I polimeri nell`arte, i polimeri per l`arte

PLASTICS IN ART ( IN CULTURAL HERITAGE )
PLASTICS FOR ART ( FOR CULTURAL HERITAGE )
Programma GIORNATA AIM del 31/10/2008
dedicata a ”Il restauro e la diagnostica degli oggetti d’arte e di design in
plastica”
By Ezio Martuscelli
PLART-31-10-08
POLYMERS SINCE THE THE BIRTH OF THE
PLASTICS INDUSTRY WERE PREFERRED ,
IN MANY APPLICATIONS, TO TRADITIONAL MATERIALS:
WOOD, METAL, GLASS, CERAMICS, IVORY, ECC:.
THE ADVANTAGES WERE THE FOLLOWING:
---EASY LAVORABILITY
---LOW PRODUCTION COST
---WEIGHT SAVING
---COLORABILITY
---IMPROVED PERFORMANCES ( NOT ALWAYS ).
THE DISAVANTACES OF PLASTICS WERE:
---UNSTABILITY AGAINST DEGRADATION FACTORS
--- NECESSITY TO USE STABILIZERS, PLASTICIZERS AND
OTHER ADDITIVES
PLASTICS=(POLYMERS)+(ADDITIVES, FILLERS, PIGMENTS)
ARE BECOMING AN INCREASING PART OF COLLECTIONS
OF MANY MUSEUMS INCLUDING THE ART MUSEUMS
AND THE SCIENCE MUSEUMS
OF GREAT INTEREST ARE:
---ARTISTIC OBJECTS MADE IN PLASTICS
--- ITEMS OF HISTORICAL AND CULTURAL INTEREST
REALIZED IN PLASTICS
BOTH TYPES BELONG TO THE BROAD FAMILY OF
CULTURAL HERITAGE
PLASTICS IN ART
PLASTICS HAD ( STILL HAVE ) AN IMPORTANT FUNCTION
IN THE STRUCTURATION OF WORKS OF ART.
THEY REPRESENTED ( REPRESENT )
A MEANS OF EXPRESSION OF ARTISTS AND DESIGNERS.
FOR SUCH A REASONS PLASTIC OBJECTS OF ARTISTIC
INTEREST ARE MORE AND MORE PRESENT IN MUSEUM
AND COLLECTIONS
PLASTICS IN ITEMS OF HISTORICAL
AND CULTURAL INTEREST
PLASTICS ARTIFACTS OF HISTORICAL INTEREST ARE
ALSO PRESENT IN MUSEUM AS THEY TESTIFY:
1 ) THE EVOLUTION OF:
--- SCIENCE; TECHNOLOGY AND INDUSTRY;
--- AN INNOVATIVE INDUSTRIAL DESIGN ;
--- THE PRODUCTION OF NEW ADVANCED MATERIALS;
2 ) EVENTS RELEVANT FOR THE HISTORY OF PEOPLES
AND NATIONS
.
J. Morgan-1994
Type of plastic objects breakdown
in museums and private collections
AGE OF OBJECTS
J. Morgan-1994
IT IS USEFUL TO DIVIDE THE PLASTIC ITEMS OF ARTISTIC
OR HISTORICAL INTEREST ACCORDING TO THE NATURE OF
THE POLYMER COMPONENT. SO WE MAY HAVE OBJECTS
MADE BY :
--- NATURAL PLASTICS ( AS EBONITE, SHELLAC, CASEIN )
--- MAN-MADE PLASTICS ( ARTIFICIAL PLASTICS:
AS CELLULOID, CELLULOSE ACETATES )
--- MAN-MADE PLASTICS ( SYNTHETIC PLASTICS:
AS BAKELITE, PVC, PMMA ECC. )
PLASTICS OF CULTURAL, ARTISTIC AND
HISTORICAL INTEREST, MAY BE ALSO
GROUPED ACCORDING TO TYPE OF
FASHIONING USED:
--Carving, Machining or Shaping,
--Casting or Moulding under heat and pressure
PLASTICS IN ART
THE CONTRIBUTION OF PLASTICS AS A MEANS OF
EXPRESSION OF ARTISTS AND THEIR RELEVANT
ROLE IN THE FINE ARTS
ARE ESSENTIALLY RELATED TO THE FOLOWING:
--- easy avaibility :
--- innovative mechanical and chemical characteristics,
--- easy manufacturing and processing
--- easy mouldability- mouldable alternative to carving
--- easy colorability by using pigments
--- relatively low cost
Con la scoperta delle plastiche di sintesi e lo sviluppo di nuovi pigmenti fu possibile
realizzare materiali caratterizzati da una ampia e diversificata gamma di colori.
