Conservation of wood with Acrylics

LadislavLadislav ReinprechtReinprechtTechnical University of Technical University of ZvolenZvolen

Faculty of Wood Sciences and TechnologyFaculty of Wood Sciences and TechnologyT.G.MasarykaT.G.Masaryka 24, 960 53 24, 960 53 ZvolenZvolen

SlovakiaSlovakia

CONSERVATION OF WOOD CONSERVATION OF WOOD WITH ACRYLICSWITH ACRYLICS-- selected experimentsselected experiments

Consolidation, reinforcement and stabilisation of decorated wooden artefacts

COST ACTION IE0601, Prague, 30-31 March 2009

Substances for wood conservation

Natural- beeswax, Montana wax, paraffin wax, colophony, mastic, dammar, shellac, bone glue, drying vegetable oils, sucrose, etc.

Synthetic - acrylics, unsaturated polyesters, epoxides, aminoplasts, phenoplasts, polyurethanes, polyethylene-glycols, etc.

Substances for wood conservation- General requirements

good penetration into wood compatibility with materials protective chemicals, glues, paintings, ...

(e.g. materials used during the previous interventions)

compatibility with technological operations good additional treatment of conserved wood by gluing, painting, ...

minimal influence on sorption properties of wood no dimensional changes of conserved wood

(e.g. swelling or shrinkage of wood during their penetration into wood, or during their hardening in wood)

long-term dimensional stability of wood (especially of the water-logged archaeological wood) minimal influence on aesthetic appearance of conserved wooden object strengthening of wood integration of loose or broken parts of wood stability against weathering, fire, and biological deterioration no toxicity and minimal impact on environment reversibility of the intervention (i.e. possibility to remove the conservation product from wood in the future)

Synthetic substances - Advantages

Availability Reasonable price Stability (composition, polymerization degree, properties), Possibility to prepare special polymers (according to the specific

needs of conservator)

Usually better properties (physical, physical-chemical, resistance against weathering, resistance against biological agents)

Disadvantage:Non-reversible process at using of thermosetting types (e.g. unsaturated polyesters, epoxides, aminoplasts, phenoplasts)

Acrylics - polyacrylates

Preparation by polymerization of esters of acrylic and methacrylic acids CH2=CH-COOR CH2=C(CH3)-COOR

Application forms polymers and copolymers (polyacrylates) monomers polymerized in wood by in situ method

Important types for wood conservation polymethylmethacrylate PMMA (Acrylit X 20/5, Bedacryl L, etc.) polyethylmethacrylate - PEMA (Acryloid B72, Paraloid B72, etc.) polybutylmethacrylate - PBMA (Bedacryl 122X, Paraloid B67, Plexisol P 550,

Solakryl BT 55, etc.) polymethylacrylate - PMA polyethylacrylate - PEA polybutylacrylate - PBA copolymer - MMA/EA (Paraloid B82, Plextol B 500, etc.) copolymer - MA/EMA copolymer - MMA/BMA (Elvacite 2013, Osolan KL, Solakryl BMX, etc.)

Acrylics - polyacrylates

Characteristics colourless, transparent, hard but sufficiently elastic

Solubility in less-polar organic solvents (in toluene, xylene, or acetone) Application 10-20 % solutions (high dynamic viscosity 5-30 mPa.s) Advantages good resistance against weathering and high temperatures

reversible process copolymers (MMA/BMA) specific properties of cons. wood

Disadvantage: The solvent evaporates slowly from the conserved wood (several weeks even months), which can sometimes cause the backwards migration of acrylic polymer to the wood surface.

Acrylics polyacrylates- Selected experiments

Technical University of Zvolen, Slovakia

1) Influence on decay processes in wood

2) Strengthening of decayed wood

3) Stabilization of wood surfaces

4) Conservation of wooden sculptures

Acrylics polyacrylates

Influence on decay processes in wood

Acrylics - Influence on decay processes in wood(Reinprecht et al. 2001, Tiralov and Reinprecht 2004)

Wood species

Beech (Fagus sylvatica L.) Spruce (Picea abies /L./ Karst.)

50

25

15

Acrylics Influence on decay processes in wood(Reinprecht et al. 2001, Tiralov and Reinprecht 2004)

Paraloid B-72 (copolymer of methylacrylate and ethylmethacrylate)

transparent granules, soluble in toluene, acetone and some other organic solvents filing of lumina and creation of films on S3 surfaces of wood cell walls

Modification of wood1) Paraloid B-72 (2 % or 10 % toluene solutions P2 or P10)2) Fungicide TCMTB (0.1 % or 0.33 % T0.1 or T0.33)3) Paraloid B-72 + Fungicide TCMTB

MODIFICATIONMETHODS

Paraloid B-72 was applied

1) separately2) together with the TCMTB

fungicide (Busan 1160)a) impregnation with mixture

(Paraloid + TCMTB)b) double impregnation

drying

BEECH WOODSPRUCE WOOD

IMPREGNATION0,8MPa, 180 min, 20 C

weighting, stabilisationdrying

PARALOID TCMTB

TCMTB

mixtureweighting

stabilisation

IMPREGNATION0,8MPa, 180 min, 20 C

PARALOID

R1RTCMTBRPARALOID

R2RPARALOID


Mycological test of modified wood samples Standard EN 113 - duration 16 weeks Resistance against the brown-rot fungi:

Coniophora puteana (Schum. ex. Fr.) Gloeophyllum trabeum (Pers. ex Fr.)

