Permanent Refreshment of Acetate Media - A story about passion on innovation. NOA, Nadja...

transcript

Permanent Refreshment of Acetate Media -

A story about passion on innovation.

CREATING

ARCHIVE

INNOVATIONS

Nadja Wallaszkovits,

n.wallaszkovits@noa-archive.com

1936 Wolfgang Sichardt, Switzerland Magnetophon K2

1939 Leandro Mazzoni, Albania Magnetophon K6

1939-40 Armando Leça, Portugal Magnetophon K4 (Ser.Nr. 1260)

1940-43 Alfred Quellmalz, Southern Tyrol Magnetophon K4 (Ser.Nr. 1297)

Welcome to the new NOA Research

Department!

The vinegar syndrome is a quite complex of interactions:

hydrolytic de-esterification of the cellulose acetate that produces acetic

acid – autocatalytic

chain scission of the cellulose acetate polymer – most dreaded, can lead

to total material breakdown

Both reactions are theoretically reversible hydrolytic processes, but the

reaction to revert would need very high temperature as a trigger

(melting of the material at a melting point of 140°C).

Introduction

So therefore, concerning audio-visual materials, the vinegar syndrome

cannot be reverted, but slowed down. Various storage efforts are based

on this knowledge.

A third reaction involved has been monitored already very early in history,

but seems to be an underestimated factor in recent a/v media related

research activities:

loss of plasticiser (and other volatile substances)

relevant for the elasticity and playability of aged a/v media

Introduction

Internal Plasticisers

chemically reacted with the polymer

long pendant groups are attached to the polymer chains (copolymerisation, side chain grafting)

more flexibility of the material can be reached

internal plasticizers are inherently part of the plastic and remain part of

the product – usually not affected by plasticiser loss

External Plasticisers

Interact physically, not chemically reacted with the polymer

basically polymer mixtures

most important in commercial applications

Graphics by http://www.greener-industry.org.uk/pages/pvc/1_pvc_AP.htm

small size

low molecular weight

= plasticiser molecule

high vapour pressure

high rate of diffusion

high plasticiser efficiencyhigh volatility

polarity

low hydrogene bonding

= polymer

Graphics:

http://www.naturagart.co.uk

big size

high molecular weight

= plasticiser molecule

low vapour pressure

low rate of diffusion

lower plasticiser efficiencylow volatility

polaritystrong hydrogene bonding

= polymer

Graphics:

http://www.naturagart.co.uk

Diffusion of plasticiser is depending on

• size of the surface exposed to the atmosphere

• thickness of the diffusion zone

• diffusion coefficient – raises with plasticiser concentration

• saturation concentration & vapour pressure of the plasticiser

• plasticiser concentration & vapour pressure of the atmosphere

• temperature

• atmospheric pressure (vacuum accelerates)

the higher/bigger, the faster

Typical example for diffusion of plasticiser

depending on the size of the surface exposed to the atmosphere

Inner parts – tighter pack – less exposed

Outer parts – less tight pack – comparatively big regions exposed to atmosphere

Which materials can be affected?• Basically: all data carriers produced from plastics containing

plasticisers and/or other volatile components

In particular:

cellulose acetate (CA)

cellulose mixed esters

polyvinyl chloride (PVC)

To less extent eventually:

polyethyleneterephthalate (PET)

biaxial oriented polyethyleneterephthalate (boPET, Mylar)

polyethylennaphthalate (PEN)

→ detailed production process often unknown

→ use and characteristics of plasticisers unknown

Examples for affected A/V materials

• Instantaneous „wax“ cylinders, as volatile components may be in the

mixture (usually metallic soap with added wax and inorganic

stabilizers)

• Shellac discs: contain camphor, castor oil, ethylphathalate,

triphenylphosphate, tricresylphosphate and other volatile components

and plasticisers

• Photographic/cinematographic film materials on nitrocellulose base

• Photographic/cinematographic film/ magnetic tape materials on

cellulose-acetate base

• Instantaneous discs on PVC base (e.g “Decelith”)

substrate magnetic coating

• shrinks to a lower degree

or stays inherently stable

Theoretically: maximal shrinkage of ~ 15-20%!

In practice typically ~ 5-10%

Evaporation of plasticisers

Plasticiser and other volatile

components

• evaporate from the substrate

• result: brittleness, deformation,

shrinking, loss of elasticity,

loss of tensile strength

→ worst case: unplayable

magnetic layer

substrate

Wypych, George:

Handbook of Plasticizers,

Second Edition, 2012

Chapter 11

Plasticizers Use and Selection

for Specific Polymers

List of polymers

containing plasticiser(s)

Problem solving approaches

Vinegar syndrome:

• First detected 1948

• First problem solving approach: 1923!