Sinistra, catalogo della Catalin che commercializzava resine fenoliche ( 1936 ).
Destra, campionario di resine in acetato di vinile
EXAMPLES OF ARTISTIC ITEMS
MADE IN PLASTICS
Early artistic items
innatiral plastics
(ebanite)
1878-1900
Oggetti artistici in plastica naturale, ebanite, prodotti tra
il 1878 e il 1900
Shellac
Early artistic items
in plastics
Sinistra, dagherrotipo, periodo della guerra civile americana ottenuto
per stampaggio per compressione di una miscela di Shellac e segatura.
Destra, dagherrotipo con la rappresentazione dello sbarco di
Colombo. Prodotto da A.S. Pech and Company da una pittura
di John Vanderlyn. Lo stampo è stato preparato e inciso da
F. B. Smith e Hartman
Opera di Naum Gabo ( 1890-1977 ), dal titolo
“Construction in Space with Crystalline Centre” (1938-40 ).
PMMA e CELLULOIDE, 324 x 470 x 220 mm.
THE TRANSPARENT
SCULPTURES IN PMMA
OF Bruce Beasley ( USA ).
Le sculture trasparenti in PMMA, ottenute per colata o casting
da Bruce Beasley ( USA ). Destra, Stamper’s Lighthouse, 1967.
Sinistra, Apolymon,1968-70.
Scultura, “Lot’s Wife”,
ricavata per CARVING da un blocco di polimetilmetacrilato da
A. Fleischmann, ( I.C.I., Plastics Division )
Marcello Morandini,
sculture in plexiglass
PMMA in bianco e
nero.
Guido Drocco, Franco Mello, Cactus, elemento decorativo con
funzione di attaccapanni in poliuretano espanso, Gufram, 1972
Scultura in poliuretano espanso “Pere
Cadute”, di Piero Gilardi,
anno 2000
Sculture di Paolo Grassino
Sinistra, Cardiaco, 2006 ( in PVC espanso, resine
acriliche e polistirene ).
Destra, Branco, 2002 ( in PVC espanso e legno ).
Manufatto artistico basato sull’utilizzo di fibre sintetiche
( nylon ) e plastiche, realizzato da Naum Gabo
Oggetto Fenicio,
polimetilmetacrilato,
poliestere e Legno.
Scultura di
Vannetta Cavallotti
La maschera e il teatro, resina, bronzo e gesso.
Opera di Vannetta Cavallotti
Tavolo cigno, polimetilmetacrilato, poliestere e legno. Opera di
Vannetta Cavallotti
I POLIMERI DI SINTESI IMPIEGATI COME LEGANTI
E VERNICI NELL’ARTE PITTORICA
BINDERS AND VARNISH
LAYER STRUCTURE
OF PAINTINGS
Acrylic binders and varnishes
in paintings
Dipinti su tela di artisti moderni che hanno impiegato leganti acrilici sintetici.
