Effect of Delignification Pretreatment and Furfurylation on Practical Properties of Alder Wood (Alnus spp.)

Abstract

Partial delignification of alder wood specimens was performed with alkaline sulfite and peracetic acid (PAA) methods, and subsequently the delignified samples were saturated with furfuryl alcohol, as an eco-friendly chemical. The aim of delignification before furfurylation was to facilitate the penetration of furfuryl alcohol into the cell wall, in order to overcome the weak mechanical properties and hydrophilicity of alder wood as a fast growing species. The results showed that alkaline delignification removed a lower percentage of lignin despite more significant mass loss as compared to peracetic acid delignification method, which indicates more carbohydrates degradation in alkaline delignification. Infrared spectroscopy also confirmed more retention of carbohydrates in the sample delignified with peracetic acid. The polymerization of furfuryl alcohol in the cell cavities decreased the access of water molecules to the hydroxyl groups of the cell wall, increased the contact angle, and decreasing surface wettability. This effect was more noticeable in the PAA-delignified samples. Mechanical tests revealed that the delignified samples with peracetic acid had higher mechanical strength and modulus, compared to the alkaline sulfite delignified samples. This was attributable to the maintenance of carbohydrates during the delignification process.