Why do good floppy disks go bad?

[Tom Gardner]

Sorry, to a EE they are all epoxies, but:

"BINDER: A polymer such as polyester-polyurethane used to bind magnetic
particles together and adhere them to the base film in the manufacturing of
magnetic media."
http://www.fujifilmusa.com/shared/bin/Magnetic_Media_Terminology.pdf

"Polyester polyurethane is the workhorse of polyurethane films. It offers
excellent strength and long-term stability"
http://www.apiusa.com/polyesterpolyure.html 

I think properly cured all binders used are pretty stable.

Tom

-----Original Message-----
From: Chuck Guzis [mailto:cclist at sydex.com] 
Sent: Thursday, April 07, 2016 10:47 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Why do good floppy disks go bad?

On 04/07/2016 10:06 PM, Tom Gardner wrote:

> And it's not likely the binder, fully cured epoxies are also very 
> stable. Note disks do not have the tension problem that tape has.

There, I have to respectfully disagree.  Floppy disks do not use an epoxy
binder, but usually a polyurethane-based one. (Most are proprietary
formulations).  Hard disk coatings usually use an epoxy-phenolic binder, but
they're not on a flexible substrate.

Polyurethane isn't forever and tends to be somewhat hygroscopic.

--Chuck