CENTRO, Riccardo Pierallini, “Festa del’uva a Mendrisio”, pittura acrilica
SINISTRA, Pierluigi Pusole, “Noi cannoni”, 1986, acrilico su tela;
DESTRA, Stefano Fioresi, “Medusa”, acrilico e resina su tela
EXAMPLES OF PLASTICS ITEMS WITH
HISTORICAL INTEREST
Manufatti che certificano il processo iniziale
della sostituzione dell’avorio e del corno con
materie plastiche
Sinistra, pettini in corno( 1700-1800 )
Destra, pettini in celluloide, polimero artificiale
a base di nitrato di cellulosa e canfora
%
Sinistra, le prime palle da biliardo realizzate
in bakelite.
Destra, Tasti per pianoforte e organo, ottenuti per
stampaggio di resine stirene/acrilonitrile ( SAN ) e
acrilonitrile/butadiene/stirene ( ABS ). Prima
della scoperta delle plastiche venivano fatti in avorio.
EBONITE
RADIO-RICETRASMITTENTE, L'Ondina campale S n° 3
conservata nel Museo dell'Arsenale
della Marina Militare a La Spezia, il frontale è in ebanite.
Spedizione del dirigibile « Italia » al Polo Nord nel 1928
Disco in gommalacca - a 78 1/min (o 78 giri). Dischi
in gommalacca vengono fabbricati fino al 1960 ca.,
ma il mercato subisce un forte ridimensionamento con
l'introduzione, negli anni 1950, del disco vinile
(Long playing record).
Sinistra, disco per grammofono e radio in bakelite ( 1935 ).
Destra, Dischi realizzati in plastica vinilica mostrati per la prima
volta alla “Century of Progress, the World Fair” nel 1923
.
Il kinetoscope di T. Edison con accanto alcune
delle prime bobine di pellicole flessibili in celluloide
Primi gioielli in plastica ( bakelite ).
Sinistra, bracciale con applicazioni in metallo raffiguranti
piccole stelle Inghilterra - 1920 ).
Destra, parure in bakelite e acciaio, Francia, 1925.
Questi oggetti testimoniano la nascita di un nuovo
settore quello della bijouterie artistica in plastica.
Prime FOUNTAIN PENS prodotte
in celluloide colorata dalla
Watermans ( serie Patrician ), anni
1929-1938 ( Sostituzione dell’ebanite )
DEGRADATION AND CONSERVATION ISSUES
THE CONSERVATION OF ARTISTIC AND HISTORICAL
PLASTICS OBJECTS RISES MANY AND VARIED
PROBLEMATC ISSUES FOR THE FOLLOWING REASONS:
--- Plastics Comprise a wide range of materials having different
chemical structure and physical properties.
---Plastics are compounded with different kind of
substances ( Additives, Fillers, Pigments, Ecc: ).
---Degradation behaviour is strongly determined by the above
parameters
THE PROPER CONSERVATION OF PLASTICS ARTEFACTS
STORED IN COLLECTIONS AND MUSEUMS
REPRESENTS AN ISSUE OF GREAT CONCERN AS THERE
IS STILL A LACK OF KNOWLEDGE IN THE AREA OF
PLASTICS CONSERVATION THAT INCLUDES:
---RESTORATION
---PROTECTION
---PREVENTION
---MAINTENANCE
PLASTICS ARE MULTICOMPONENT SYSTEMS
Plastics materials are normally compounded with a
variety of
ingredients in amounts varying from fractions of a
percent to tens of percent.
Additives are used to assist the manufacturing
process,
improve the service performance of the product,
alter the appearance of the material or reduce cost.
%
Typical additives include colourants, opacifiers,
fillers, stabilisers, anti-degradants, uv absorbers,
plasticisers, lubricants, or even other polymers.
Additionally, the material may contain
adventitious impurities.
I FATTORI DI DEGRADAZIONE DI UN MANUFATTO IN
PLASTICA
FATTORI INTERNI
- caratteristiche chimiche e fisiche dei
polimeri
- natura chimica, funzione e reattività degli
additivi;
- tipologia dei processi di lavorazione;
- prodotti di degradazione.
