PAPER making! g! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ® Volume 9, Number 2, 2023
strength of fibre material [2]. Therefore, how to increase the fire retardancy of natural fibre- based material has been a challenge for engineers. Contributions such as attaching common fire retardant materials like Mg(OH) 2 and fly ash had been researched. Geo- polymer acts like inorganic polymer with non-carbon element, mainly silica-based network structure, which provides excellent mechanical properties, and high compressive strength up to 100 MPa [3]. Meanwhile, the geopolymer shows high fire retardancy compared with polymers. Thus, geopolymer like concretes have dominated the construction material with its expected characteristics. All above, an optimized system consisting of natural fibre and silica geopolymer was developed by adding 40% colloidal silica solution with Potassium hydroxide into natural fibre board as matrix. This system aims on increasing the fire retardancy of the board by attaching the matrix onto the fibre providing a protection layer. By adjusting the silica versus potassium ratio, the effect of fire retardancy changed. Comparing different systems with several fire property tests; the most appropriate concentration was found. “MD F Recycling: Recovering fibres from fibreboards for further material utilisation with a focus on the chemical and morphological alteration of the recovered fibres”, Fahriye Yağmur Bütün Buschalsky, Georg -August-Universitat, Goettingen, PhD thesis, 2023. The present research was performed within the scopes of the DFG Research Training Group 1703 “Resource Efficiency in Interorganizational Networks” and AiF Project GmbH (project No. 16KN065229), which aims at developing a new fibreboard recycling technique based on thermo-hydrolytic disintegration by focusing on the further material usage of the waste fibreboards while preserving the fibrous morphology of the wood element and increasing the added-value compared to combustion (energy recovery). The results have been gathered in total as six manuscripts for being published or are submitted for publishing elsewhere. Medium density fibreboard (MDF) is uniform, dense, smooth, and free of knots and grain patterns, and is an excellent substitute for solid wood in many applications. As the name suggests, the MDF has density range between 500 to 800 kg m-3 and is manufactured by hot-press consolidation with a thermo-setting adhesive resulting in an entire inter-fibre bonding of the fine lignocellulosic fibres. MDF is the second most important wood-based panel (WBP) after particleboard, hence, the global MDF production has reached above 90 million m3 in 2017 and 2018. MDF tends to be used in indoor applications such as furniture, laminate flooring and panelling. It is estimated that nearly 50 million m3 of waste MDF was generated across the world in 2016 alone. Alternative approaches for the disposal of this waste are missing and need to be considered, such as recycling the waste into further value-added uses. However, a commercially viable method for MDF recycling has not been found yet. Additionally, energy recovery (combustion for energy production) is not an option in many EU countries, due to the lack of sufficient incinerator capacity for burning waste MDF. Therefore, large volumes of MDF must have accumulated across Europe. Furthermore, introducing the recovered fibres back into the MDF manufacturing as a raw material requires careful control to avoid upsetting the process or affecting the board quality. In order to preserve the fibrous morphology of the recovered lignocellulosic fibre material, while releasing the fibres from the thermosetting resin matrix, the thermo-hydrolytic disintegration process would be the best option. Thus, in this thesis, the thermo-hydrolytic disintegration process has been chosen as the main technique for recovering the wood fibres from waste fibreboards. As a result of this disintegration process, recovered fibres (RF) and disintegration water (DW) were obtained. Obtained recovered fibres, when compared to virgin fibres (VF), were found to be shortened which could be attributed to the disintegration conditions and have altered chemical properties resulting in higher pH and formaldehyde emissions due to the remaining resin. Moreover, RF were further utilized for
Technical Abstracts
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