Browsing by Author "Yordanov I."

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    Effect of Hot-Pressing Temperature on the Properties of Eco-Friendly Fiberboard Panels Bonded with Hydrolysis Lignin and Phenol–Formaldehyde Resin
    (2024-04-01) Valchev I.; Savov V.; Yordanov I.; Petrin S.; Antov P.
    Lignin is the natural binder in wood and lignocellulosic plants and is regarded as the main natural and renewable source of phenolic compounds. Its incorporation in the composition of fiberboards will enhance both the environmental performance of the panels and the complex use of natural resources. In recent years, the increased valorization of hydrolysis lignin in value-added applications, including adhesives for bonding fiberboard panels, has gained significant research interest. Markedly, a major drawback is the retention of lignin in the pulp until the hot-pressing process. This problem could be overcome by using a small content of phenol–formaldehyde (PF) resin in the adhesive mixture as an auxiliary binder. The aim of this research work was to investigate and evaluate the effect of the hot-pressing temperature, varied from 150 °C to 200 °C, in a modified hot-press cycle on the main physical and mechanical properties of fiberboard panels bonded with unmodified technical hydrolysis lignin (THL) as the main binder and PF resin as an auxiliary one. It was found that panels with very good mechanical properties can be fabricated even at a hot-pressing temperature of 160 °C, while to provide the panels with satisfactory waterproof properties, it is necessary to have a hot-pressing temperature of at least 190 °C.
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    Effect of Hot-Pressing Temperature on the Properties of Eco-Friendly Fiberboard Panels Bonded with Hydrolysis Lignin and Phenol–Formaldehyde Resin
    (2024-04-01) Valchev I.; Savov V.; Yordanov I.; Petrin S.; Antov P.
    Lignin is the natural binder in wood and lignocellulosic plants and is regarded as the main natural and renewable source of phenolic compounds. Its incorporation in the composition of fiberboards will enhance both the environmental performance of the panels and the complex use of natural resources. In recent years, the increased valorization of hydrolysis lignin in value-added applications, including adhesives for bonding fiberboard panels, has gained significant research interest. Markedly, a major drawback is the retention of lignin in the pulp until the hot-pressing process. This problem could be overcome by using a small content of phenol–formaldehyde (PF) resin in the adhesive mixture as an auxiliary binder. The aim of this research work was to investigate and evaluate the effect of the hot-pressing temperature, varied from 150 °C to 200 °C, in a modified hot-press cycle on the main physical and mechanical properties of fiberboard panels bonded with unmodified technical hydrolysis lignin (THL) as the main binder and PF resin as an auxiliary one. It was found that panels with very good mechanical properties can be fabricated even at a hot-pressing temperature of 160 °C, while to provide the panels with satisfactory waterproof properties, it is necessary to have a hot-pressing temperature of at least 190 °C.
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    Effect of the Adhesive System on the Properties of Fiberboard Panels Bonded with Hydrolysis Lignin and Phenol-Formaldehyde Resin
    (2022-05-01) Savov V.; Valchev I.; Antov P.; Yordanov I.; Popski Z.
    This study aimed to propose an alternative technological solution for manufacturing fiberboard panels using a modified hot-pressing regime and hydrolysis lignin as the main binder. The main novelty of the research is the optimized adhesive system composed of unmodified hydrolysis lignin and reduced phenol–formaldehyde (PF) resin content. The fiberboard panels were fabricated in the laboratory with a very low PF resin content, varying from 1% to 3.6%, and hydrolysis lignin addition levels varying from 7% to 10.8% (based on the dry wood fibers). A specific two-stage hot-pressing regime, including initial low pressure of 1.2 MPa and subsequent high pressure of 4 MPa, was applied. The effect of binder content and PF resin content in the adhesive system on the main properties of fiberboards (water absorption, thickness swelling, bending strength, modulus of elasticity, and internal bond strength) was investigated, and appropriate optimization was performed to define the optimal content of PF resin and hydrolysis lignin for complying with European standards. It was concluded that the proposed technology is suitable for manufacturing fiberboard panels fulfilling the strictest EN standard. Markedly, it was shown that for the production of this type of panels, the minimum total content of binders should be 10.6%, and the PF resin content should be at least 14% of the adhesive system.
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    Effect of the Adhesive System on the Properties of Fiberboard Panels Bonded with Hydrolysis Lignin and Phenol-Formaldehyde Resin
    (2022-05-01) Savov V.; Valchev I.; Antov P.; Yordanov I.; Popski Z.
    This study aimed to propose an alternative technological solution for manufacturing fiberboard panels using a modified hot-pressing regime and hydrolysis lignin as the main binder. The main novelty of the research is the optimized adhesive system composed of unmodified hydrolysis lignin and reduced phenol–formaldehyde (PF) resin content. The fiberboard panels were fabricated in the laboratory with a very low PF resin content, varying from 1% to 3.6%, and hydrolysis lignin addition levels varying from 7% to 10.8% (based on the dry wood fibers). A specific two-stage hot-pressing regime, including initial low pressure of 1.2 MPa and subsequent high pressure of 4 MPa, was applied. The effect of binder content and PF resin content in the adhesive system on the main properties of fiberboards (water absorption, thickness swelling, bending strength, modulus of elasticity, and internal bond strength) was investigated, and appropriate optimization was performed to define the optimal content of PF resin and hydrolysis lignin for complying with European standards. It was concluded that the proposed technology is suitable for manufacturing fiberboard panels fulfilling the strictest EN standard. Markedly, it was shown that for the production of this type of panels, the minimum total content of binders should be 10.6%, and the PF resin content should be at least 14% of the adhesive system.