Evaluation by the losses of mass - mF (%)


Mycological test losses of mass of modified beech samplesBEECH WOOD

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Coniophora puteana Gloeophyllum trabeum

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Mycological test losses of mass of modified spruce samplesSPRUCE WOOD

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1.96*Std. Err.1.00*Std. Err.Mean

Gloeophyllum trabeumConiophora puteana

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Conclusions Polyacrylate (Paraloid B-72) do not increased

resistance of wood against brown-rot fungi. Hypothesis: The fungi (C. puteana, G. trabeum) and their enzymes were able to penetrate

through the polyacrylate film on the S3 surface of wood cell walls.

Better results have been achieved if the polyacrylatewas combined with the TCMTB fungicide.

Double impregnation very good effect of the TCMTB. The mass losses of modified beech and spruce wood were obviously close to zero.

Mixture impregnation worse effect of the TCMTB. It was caused probably by blocking of the TCMTB fungicide molecules with the larger polyacrylatemacromolecules.


Strengthening of decayed wood

Acrylics Strengthening of decayed wood(Reinprecht and Varnska 1998, 1999)

Decayed wood species1) Spruce naturally damaged in roof structure

- specimens 500 x 30 x 30 mm (bending test) and 30 x 20 x 20 mm (compression and hardness tests) have been prepared from one 125-year old beam from roof structure in the historical town of Bansk tiavnica, Slovakia

- more or less homogeneously damaged by insect galleries (diameter from 0.5 mm to 2 mm from the family of Anobiidae), and by medium fungal decay due to brown-rot fungi

2) Spruce damaged in laboratory by C. puteana- specimens 120 x 8.5 x 8.5 mm (bending test) have been intentionally damaged by the

brown-rot fungus Coniophora puteana during defined time intervals: 2, 4, 6, 8, or 10 weeks various losses of mass m

Acrylics Strengthening of decayed wood(Reinprecht and Varnska 1998, 1999)

Solakryl BT 55 (polybutylmethacrylate) Its efficiency compared with some other conservation agents

(shellac, epoxy, MF-resin, PEG 1000)

Conservation method

Solution: 27.5 % toluene solution of Solakryl BT 55 Moisture of wood: w ~ 8 % Impregnation: p = 0.8 MPa, t = 20 C, = 3 hours

Acrylics Strengthening of decayed wood(Reinprecht and Varnska 1998)

Conservation of naturally damaged spruce

Bending MOE Compression II Brinell hardness

-40-20

020406080

100120140160

MF - resin SolakrylBT 55

PEG 1000

[%]

-40-20

020406080

100120140160


PEG 1000

[%]

-500

50100150200250300350400450


PEG 1000

[%]


Conclusions No 1

Solakryl BT 55,R-[CH2-C(CH3)-COOC4H9]n -X

had a slightly positive effect on the mechanical properties of biodamaged spruce wood:- modulus of elasticity,- compression strength parallel to grain,- hardness.


Conservation of spruce decayed by C. puteana

SPRUCE DEGRADED BY CONIOPHORA PUTEANA MOEd = 3.4497 m (R = 0.8165) n = 50

Loss of mass - m [%]

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Conservation of spruce decayed by C. puteana


Conclusions No 2

Solakryl BT 55,R-[CH2-C(CH3)-COOC4H9]n -X

slightly increased the MOE of spruce woodintentionally damaged by the brown-rot fungus Coniophora puteana.


Stabilization of wood surfaces

Acrylics Stabilization of wood surfaces (Mamoov and Reinprecht 2008)

Wood speciesLarch wood (Larix decidua Mill.)Spruce wood (Picea abies /L./ Karst.)

Acrylic coatings

Tikkurila OY FinlandValtti Colour Card

1) Basic layer

2) 2 x Surface layers


Natural ageing1) One year exposition in exterior under 902) One year exposition in interior

Evaluation I.) Microscopic analyses REM (TESCAN VEGA TS 5130)

a) penetration of the coatings into wood b) defects in the coatingsc) changes in the thickness of the coatings

II.) Colour analyses - spectrophotometer (MINOLTA CM2600d)a) CIELAB changes in the L*a*b* colour spaceb) Spectra and differential spectra


Microscopic analyses penetration, defects, thickness of coatingsFig. 1 Detail of the sample T3 = T/(3147) / Piceaabies penetration of the coating into early wood tracheids; cross-section of the coating is inconsistent

Fig. 2 The surface and the cross-section of the sample T4 = T/(Interior)/ Picea abies bubbles in the coating; penetration into early wood tracheids; Thickness: h ~ 130 m


