On 1/22/2016 12:05 PM, lists wrote:
> Also,
> remember, hydrolysis is a bi-directional chemical reaction.  Not only is
> there a threshold at which hydrolysis will occur, there is also a threshold
> at which hydrolysis will run in the other direction and the oligomers will
> cross-link back into polymers.

Hi, Peter,

That was definitely Bertram and Cuddihy's conjecture, but in the work 
that Ric Bradshaw did at IBM, he has seen evidence that this is not the 
case. As I understand it, he draws the following distinction:

In basic chemical theory, the reaction is bidirectional, but in the 
filled matrix that is the recording tape binder, there is little 
likelihood that the ends of the severed long chain molecules will find 
receptive "landing sites" [RLH's phrase, not RWB's] and even less 
likelihood that they will find the original points from which they were 
severed.

So, while there may be some random cross linking, the physical presence 
of the magnetic particles, lubricants, and other components of the mag 
coat matrix interferes with the reversing of the process. I believe I 
can state Bradshaw's conjecture as: yes, there may be some re-linking, 
but it never will come close to the original condition on day of 
manufacture. In other words, once it goes down this path, it's never 
coming all the way back.

Thank you for the clarification of Richardson's hypothesis. I don't 
think I ever got that out of what I've read of his, but I have not read 
all of the material he sent as some was sent under non-disclosure and I 
do not recall opening it. I felt if I read it and integrated it into my 
understanding, I might inadvertently disclose something. At one point in 
my past life, I commented, "I have signed so many NDAs that I can't even 
talk to myself!"

Also, thanks for confirming the existence of a threshold in the onset of 
hydrolysis. That makes sense.

One other question. One of your recent posts seems to suggest that the 
hydrophilic nature of the carbon black or other back-coating materials 
was part of the plan. Was it? Or was carbon black chosen to be 
conductive to dissipate the static charge which, under certain 
conditions can spark over and print a "tick" to the tape? Perhaps the 
hydrophilic nature of carbon black was either ignored or not known by 
the designers--or they thought that it wouldn't be an issue. It would be 
much more expensive to deposit a copper or silver (and probably even 
aluminum) thin film on the back side of the base film to provide that 
conductivity.

Thanks!

Cheers,

Richard
-- 
Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada                             647 479 2800
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.