The thermal insulation of buildings using wood fiber insulation boards (WFIBs) constitutes a positive contribution towards climate change. Thereby, the bonding of wood fibers using mainly petrochemical-based resins such as polymeric diphenylmethane diisocyanate (pMDI) is an important measure to meet required board properties. Still there is a need to reduce or partial substitute the amount of these kinds of resins in favor of a greener product. This study therefore focusses on the feasibility of reducing the amount of pMDI by 50% through the addition of 1% BioPiva 395 or Indulin as two types of softwood Kraft-Lignin and lignin rich canola hulls together with propylene carbonate as a diluent. A panel density of 160 kg/m3 and a thickness of 40 mm was aimed. The curing of these modified pMDI was investigated by using two types of techniques: hot-steam (HS) and innovative hot-air/hot-steam-process (HA/HS). The WFIBs were then tested on their physical-mechanical properties. The equilibrium moisture content (EMC) was determined at two different climates. An exemplary investigation of thermal conductivity was conducted as well. The WFIBs did undergo a further chemically based analysis towards extractives content and elemental (C, N) composition. The results show that it is feasible to produce WFIBs with lower quantities of pMDI resin and added lignin with enhanced physical-mechanical board properties, which were lacking no disadvantages towards thermal conductivity or behavior towards moisture, especially when cured via HA/HS-process.
Crude oil as a non-renewable resource is presenting challenges for the future in many industrial sectors. Due to the dwindling of these resources, costs are increasing negatively affecting the wood based panels industry, which uses mainly petrochemical resins as components for binding agents. In addition harmful formaldehyde emissions arising from conventionally produced wood composites are demonstrable. In order to substitute these conventional binding agents for wood based panels, in particular medium density fiberboards (MDF), Laccase-Mediator-Systems (LMSs) were investigated in several researches. A popular and reliable method used to test the suitability of LMSs is the measurement of their oxygen consumption on wood fibers in aqueous suspension. This enzymatic catalyzed oxidation was the object of this study. The mediators 4-hydroxybenzoic acid (HBA), vanillic acid (VanA), vanillic alcohol (VAl), ethylvanillin (EVan), acetovanillone (AVan), ferulic acid (FA), caffeic acid (CA) and guajacol (Gu) were tested as possible components of the LMSs. The study showed that all of the LMSs have oxidized wood fibers more efficiently than laccase on its own. Among the different mediators, vanillic alcohol, guajacol and caffeic acid in LMSs have shown the fastest O 2 consumption.
In most countries, fibreboards are not recovered after utilization but burned for energy production. This study aims at recovering fibres from industrial fibreboards and reusing them as reinforcement elements in wood polymer composites (WPC). Recovered fibre (RF) material was generated by the thermo-hydrolytic disintegration of medium and high density fibreboards bonded with urea-formaldehyde resin. Various formulations of RF and polypropylene were used with or without the addition of the coupling agent to manufacture WPC using a co-rotating extruder. Test specimens were produced via injection moulding whereby those containing 'virgin' fibres served as a reference with respect to mechanical and physical properties. WPC formulations containing RF and 'virgin' fibres exhibited similar results, but composites containing RF exhibited improved mechanical and water-related properties, especially without coupling agent. The study indicates that recovered fibres are suitable to produce WPC with very similar physico-mechanical properties as those from 'virgin' fibres.
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