Inventor:

Johann Jacob Friedrich Stock

Munich

„Method for the conservation and regeneration of celluloid and objects thereof“

e.g. collar stiffeners…

• Phonogrammarchiv in cooperation with the OFI (Austrian Research

Institute for Chemistry and Technology in Vienna) has developed a

method to permanently refresh the elasticity of the material, so that the

playability is given or regained for long time.

• During this chemical treatment it is possible to increase the

concentration of plasticiser in the material. As a quite positive side

effect, the treatment is able to significantly slow down the vinegar

syndrome or – depending on the degradation degree of the individual

tape – even stop it

• Diffusion process in the liquid phase, chemical equilibrium is re-

established or approximated

• The reconditioning fluid comprises one or more liquids selected in

such a way that it is substantially inert compared to the data carrier

• This means, that the fluid does not form any chemical bond with the

data carrier, and does not diffuse into or swell the data carrier

• The reconditioning fluid comprises a non-volatile plasticiser or a

mixture thereof

• The concentration of the plasticiser in the reconditioning fluid is

selected such that the gradient of the change in volume of the data

carrier owing to the replacement of plasticiser with the reconditioning

fluid is positive

• With such a fluid, the data carrier can remain in contact with the

conditioning liquid for a long time, the plasticiser being able to

penetrate into the data carrier without problem

Decades…

Refreshed in 2012, today still the same flexibility

before after

Aim in the cooperation with NOA:

Provide a substantial preservation treatment that offers the archives

- more time for preservation and prioritisation decisions

- more quality in transfers and

- less resource intensive climate control

Challenge:

From an academic patent to the market:

A hell of a work.

Introducing methods to control the process – from destructive chemical

analysis methods to non-destructive verification and quality control

• Optical quality control

• Mechanical quality control

• Chemical verification

• Introduction of environmentally beneficial chemicals, unproblematic in

handling (REACH conform)

…non toxic

…non flammable

…applicable without risk!

Optical control setup

IT8 Target

original

after treatment

before treatment

Mechanical control setup

Mechanical reference values indicated by

SMPTE:

3N for 16mm

5N for 35mm

minimum: 1N (35mm)

maximum: 7N (16mm and 35mm)

Chemical verification

Gravimetric verification

of plasticiser diffusion

by laboratory scale

Chemical verification of treatment success (quantification) by

Gaschromatographic (GC) analysis:

1 0 . 0 0 1 2 . 0 0 1 4 . 0 0 1 6 . 0 0 1 8 . 0 0 2 0 . 0 0 2 2 . 0 0 2 4 . 0 0 2 6 . 0 0 2 8 . 0 00

5 0 0 0 0 0

1 0 0 0 0 0 0

1 5 0 0 0 0 0

2 0 0 0 0 0 0

2 5 0 0 0 0 0

3 0 0 0 0 0 0

3 5 0 0 0 0 0

4 0 0 0 0 0 0

4 5 0 0 0 0 0

5 0 0 0 0 0 0

5 5 0 0 0 0 0

6 0 0 0 0 0 0

6 5 0 0 0 0 0

7 0 0 0 0 0 0

7 5 0 0 0 0 0

8 0 0 0 0 0 0

8 5 0 0 0 0 0

9 0 0 0 0 0 0

9 5 0 0 0 0 0

T i m e - - >

A b u n d a n c e

T I C : F O L I E 4 . D \ d a t a . m s

1 0 . 0 0 1 2 . 0 0 1 4 . 0 0 1 6 . 0 0 1 8 . 0 0 2 0 . 0 0 2 2 . 0 0 2 4 . 0 0 2 6 . 0 0 2 8 . 0 00

5 0 0 0 0 0

1 0 0 0 0 0 0

1 5 0 0 0 0 0

2 0 0 0 0 0 0

2 5 0 0 0 0 0

3 0 0 0 0 0 0

3 5 0 0 0 0 0

4 0 0 0 0 0 0

4 5 0 0 0 0 0

5 0 0 0 0 0 0

5 5 0 0 0 0 0

6 0 0 0 0 0 0

6 5 0 0 0 0 0

7 0 0 0 0 0 0

7 5 0 0 0 0 0

8 0 0 0 0 0 0

8 5 0 0 0 0 0

9 0 0 0 0 0 0

9 5 0 0 0 0 0

T i m e - - >

A b u n d a n c e

T I C : F O L I E 5 . D \ d a t a . m s

Before treatment After treatment

Based on the destructive GC tests:

Creating a reference curve to verify the treatment success by

means of non destructive methods:

Attenuated Total Reflectance – Fourier Transform Infrared

Spectroscopy (ATR-FTIR)

Chemical verification of

de-acidification process

Chemical verification of deacidification by refractive methods

Many thanks also to the project consultants:

Dr. Peter Liepert

Dr. Lidija Spoljaric-Lukacic

Univ. Prof. Dr. Erich Schmid

Dr. Josef Bailer

Dr. Wolfgang Werther

For more information about the refreshment and the resulting

product, please contact

CREATING