Epoxy

For discussions about bikes and equipment.
KM2
Posts: 444
Joined: 23 Oct 2008, 5:38pm

Re: Epoxy

Postby KM2 » 25 Feb 2020, 8:30am

Thanks cycleruk, epoxy can be used.
Hopefully do it today.

rjb
Posts: 3629
Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: Epoxy

Postby rjb » 25 Feb 2020, 8:44am

Just a little warning if you are using anything with acetone. It can melt your plastic lenses. So be careful if you have plastic lenses in your specs. I had plastic lenses in my specs as my optician recommended these for cycling as less prone to shattering in the event of an accident. They got splashed with acetone and started dissolving. :shock:
At the last count:- Focus Variado, Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin, Raleigh 20, Falcon K2 MTB dropped bar tourer, Longstaff trike conversion on a Falcon corsa. :D

Brucey
Posts: 37358
Joined: 4 Jan 2012, 6:25pm

Re: Epoxy

Postby Brucey » 25 Feb 2020, 11:04am

thatsnotmyname wrote:
Brucey wrote:I just wanted to correct the misinformed statement 'all ABS is brittle'.

It isn't.


That's not what I said though, Brucey, is it? My actual words (you can read them for yourself upthread) were "ABS is quite brittle.." which it is. Like I said earlier, if you want to get into a debate about the relative rigidity of certain formulations of ABS, then you'd probably need to talk to a polymer chemist. Meanwhile, I'll stick to ABS 'being brittle', because it generally is.


this is what you said

thatsnotmyname wrote:…... but that's not in debate here. And neither is the fact that ABS is brittle, because it is.


Which is wrong. For a second time.

ABS is not an inherently brittle plastic, amongst other reasons because it is not just one thing.

A significant issue with it in many uses (eg crash helmets) is its solvent resistance; putting the wrong stickers on crash helmets can ruin them; this can apply to almost any helmet material but it is arguably more likely with ABS than some others . However this also allows the material it to be solvent welded/glued (not recommended in helmets of course), so it is not all bad I suppose.

FWIW if making a repair then a solvent weld/solvent based joint may not be anywhere near the strength of the original material. Nor is a heat based weld likely to be, in many cases, either. However if you are going to try a heat based weld, normal practice is to build up the joint so it is thicker than the surrounding material, and for that you need filler. The best filler is usually exactly matching material, and often you can take shavings from other parts of the assembly and use them as filler for small repairs.

cheers
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thatsnotmyname
Posts: 375
Joined: 23 Jan 2020, 10:23am

Re: Epoxy

Postby thatsnotmyname » 25 Feb 2020, 11:24am

Brucey wrote:Which is wrong. For a second time.

ABS is not an inherently brittle plastic, amongst other reasons because it is not just one thing.


Christ Brucey, you're really having a bit of a shocker here...

ABS is universally acknowledged (by everyone except you, it would seem) to have poor fatigue/flex resistance. Or to put it another way, it's 'generally a bit brittle'. So it is perfectly reasonable to suggest that it is indeed inherently brittle. Your light switches at home are probably made out of it - try bending one of them and see how far you get before it snaps. I can only assume that you are confusing ABS with some other, less brittle plastic, like maybe PE or PU. But really, this is such a stupid argument, I can't even believe we're having it. Why not just gracefully withdraw and we'll say no more about it?

Brucey
Posts: 37358
Joined: 4 Jan 2012, 6:25pm

Re: Epoxy

Postby Brucey » 25 Feb 2020, 12:17pm

if you don't understand materials science I would suggest that you refrain from making absolute statements about it; they are not helping anyone. I'm not commenting further on this because it is rapidly turning into an irrelevant conversation at best. Ignorance is no crime but ignorance combined with belligerence is.
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thatsnotmyname
Posts: 375
Joined: 23 Jan 2020, 10:23am

Re: Epoxy

Postby thatsnotmyname » 25 Feb 2020, 12:28pm

Brucey wrote:if you don't understand materials science I would suggest that you refrain from making absolute statements about it; they are not helping anyone. I'm not commenting further on this because it is rapidly turning into an irrelevant conversation at best. Ignorance is no crime but ignorance combined with belligerence is.


