Personne : Landry, Véronic
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Landry
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Véronic
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Université Laval. Département des sciences du bois et de la forêt
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Publication Restreint Weathering of wood coated with semi-clear coating : study of interactions between photo and biodegradation(Elsevier, 2018-02-07) Landry, Véronic; Cogulet, Antoine; Blanchet, Pierre; Morris, PaulIn order to clarify the relationship between photodegradation and biological degradation, wood specimens finished with a semi-clear coating were degraded under a xenon lamp for different periods of time. The specimens were then inoculated one of two black stain fungi (Aureobasidium pullulans and Epicoccum nigrum). Colonization was monitored visually and by colorimetric analyses. The extent and the nature of the degradation were evaluated using different techniques. The chemical composition was studied by Fourier Transform Infrared Spectroscopy (FTIR) and the physical changes by both microscopic analyses and adhesion tests. The results obtained from FTIR did not provide relevant information. Coating thickness and adhesion were found to decrease as photodegradation increased. Microscope observations detected numerous bubbles trapped in the coating films. These bubbles were found to become holes following photodegradation and the decrease in coating thickness. It was established that more severe photodegradation led to more extensive colonization of the specimens. The fungi seemed to use transpressorium to go through the protective layer and take advantage of organic matter present at the wood/coating interface. Funguscolonization was also found to decrease the coating adhesion in the early stages of the exposure process.Publication Accès libre Evaluation of the impacts of four weathering methods on two acrylic paints : showcasing distinctions and particularities(Rogers Publishing Ltd., 2019-02-15) Landry, Véronic; Cogulet, Antoine; Blanchet, PierreTwo commercial waterborne wood acrylic paints were applied to wood samples and the weathering resistance of samples was tested using four different weathering methods: outdoor exposure in Arizona (USA), Florida (USA), and the province of Quebec (Canada), and accelerated weathering in a QUV (fluorescent) weatherometer. Degradation was characterised by colorimetric and FTIR analyses. FTIR confirmed the importance of paint composition in the resistance of samples to weathering. Polymer sensitivity to UV radiation was clearly evident. An interpretation of discoloration in terms of either the energy received by the samples or the length of exposure is presented. Strong differences existed between the four weathering methods. Particularities of each method are discussed and recommendations regarding their application for effective testing are proposed. Overall, in addition to accelerated weathering tests, we conclude that it is necessary to test paints in an end-use environment for accurate assessment of their likely performance. This study confirms the multifactorial aspect of the weathering process.Publication Restreint Wood degradation under UV irradiation : a lignin characterization(Elsevier, 2016-03-06) Landry, Véronic; Cogulet, Antoine; Blanchet, PierreThe photodegradation of white spruce by artificial ageing was studied by several techniques: colourimetry, FTIRATR and FT-Raman spectroscopy. Samples were exposed at a xenon lamp for 2000 h. Two distinct colour changes were found by colourimetric analysis, yellowing and silvering. These colour modifications indicate the formation of chromophoric structures which supports previous FTIR-ATR experiments. The degradation of lignin to generate the first chromophoric group for yellowing and then the appearance of surface layer cellulose. New carbonyl compounds conjugated with double bond at 1615 cm-1 are probably the second chromophoric group. The crystallinity index was also calculated and showed an increase of cellulose crystallinity by prior degradation of amorphous cellulose. The FT-Raman analysis confirms the wood sensitivity to photodegradation but the most remarkable results is the increase of fluorescence as a function of time. In softwood lignin, the compound able to produce fluorescence is a free rotating 5–5' linkage of one biphenyl structure. At native state these linkages are not free rotating, this phenomenon means the release of 5–5' linkage of lignin structure by cleavage of both a carbon linkages (Norrish type I reaction). These data confirm also the photosensitivity of a and ß carbon in lignin and the resistance of 5–5' linkages.Publication Accès libre The multifactorial aspect of wood weathering : a review based on a holistic approach of wood degradation protected by clear coating.(North Carolina State University. College of Natural Resources, 2017-11-22) Landry, Véronic; Cogulet, Antoine; Blanchet, PierreWood is an abundant and renewable natural resource. Its use is promoted as a way to reduce the carbon footprint in building construction. Wood structures are degraded by their environment due to weathering. This review is a meta-analysis of the main factors of degradation that belong to this phenomenon. The impact of irradiation, the role of water, oxygen, temperature, and colonization by fungi are explained. To protect against these factors, the use of coatings is the most common solution. Since currently the trend is to maintain the grain and the natural color of the wood, the use of transparent coatings is favored. This review presents the main technologies used in clear wood coatings. The durability of this protection against weathering is approached. The whole of knowledge gathered has made it possible to begin a discussion on the multifactorial aspect of wood weathering. Schemes were created to synthesize the synergistic and antagonistic effects between the degradation factors.