FATTORI ESTERNI
- calore
- umidità
- ossigeno
- luce
-inquinamento ambientale
-microorganismi
SYMPTOMS OF POLYMER
DEGRADATION
¦ lowering of thermal, mechanical, optical
and electrical properties;
¦ viscosity reduction/increase;
¦ yellowing and discoloration;
¦ embrittlement;
¦ tackiness;
¦ loss of surface gloss;
¦ surface crazing;
¦ surface chalking;
¦ loss of functional characteristics.
¦ release of volatile products.
IN PLASTICS IN HISTORICAL COLLECTIONS
The most prevalent type of degradation was cracking or crazing,
with discolouration and fading being almost as common.
< The figures reflect the number of responses to that part of the
questionnaire and not the proportion of the collection which shows
signs of degradation >J. Morgan-1994.
Influenza sull’effetto di degradazione della luce solare
di altri fattori quali l’umidità, il calore e l’inquinamento ambientale
( +++; molto alta; ++, alta; +, moderata )
Chemical modifications induced by degradation factors on
macromolecules
Statistical rupture
Cross-links
Side groups
modification
Side groups
elimination
Cyclation of
side groups
THERMOLYSIS
OXYDATION
RADIOLYSIS
HYDROLYSIS
Chemical mechanisms of statistical chain rupture
DEGRADAZIONE DELLA CELLULOIDE
LA SINTESI DEL NITRATO DI CELLULOSA
%
DEGRADAZIONE DELLA CELLULOIDE
PROCESSO DI DENITRAZIONE DEL
NITRATO DI CELLULOSA
CELLULOSA- NO2 ? CELLULOSA+ NO2
NO2 + H2O ? HO3
DEGRADAZIONE DEL POLIMETIMETACRILATO
Struttura molecolare dell’unità ripetitiva del
polimetimetacrilato (PMMA ) e il passaggio
da monomero a polimero.
%
Fotolisi di omopolimeri, causata dalle radiazioni UV:
Reticolazione del polimetilmetacrilato (PMMA)
radicale
Degradazione fotochimica del PMMA per effetto delle
radiazioni UV.
L’idrogeno terziario sul CH viene estratto e si forma un
macroradicale ( indicato dalla pallina nera in figura ).
Questi macroradicali accoppiandosi danno luogo alla
formazione di strutture reticolate.
Degrado termico del PVC
A temperature elevate (es. durante lavorazione) il polimero
PVC stacca una molecola di HCl, formando un legame
C=C
Per evitare questo processo vengono usato additivi (stabilizzanti,
nel caso di PVC stearati di Ca e Zn).
Il poli(acetato di vinile), PVAc, riscaldato progressivamente in
atmosfera di azoto inerte, a 250-300 °C sviluppa acido acetico in
quantità stechiometrica e lascia un residuo di colore scuro; il
meccanismo è molecolare, l’eliminazione di acido acetico avviene
attraverso uno stato di transizione a 6 centri.
H
C
CH
H
O
O
C
CH
H
C
H
O
H
O
C
O
C
O
CH
H
C
CH
H
C
H
O
CH3
CH3
H
C
∆
C
H
H
C
+
C
H
CH3COOH
O
CH3
CH3
δ−
C
HC
CH
H
C
H δ+ O
H
CH3COOH
C
+
O
C
CH3
THERMAL DEGRADATION OF PVC AND PVAc
Reazione che porta all’eliminazione dei gruppi
laterali con formazione di acidi e un poliene
coniugato
Stadio iniziale della reazione tra
poliammidi e poliuretani e l’anidride
nitrosa presente nell’ambiente.
THERMAL CYCLIZATION OF SIDE GROUPS
IN POLYACRYLIC ACID
Ciclizzazione dei gruppi laterali di natura
carbossilica per effetto del calore in assenza di
O2 nel caso dell’acido poliacrilico
Foto-ossidazione del
polistirene. Stadio di scissione
della catena macromolecolare
.
