp: February 06, 2015, 09:24:38 pm
content: Quote from: robrenz on February 06, 2015, 04:54:04 pmPrice: $43.43Shipping: $73.39Lol

author: Kjelt
author_rank: Super Contributor
timestamp: February 06, 2015, 09:42:48 pm
content: Lot of companies use some sort of tar for potting. That is commercially sold products.If you need a fast non optimal potting for your hobby product that can be easily reversed: silversand.

author: robrenz
author_rank: Super Contributor
timestamp: February 06, 2015, 10:16:49 pm
content: Quote from: Hero999 on February 06, 2015, 09:24:38 pmThat is 3 quarts for about $39.00 a quart including shipping.This MG chemicals on Mouserworks out to 89.40 per quart before shipping

author: IanB
author_rank: Super Contributor
timestamp: February 06, 2015, 11:14:25 pm
content: Quote from: PeterFW on February 06, 2015, 03:49:30 pmStrictly speaking, yes, that is correct. "Caulk" is a generic term for something used to seal gaps and keep water out.However, in the hardware store and around the home caulk has taken on a more specialized meaning to differentiate it from other items like silicone sealant or pitch. Caulk from the hardware store is what might be used to fill a gap between a window frame and the wall.

author: mzzj
author_rank: Super Contributor
timestamp: February 07, 2015, 07:37:22 am
content: Pot of hot glueSikaflex 221 is my choice of poison, quaranteed mess

author: ovnr
author_rank: Frequent Contributor
timestamp: February 07, 2015, 11:22:35 am
content: On silicones: Consider buying a two-part silicone, then just dipping your parts in it to get a compliant coating before immersing in epoxy. They have low enough viscosity that it's not a problem, compares to caulks and shit.

author: ivan747
author_rank: Super Contributor
timestamp: February 08, 2015, 02:04:08 am
content: Heatshrink and silicone to seal the edges.

author: LabSpokane
author_rank: Super Contributor
timestamp: February 08, 2015, 04:15:42 am
content: Quote from: PeterFW on February 06, 2015, 03:49:30 pmIf you went to any hardware store in the US and asked them to take you to the caulk, you would go to an aisle full of tubes which would have virtually every variety described here: silicone, acrylic, etc. Your current understanding is correct at least in 'Merica.

author: Chris Wilson
author_rank: Super Contributor
timestamp: February 11, 2015, 10:52:23 pm
content: Some great info and links here, and confirmation we pay too much for stuff in the UK, as if I didn't knowThanks, all very informative and useful, much appreciated.

author: Whales
author_rank: Super Contributor
timestamp: February 12, 2015, 08:25:24 am
content: I also didn't know 'caulk' could be specific in another context. The verb 'caulking' in particular feels like a "squishing anything out of a tube" word and I probably mentally extend the noun from there.Acrylic paint does not re-dissolve after it has dried, but I don't know how conductive it is or if it does something nasty like trap water. Pros however: easy to apply, easy to see any areas you have missed, washes up afterwards with water.

author: yamajason
author_rank: Newbie
timestamp: October 22, 2015, 10:43:31 am
content: Quote from: robrenz on February 06, 2015, 10:16:49 pmWhat do you think about adding Aluminum Oxide Pigment to increase the Thermal Conductivity of the Potting Compound? Got the idea from MG Chemicals 832TC Thermally Conductive Epoxy Encapsulating and Potting CompoundI am not sure how much to add or the ratio?

