Study of structural changes in the surface of white poplar wood (Populus alba L.) under accelerated weathering

Weathering is the main degradation factor of wood surface in open air spaces. Understanding of its mechanism in different woods has a great importance for wood conservation. Regarding to developed application of white poplar wood (Populus alba L.) in open air spaces, structural changes of its biopolymers was studied under accelerated weathering after 300 and 800 hours. Mass losses were measured after weathering levels. Aesthetic properties were assessed by colorimetery. Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were applied for investigation of chemical and morphological characteristics respectively. Results showed the intensive aesthetic variations after both levels of weathering. It signified the production of new chromophores and increase of carbonyl groups due to lignin decomposition. Degradation of guaiacyl unit detected more severe compared to syringyl unit of lignin. Cellulose content was decreased after weathering procedures. The degradation had been focused in amorphous cellulose after 300 hours. Mass losses data indicated to leaching of degradation products from the surface of weathered wood samples. Defibrillation and fiber fractures confirmed the decomposition of lignin in middle lamella layer and chain scission of cellulose in cell wall due to weathering effects.