Stadio iniziale del processo di degradazione
della gomma naturale ad opera dell’ozono
atmosferico.
KINETICS OF POLYMER PHOTOOXIDATION
Puglisi
Esempio di degradazione indotta dall’ossigeno che si
evidenzia attraverso abbattimento delle proprietà
meccaniche
Relation between drop in elongation at break and oxygen
uptake of PP films at 65 °C (Concetto Puglisi )
Diagramma schematico dove sono indicati gli stadi della degradazione
indotta su polimeri naturali e sintetici dall’esposizione alla luce solare.
Lunghezza d’onda e degradazione
Solamente la radiazione assorbita provoca una
fotodegradazione dei polimeri. Per ogni polimero esiste
un intervallo di lunghezze d’onda che porta al degrado.
Polimero
(nm)
Poliesteri
315
Polistirene
318, 340
Polietilene
300
Polipropilene
370 (280)
PVC
310, 370
Policarbonati
280 – 305, 330 – 360
Poliammidi
250 - 310
Esempio di degradazione indotta dall’ossigeno e della luce
che si evidenzia attraverso abbattimento delle proprietà meccaniche
(Concetto Puglisi )
Variazione dell’allungamento a rottura di campioni di
policarbonato in funzione
del tempo di esposizione alla luce solare (in mesi).
Si evidenzia l’influenza della T sulla velocità di deterioramento (curva
in alto, bassa temperatura, 25°C; curva in basso alta temperatura.
EXAMPLES OF DEGRADATION OBSERVED IN PLASTICS
ARTEFACTS OF ARTISTIC AND HISTORICAL INTEREST
CELLULOID ITEMS : DEGRADATION ISSUES
CONSERVATION, PREVENTION, MITIGATION
Royal Ontario Museum in Toronto
Of two Celluloid made fans, from 1920, one (right) is in perfect
conditions while the other (left ) has disintegrated due to unproper
conservation conditions (Stinson, 9, 1996, C&EN )
Esemplari di moderni occhiali da
sole
con montatura in celluloide
A sinistra, Collana con perle in celluloide color tartaruga, anni '50,
A destra, spilla anni '50 con base in metallo dorato lavorato con foglie
decorate a smalto giallo,con incollate perline in celluloide giallo limone.
Dalla base spiccano tre fiori, composti da una doppia serie di petali in
celluloide traforata di colore giallo pallido.
CELLULOID COMPOSITION
Reazione di nitrazione
della cellulosa che porta
all’ottenimento del nitrato
di cellulosa ( schematico ).
CELLULOIDE
nitrato di cellulosa +
Canfora
%
CELLULOID COMPOSITION
CELLULOIDE
nitrato di cellulosa +
Canfora (Plastificante)
Struttura chimica della canfora ( C10H16O ),
un chetone biciclico ( bicicloalcano ).
La canfora naturale viene estratta dal legno
della canfora ( Cinnamonum camphora ),
%
Lo schema del ciclo di produzione e
lavorazione della celluloide
Fibre naturali di origine vegetale cellulosiche
cellulosiche
COTONE
COTONE
Micrografia elettronica di una fibra di cotone ad alto ingrandimento attraverso la quale è
possibile evidenziare il fenomeno di torsione e le tipiche rugosità superficiali
CELLULOID COMPOSITION
1 ) POLYMER, CELLULOSE NITRATE
2 ) CAMPHOR AS PLASTICIZER AND
STABILIZER(20-40%)
3 ) ZINC OXIDE AS FILLER AND OPACIFIER
4 ) PIGMENTS
5 ) IMPURITIES RELATED TO SYNTHESIS
( LIGNIN, SULFURIC ACID, ACIDS, CHLORINE )
COMPOSITION IS USUALLY ASSESSED
BY SUITABLE DIAGNOSTIC TECHNIQUES
SUCH AS: FTIR, X-RAY, SEM-EDS, ECC.