author: Cliff Matthews
author_rank: Unknown
timestamp: October 22, 2015, 11:48:11 am
content: Pity, this stuff seems cheaper this side of the pond.http://www.amazon.co.uk/MG-Chemicals-Encapsulating-832B-375ML-components/dp/B005T8PYZ4

author: Chris Wilson
author_rank: Super Contributor
timestamp: October 22, 2015, 02:11:58 pm
content: This is what I am using currently, I have it down to a fine art and 500 grammes pots ten of my circuit boxes, so I build ten at a time.http://uk.rs-online.com/web/p/potting-compounds/1991430/

author: yamajason
author_rank: Newbie
timestamp: October 22, 2015, 06:30:22 pm
content: Found that you can add Calcium Carbonate Powder to increase Thermal Conductivity of the Potting Compoundseehttp://www.ebay.com/itm/EPOXY-FILLER-LOW-COST-EXTENDER-HIGHER-THERMAL-CONDUCTIVITY-ELECTRICAL-RESISTANCE-/220513516394?rd=1http://www.ebay.com/itm/EPOXY-RESIN-CIRCUIT-BOARD-POTTING-COMPOUND-WATERPROOF-MASKING-SEALANT-96-OZ-KIT-/311412419001?

author: unitedatoms
author_rank: Frequent Contributor
timestamp: October 23, 2015, 02:58:20 am
content: Just to warn you. I worked at factory with batteries for military robots being potted into compound. The process was cheapest possible, but nevertheless, the guys who made potting put together the separate shack outside the main building to keep fumes away from people.The epoxy was some very runny black liquid. Stay away of it by all means. It will ruin your health

author: tehmagicsmoke
author_rank: Contributor
timestamp: October 23, 2015, 03:33:00 am
content: Don't know if it will suit your purpose but clear spray paint or clear nail polish may work. And if you can get it I have seen liquid electrical tape in the clear flavor, I think for about $10 for a small container about 6oz.

author: Munsterfield
author_rank: Newbie
timestamp: August 29, 2018, 02:45:54 pm
content: Regarding potting electronic components, I'm really curious about masking off areas such as what Falcon69 did on his boards, by creating molds. Falcon69, if you are still following this thread, what was your experience in that mold that you created? What worked? What didn't? What material are you using for the mold, and what are you using for the potting compound?Thanks!

author: Raj
author_rank: Frequent Contributor
timestamp: September 23, 2018, 05:12:07 pm
content: There's something called reenterable potting compound

author: Smokey
author_rank: Super Contributor
timestamp: May 09, 2024, 04:59:53 am
content: What are you guys using these days for potting compound?It looks like I'm going to have to pot in a couple hundred little modules so I'm looking for something inexpensive that is hopefully also in stock somewhere and doesn't have a terribly involved mixing/dispensing process.

author: wraper
author_rank: Unknown
timestamp: May 09, 2024, 09:20:57 am
content: There are electronics grade neutral silicones. However they come in 300+ ml tubes which are very expensive, and usually you'd waste most of it due to short shelf life. However you can buy 70x (701-708) electronics grade silicones in 45ml tubes from China. They have different properties such as viscosity, self leveling and strength but all are very good IME. 708 type is the most interesting IMHO, and is what I suggest for fixing capacitors to PCB. It has quite low viscosity, even lower than most semi-flowing silicones, so easy to apply, however it does not flow by itself at all, so will stay exactly how you applied it. For potting something use 701-705 which flow/self-level. I suggest placing them in moisture barrier bag with dry silicagel pouches (of which you should have plenty if order components from major distributors), rolling an open a few times and and fixing closed with clothespin or something similar. It will prevent curing thus extending their life many times.

author: Smokey
author_rank: Super Contributor
timestamp: May 09, 2024, 10:14:31 pm
content: For the units I'm looking at now, there is a little less than 14mL that needs to be filled.If I get the 450mL tubes of something like this(MG 832B) for about $60, then that's about $1.86 of epoxy per product.https://mgchemicals.com/products/potting-compounds/epoxy-potting/black-epoxy/That's sort of my price to beat at this point. While I know it's more expensive, I do like the self mixing tube dispenser for the listed product. I'm not sure how much I should worry about the mixing dispensing process from a cost/labor standpoint. I would probably have my CM do the potting and anything that has an involved process is going to increase the cost.