Author Topic: OTC "Silasitc"?  (Read 1477 times)

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Offline timelessbeing

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Re: OTC "Silasitc"?
« Reply #25 on: February 05, 2019, 10:14:13 am »
This looks like adhesive specific to your application
https://www.rpelectronics.com/1035-85ml-rtv-silicon-clear-adhesive.html
 

Offline westfw

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Re: OTC "Silasitc"?
« Reply #26 on: February 06, 2019, 06:48:41 pm »
I'd think the GE Silicone II would work OK.For somewhat more flexibility, the crafts industry sells a wide variety of two-part silicone mold-making resins.For example: https://www.amazon.com/Smooth-Silicone-Making-OOMOO-30/dp/B004BNF3TK/https://www.smooth-on.com/product-line/mold-max/
 

Offline stj

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Re: OTC "Silasitc"?
« Reply #27 on: February 07, 2019, 01:23:39 am »
there is a chinese company that specialises in silicone products.

705 is a specially usefull one because you can seal windows, leds etc.
https://www.ebay.co.uk/itm/302814126123
 

Offline timelessbeing

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Re: OTC "Silasitc"?
« Reply #28 on: February 07, 2019, 08:39:40 am »
There's also this stuff



Available for cheap from the usual suspects.

It's thermally conductive which is good if you need to spread the heat around. (But it cures firm like adhesive.)
 

Online Gary350z

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Re: OTC "Silasitc"?
« Reply #29 on: February 07, 2019, 09:01:20 pm »
I'd never heard the term "silastic" until watching EEVblog. I think it just refers to a type of silicone glue that cures to a rubbery state and is non-corrosive.

Silastic (a portmanteau of 'silicone' and 'plastic') is a trademark registered in 1948 by Dow Corning Corporation for flexible, inert silicone elastomer.
https://en.wikipedia.org/wiki/Silastic

Where I used to work, everyone called it RTV (room temperature vulcanizing).

If I recall correctly, I have heard that as it cures it gives of ammonia(?) which corrodes copper. I don't know if this is true or not.
 

Offline BurningTantalum

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Re: OTC "Silasitc"?
« Reply #30 on: February 07, 2019, 09:28:07 pm »
Just to clear this up: Dave is Australian, and the term 'Silastic' is, as detailed, a trade name of Dow Corning, but is used in Australia as a generic term for any sealant goop (Viz: Hoover, Doona, Graviner etc.)
BT
 

Offline graeme.c.payne

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Re: OTC "Silasitc"?
« Reply #31 on: February 08, 2019, 01:46:35 am »
My memory is that "Silastic" was (is?) an early brand name for some silicone adhesives. (USA)

For electronics, silicones are widely used for hording parts in place, vibration damping, and encapsulating parts or assemblies.

For use in electronics, the silicone must NOT create any acid while curing. If it smells like vinegar at any time, don't use it! It will eventually cause corrosion. A silicone adhesive safe for electronics WILL cost more than what the home center carries, because it is a specialty product.

An example of a suitable product is this, from Amazon (USA): GC ELECTRONICS 19-155 ADHESIVE, SILICONE, TUBE, 3FL.OZ.(US) (1 piece) https://www.amazon.com/dp/B004SPJN6K/ref=cm_sw_r_cp_apa_i_ZnexCb4WZPT1X




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Offline LukeW

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Re: OTC "Silasitc"?
« Reply #32 on: February 10, 2019, 11:18:46 am »
Generally, when choosing a material like this, these are the factors we're interested in:

- Neutral-cure silicone. A lot of hardware-store 1-pack silicones are acetoxysilane based which will release acetic acid in the curing reaction, which will corrode nearby things - you don't want this, you really want a neutral-cure silicone. This is probably the most important thing, and if you can buy a neutral-cure Home Depot silicone for a couple of bucks it's probably fine.

- One-pack, because it's more convenient than mixing a binary system.

