Chemical and physical changes in paints or painted wood due to ageing: Dissertation

Pirjo Ahola

Research output: ThesisDissertation

Abstract

Repainting exterior cladding has been estimated to be one of the highest costs in the maintenance of small wooden houses over a long-term period (80 years) because of the relatively short interval of painting. Reportedrot damage in wooden exterior cladding in Norway and Sweden raised the question of the part played by paints in the damage. Consequently, many studies on the problem of the durability and performance of painted wood have been started in Nordic laboratories and institutes. The aim of this study was to analyze chemical and physical changes in paint and painted wood due to ageing. The paints were experimental products based on alkyd, acrylate and oil binders, which are the most widely used in coatings for wooden substrate. Chemical changes were analyzed by Fourier transform infrared spectroscopy. In addition to the chemistry of ageing, the flexibility of the paints, the condition and moisture transport properties of the painted wood and the adhesion between the paints and the substrate were monitored vs. ageing. The painted specimens were subjected to both artificial exposure in a weathering device and to natural exposure. Only the influence of relatively short-term artificial ageing periods (250 h, 500 h and 1000 h) and natural ageing for 1 - 2 years were included in this study. The unpigmented stains failed during the longest exposure. The ultraviolet stabilizer in the stain did not give any longer-term protection against light. The alkyd and oil paints underwent various chemical changes due to their susceptibility to auto-oxidation reactions of carbon-carbon double bonds along the fatty acid chain. The drier containing zirconium accelerated crosslinking reactions more than the lead drier in the alkyd paints. The acrylate paints were relatively inert to external stresses. The changes in moisture transport properties of the acrylate emulsion paints were probably due to the migration of smaller molecules. The cracking tendency of the combination paints based on the alkyd and acrylate binders was assessed to result from their relatively high water permeation properties, which caused cracking in the wood substrate and thus internal stresses in the paint film itself. The cracking of the solvent-borne paints was suggested to be due to the very low flexibility of the paint.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • University of Helsinki
Supervisors/Advisors
  • Sundholm, Franciska, Supervisor, External person
Award date19 Nov 1993
Place of PublicationEspoo
Publisher
Print ISBNs951-38-4393-9
Publication statusPublished - 1993
MoE publication typeG4 Doctoral dissertation (monograph)

Fingerprint

paints
cracking
dyes
oils
carbon
Fourier transform infrared spectroscopy
durability
crosslinking
weathering
automobiles
films (materials)
coatings
emulsions
Norway
adhesion
Sweden
chemistry

Keywords

  • chemical properties
  • physical properties
  • revisions
  • paints
  • painting
  • coatings
  • cladding
  • wood
  • wooden structures
  • walls
  • external walls
  • weathering
  • life (durability)
  • renovating
  • repairs
  • small houses
  • damage
  • deterioration
  • spectroscopy
  • moisture
  • adhesion
  • light (visible radiation)
  • cracking (fracturing)

Cite this

Ahola, P. (1993). Chemical and physical changes in paints or painted wood due to ageing: Dissertation. Espoo: VTT Technical Research Centre of Finland.
Ahola, Pirjo. / Chemical and physical changes in paints or painted wood due to ageing : Dissertation. Espoo : VTT Technical Research Centre of Finland, 1993. 94 p.
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abstract = "Repainting exterior cladding has been estimated to be one of the highest costs in the maintenance of small wooden houses over a long-term period (80 years) because of the relatively short interval of painting. Reportedrot damage in wooden exterior cladding in Norway and Sweden raised the question of the part played by paints in the damage. Consequently, many studies on the problem of the durability and performance of painted wood have been started in Nordic laboratories and institutes. The aim of this study was to analyze chemical and physical changes in paint and painted wood due to ageing. The paints were experimental products based on alkyd, acrylate and oil binders, which are the most widely used in coatings for wooden substrate. Chemical changes were analyzed by Fourier transform infrared spectroscopy. In addition to the chemistry of ageing, the flexibility of the paints, the condition and moisture transport properties of the painted wood and the adhesion between the paints and the substrate were monitored vs. ageing. The painted specimens were subjected to both artificial exposure in a weathering device and to natural exposure. Only the influence of relatively short-term artificial ageing periods (250 h, 500 h and 1000 h) and natural ageing for 1 - 2 years were included in this study. The unpigmented stains failed during the longest exposure. The ultraviolet stabilizer in the stain did not give any longer-term protection against light. The alkyd and oil paints underwent various chemical changes due to their susceptibility to auto-oxidation reactions of carbon-carbon double bonds along the fatty acid chain. The drier containing zirconium accelerated crosslinking reactions more than the lead drier in the alkyd paints. The acrylate paints were relatively inert to external stresses. The changes in moisture transport properties of the acrylate emulsion paints were probably due to the migration of smaller molecules. The cracking tendency of the combination paints based on the alkyd and acrylate binders was assessed to result from their relatively high water permeation properties, which caused cracking in the wood substrate and thus internal stresses in the paint film itself. The cracking of the solvent-borne paints was suggested to be due to the very low flexibility of the paint.",
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author = "Pirjo Ahola",
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Ahola, P 1993, 'Chemical and physical changes in paints or painted wood due to ageing: Dissertation', Doctor Degree, University of Helsinki, Espoo.

