[Nhcoll-l] Update on jar lid liner issue

[Dirk Neumann]

Dear all,

sorry for picking this discussion up again (after returning from vacation).

It may not only be the chemical & physical composition of the liner that 
may cause or accelerate its deterioration, but also additives and/or 
denaturing agents added to the ethanol which may speed up degradation of 
plastics. I am not sure if Canadian Museums have to use denatured or 
undenatured ethanol. In Europe a large variety of denaturing agents has 
been used during the last century, leading to quite complex chemical 
mixtures after topping up evaporation losses for decades. As a matter of 
fact, this tends to give single lots a unique chemical history. 
Destruction might even speed up if aggressive additives do have higher 
evaporation rates compared to ethanol (resulting in a very reactive, 
highly concentrated small gas atmosphere between fluid surface & lid).

"Cracking of [some] plastics" might also be expedited from degradation 
products of/or residual formaldehyde escaping from formalin fixed specimens.

As far as I know, the colleagues in Bern/Switzerland have been testing 
Teflon liners designed for (standardised metal) twist-off lids with 
promising results, but I do not have first-hand information on this.

All the best
Dirk

Am 01.08.2012 19:33, schrieb Paul Callomon:
>
> Colleagues,
>
> Realizing the possible implications for us all of age-related failure 
> of jar lid liners, I have been doing some survey work. The results are 
> encouraging.
>
> -The supplier of the liners, O. Berk (KOLS Containers in those days) 
> have confirmed that the liner in question is a generic version of the 
> Tekniplex F217 liner that differs from the brand-name version only in 
> the blowing agent that is used to foam the center core. The outer 
> skins are solid low-density polyethylene, and the center is foamed LDPE.
>
> -I retrieved and tested several other jars using the same lid that 
> were put into service in the same or following year (2000-01). The 
> lids thus came either from the same batch as the failed one, or from 
> another batch that was purchased shortly after. I carried out a simple 
> visual examination followed by a pliability test. For the latter, I 
> lifted the edge of the liner (it is glued to the inside of the lid) in 
> two places using a dental hook and folded a flap over until it touched 
> the surface of the liner (folded double). When it had returned, I 
> inspected the surface. The material showed some wrinkling from this 
> treatment, as is normal, but no cracking or crazing. This is the same 
> thing that happens with a brand new liner, and although the wrinkling 
> remains to a certain extent, this does not seem to compromise sealing.
>
> -By contrast, the failed liner snapped when folded over, and its 
> surface is covered with a combination of fractal (branching) crazing 
> as well as the cell-like crazing one sees in old ceramic glazes. The 
> material has thus clearly undergone a major chemical change, and a 
> colleague has generously offered to run tests to try and diagnose this.
>
> In conclusion, it seems that this might have been a single incident. 
> The next step is to trace the history of the contents (13 separate 
> specimen lots in glass tubes) and see what treatments were used on 
> them that might have caused this problem.
>
> *Paul Callomon*
>
> Collections Manager in Malacology, Invertebrate Paleontology and 
> General Invertebrates
>
> The Academy of Natural Sciences of Drexel University
>
> 1900 Benjamin Franklin Parkway
>
> Philadelphia, PA  19103
>
> callomon at ansp.org
>
> Tel. 215-405-5096
>
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-- 
Dirk Neumann

Tel: 089 / 8107-111
Fax: 089 / 8107-300
email: Dirk.Neumann(a)zsm.mwn.de

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Dirk Neumann, Sektion Ichthyologie / DNA-Labor
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---------

Dirk Neumann

Tel: +49-89-8107-111
Fax: +49-89-8107-300
email: Dirk.Neumann(a)zsm.mwn.de

postal address:

Bavarian Natural History Collections
The Bavarian State Collection of Zoology
Dirk Neumann, Section Ichthyology / DNA-Lab
Muenchhausenstr. 21
81247 Munich (Germany)

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