- RTV (room-temperature vulcanising), i.e. it chemically sets and crosslinks by itself at room temperature, going hard with the desired shore and mechanical properties.

- Has some "bounce", which is the main motivation for choosing a silicone over a polyurethane.

- Cheap and locally available for you in a non-bulk pack.

- High dielectric strength, although if you're not using it for HV applications anything is probably fine.

Personally, I like Dow Corning 738, which is available in a small tube.

It's actually documented as an engineering material - it has a datasheet, and if we want to know, say, the dielectric strength, it's documented.

https://www.ellsworth.com/products/by-manufacturer/dow/sealants/silicone/dow-738-electrical-sealant-silicone-white-90-ml-tube/
 

Online xavier60

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Re: OTC "Silasitc"?
« Reply #33 on: February 17, 2019, 08:40:14 am »
Dave and others often talk about components being tied down with silastic.  I have found the OG Dow/Corning 732 stuff, but it is pricey and not available in small quantities (way more than I would use in time without it going bad).  Is there anything really special about it other than it is a neutral cure silicone?  I was thinking of grabbing some GE Silicone II, which is also neutral cure and is available at any home store in small tubes.  Does anyone have experience with that product, or have any recommendations for an alternative that is readily available?
I have been using ThreeBond(Japan) 1530C for years. It is moisture curing and non corrosive. Because it self levels, it gives a neat result.
The product isn't easily available in Australia. It is now available on ebay in retail blister pack. Be certain to read the review.
https://www.ebay.com/p/2-Pcs-Tube-Tb1530c-All-Purpose-Adhesive-Glue-Clear-Extra-Strong-Wood-Elasticity/18024574076?iid=173609103986
« Last Edit: February 24, 2019, 06:31:43 pm by xavier60 »
Hioki AS100D vom, HP 54645A dso, Fluke 87V dmm, AN8008 dmm, Agilent U8002A psu, New! FY6600 function gen.
 

Online djacobow

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Re: OTC "Silasitc"?
« Reply #34 on: February 17, 2019, 12:24:46 pm »
What do you guys think of zip ties for caps? Just put a few extra holes in the PCB design and feed the tie around the back. Seems like it would work nicely for elcos on their sides. Maybe with some silpat or other foam to provide tension.
 

Offline stj

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Re: OTC "Silasitc"?
« Reply #35 on: February 17, 2019, 04:28:22 pm »
that's not new, it was common in the 70's, 80;s etc when linear psu's had bigger caps.
 

Online coppercone2

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Re: OTC "Silasitc"?
« Reply #36 on: February 18, 2019, 01:26:01 am »
What do you guys think of zip ties for caps? Just put a few extra holes in the PCB design and feed the tie around the back. Seems like it would work nicely for elcos on their sides. Maybe with some silpat or other foam to provide tension.

its better then goo
 

Offline timelessbeing

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Re: OTC "Silasitc"?
« Reply #37 on: February 18, 2019, 12:02:45 pm »
I think goo helps dissipate heat from caps
 

Offline stj

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Re: OTC "Silasitc"?
« Reply #38 on: February 18, 2019, 12:29:05 pm »
I think goo helps dissipate heat from caps

so does putting ceramic caps in parallel with them to remove high frequency noise the electrolytic cant deal with.
(another old trick from the 70's)
 

Offline timelessbeing

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Re: OTC "Silasitc"?
« Reply #39 on: February 18, 2019, 12:36:33 pm »
I thought ripple current causes them to heat up.
 

Offline stj

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Re: OTC "Silasitc"?
« Reply #40 on: February 18, 2019, 12:49:37 pm »
they heat because the esr is not low enough to react in time to fast ripple.
these days we have low esr caps for that - back then you put several in parallel along with some ceramics.
 

Online jc101

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Re: OTC "Silasitc"?
« Reply #41 on: February 20, 2019, 01:27:37 am »
I use Dow Corning (now DOWSIL) 744, it was designed to be safe on electronics etc.
 


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