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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 17th Aug 2017, 12:06 pm   #1
telstar
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Default Polystyrene knobs and button repair

In an effort to repair a push button from a Philips radio, I discovered a 2-part glue for this operation. It is made by JB (US), and obviously you have to read the instructions very carefully. It "welds" various plastics and also polystyrene together if broken.
Cheers
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Old 17th Aug 2017, 4:30 pm   #2
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Default Re: Polystyrene knobs and button repair

And it is called?

Gordon
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Old 17th Aug 2017, 5:37 pm   #3
paulsherwin
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Default Re: Polystyrene knobs and button repair

JB-Weld? I've heard of it but never used it. I always assumed it was just another epoxy glue like Araldite.
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Old 17th Aug 2017, 7:21 pm   #4
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Default Re: Polystyrene knobs and button repair

JB Weld do a couple of two-part epoxies specially for plastics: https://www.jbweld.com/collections/p...-composite-pvc. I've never used their products so am interested to hear about this one as I've always found epoxy pretty hopeless on 'modern' plastics; OK on Bakelite though.
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Old 18th Aug 2017, 5:19 am   #5
David G4EBT
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Default Re: Polystyrene knobs and button repair

Interesting use of the term 'weld'. Welding is the process of melting the parent material (most often metal), and adding a similar material so that the whole joint flows together until it sets and becomes one. I've no experience of JB Weld products, but 'bonding' is not 'welding' - it's sticking things together. All that really matters is whether or not the product is effective.

The info on each product in the range makes it clear which materials that particular product is unsuitable for. Any product which doesn't melt the parent plastic and join it together with a compatible material isn't 'welding' - it's 'gluing'. That said, consider how effective glass-bond glue is in sticking rear view mirrors to car windscreens. I've never know one fall off.

I see that the products in the range that I looked at cure to 'off-white' which might be a problem with transparent plastics where appearance is important. Suffice to say that it worked for Mike - hence, the thread.

I've never been overly impressed with Araldite products.
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Old 18th Aug 2017, 6:17 am   #6
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Default Re: Polystyrene knobs and button repair

I have used their plastic weld and its fantastic stuff.It dries clear with a slightly yellowish tinge.I had a Thorens TD150,the lid was broken into 4 pieces.Its absolutely solid now.Have used it on other types of plastic successfully too.
Mick
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Old 18th Aug 2017, 7:58 am   #7
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Default Re: Polystyrene knobs and button repair

In the old days we used to repair such things using RS switch cleaner - I seem to recall it was based on carbon tetrachloride then. It would dissolve a vast number of plastics very well! You'd have the elfin safety police at the door these days, I suspect!
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Old 18th Aug 2017, 11:40 am   #8
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Default Re: Polystyrene knobs and button repair

Your doctor wouldn't be too pleased either: From Wikipedia

Carbon tetrachloride is one of the most potent hepatotoxins (toxic to the liver), so much so that it is widely used in scientific research to evaluate hepatoprotective agents.[7][14] Exposure to high concentrations of carbon tetrachloride (including vapor) can affect the central nervous system, degenerate the liver[14] and kidneys,[15] and prolonged exposure may lead to coma or death.[16] Chronic exposure to carbon tetrachloride can cause liver[17][18] and kidney damage and could result in cancer.[19] See safety data sheets.[20]
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Old 18th Aug 2017, 11:51 am   #9
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Default Re: Polystyrene knobs and button repair

Quote:
Originally Posted by AC/HL View Post
Your doctor wouldn't be too pleased either: From Wikipedia
I don't disagree, however most dangerous stuff can be used sensibly and safely when information is provided. I use hydrochloric acid for making printed circuits for example. I do avoid drinking it or breathing the fumes though!
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Old 18th Aug 2017, 2:40 pm   #10
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Default Re: Polystyrene knobs and button repair

And to think we were made to clean the benches down every Saturday at 5 -30 pm using you guessed it , Carbon Tetrachloride the room was full of fumes I remember feeling light headed , this was back in the Sixties , no health and safety then. Mick.
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Old 18th Aug 2017, 3:26 pm   #11
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Default Re: Polystyrene knobs and button repair

You can get "plastic weld" from model shops which really does weld (poly) styrene and some other common plastics. It is a very runny liquid, normally applied by brush to the joint line of close fitting parts. It then wicks into place, partially dissolving the components at the interface to form a weld. You can dissolve chips of the material to create a more viscous filler. Then of course there is modelmakers polystyrene cement which is more specific but still useful.

