Abstract
The main aim of the presented research was to compare the influence of selected ageing factors, such as UV radiation and complex artificial weathering methods, on the colour, wettability and roughness changes in garapa, tatajuba, courbaril and massaranduba from South America—tropical wood species that are popular for external usage in European countries. Both processes caused wood surfaces to become darker and turn to shades of brown. The highest total colour changes were shown in courbaril wood (wood with the highest extractives content). The wood surface roughness demonstrated variation, depending on the wood section and measurement direction, and increased after ageing treatments. Changes in surface contact angle were significant after the inclusion of water and drying in the weathering process (wettability decreased). Anatomical analyses of the tested tropical woods revealed structural changes after used artificial weathering treatments (distortion between cell elements, degradation of the middle lamella, micro-cracks in cell walls, thinning and degradation of parenchyma cells, cracks along pits within vessels). As a result of desorption tension, the changes caused by UV irradiation were much smaller than those caused by full artificial weathering. Fourier-transform infrared spectroscopy (FTIR) analysis indicated the occurrence of lignin and hemicelluloses oxidative changes after the weathering process which resulted in the formation of carbonyl and carboxyl compounds. The depolymerisation of cellulose was also identified. The results show that the observed changes may affect the long-term durability of finishes applied over wood subjected to weathering factors for a short period before finishing.
Highlights
During the external exposure of wood there are some key procedures which should be followed to reduce the effects of weathering
The previous studies conducted on softwoods [35], and tropical wood species as well [36], confirmed that the most rapid changes in ∆E* occurred during the first stages of UV radiation
Similar observations were made by Mamoňová and Reinprecht [44], who tested tropical wood species weathered in natural conditions
Summary
During the external exposure of wood there are some key procedures which should be followed to reduce the effects of weathering. The natural weathering was defined as a process of irreversible changes to the appearance and properties of wood effected by the long-term impact of outdoor factors, such as the solar radiation, air and oxygen contained within it, and changes in the temperature and humidity (no direct influence of biotic factors should be assumed) [1,2,3,4,5,6,7] This complex phenomenon is caused by solar radiation, hydrolysis, and the leaching of wood components [8,9,10]. Chev.) wood species, as these are popular for external usage in European countries
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
