Abstract
The potential of using residual softwood fibers from the pulp and paper industry for producing eco-friendly, zero-formaldehyde fiberboard panels, bonded with calcium lignosulfonate (CLS) as a lignin-based, formaldehyde free adhesive, was investigated in this work. Fiberboard panels were manufactured in the laboratory by applying CLS addition content ranging from 8% to 14% (on the dry fibers). The physical and mechanical properties of the developed composites, i.e., water absorption (WA), thickness swelling (TS), modulus of elasticity (MOE), bending strength (MOR), as well as the free formaldehyde emission, were evaluated according to the European norms. In general, only the composites, developed with 14% CLS content, exhibited MOE and MOR values, comparable with the standard requirements for medium-density fiberboards (MDF) for use in dry conditions. All laboratory-produced composites demonstrated significantly deteriorated moisture-related properties, i.e., WA (24 h) and TS (24 h), which is a major drawback. Noticeably, the fiberboards produced had a close-to-zero formaldehyde content, reaching the super E0 class (≤1.5 mg/100 g), with values, ranging from 0.8 mg/100 g to 1.1 mg/100 g, i.e., equivalent to formaldehyde emission of natural wood. The amount of CLS adhesive had no significant effect on formaldehyde content.
Highlights
This study demonstrated that wood and expanded polystyrene foam wastes are sustainable materials for producing composite wood-based panels that are still durable in a moist environment
The laboratory-fabricated panels, bonded with 14% calcium lignosulfonate (CLS), exhibited MOE values of the laboratory-fabricated strength (MOR) and modulus of elasticity (MOE) values, comparable with the minimum standard requirements for medium-density fiberboards (MDF) panels used in dry conditions [113]
The formaldehyde content of the fiberboard panels bonded with various amount of CLS adhesive, tested in accordance with the perforator method [110], was remarkably low and significantly different with the value of the reference panel (REF10), ranging from 0.8 mg/100 g to 1.1 mg/100 g, i.e., equal to formaldehyde release of natural wood, which allowed for their classification as eco-friendly wood-based panels
Summary
The wood-based panel industry, with its wide variety of products for a number of end-uses, such as construction and furniture manufacturing, is one of the fastest growing industries worldwide, characterized by a clear upward trend for many years [1,2,3]. The possibilities to reduce the increased consumption of wood raw materials include recycling of waste wood-based panels at the end of their life cycle [5,6,7,8,9,10], utilization of alternative raw materials [11,12,13,14,15], and use of waste lignocellulosic materials [16,17,18]
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