Stongest Plastic Glue (thanks)

[Jones, Rodney]

> -----Original Message-----
> From: ||| Philip Pilgrim ||| [mailto:thelab at sprint.ca]
> Sent: 26 January 2000 12:56
> To: synth-diy at mailhost.bpa.nl
> Subject: Re: Stongest Plastic Glue (thanks)
> 
> 
> Thanks for all of the glue help. I eneded up using a pvc specific glue
that seemed > to bond well. I then encapsulated the whole joint with 24hr
epoxy. It seems very 
> strong. Here are some things I learned from all of the emails and talking
to 
> people:
> 
> 1. The longer epoxy's rated cure time, the stronger the joint (ie: 24hr
Epoxy is 
> stronger than 15min Epoxy is stronger than 5minEpoxy)
> 
> 2. When working with moulded plastics, it is better to use glues that
"weld" the 
> plastic (they eat it into a gelly then harden thus fuseing the two pieces)
Most 
> adhesives are just surface bonders.
> 
> 3. The mixing of fibreglass strands in the epoxy is quite clever. I only
received 
> this email 30mins after I epoxied the plastic bits :(
> 
> 4. Italian designed synths are frail
> 
> Thanks all
> Philip
> 
> 
> Philip Pilgrim                 The Lab
> 5 Evan's Drive              Synth Mods/Repair
> Hammond's Plains        Software 
> N.S. Canada                http://www.robotnik.com/the_lab
> B4B 1M8
> 


I would also add my experiences after using epoxy for more than twenty years
(I even built a boat with the stuff, and used to buy resin + hardener by the
gallon...)

5. Heat speeds up the curing process, but doesn't improve strength.

6. Roughening the surfaces to be mated improves the bonding strength

7. Some plastics have a waxy feel (like nylon); Epoxy doesn't bond well with
these.

8. Normal 50/50 epoxy sets hard and rigid. If the thing being fixed is
designed to flex, then a more durable bond will result from a 40/60
(resin/hardener) mix.

9. If you want to create a thick non-flowing mixture (like a filler), there
is a silicon 'fluff' that can be added.

10. If it gets too cold, both the resin and hardener can go 'off' (crystals
form, and remain even after warming-up). 

11. The curing is a chemical reaction, and produces heat. If it's a warm
day, and the mixture exceeds a certain critical mass (half a pint or so),
you can get a sort of thermal runaway, where the mixture heats up beyond
boiling point and turns into a solid brick in seconds. Fires have been
caused!

Rod
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