Ken
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Old 18th Aug 2017, 3:41 pm   #12
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Default Re: Polystyrene knobs and button repair

Wilkinson's plastic glue is also very effective. It's a solvent, but with a gel consistency, which makes it much easier to use for some jobs than plain solvent.
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Old 18th Aug 2017, 4:28 pm   #13
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Default Re: Polystyrene knobs and button repair

Plastic Weld is usually Methylene Chloride or Dichloromethane (same thing) it evaporates very quickly and is very thin, ideal for those small cracks. It also dissolves/welds Perspex. For re-assembling broken polystyrene parts, the cement is better, a bit gloopy and dries more slowly.
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Last edited by merlinmaxwell; 18th Aug 2017 at 4:29 pm. Reason: clarification
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Old 18th Aug 2017, 5:00 pm   #14
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Default Re: Polystyrene knobs and button repair

I wish I knew how dangerous CTC was when I worked for BR during the 1950/ 60 era, we had it in 40 gallon barrels and used it for contact cleaning. We also cleaned our flat caps on the Saturday night shift, on a regular basis. We had a lot of asbestos insulation around, not every one was cautious with it as they should have been. Pleased to say still around and kicking
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Old 19th Aug 2017, 12:13 pm   #15
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Default Re: Polystyrene knobs and button repair

Try "PLASTI-ZAP" it has worked very well on ABS.

Trevor
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Old 29th Aug 2017, 1:08 pm   #16
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Default Re: Polystyrene knobs and button repair

The adhesive worked very well indeed. For the underside of the button (that fits around the metal shaft) I bought some polystyrene channelling and cut a section off and stuck it in the appropriate place.
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Old 30th Aug 2017, 7:20 am   #17
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Default Re: Polystyrene knobs and button repair

I'd have thought the best thing to glue polystyrene parts together would be 'polystyrene cement'. (airfix glue). This stuff does slightly dissolve the plastic together.

If you need to reinforce any polystyrene broken bits on anything, you can buy it in sheet, rod, pin, shim or strip form including the correct glue from modelmakers' supplies shops. Anyone familiar with model train magazines will have seen adverts for Plastikard...they're still going and have a web shop.

ABS plastic can be welded with the stuff you get for water pipes. This appears to be a solvent with a gel thickener.
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Old 30th Aug 2017, 11:48 am   #18
telstar
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Default Re: Polystyrene knobs and button repair

Apparently, the model shop owner actually recommended this 2-part adhesive and stated that it gave a much stronger joint over the sort of ordinary adhesive used on model aircraft.
I once tried an ordinary polystyrene adhesive on perspex (the Philips 290U grille that shrinks) but it did not work. This 2-part adhesive seems to be more suitable for that as well (according to another person on this thread).
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Old 1st Sep 2017, 8:26 pm   #19
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Default Re: Polystyrene knobs and button repair

I have mentioned in the avometer survey thread a 'built up' repair to a chipped black bakelite pillar surrounding a terminal. 4 parts araldite rapid to 1 part water based acrylic (artist's) paint. The setting time was very long- 4 or 5 days-but this ended up being an advantage since the shape could be gently moulded/wiped and monitored for the first half a day to maintain the correct shape. It went even better than i was hoping for.
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Old 5th Sep 2017, 3:54 pm   #20
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Default Re: Polystyrene knobs and button repair

The 2-part adhesive actually takes 5 minutes to join the two pieces together. It actually cures in 1 hour to a really strong bond - what more could you ask for?
I tried to obtain a replacement push button from the Netherlands radio forum. Someone said they had one but did not send it, nor could I contact them about it afterwards (no reply).
Cheers
Mike
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