plastics in collections - materials science · where are plastics found in collections? ......

Brenda KeneghanConservation DepartmentVictoria & Albert Museum

Plastics in Collections

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Where are plastics found in collections?

Furniture

Toys

Textiles, accessories

Sculpture

Jewellery

Archives

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Chairs made from recycled plastics

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Polystyrene Phenol formaldehyde (Bakelite)

Cast phenolic resin (Catalan)

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Degradation of plastics

Two types of degradation

Physical degradation

Chemical degradation

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Physical degradation

Caused by

Fluctuating temperature

Fluctuating relative humidity

Migration or loss of plasticisers

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Physical damage

Shrinkage or expansion

Cracking or tearing

Loss of flexibility

Change in rigidity

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Chemical degradation

CausesUV light

Temperature

Humidity

Oxygen

Ozone

Exhaustion of various stabilisers

Air pollutants

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Chemical damage

Discoloration or dullness

Cracking & brittleness

Bloom

Tackiness that attracts dirt

Odours

Leaching of liquids

Crazing

Crumbling

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Mechanical damage

Surface scratches

Wear

Cracks / chips

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Degradation of plastics

Main causes

Oxygen

Light

Heat

Moisture

Ozone or other atmospheric contaminants

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Plastics susceptible to degradation

Most vulnerable

Natural rubber

Cellulose Nitrate

Cellulose Acetate

PVC

Polyurethane

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Degradation of plasticsPlastic Typical Damage

Ebonite Metal corrosion

Rubber Crumbles or becomes tacky

Cellulose nitrate Crazes & becomes “sugary” and cracks. Acidic or Camphor

smell. Droplets may appear on surface. Metal corrosion.

Cellulose acetate Crazes & becomes “sugary”. Cracks. Droplets may appear on

surface. Metal corrosion.

Casein Cracks. Crazes.

Phenol formaldehyde (Bakelite) Discolours or becomes dull.

Urea formaldehyde Discolours or becomes dull.

Poly(vinylchloride) (PVC) Yellows, hardens, becomes brit t le & st icky.

PMMA (Perspex) Crazes & cracks.

Poly(ethylene) Yellows.

Poly(styrene) Becomes britt le & discolours.

Poly(urethane) foam Crumbles or becomes hard & tacky.

Poly(amide) (Nylon) Yellows.

Poly(ester) Discolours.

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Warning signs of deterioration

Warning Odours

Vinegar - produced by degrading cellulose acetate

Camphor - often a sign of cellulose nitrate degradation

Sharp or acidic - nitric or hydrochloric acid from cellulose nitrate or PVC respectively

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Warning signs of deterioration

Other Signs

Corrosion of metal in vicinity

Shredded paper, card or textile

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Examples

Natural rubber oxidation

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Examples

Cellulose nitrate becoming ‘sugary’

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Examples

Cellulose nitrate

Shredded tissue paper

Corroded metal

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Examples

Cellulose acetateVinegar smell

Warping & cracking

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Examples

Cellulose acetate

Vinegar smell

Warping

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Examples

Polyvinyl chloride

Darkening

Sticky surface

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Examples

Polyvinyl chloride

Darkening

Sticky surface

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Examples

Polyvinyl chloride

Darkening

Sticky surface

Residue of documentation

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Examples

Polyvinyl chloride

Sticky surface

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Examples

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Examples

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Examples

Polyurethane

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Examples

Cracking & delamination

Polyurethane

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Examples

Polyurethane

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Examples

Cracking & delamination

Polyurethane

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Examples

Polyurethane

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Conservation

Two approaches to conservation:

– Preventive or passive

– Interventive or active

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Preventive Conservation

Preventive or passive conservation is the control of the environment surrounding an object in an attempt to prevent any or further degradation.

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Long term storage recommendations

Material Max light

(lux)

Max u.v. level

(W/lumen)

Temperature

(oC)

Relative

Humidity (%)

Cellulose nitrate / Cellulose acetate

50 75 2 – 5 20 - 30

Casein & synthetics

50 75 5 – 25 50 - 60

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Material Max light

(lux)

Temperature

(oC)

Relative

Humidity (%)

Moving image colour

film

50 – 5 30 - 40

Optical media 50 +20 40

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Additional recommendations

Use filters on windows to eliminate u.v. radiation

Exclude unnecessary light in stores

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Separate from objects made from paper, cellulosic textiles, silver, iron and composites

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Inhibiting degradation using adsorbents

Adsorbents used include:

Activated charcoal

Molecular sieves (Zeolites)

Oxygen scavengers (Ageless™)

Silica gel

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Inhibitive Conservation - Activated charcoal cloth

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Inhibitive Conservation - Molecular sieve sachets

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Inhibitive Conservation - Ageless

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Inhibitive Conservation - Ageless

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Inhibitive Conservation – Silica gel

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Inhibiting degradation using adsorbents

Indicator systems used include:

