Why do good floppy disks go bad?

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: 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