[Nhcoll-l] Phenolic lids in alcohol

Mon Jun 16 09:38:32 EDT 2014

Thanks Dries. Could not agree more!  Cathy

From: A.J.van_Dam at lumc.nl [mailto:A.J.van_Dam at lumc.nl]
Sent: Monday, June 16, 2014 9:32 AM
To: Hawks, Catharine; dirk.neumann at zsm.mwn.de; CAHawks at aol.com; halford at sfu.ca; prc44 at drexel.edu
Cc: nhcoll-l at mailman.yale.edu
Subject: RE: [Nhcoll-l] Phenolic lids in alcohol

To add to Cathy's and Dirk's comments:

Do not forget to consider in your choice of container the oxygen diffusion rates of plastics since most organic degradation processes are triggered by oxidation reactions.
Most plastics like PP, PE (low and high density) and also PTFE (coated liners) have relatively high permeability constants for oxygen. PET has a significant lower value, but the best impermeable and stable material is (borosilicate) glass.

Kind regards,

Dries
Andries J. van Dam, conservator

Museum of Anatomy
Leiden University Medical Center
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Director Alcomon Company
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From: nhcoll-l-bounces at mailman.yale.edu<mailto:nhcoll-l-bounces at mailman.yale.edu> [mailto:nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Hawks, Catharine
Sent: maandag 16 juni 2014 12:43
To: 'Dirk Neumann'; CAHawks at aol.com<mailto:CAHawks at aol.com>; halford at sfu.ca<mailto:halford at sfu.ca>; prc44 at drexel.edu<mailto:prc44 at drexel.edu>
Cc: nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu>
Subject: Re: [Nhcoll-l] Phenolic lids in alcohol

And adding to Dirk's comments:

Polyvinyl chloride (PVC) is generally unstable. Polypropylene can be formulated to be reasonably stable, but not necessarily stable to fluid preparations. LDPE is quite good, depending upon the plasticizer used in the polymer. High density polyethylene has a higher melting point and is generally more stable over the long term.

The only really stable polymer is internally plasticized polyethylene terephthalate, which works well in films (even very thick films), but does lend itself to molding and casting.

Cathy

From: nhcoll-l-bounces at mailman.yale.edu<mailto:nhcoll-l-bounces at mailman.yale.edu> [mailto:nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Dirk Neumann
Sent: Monday, June 16, 2014 2:06 AM
To: CAHawks at aol.com<mailto:CAHawks at aol.com>; halford at sfu.ca<mailto:halford at sfu.ca>; prc44 at drexel.edu<mailto:prc44 at drexel.edu>
Cc: nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu>
Subject: Re: [Nhcoll-l] Phenolic lids in alcohol

... just to add to Catharine Hawks:

phenolic plastic is a phenol formaldehyde resin plastic belonging to the group of thermosetting polymers such as Bakelite. In general, all plastics based on formaldehyde polymers / using formaldehyde for condensation of the polymer chains have issues if coming into secondary contact with free formaldehyde after polymerisation, which induces breaking of polymer chains. In specimen jars with (initially) formalin fixed material this may be leaking residual formalin escaping from specimens, as Catharine already said.

All plastics belonging to this group of thermosetting polymers should be avoided in (wet) collections. If plastic can be avoided, LDPE / HDPE (= Low/High Density Polyethylen) should be preferred, as PE-Plastic are the most stable plastics we have for collections (Polypropylene & PVC may also cause issues depending on how the collection is / has to be maintained).

All the  best
Dirk

Am 16.06.2014 01:26, schrieb CAHawks at aol.com<mailto:CAHawks at aol.com>:
One problem with phenolic caps is that the polymer probably contains formaldehyde. Exposed to trace formaldehyde from fixation of specimens subsequently stored in alcohol, the polymer will deteriorate (that old, "like dissolves like" concept). Any specimen fixed in formalin and later transferred to alcohol should have some unfixed formaldehyde in the alcohol given that fixation is a equilibrium reaction.

Cathy

Catharine Hawks, PA-AIC, FIIC
Conservator, NMNH
(h) 703.876.9176
(o) 202.633.0835
mobile 703.200.4370
moblile 202.701.8458
hawksc at si.edu<mailto:hawksc at si.edu>

In a message dated 6/13/2014 5:22:28 P.M. Eastern Daylight Time, halford at sfu.ca<mailto:halford at sfu.ca> writes:
When phenolic capped vials are stored as you describe the caps can expand over time and eventually fall off, potentially leading to lots becoming mixed in the bottom of the holding vessel.  It's better to discard the cap and replace it with a loose plug of cotton.  Face the  neck of the vial up so no air bubbles become trapped.
Steve.

Steve Halford (halford at sfu.ca<mailto:halford at sfu.ca>)
Museum Technician (Retired)
Department of Biological Sciences
Simon Fraser University

On Fri, Jun 13, 2014 at 10:28 AM, Callomon,Paul <prc44 at drexel.edu<mailto:prc44 at drexel.edu>> wrote:
Folks,

We have noticed that in cases where a phenolic resin cap is immersed in alcohol (70-80% ethanol) for long periods (such as when a vial with a sample is included in a larger alcohol-preserved lot) the alcohol becomes discolored. I presume the resin is leaching something. Does anyone know of any published work on this?

Paul Callomon
Collection Manager, Malacology, Invertebrate Paleontology and General Invertebrates
________________________________
Academy of Natural Sciences of Drexel University, Philadelphia
1900 Benjamin Franklin Parkway, Philadelphia PA 19103-1195, USA
callomon at ansp.org<mailto:callomon at ansp.org> Tel 215-405-5096<tel:215-405-5096> - Fax 215-299-1170<tel:215-299-1170>

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