Derrick et.Al.
1992
Naum Gabo,
< known for his sculptural experiments with constructivism >
Head of a Woman, c. 1917-20, celluloide e metallo,
Museum of Modern Art, NY
THE THERMAL DEGRADATION OF CELLULOSE NITRATE
CAUSES THE DENITRATION WITH SIDE GROUPS
ELIMINATION THAT IN PRESENCE OF WATER FORM
NITRIC ACID
CELLULOSE- NO2 ? CELLULOSE+ NO2
NO2 + H2O ? HNO3
< once initiated the process becomes auto catalytic
when oxygen and humidity are present >
ARTEFACTS IN CELLULOID: SYMPTOMS OF DEGRADATION
---CRAZING AND CRACKING
--- DISCOLORATION
---LIQUID PRODUCTION ON THE SURFACE
( aqueous zinc nitrate solution following reaction
between ZnO And HNO3 )
---CORROSION OF METAL COMPONENT IN
CONTACT WITH ITEMS
---LIQUID EXUDATE, from which crystals of
CaSO4-dihydrate separate ))
IMPORTANCE OF PROPER DIAGNOSTIC TECHNIQUES
FTIR
CELLULOSE
NITRATE UNAGED
absorbances of
NO2 at 1650cm-1
of CO at 1733
cm-1
FTIR
CELLULOSE
NITRATE AGED
DEGRADATION SENSORS-INDICATORS
Strips of filter paper impregnated with Cresol Purple are good
detector of offgasing nitrogen dioxide from a celluloid items.
The paper turns from yelllow to red as pH decreases from 2.8 to 1.2.
The sensor indicates that one knob (right ) is decomposing but the
other is not ( Stinson-1996 )
MAIN CAUSES OF DEGRADATION OF CELLULOID
SCULPTURES OF NAUM GABO AND A. PEVSNER
( 1917-1926 )
1 ) PAST STORAGE AND DISPLAY CONDITIONS
2 ) COMPOSITION INCLUDING ADDITIVES AND
IMPURITIES
3 ) THE PHYSICAL CONSTRUCTION OF THE
ARTEFACTS
According to M. Derrick et Others (1992)
CONSERVATION AND MITIGATION MEASURES
SUGGESTED FOR THE CELLULOID SCULPTURES
OF NAUM GABO AND A. PEVSNER ( 1917-1926 )
The goal of conservation is to stop the degradation without altering
the appearence or structure of artefact then the only way to halt
the deterioration process is to freeze the item.
This cannot be done thus a practical solution must be
deviced that minimises the damage extending the life time of the
object.
%
PRACTICAL SUGGESTIONS:
--- reduce fluctuation of temperature and humidity
--- lower the temperature in storage or display room
--- protect the object from UV light, this reduce thermally and
photolytically degradation process
---create an optimum closed environment to avoid that the degradation
becomes autocatalytic when O2 and H2O are available.
%
This means that display cases which can maintain a
low relative humidity, provide protection from UV light
and minimize the degradation process, must be designing
for every single item.
Moreover celluloid artefacts should be never stored in proximity
of other kind of items made by plastics that suffer the attack of
HNO3 such as Casein.
GENERAL CONCEPT OF ANTAGONISTIC MATERIALS
AND BAD NEIGHBOURS
POLYURETHANE BASED
ITEMS : DEGRADATION ISSUES
CONSERVATION, PREVENTION,
MITIGATION
Schema della reazione tra un
diisocianato e un diolo che porta
alla sintesi dei poliuretani.
In alto: struttura molecolare del poliglicole etilenico.
In basso: struttura dell’unità ripetitiva di una
macromolecola di un poliuretano ottenuta per reazione del
poliglicole con MDI.
Il polimero si caratterizza poliglicole con MDI. Il polimero
si caratterizza per la presenza di blocchi flessibili e rigidi .
