|
Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
|
Thread Tools |
7th Oct 2015, 9:20 am | #1 |
Octode
Join Date: Jul 2014
Location: Petersfield, Hampshire, UK.
Posts: 1,043
|
Epoxy resin
Hi,
What's the best epoxy resin or other material ? I used to use araldite but now find it soft when cured I want to form a small amount glued to brass and then file it to shape Any ideas please ? Cheers Pete |
7th Oct 2015, 9:32 am | #2 |
Dekatron
Join Date: Jun 2013
Location: East Sussex, UK.
Posts: 3,315
|
Re: Epoxy resin
The quick setting type always seems to stay slightly soft. The original is much harder, but takes a day to harden. Don't use it in cold temperatures as it takes even longer.
|
7th Oct 2015, 9:50 am | #3 |
Hexode
Join Date: Dec 2014
Location: Scarborough, North Yorkshire, UK.
Posts: 473
|
Re: Epoxy resin
JB weld is without question the best you can buy.
Mick |
7th Oct 2015, 10:08 am | #4 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
|
Re: Epoxy resin
There are several glues sold as Araldite. You want the one which takes days to cure. It used to be sold as 'Araldite Precision' but it may be called something else now.
|
7th Oct 2015, 10:11 am | #5 |
Octode
Join Date: Jan 2014
Location: Oban, Scotland, UK.
Posts: 1,118
|
Re: Epoxy resin
If you need to build up any amount of depth or bulk then get a small tub of fibre-glass repair resin from the car accessory shop.
It dries harder than any epoxy I've ever used and can be filed to shape in any thickness. |
7th Oct 2015, 11:39 am | #6 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
|
Re: Epoxy resin
I've tried all sorts and without a doubt, Plastic Padding 'Super Steel Epoxy Weld' is way out in front of anything else. (It's widely avaiable from the likes of Halfords and on e-bay for about £6.00). It's a nonsense to use the term 'weld' of course, because the process of welding involved melting the parent metal of two items being welded, and adding more molten metal into the motlen pool via a welding rod - most often via either electric arc, MIG or oxy acetylene.
But setting that bit of marketing hype to one side, the product itself is a two-part epoxy which sets really hard in a couple of minutes or so. Though it's claimed that it contains particles of steel, it doesn't conduct electricity. I've tested a short length of it applied to a strip of glass, using an insulation tester at 1000V - infinite resistance. Hence, I've used it in such applications as sealing the ends of electrolytic caps that I've re-stuffed. Ive also used it for repairing Bakelite cabinets prior to spraying them, and for filling unwanted holes in die-cast aluminium boxes to re-use them. The appearance when set is gloss black, but when filed or sanded, is darkish grey. It files and sands excellently. I don't often find much use for Araldite - too soft and no better than the stuff sold in Pound shops. Hope that's of interest.
__________________
David. BVWS Member. G-QRP Club member 1339. |
7th Oct 2015, 12:04 pm | #7 |
Octode
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
|
Re: Epoxy resin
That's interesting, I thought it was the way I mixed it. I also have experienced Araldite to set with a small amount of pliancy compared to how I remembered it. My earliest memory was in the 60's when it was, I think, still a fairly high tech adhesive. I remember my dad "curing" the repairs in the oven.
Good tip about the automotive stuff, i never thought about it and I have a stock in the garage. is it any good for "potting" circuits that I sometimes build for use in vibration sensitive applications? |
7th Oct 2015, 12:13 pm | #8 | |
Octode
Join Date: Jan 2012
Location: Wimbledon, London, UK.
Posts: 1,464
|
Re: Epoxy resin
Quote:
If I were you, I would look at proper potting-compound; I would think it is still available. Don't use silicone bath-sealant, because this releases acetic acid as it cures (vinegary smell) and this will attack any components embedded in it. Colin. |
|
7th Oct 2015, 12:34 pm | #9 |
Octode
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
|
Re: Epoxy resin
Thanks.
Yes I am aware of the acetic acid issue in normal domestic silicone compounds. I imagine the first thing that would do is attack the solder and fairly rapidly too. Normal potting compound is available, I have used it, but its a very expensive commodity. At least in the quantities I would use. A. |
7th Oct 2015, 12:40 pm | #10 |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
|
Re: Epoxy resin
Araldite Precision - yes, the slow-setting stuff - sets hard but it has to be well mixed in the correct ratio. And curing at 50°C helps too. Once set, subsequent heating does not make it any harder.
