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ARSCLIST  May 2007

ARSCLIST May 2007

Subject:

Re: 'New' solution for stickey shed

From:

"[log in to unmask]" <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Mon, 14 May 2007 13:08:20 -0400

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text/plain (87 lines)

Sorry:

Non-backcoated tape can suffer from binder hydrolysis. We have seen it many
times. It is less common than on backcoated tape, but it does occur. (Why
this may be so is a controversial topic for different thread)

As to whether a chemical solution might work; yes it is possible. There
can, however, be problems with this solution.

If one looks at the published chemistry of the hydrolysis problem, there is
a fairly obvious answer. When the long-chain molecules interact with
moisture, the hydrolysis reaction breaks the long-chain polymers into
short-chain, low-molecular-weight oligomers. The chemistry of the polymers
and the oligomers is different. We have identified chemicals that will
dissolve the short-chain oligomers but do not react with the polymers.
Since it is the short-chain oligomers that represent the "sticky-shed"
problem, if you remove them and leave only the long-chain polymers, the tape
will not be "sticky". Of course, we have also seen the removal of the
oligomers cause deformation of the tape surface. It depends on how badly
hydrolysed the tape is.

If one is just removing the offending oligomers, why then does the author of
the article find that his tapes seem to remain stable after the treatment?
One might expect that continued exposure would simply cause additional
hydrolysis of the remaining polymers. Well, looking at the chemistry again,
most early binders were made up of a combination of shorter-length and
longer-length polymers. The mix is dependent on who made the tape and the
quality control procedures. It is a lot more difficult (and expensive) to
make sure all of the binder is only the longer-length polymers. Testing has
shown that the longer the polymer, the more stable (resistant to
hydrolysis). Thus, if the shorter-length polymers in the binder hydrolyze,
and the resultant oligomers are chemically removed from the tape, what is
left is the longer-chain polymers that are more stable. These polymers can
still hydrolyze but, since they are more stable, it is possible that
reasonable storage might result in a tape that does not exhibit
"sticky-shed" even after many years.

As I stated earlier, the process could work and we have experimented with
similar procedures. We do not use these procedure, however, except in very
rare instances and only on small sections of tape. I don't know how many
tapes or variety of tapes the particular individual who wrote the article
has tested but, in some instances, the procedure can PERMANENTLY deform the
tape if the entire tape is treated. Warning: once you have used the
oligomer extraction method, you can't put the oligomers back in the tape if
you find out you extracted too much of the tape material.

Peter Brothers
SPECS BROS., LLC
973-777-5055
[log in to unmask]

Tape restoration and disaster recovery since 1983

Peter Brothers
SPECS BROS., LLC
973-777-5055
[log in to unmask]

Tape restoration and disaster recovery since 1983


-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Sunday, May 13, 2007 10:13 PM
To: [log in to unmask]
Subject: Re: [ARSCLIST] 'New' solution for stickey shed

So someone posted in a response that there is no
documented example of a non-back coated tape
exibiting sss.

Is this correct? I am sure I have some OR tapes that
have SSS and are not BC'd.

Joe Salerno
713-6688650
Industrial Video Services
http://joe.salerno.com

Konrad Strauss wrote:
> Don't know if anyone here frequents the TapeOp message board, but some may
> find this interesting.
>
> http://messageboard.tapeop.com/viewtopic.php?t=44638
>

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