Ageless™ Eye

A-D (acid detection ) strips

Chemical-impregnated string

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Inhibitive Conservation – Ageless Eye

Oxygen freeOxygen present

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Inhibitive Conservation – Acid detection strips

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Other methods of inhibiting degradation

Enclosing plastics

Low temperature storage

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Active conservation

No standard processes of interventive conservation for plastic materials

Any interventive treatments present risks of further damage to objects due to potential reaction between treatment and object - e.g. adhesive solvent may cause crazing & cracking

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Active conservation

Cleaning plastics

Joining plastics

Consolidating, impregnating and filling plastics

Labelling plastics

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Pre-treatments and adhesive types used by the plastics industry

Plastic type Pretreatment/preparation Adhesive types

cellulose nitrate and acetates clean with isopropanol epoxies, polyurethanes, acrylics,

cyanoacrylates (may cause

ESC while uncured)

phenol, melamine and urea

formaldehydes

abrasion and solvent cleaning epoxies acrylics, polyurethanes

plasticised polyvinyl chloride clean with ketone epoxies, polyurethanes, acrylics,

cyanoacrylates

polyethylene and polypropyene flame or plasma treatment to oxidise

surfaces

epoxies

polymethylmethacrylate clean mechanically epoxies, cyanoacrylates, acrylics

(greater bond strengths than

original plastic)

polyethylene terephthalate abrasion or solvent cleaning with toluene epoxies, polyurethanes, polyesters

Recommended adhesives for joining industrial plastics

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Pre-treatments and adhesive types used by the plastics industry

Plastic type Pretreatment/preparation Adhesive types

polystyrene clean mechanically water-based, solvent-free

(particularly for polystyrene

foams) or hot-melt

acrylonitrile-butadiene-styrene clean mechanically epoxies, acrylics, cyanoacrylate

(greater bond strengths than

original plastic)

polycarbonate clean mechanically epoxies, urethanes and

cyanoacrylates (greater bond

strengths than original

plastic)

polyamide (nyon) dry to less than 0.5% moisture content epoxy (adhesion of nylon is

unreliable)

polytetrafluoroethylene plasma treatment epoxy, polyurethanes (adhesion of

PTFE is unreliable)

Recommended adhesives for joining industrial plastics

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Solvent effects - examples

Plastic Solvents likely cause problems

Poly(propylene) Chloroform, Toluene, Butyl acetate. Amyl chloride

Poly(styrene) Diethyl ether, Cyclohexane, Chloroform, Butyl acetate, Trichloroethane,

Toluene, Acetone

PVC Cyclohexane, Ethyl acetate, Diethyl ether, Trichloroethane

Perspex Alcohols, Phthalate (plast icisers), Acetone, Carbon tetrachloride. Chloroform,

Cyclohexanone,

ABS

(acrylonitrile-

butadiene-

styrene)

Dichloroethene, Trichloroethane, Acetone, methanol, Propanol/ Toluene

Nylon Aniline

Polycarbonate Acetone, Diethyl ether, Chloroform, Trichloroethene, Cyclohexanone,

Polyethylene Chloroform, Cyclohexanone, Toluene

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Consolidating plastic foams

Mainly polyurethane foams have been treated with various consolidants.

e.g. Sturgeon glue

gelatine

methyl celluloses

Plextol B-500 (an acrylic dispersion)

Impranil (polyurethane dispersion in water)

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Filling plastic foams

Several polyurethane foam sculptures have been treated by filling with:

blend foam crumbs mixed with warm Beva 371, a heat activated adhesive based on acrylic and ethylene vinyl acetate polymers

Lascaux 360 HV, an acrylic adhesive mixed with original foam crumbs

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Labelling plastics

No barrier coating

Liquitex acrylic coating in water

Tie-on labels

Soft pencil

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Preservation

Try to identify plastic to see if you have any of the vulnerable types

Chronology - when each was introduced

Style & Design

Trademarks (caution - Bakelite)

Transparency - colour

Tests (some chemical spot tests but not totally reliable). Instrumental analysis best.

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Preservation

If vulnerable types are identified - monitor closely

Check every 6 months

Isolate any degrading objects to prevent damage to neighbouring objects or fabric of building

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Dos & Don’ts

Store in stable temperature and humidity

Check your collections every six months

Isolate any object that has a smell of : camphor, vinegar or other acid

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Further Information Plastics - Collecting & Conserving. Edited by Anita Quye & Colin

Williamson, NMS Publishing Ltd, 1999

Saving the Twentieth Century: The Conservation of Modern Materials, Proceedings of a conference symposium 15-20 September 1991, Edited by David Grattan, Canadian Conservation Institute (CCI), Ottawa, Canada(CCI, Ottowa, 1993)

Early Plastics Perspectives 1850 - 1950, Edited by Susan Mossman, Leicester University Press, 1997

Material Characterization Tests for Objects of Art & Archaeology. N. Odegaard, S. Carroll, and W.S. Zimmt. Archetype Publications, London, 2000

Plastics Historical Society

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