نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 دانشجوی کارشناسی ارشد گروه مهندسی چوب و فرآورده های سلولزی، دانشکده منابع طبیعی، دانشگاه علوم کشاورزی و منابع طبیعی، ساری، ایران
2 دانشیار گروه مهندسی چوب و فرآورده های سلولزی، دانشکده منابع طبیعی، دانشگاه علوم کشاورزی و منابع طبیعی، ساری، ایران.
3 استادیار/ دانشکده منابع طبیعی، دانشگاه کشاورزی و منابع طبیعی ساری
4 استاد گروه مهندسی چوب و فرآورده های سلولزی، دانشکده منابع طبیعی، دانشگاه علوم کشاورزی و منابع طبیعی، ساری، ایران
5 دانشیار گروه مهندسی چوب و فرآورده های سلولزی، دانشکده منابع طبیعی، دانشگاه علوم کشاورزی و منابع طبیعی، ساری، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and objectives: One approach to fabricating natural fiber-reinforced composites that preserves fiber alignment and enhances overall properties, involves partial delignification of wood followed by resin impregnation. The partial delignification of wood structure can facilitate monomer penetration into the cell wall and enable reactions with carbohydrates. Some delignification methods, such as alkaline sulfite-methanol, and ASAM (Alkaline Sulfite Anthraquinone Methanol), are preferred over conventional processes (soda and Kraft) due to advantages including less carbohydrate degradation and lower environmental impact. This study aimed to comparatively investigate the effects of different partial delignification methods followed by phenol–formaldehyde resin impregnation on the mechanical properties and dimensional stability of paulownia wood.
Materials and methods: Samples obtained from fast-growing paulownia wood were subjected to partial delignification using three methods—alkaline sulfite, alkaline sulfite-methanol, and ASAM—followed by impregnation with phenol-formaldehyde resin. Weight loss and Klason lignin were measured after the delignification pretreatment. Weight percent gain (WPG) following resin impregnation, as well as changes in chemical structure by Fourier Transform Infrared Spectroscopy, physical properties, and mechanical performance of the resulting composite, were subsequently evaluated.
Results: Based on the results, ASAM delignification, with higher lignin removal compared to sulfite-methanol and sulfite methods, led to greater penetration of phenol-formaldehyde resin into the wood samples. Fourier transform infrared (FTIR) spectroscopy in the sulfite-delignified samples confirmed the formation of ether bonds between the hydroxyl groups of wood and the phenol-formaldehyde resin, while in the Asam-delignified samples, self-condensation of the resin without ether bond formation was evident. The best physical properties were observed in the ASAM-delignified samples (48% improvment in water-repellent efficiency and 160% increase in anti-swelling efficiency compared to the control sample). Impregnation with phenol formaldehyde following alkaline sulfite and ASAM delignification resulted in a 12% increase and 49% decrease in bending strength respectively, compared to the control sample impregnated with resin. The removal of lignin from the wood, as the main factor creating cell wall rigidity, in the ASAM-delignified samples caused a decrease in bending modulus and elasticity, which was not compensated by the formation of a three-dimensional phenol-formaldehyde polymer network in the wood structure.
Conclusion: The ASAM process, by effectively removing lignin while maintening cellulose, exhibited the best performance in enhancing physical properties. However, despite retaining the highest amount of resin, it showed the lowest bending properties and modulus of elasticity. In contrast, the alkaline sulfite process, despite its weaker performance in improving dimensional stability, yielded the highest bending strength. Since the method and extent of delignification affect the strength of wood, careful selection of the delignification method and optimization of its efficiency are essential for improving the properties of the final product.
کلیدواژه‌ها [English]
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