'Ignorance' seems to be your preferred hangout on this occasion though, Brucey. ABS is generally acknowledged to be brittle. It is an act of absurd ignorance and pedantry to deny that. You challenged my original statement with a dismissive comment about motorcycle helmets, without fully understanding the point you were trying to make. And then you got found out. You seem to know a lot about bike stuff, but your pretence to knowledge about ABS is just embarrassing. Finally, you don't have to be a 'materials scientist' to understand the basic properties of ABS. I'm not a materials scientist - but I'm also pretty certain that you are demonstrably not one either.

DevonDamo
Posts: 299
Joined: 24 May 2011, 1:42am

Re: Epoxy

Postby DevonDamo » 25 Feb 2020, 1:21pm

I'm definitely not a materials scientist, but I do have a dog in this race as my whitewater kayak, motorbike fairing and car bumpers are all made of ABS, so fragility would be a concern. Google and Wikipedia have nothing but praise for ABS, with the predominant properties mentioned being impact-resistance and toughness. However, if you change your search term to 'ABS brittle' you will get pages and pages of reports from disappointed 3D printer owners who've used ABS filament. It would appear that any 'reputation' for brittleness comes via this specific route, so may be an artefact of the heating, fine extrusion and rapid cooling?

thatsnotmyname
Posts: 375
Joined: 23 Jan 2020, 10:23am

Re: Epoxy

Postby thatsnotmyname » 25 Feb 2020, 1:45pm

DevonDamo wrote:I'm definitely not a materials scientist, but I do have a dog in this race as my whitewater kayak, motorbike fairing and car bumpers are all made of ABS, so fragility would be a concern. Google and Wikipedia have nothing but praise for ABS, with the predominant properties mentioned being impact-resistance and toughness. However, if you change your search term to 'ABS brittle' you will get pages and pages of reports from disappointed 3D printer owners who've used ABS filament. It would appear that any 'reputation' for brittleness comes via this specific route, so may be an artefact of the heating, fine extrusion and rapid cooling?


I suspect most people have a dog in the race, if they have any plastic household appliances - as chances are they are made in ABS. The thing is, it can't technically be 'fragile' while also being 'tough and 'impact resistant'. It certainly is tough, and impact resistant - which makes it ideal for applications like bumpers, fairings, extrusions, Brucey's crash helmets and the like. But its 'fragility' comes from its fatigue resistance and its poor tolerance of flex. Describing it as brittle is perfectly reasonable on that basis. 3D printing is just another way of delivering/forming ABS in a fluid state. There's no reason why 3D printing in ABS should result in a type of ABS which is any more or less brittle than any other.

2_i
Posts: 7
Joined: 25 Feb 2020, 3:12am

Re: Epoxy

Postby 2_i » 25 Feb 2020, 1:48pm

I routinely make electronic enclosures out of ABS butt gluing the sides, proceeding with acetone, and some of the enclosures carry my electronics on a bike. It would never even cross my mind to substitute the acetone with epoxy. Somewhere there I saw a DIY container for Brompton made out of ABS sheets joined with the glue out of ABS dissolved in acetone.

2_i
Posts: 7
Joined: 25 Feb 2020, 3:12am

Re: Epoxy

Postby 2_i » 25 Feb 2020, 1:58pm


KM2
Posts: 444
Joined: 23 Oct 2008, 5:38pm

Re: Epoxy

Postby KM2 » 25 Feb 2020, 6:33pm

Box now done. Thanks for the help.

Brucey
Posts: 37358
Joined: 4 Jan 2012, 6:25pm

Re: Epoxy

Postby Brucey » 25 Feb 2020, 6:47pm

did you use epoxy in the end? If so you arguably had little to lose, in that if an epoxy repair fails on this type of plastic, it often fails at the interface between the epoxy and the ABS. Which means if the repair doesn't hold, you can have another go, using a different method if you like.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

KM2
Posts: 444
Joined: 23 Oct 2008, 5:38pm

Re: Epoxy

Postby KM2 » 25 Feb 2020, 8:25pm

Yes, epoxy. If it peels then I'll try another but the web page above said it will bond.