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Difficulties to combine biological degradation factors with artificial weathering

Difficulties to combine biological degradation factors with artificial weathering Focussing on how to measure and evaluate. Introduction. Standardised methods: European: EN 927 International: ISO  Problems: critical values. performance assessment. Introduction.

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Difficulties to combine biological degradation factors with artificial weathering

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  1. Difficulties to combine biological degradation factors with artificial weathering Focussing on how to measure and evaluate

  2. Introduction • Standardised methods: • European: EN 927 • International: ISO •  Problems: critical values performance assessment

  3. Introduction • Natural weathering, CEN/TC139/WG2: • accelerated natural exposure • Climatic Index • + mimicry • - transfer of biological degradation patterns • Artificial ageing: • UVS equipment (UV-CON, QUV with spray option) • Wheater-O-meter (WOM) • + fast • - physico-mechanical

  4. Introduction • Solution: • combined or sequential testing of physico-mechanical and biological ageing • short-term • critical levels • special focus on biological performance

  5. Weathering and assessment • Natural weathering: • - mimicry • disadvantages: • weather • sample variability • harmonisation of specimens and exposition • disadvantages: • macro- and microclimate

  6. Weathering and assessment • Artificial weathering: • higher reproducibility • more confidence in: • machines • ageing cycles • less time consuming • better control

  7. UV light water spray cold period dark & dry

  8. Weathering and assessment • Assessment parameters: • chalking • flaking • blistering • cracking • adhesion Not necessary critical for all coatings • degradation phenomena on wood ‘missing’: • biological • erosion • additional

  9. Weathering and assessment • Needs for methodology: • optimisation • prioriy of parameters • substrate: • hardwood  softwood • porosity, vessel grouping • dimensional stability • extractives • sample size: boards  window frame corners

  10. Biological factors Biological factors can be essential part of paint degradation:

  11. Biological factors Biological factors can be essential part of paint degradation:

  12. Biological factors • Standard tests: prEN927 3-5, EN152 • artificial weathering Alternative tests: • susceptibility • fungal growth on, through, in the coating and the substrate • impact analysis

  13. Biological factors Additional parameters: • film thickness • water and water vapour permeability • porosity • surface roughness

  14. Blue stain testing Blue stain testing basics EN152: + WOM • coating not on the vermiculite medium (contact with uncoated side) • Aureobasidium pullullans and Sclerophoma pithyophila • evaluation of surface blue staining and zone free of blue stain

  15. Blue stain testing Reversed method: • coating on the vermiculite medium, other sides sealed • Aureobasidium pullullans and Sclerophoma pithyophila • evaluation of surface blue staining and interior presence of blue stain

  16. Blue stain testing Internal presence of blue stain in service: not just a blue free zone

  17. Conclusions • Modern coatings: low VOC + low biocidal content • Increased impact of biological factors • Yearly changes in impact of biological coating degradation • Reproducible testing: artificial ageing + laboratory test method • Artificial ageing should be specific for wood • Wood coatings mainly fail due to moisture impact (swelling / shrinkage) • Blue stain in service testing of coatings differs testing fungicidal impact • Modern water- borne wood coatings should be able to • resist biological factors... • by means non-biocidal components or parameters...

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