development of styrene-free unsaturated resins and acrylic ...€¦ · radical coplymerization of...
TRANSCRIPT
ICARST 2017
IAEA-Vienna 24 to 28 April 2017
Development of styrene-free unsaturated resins and acrylic
monomers for the consolidation of wooden cultural heritage
artefacts by radiation-curing
Khôi TRAN, Senior Researcher CEA
ARC-Nucléart, Grenoble, France
47 years of gamma irradiation for conservation of
cultural heritage artefacts
Ramses II mummy in Musée
de l’Homme, Paris
1977
Sculpture in the irradiation chamber,
2000
Frozen baby mammoth Siberia, 2010
Cobalt 60 sources Irradiation facility
Statues: insect eradication Consolidation with radiation-curing resin
Resin impregnation facility: vacuum/pressure tanks
Radical coplymerization of styrene-unsaturated polyester resin
Liquid state:
48% styrene
52% U-Polyester
Gelification under
gamma irradiation
Solid by cross-linking
of polyesters by poly
styrene
Dose : 30-50 kGy at 0.5 to 1kGy/hour
Drawbacks of Styrene UP resins: irreversibility, unsoluble,
and safety regulations more severe on styrene monomer
Alternative to Styrene-UP resins:
1) Styrene-free resins such as :
Advalite® resins from Reichhold Co. : vinyl hybrid resin
Atlac® resins from DSM Co. : vinyl ester resin
Viscosity : 200 to 300 mPa.s or cp
but still crosslinked after radiation-curing !
2) Acrylic monomers with low vapour pressure
Viscosity : 15 mPa.s
2-Hydroxy-ethyl-methacrylate
2-Hydroxy-propyl-methacrylate
in principle reversible, forming a gel in contact with water
Acrylic resins and acrylic monomers are very
sensitive to oxygen inhibition : sticky surface, degraded wooden
surface not well consolidated
Radical polymerization in inert atmosphere, as nitrogen, or surface barrier
Radiation-curing of monomers in current solvents such as
isopropanol, ethyl acetate,… : partial consolidation of the wood
after solvent evaporation, more deontological respect than total
or full filling of the wood porosity by the resin
Radiation-curing control by FTIR
DSC Advalite à 20°C/min
Tg = 55°C
DSC HEMA à 20°C/min
Tg = 66°C
DSC HPMA à 20°C/min
Tg = 55°C
DSC HPMA 80 4HBA 20
Tg = 50°C
DSC Analysis of resins and monomers
Solid state NMR spectroscopy of radiation-cured HPMA monomer
Carbons assigned to vinylic carbons in the range 110-120 ppm vanish and give rise
to two new signals in the range 60-40 ppm : complete polymerization
No change in other signals or no new ones : No crosslinking
Sound wooden samples for consolidation by resins and monomers
fir samplesbeech samples
Colorimetry analysis of consolidated samples
Fir
Beech
0
2
4
6
8
10
12
14
16
18
20
PARALO ÏDE B72 20%
STYRÈNE POLYESTER
ADVAL ITE 2 ,0
ATLAC 80 HPMA 20
HEMA HPMA HPMA 80 4HBA 20
HPMA 40 2BUTANOL
60
HPMA 40 IPA 60
HPMA 80 ACE 20
ΔE
Sapin Hêtre
beech
Delta E values obtained from colorimetry measurements on consolidated
samples
fir
0
10
20
30
40
50
60
70
80
Styrènepolyester Paraloïde
B72
Advalite ATLAC 80HPMA 20
HEMA HPMA HPMA 804HBA 20
HPMA 40IPA 60
HPMA 402Butanol
60
HPMA 80ACE 20
Resi
n c
onte
nt
in w
ood (
%)
Sapin Hêtre
% 𝐼𝑚𝑝𝑟e𝑔𝑛𝑎𝑡𝑖𝑜𝑛= ( 𝐹𝑖𝑛𝑎𝑙 weight − 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 weight )/( 𝐹𝑖𝑛𝑎𝑙 weight)
fir beech
Impregnation rate : resin or monomer content in wood
Volumic changes of treated samples
-3
-2
-1
0
1
2
3
4
5
Paraloïd B72 20ACE 80
Styrene polyester Advalite HPMA HPMA 40 IPA 60 HPMA 80 ACE 20
Volu
me c
hange
(Fin
al V
olu
me
-in
itia
l volu
me
)/In
itia
l V
olu
me (
%) Fir Beech
0
500
1000
1500
2000
2500
Bois brut Paraloïde Styrènepolyester
Advalite ATLAC 80HPMA 20
HEMA HPMA HPMA 804HBA 20
HPMA 40IPA 60
HPMA 402Butanol60
HPMA 80ACE 20
Ela
stic
Modulu
s (M
pa) Sapin Hêtre
𝑀𝑜𝑑𝑢𝑙𝑒 𝑠𝑝é𝑐𝑖𝑓𝑖𝑞𝑢𝑒=(𝑀𝑜𝑑𝑢𝑙𝑒 é𝑙𝑎𝑠𝑡𝑖𝑞𝑢𝑒 𝑒𝑛 𝑓𝑙𝑒𝑥𝑖𝑜𝑛)/𝐷𝑒𝑛𝑠𝑖𝑡é
fir beech
Mechanical Testing on consolidated samples
Wood Styrene Polyester Advalite HPMA HPMA40ACE60
fir
beech
X-ray radiography of impregnated samples
SEM Observations on consolidated samples
Full filling of the pores by HEMA or
HPMA Partial filling of the pores
by HPMA at 40% in solvent
-3
-2
-1
0
1
2
3
4
5
6
Cycle humide 1 Cycle sec 1 Cycle humide 2 Cycle sec 2 Cycle humide 3
ΔV
(%
)
Bois brut Paraloïd B72 20 ACE 80 Styrène polyester Advalite 2,0
ATLAC 80 HPMA 20 HEMA HPMA pur HPMA 80 4HBA 20
HPMA 40 IPA 60 HPMA 40 2Butanol 60 HPMA 80 ACE 20
Ageing of consolidated samples in humid and dry atmospheres
Application on
historical artefacts
HPMA HPMA 40 IPA 60 Advalite
HPMA HPMA 40 IPA 60 Advalite
before after
HPMA-EtAc 80/20
Conclusion
Advalite resin can be an alternative to styrene-UP resin, but
irradiation in inert atmosphere
HPMA acrylic monomer is more promising than HEMA for :
less sensitive to humidity
acrylic polymer : better durability
possibility of partial consolidation using solution of
monomer in solvent
possibility of radiation-curing in air by using
solutions of monomer
Deontological criteria in conservation of cultural heritage
(reversibility-solubility; durability; partial consolidation; product
availability; implementation on artefacts) are more satisfied by
application of acrylic monomers such as hydroxy-acrylates
• Other process (additives) for radiation-curing of acrylic
monomers/resins in air ?
• More hydrophobic momomers such as butyl-methacrylayte
• Mixture of monomers and acrylic polymers (Paraloid B72) to increase
viscosity and less shrinkage upon polymerization.
• Development of flexible, elastomer resins for consolidation of
degraded leather or other soft materials. Use of 2-ethyl-hexyl
methacrylate for instance
• Research on aqueous colloidal, dispersions of monomers/oligomers
cured by irradiation, for archaeological waterlogged artefact
consolidation
• Grafting by irradiation of monomers on cellulosic materials? wood,
paper ?
Perspectives
Thank you for your attention