Poliuretanes
-Properties
-attacked by aromatic solvents, chlorinated solvents, ozone, and nitrogen oxides
-slow burning with bright flame and sharp odor (toxic fumes)
-thermosetting (rigid) or thermoplastic (elastomeric);
-serviceable temperature range = -50 to 70;
-excellent hardness, gloss, and resistance to weathering,
abrasion, acids, and alkalis;
Applications
-elastomer, sealants, adhesives, films, furniture, mattresses, laminates,
carpet cushions, upholstery, soundproofing, flotation devices, packaging,
and filtration
PIERO GILARDI: NATURA MORTA CON ANGURIE-1967
RESTORATION AND CONSERVATION ACTIONS
REALIZED IN A POLYURETHANE EXPANDED SHEET
THE VARIOUS ELEMENTS, AFTER PAINTING, ARE
GLUED TO THE SUPPORT
%
Progetto Raffaello1999, International Network for the Conservation of Contemporary Art A. Rava, 2000, Kermes
STATE OF CONSERVATION
After 30 years the base material ( PU-ether ), following
to degradation due to environmental factors is brittle
having lost all elasticity.
The painting is based on polyvinylacetate.
The glue is based on rubber latexes.
SOME OF DAMAGES BEFORE RESTORATION
RESTORATION-MATERIALS
---a polyethylene net for lining
---a water dispersion of an acrylic resin ( Lascaux 360 )
as adhesive.
--- nylon thread
---unsaturated polyester for structural support
EXAMPLE OF USE OF POLYMERS FOR THE
CONSERVATION OF CULTURAL HERITAGE
ACRYLIC MONOMERS AND RESINS
DETAILS AFTER
RESTORATION
DEGRADATION CYCLE OF PLASTICS
Emission
Volatile degradation
degradation
products
INTERNAL FACTORS
EXTERNAL FACTORS
additives colorants, opacifiers,
fillers, stabilisers,
anti-degradants, uv absorbers,
plasticisers, lubricants,
impurities
Heat,
humidity,
light,
oxygen,
environmental pollutants
Absorption
Acid gases (i.e. SO 2)
TYPICAL VOLATILE EMISSION PRODUCTS: NO2, CH3COOH, HCl, Ecc.
GENERAL RECOMMENDATIONS FOR THE CONSERVATION
OF ITEMS IN PLASTICS
--Identify plastics components
--Detect early signs of degradation by regular examination
and by using proper sensors.
--Remove harmful contaminants and degradation products.
-- Identify all symptoms of deterioration.
--Adopt the most appropriate restoration and protection
methodologies
--Apply proper prevention techinques to control and
reduce degradation (use of suitable scavengers )
%
GENERAL RECOMMENDATIONS FOR THE CONSERVATION
OF ITEMS IN PLASTICS
STORAGE AND DISPLAY
1) Control of the following factors:
GENERAL
---light, temperature,
humidity, ventilation, cleaning.
RECOMMENDATIONS
FOR in acid free tissue.
2) Artefact should
be individually wrapped
THE
CONSERVATION
3) Items made
by plastics
with a high plasticiser content
(e.g. cellulose
andINacetate
and polyvinylchloride)
OFnitrate
ITEMS
PLASTICS
should not contact themself or other objects.
GENERAL RECOMMENDATIONS FOR THE
CONSERVATIONOF ITEMS IN PLASTICS
Artefacts should be kept in cases hermetically sealed
with inside a controlled “micro-environment”
environment to:
--exclude all external harmful agents;
--clean the atmosphere inside by using suitable Scavengers;
--monitor early signs of deradation by using proper and specific
Sensors.
DEGRADATION SENSORS-INDICATORS
Strips of filter paper impregnated with Cresol Purple are good
detector of offgasing nitrogen dioxide from a celluloid items.
