The pulp and paper industry generates substantial amounts of solid waste and wastewater, which contain waste fibres. The potential of using these recycled wood fibres for producing eco-friendly composites that were bonded with a formaldehyde-free adhesive (magnesium lignosulfonate) and their use in structural applications was evaluated in this study. Fibreboards were produced in the laboratory with a density of 720 kg·m⁻³ and 15% magnesium lignosulfonate gluing content, based on the dry fibres. The mechanical properties (bending strength, modulus of elasticity and internal bond strength), physical properties (thickness swelling and water absorption) and formaldehyde content were determined and compared with the European Standards requirements for wood-based panels. In general, the laboratory-produced panels demonstrated acceptable mechanical properties, such as bending strength (18.5 N·mm⁻²) and modulus of elasticity (2225 N·mm⁻²), which were higher than the minimum requirements for type P2 particleboards and equal to the requirements for MDF panels. The moisture properties, i.e., thickness swelling (24 h) and water absorption (24 h) significantly deteriorated. The free formaldehyde content of the laboratory-produced composites (1.1 mg/100 g) reached the super E0 grade (≤1.5 mg/100 g), which allowed for their classification as eco-friendly, low-emission wood-based composites. The L-type corner joints, made from the developed composites, demonstrated significantly lower bending capacity (from 2.5 to 6.5 times) compared to the same joints made from MDF panels. Nevertheless, the new eco-friendly composites can be efficiently utilised as a structural material in non-load-bearing applications.

中文翻译：

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木质素磺酸镁粘结的再生木纤维环保复合材料的结构应用

纸浆和造纸工业产生大量的固体废物和废水，其中包含废物纤维。在这项研究中，评估了使用这些再生木纤维生产与无甲醛粘合剂（木质素磺酸镁）粘合的环保复合材料的潜力及其在结构应用中的用途。实验室生产的纤维板密度为720 kg·m ^-3基于干纤维的木质素磺酸镁胶合含量为15％。确定了机械性能（弯曲强度，弹性模量和内部粘合强度），物理性能（厚度膨胀和吸水率）和甲醛含量，并将其与欧洲标准对人造板的要求进行了比较。通常，实验室生产的面板显示出可接受的机械性能，例如弯曲强度（18.5 N·mm ^-2）和弹性模量（2225 N·mm ^-2）），高于P2型刨花板的最低要求，并且等于MDF面板的要求。水分性质，即厚度膨胀（24h）和吸水率（24h）显着降低。实验室生产的复合材料中的游离甲醛含量（1.1 mg / 100 g）达到E0级（≤1.5mg / 100 g），可以归类为环保，低排放的木质复合材料。与由MDF面板制成的相同接缝相比，由开发的复合材料制成的L型角接缝具有明显更低的弯曲能力（从2.5到6.5倍）。然而，新型环保复合材料可以有效地用作非承重应用中的结构材料。