Chemical and physical changes in paints or painted wood due to ageing : Dissertation. / Ahola, Pirjo.

Espoo : VTT Technical Research Centre of Finland, 1993. 94 p.

Research output: ThesisDissertation

TY - THES

T1 - Chemical and physical changes in paints or painted wood due to ageing

T2 - Dissertation

AU - Ahola, Pirjo

N1 - Project code: PUU2010

PY - 1993

Y1 - 1993

N2 - Repainting exterior cladding has been estimated to be one of the highest costs in the maintenance of small wooden houses over a long-term period (80 years) because of the relatively short interval of painting. Reportedrot damage in wooden exterior cladding in Norway and Sweden raised the question of the part played by paints in the damage. Consequently, many studies on the problem of the durability and performance of painted wood have been started in Nordic laboratories and institutes. The aim of this study was to analyze chemical and physical changes in paint and painted wood due to ageing. The paints were experimental products based on alkyd, acrylate and oil binders, which are the most widely used in coatings for wooden substrate. Chemical changes were analyzed by Fourier transform infrared spectroscopy. In addition to the chemistry of ageing, the flexibility of the paints, the condition and moisture transport properties of the painted wood and the adhesion between the paints and the substrate were monitored vs. ageing. The painted specimens were subjected to both artificial exposure in a weathering device and to natural exposure. Only the influence of relatively short-term artificial ageing periods (250 h, 500 h and 1000 h) and natural ageing for 1 - 2 years were included in this study. The unpigmented stains failed during the longest exposure. The ultraviolet stabilizer in the stain did not give any longer-term protection against light. The alkyd and oil paints underwent various chemical changes due to their susceptibility to auto-oxidation reactions of carbon-carbon double bonds along the fatty acid chain. The drier containing zirconium accelerated crosslinking reactions more than the lead drier in the alkyd paints. The acrylate paints were relatively inert to external stresses. The changes in moisture transport properties of the acrylate emulsion paints were probably due to the migration of smaller molecules. The cracking tendency of the combination paints based on the alkyd and acrylate binders was assessed to result from their relatively high water permeation properties, which caused cracking in the wood substrate and thus internal stresses in the paint film itself. The cracking of the solvent-borne paints was suggested to be due to the very low flexibility of the paint.

AB - Repainting exterior cladding has been estimated to be one of the highest costs in the maintenance of small wooden houses over a long-term period (80 years) because of the relatively short interval of painting. Reportedrot damage in wooden exterior cladding in Norway and Sweden raised the question of the part played by paints in the damage. Consequently, many studies on the problem of the durability and performance of painted wood have been started in Nordic laboratories and institutes. The aim of this study was to analyze chemical and physical changes in paint and painted wood due to ageing. The paints were experimental products based on alkyd, acrylate and oil binders, which are the most widely used in coatings for wooden substrate. Chemical changes were analyzed by Fourier transform infrared spectroscopy. In addition to the chemistry of ageing, the flexibility of the paints, the condition and moisture transport properties of the painted wood and the adhesion between the paints and the substrate were monitored vs. ageing. The painted specimens were subjected to both artificial exposure in a weathering device and to natural exposure. Only the influence of relatively short-term artificial ageing periods (250 h, 500 h and 1000 h) and natural ageing for 1 - 2 years were included in this study. The unpigmented stains failed during the longest exposure. The ultraviolet stabilizer in the stain did not give any longer-term protection against light. The alkyd and oil paints underwent various chemical changes due to their susceptibility to auto-oxidation reactions of carbon-carbon double bonds along the fatty acid chain. The drier containing zirconium accelerated crosslinking reactions more than the lead drier in the alkyd paints. The acrylate paints were relatively inert to external stresses. The changes in moisture transport properties of the acrylate emulsion paints were probably due to the migration of smaller molecules. The cracking tendency of the combination paints based on the alkyd and acrylate binders was assessed to result from their relatively high water permeation properties, which caused cracking in the wood substrate and thus internal stresses in the paint film itself. The cracking of the solvent-borne paints was suggested to be due to the very low flexibility of the paint.

KW - chemical properties

KW - physical properties

KW - revisions

KW - paints

KW - painting

KW - coatings

KW - cladding

KW - wood

KW - wooden structures

KW - walls

KW - external walls

KW - weathering

KW - life (durability)

KW - renovating

KW - repairs

KW - small houses

KW - damage

KW - deterioration

KW - spectroscopy

KW - moisture

KW - adhesion

KW - light (visible radiation)

KW - cracking (fracturing)

M3 - Dissertation

SN - 951-38-4393-9

T3 - VTT Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Ahola P. Chemical and physical changes in paints or painted wood due to ageing: Dissertation. Espoo: VTT Technical Research Centre of Finland, 1993. 94 p.