For potting circuits, generally something slightly flexible is needed, to cope with thermal expansion of the potted circuitry getting warm. There is also the fact that when epoxy sets, it shrinks - the molecules pull closer together - and if its sets hard, there is a permanent stress on the embedded components. Adding a filler might well help! A filler reduces the shrinkage, makes it harder, and tougher so less liable to crack (the minute particles of filler act to deflect any crack as it starts so it doesn't propagate). Aluminium oxide is great, as is silica - but for domestic use you might well try powdered talc from the bathroom. Just be sure it is well dried first, by baking for a few hours and stirring. |
7th Oct 2015, 1:23 pm | #11 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
|
Re: Epoxy resin
Hot melt glue makes a good cheap'n'cheerful potting compound.
I've never had problems with Araldite Precision and use it for all demanding applications. I agree that Araldite Rapid (?) is little better than the generic Poundland stuff. |
7th Oct 2015, 1:35 pm | #12 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
|
Re: Epoxy resin
ISTR that Araldite was the stuff that English Electric used to glue the wings on Lightning aircraft. I think they may have used it in a controlled environment.
__________________
Richard Index: recursive loop: see recursive loop |
7th Oct 2015, 1:40 pm | #13 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
|
Re: Epoxy resin
It was also used on Concorde.
|
7th Oct 2015, 2:03 pm | #14 |
Hexode
Join Date: Jul 2009
Location: Wokingham, Berkshire, UK.
Posts: 437
|
Re: Epoxy resin
Heat, not excessive heat, always speeds up the curing time. I think standard epoxy (Araldite) is best.
John |
7th Oct 2015, 2:25 pm | #15 |
Heptode
Join Date: May 2003
Location: Bexhill on Sea, East Sussex, UK.
Posts: 746
|
Re: Epoxy resin
You could try "Milliput " standard.
I bought some to try and make a knob for a reel recorder , left it to harden over night and it's solid. I'm pleased with it... It bonds to metals ,wood,plastics, glass brick etc. Costs about £ 2.0 from a hardware shop. You could google it for more info. Peter W ..Reelguy..... |
7th Oct 2015, 2:27 pm | #16 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
|
Re: Epoxy resin
Whenever I've used pound store epoxy (which seems to set whenever the heck it feels like it), I have mixed it on a beermat with a matchstick; and observed the setting of the excess adhesive on the beermat as a guide.
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments. |
7th Oct 2015, 3:01 pm | #17 | |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,086
|
Re: Epoxy resin
Quote:
The snag is that they often don't write on the tube what kind it is. I think the "exterior" kind was the OK one. There are other kinds of specialist silicone rubber too. Don't pot circuits with anything with added "steel". Just because it doesn't conduct doesn't mean it won't cause trouble - the obvious problem (could be a feature in some situations) would be a significant magnetic permeability. Going back on topic: I have noticed that Araldite is not as good as it was. There are several setting speeds available and I always found the intermediate one the best compromise - setting in about half an hour. The latest ones seem to set in a few minutes - often too fast. Although they didn't like to mention it, the hardness/rubberiness of the final result could be varied by the ratio of the two components. I notice that the Araldite brand is no-longer used for just epoxy resins - so be careful what you are buying! |
|
7th Oct 2015, 6:14 pm | #18 |
Nonode
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,346
|
Re: Epoxy resin
True Araldite is hard, strong and very rigid. I cast a racing seat back for my cammy Velo 50+ years ago, and my goodness that was hard. I still have a green tube of traditional araldite from the '60s, and recently acquired some more 20+ year old tubes of both rapid and traditional. So far I have never seen any softness if mixed correctly. "Plastic Padding" was (probably still is) a polyester resin, generally regarded as cheaper and inferior to epoxy resins.
I regularly use non-acidic silicone sealant (available from CPC), but also I get tubes of Loctite 5920, an orange coloured sealant which I use for all sorts of stuff. I would certainly consider using that for small scale potting jobs. Les. |
7th Oct 2015, 6:31 pm | #19 | |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
|
Re: Epoxy resin
Quote:
Al. |
|
7th Oct 2015, 6:36 pm | #20 | |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
|
Re: Epoxy resin
Quote:
Al. |
|