REFLECTOR: Flox question, (epoxy bonds)

[Laurence Coen]

John,

I'm not a chemical engineer nor do I pretend to understand what is going on 
at the molecular level in epoxy but I tend not to "doubt" the people who did 
the research and testing of bonding methods.  It has also been pointed out 
that the surface prep should done just prior to the lay-up since the active 
cross-linking sites will "heal" over time.  You do a disservice to the group 
when you trivialize the importance of proper bonding techniques.

Larry Coen :^(


--------------------------------------------------
From: "John Dibble" <aminetech at bluefrog.com>
Sent: Monday, May 12, 2008 2:00 PM
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Subject: Re: REFLECTOR: Flox question, (epoxy bonds)

> Larry,
>
> I doubt that sanding or peel-ply breaks any significant amount of chemical 
> bonds to
> have a measurable effect.  If that did happen, you would have the same 
> starting
> materials - liquid resin and hardener - that you started with.  I think 
> what they do
> do is 1) increase the surface area, and 2) create tiny crevasses that 
> produce an
> interlocking effect when filled with the layup epoxy.
>
> John
>
> Laurence Coen wrote:
>
>> The chemical bond is called cross-linking. If you do a lay-up over cured
>> epoxy there will be no cross-linking which is an absolute no-no.  If you
>> sand the cured epoxy or use peel-ply you break some bonds in the cured 
>> epoxy
>> and they become available for cross-linking to the next lay-up so they 
>> are
>> chemically bonded.  Done correctly either method will produce a chemical
>> bond.
>>
>> Larry Coen
>> N136LC (Still in one piece).
>>
>> --------------------------------------------------
>> From: "Matt Bucko" <mbuc310 at cox.net>
>> Sent: Sunday, May 11, 2008 12:12 PM
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Subject: Re: REFLECTOR: Flox question
>>
>> > Thanks. The chem bond maked sense.
>> > Matt
>> >
>> > -----Original Message-----
>> > From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
>> > Behalf Of Andy Millin
>> > Sent: Sunday, May 11, 2008 3:34 AM
>> > To: 'Velocity Aircraft Owners and Builders list'
>> > Subject: Re: REFLECTOR: Flox question
>> >
>> >
>> > Hey Matt,
>> >
>> > Yes, you can do it as you describe.
>> >
>> > As you describe it, you will have a Mechanical Bond.  I think that is 
>> > the
>> > right term.  Think of it as two pieces that are glued together.
>> >
>> > If you did it all in one step, then you will have a Chemical Bond (not
>> > sure
>> > of terminology).  This way you have one piece.  I believe it is 
>> > stronger
>> > this way.  I would do it this way.
>> >
>> > FWIW,
>> >
>> > Andy
>> >
>> >
>> >
>> > -----Original Message-----
>> > From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>> > Behalf Of Matt Bucko
>> > Sent: Saturday, May 10, 2008 11:22 PM
>> > To: Velocity Aircraft Owners and Builders list
>> > Subject: REFLECTOR: Flox question
>> >
>> >
>> > I am going to put in layup B on the wing/winglet joint. I will be 
>> > running
>> > 2
>> > beads of flox before I put the lay up on. One bead on each part, 
>> > outside
>> > edge.  Any reason I cannot let the flox cure, sand and then apply the
>> > glass?
>> > Or should I apply the glass layup to wet flox, with the foam slurried?
>> >
>> > Matt
>> >
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