Microscopic analyses penetration, defects, thickness of coatingsFig. 4 Surface of the sample T2 = T/(3151 -Exterior)/ Picea abies smooth surface of the coating with frequent bubble occurrence; edges of the bubbles are sharply defined

Fig. 3 The cross-section of the sample T2 = T/(3151 - Exterior) / Picea abies bubbles in the coating; Thickness: h ~ 95 m


Microscopic analyses thickness of coatings after 1-year ageing

710,375,987,81Coefficient of variation [%]

13101210Object Count

141,3100,1103,8108,1Maximal value

104,575,0986,2686,29Minimal value

9,039,055,677,46Standard deviation

129,1087,2494,8395,53Mean value

T4(Interior)T3(3147)T2(3151)T1(3151)

TYPE OF SURFACE TREATMENT WITH ACRYLICSTHICKNESS OF THE COATING AFTER 1-YEAR AGEING

[m]


Colour analyses differential spectra of acrylics after 1-year ageingT1 acrylic on larch in exteriorT2, T3 acrylics on spruce in exteriorT4 acrylic on spruce in interior

-60

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0350 400 450 500 550 600 650 700 750

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DIF_T1 DIF_T2 DIF_T3 DIF_T4AVG_DIF_T1 AVG_DIF_T2 AVG_DIF_T3 AVG_DIF_T4


Conclusions Acrylic paints partly penetrated into tracheids of early

wood of coniferous.

Quality of the aged paints valued by their:- microscopic structure (bubbles, cracks), - thickness decreases, - colour changes,

was influenced by more factors: - the wood species, - the type of basic paints,

- the interior or exterior exposition.


Conservation of wooden sculptures

Acrylics Conservation of wooden sculptures(Reinprecht 1991)

Two iconsLime tree (Tillia sp.)PolychromyLength: 620 or 670 mmWeight: 2 873 or 2 608 gDamaged by insect galleries (Anobium punctatum) and brown-rot


Solakryl BT 55 (polybutylmethacrylate) filing of lumina and creation of films on S3 surfaces of wood cell walls 22,5 % toluene solution

Conservation method Impregnation: p = 0.6 MPa, t = 20 C, = 90 min

(1 = 15 min, 2 = 30 min, 3 = 45 min) Conditioning: = 45 days, t = 20 2 C, = 50 3 %


Retention m (%) of 22.5 % Solakryl BT 55 into icons_________________________________________________

1. icon 2. iconImpregnation: 1 = 15 min 107.3 125.32 = 30 min 133.7 137.8 3 = 45 min 141.0 144.3 Conditioning: 15 days 66.0 43.645 days 36.6 34.0

Theoretical solids 31.7 32.5


Microscopic analysesThe polyacrylate integrated the wooden spilling dust inside the corridors and prevented it from falling out, and partially also strengthened the cells damaged with rot.


Conclusions Polyacrylate (Solakryl BT 55) integrated and

partly strengthened the bio-damaged sculptures from lime tree.

Evaporation of toluene from conserved sculptures is a long process it can last 2 months.

References to experiments

Reinprecht L (1991): Retaurovanie pokodenho dreva polyakryltmi, epoxidmi, fenoplatmi a aminoplastmi. (Restoring of damaged wood with polyacrylates, epoxides, phenoplasts and aminoplasts) In: Pokroky vo vrobe a pouit lepidiel v drevopriemysle, 10. Sympzium, VLD Zvolen Czechoslovakia, p. 312-325.

Reinprecht L, Varnska S (1998): Bending properties, compression strength and hardness of wood modified with synthetic polymers. In: Wood Structure and Properties, 3rd International Symposium, Arbora Publishers Zvolen Slovakia, p. 157-162.

Reinprecht L, Varnska S (1999): Bending properties of wood after its decay with Coniophora puteanaand subsequent modification with selected chemicals. In: International Research Group on Wood Preservation, Section 4 Wood Protecting Chemicals, 30th Annual Meeting in Rosenheim - Germany, IRG/WP/99-40146, 11 p.

Reinprecht L, Tiralov Z, imekov M (2001): Hniloba dreva konzervovanho akryltmi. (The rot of wood conserved by acrylates). In: Sbornk z konzervtorskho a restaurtorskho semine, eskBudjovice - Czech Republic, p. 46-49.

Tiralov Z, Reinprecht L (2004): Fungal decay of acrylate treated wood. In: International Research Group on Wood Preservation, 35th Annual Meeting, Section 3 Wood Protecting Chemicals, Ljubljana - Slovenia, IRG/WP/04-30357, 7 p.

Mamoov M, Reinprecht L. (2008): truktra a farba akryltovch nterov po ronej expozcii v exteriri a interiri. (Structure and colour of acrylate coating after inner and outer yearlong exposition) In: Interaction of Wood with Various Forms of Energy, TU Zvolen - Slovakia, p. 91-97.

Ladislav Reinprecht: CONSERVATION OF WOOD WITH ACRYLICS CONSERVATION OF WOOD WITH ACRYLICS -- selected experimentsselected experiments

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Conservation of wood with Acrylics

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