The paper turns from yellow to red as pH decreases from 2.8 to
1.2. The sensor indicates that one knob (right ) is decomposing but
the other is not ( Stinson-1996 )
A scavenger is a chemical based device suitable to remove
or inactivate impurities or unwanted products suitable to
improve the environmental conditions in museum glass show
cases.
EXAMPLES OF SCAVENGERS
---Humidity scavenger
-Silicagel, with a blu colored indicator that change color in rose
following idration;-Artsorb, costituted by amorphous silica
and litium chloride.
---Chemicals scavengers
-Active carbon-Zeolites, silicates of Al, Ca, Na
---Oxygen scavengers
Ageless, based on fine powdered iron that in presence of O2 form
oxides and hydroxides.
--- Acids scavengers
used to neutralize traces of halogen, nitrogen sulppur anions
formed during aging
---. Free radical scavengers
The difficulties in applying the above concepts of
conservation relay upon the fact that an ideal
environment for a certain type of plastics may be
detrimental for an other types.
Moreover sensors and scavengers have to be
designed for class of homogenous plastics taking into
consideration also the kind of additives present as
well as their activity and function.
MANY PLASTICS ITEMS ARE PART OF CULTURAL
HERITAGE
UNFORTUNATELY THEY ARE QUITE SENSIBLE TO
DEGRADATION. THE CONSERVATION OF PLASTICS IS
MORE COMPLICATED, IN COMPARISON TO OTHER
MATERIALS, FOR THE FOLLOWING REASONS:
--- Plastics Comprise a wide range of materials having different
chemical structure and physical properties, thus each type reacts
against degradation factors in a different manner.
---Plastics are compounded with different kind of
substances ( Additives, Fillers, Pigments, Ecc: ) that take part to
degradation or even induce degradation.
---Degradation behaviour is strongly dependent by, a difficult to
assess, combination of the above factors.
At the moment the mechanisms of
degradation and stabilization of polymers
are almost well known.
On the contrary the “operative”
conservation of plastics based artefacts is
an open problematic issue that still require
large research efforts.
POLYMERS FOR THE CONSERVATION
OF WORKS OF ART
Parylene process
Parylene is the generic name for the poly-para-xylylenes,
the various members of a family of polymers developed by
Union Carbide Corporation, able to form, following a vapour
deposition polymerization, coatings and films made up
of linear highly-crystalline polymers.
The chemistry of treatments of consolidation and strengthening
of works on paper based on the use of polymers ( Status of art )
By E. Martuscelli
The phases of the Parylene process, based on a vapour
deposition polymerization technology
Photo of Taiwan Plant Atlas plates
(published in 1911)
coated with:Left, Parylene-C;
Right, Parylene-N.
Water dropping test on Parylene-N and Parylene-C
coated paper surfaces.
Left, no-treatment; Center, Parylene-C at 1 µm;
Right, Parylene-N at 1 µm.
Consolidation effect
Of Parylene on works
on paper
SEM micrographs of newsprint paper surfaces coated
with Parylene-N and Parylene-C.
Top: no-treatment. Bottom-Left: Parylene-C. Bottom –Right: Parylene-N.
Untreated book after 4
months of immersion in
water followed by 3
months of storage while
still wet.
Treated book after 4
months of immersion in
water followed by 3
months of storage while
still wet.
Parylene treatments of books
Consolidation of a
silk and gold made
Textile fragment by
Parylene process
Frammento di un tessuto serico-aureo (XIII-XIV secolo d.C.)
rinvenuto a S. Fruttuoso diCamogli (Liguria, Italia).
Il reperto, un tessuto misto costituitoda filamenti di seta e da
sottilifili d’oro è stato consolidato con il processo Parylene.
There is a growing …concern about the
deterioration of plastics in museum and private
collections, especially the early cellulosic materials…….
Concerted effort is still needed to…establish
the conditions under which artefacts…may be safely
stored and displayed.
Procedures for arresting deterioration in materials
already affected also need to be established so that
restorative techniques may be reaserched and applied
[J. Morgan,1994].
END