Younesi-Kordkheili Hamed, Pizzi Antonio
Department of Wood and Paper Sciences and Technology, Faculty of Natural Resources, Semnan University, Semnan 35131-19111, Iran.
LERMAB-ENSTIB, University of Lorraine, 27 rue Philippe Seguin, 88000 Epinal, France.
Polymers (Basel). 2021 Oct 12;13(20):3502. doi: 10.3390/polym13203502.
The research aim of this work is to determine the influence of lignin modification methods on lignin-phenol-formaldehyde (LPF) adhesive properties. Thus, glyoxal (G), phenol (P), ionic liquid (IL), and maleic anhydride (MA) were used to modify lignin. The modified lignins were used for phenol substitution (50 wt%) in phenol-formaldehyde adhesives. The prepared resins were then used for the preparation of wood particleboard. These LPF resins were characterized physicochemically, namely by using standard methods to determine gel time, solids content, density, and viscosity, thus the physicochemical properties of the LPF resins synthesized. The panels dimensional stability, formaldehyde emission, bending modulus, bending strength, and internal bond (IB) strength were also measured. MA-modified lignin showed by differential scanning calorimetry (DSC) the lowest temperature of curing than the resins with non-modified lignin and modified with IL, phenolared lignin, and glyoxal. LPF resins with lignin treated with maleic anhydride presented a shorter gel time, higher viscosity, and solids content than the resins with other lignin modifications. Equally, the particleboard panels prepared with LPF resins with maleic anhydride or with ionic liquid had the lowest formaldehyde emission and the highest mechanical strength among all the synthesized resins. The dimensional stability of all panels bonded with modified lignin LPF resins presented no difference of any significance.
本研究的目的是确定木质素改性方法对木质素-酚醛（LPF）胶粘剂性能的影响。因此，使用乙二醛（G）、苯酚（P）、离子液体（IL）和马来酸酐（MA）对木质素进行改性。改性木质素用于酚醛胶粘剂中50 wt%的苯酚替代。然后将制备的树脂用于制备刨花板。这些LPF树脂通过物理化学方法进行表征，即使用标准方法测定凝胶时间、固体含量、密度和粘度，并以此来表征合成的LPF树脂的物理化学性质。还测量了板材的尺寸稳定性、甲醛释放量、弯曲模量、弯曲强度和内结合（IB）强度。通过差示扫描量热法（DSC）测定，与未改性木质素以及用IL、酚化木质素和乙二醛改性的树脂相比,MA改性木质素表现出最低固化温度；与其他木质素改性的树脂相比，用马来酸酐处理的木质素LPF树脂凝胶时间更短、粘度更高且固体含量更高；同样，用马来酸酐或离子液体的LPF树脂制备的刨花板在所有合成树脂中甲醛释放量最低且机械强度最高；所有用改性木质素LPF树脂粘结的板材的尺寸稳定性均无显著差异。
