Wood sandwich panel consists of high-density surface wood layers and low-density material. Low-dense core layer is considered to own sufficient mechanical properties for insulation and construction applying. Thermoset polymeric foam is inserted in core layer due to the reasons of material saving, reactivity during production process as well as reduced cooling stage after manufacturing. Wood flour used as water carrier is mixed with reactants to support blowing process in polymeric matrix. In principle, foaming process starts in continuous hot press machine, where entire sandwich wood panel is developed. In previous preliminary test, polyurethane as well as dimethylol dihydroxyethyleneurea (DMDHEU) were mixed with wood flour and investigated for reaction on high temperature. Some limitations had been observed during the generatation of polyurethane rigid (PUR) foam in hot pressing machine. PUR foam is typically produced by mixing two main components (polyols and isocyanates). The reacting foam begins to arise once both reactants are combined, which is undesirable result. To inhibit its reactivity, isocyanate is formed with a hydrogen active compound. This adduct is known as blocked isocyanate. The isocyanate group in blocked isocyanate will be released on elevated temperature, thus mixing blocked isocyanate with polyol provides one-component product for thermal curing. After unblocking stage by heating, gelling and foaming reaction will continue as normal foaming process, consequently foam structure is built up. In this research, industrially blocked TDI (Desmodur© BL 1100/1) was mixed with polyol (Desmophen© 1240) and wood flour for curing at 180°C in press machine with and without covering by veneered sheet. In another test, mixed with wood flour DMDHEU was examined on related procedure in hot pressing. The properties of produced material structures were investigated in order to identify optimal parameters and adapt the chemical makeup for further experiments.
Keywords: Polyurethane, rigid foam, lightweight wood panel, DMDHEU
Authors
Sae-Ueng, K.
Center for Wood Science, University of Hamburg, Hamburg, Germany
Andreas Krause
Center for Wood Science, University of Hamburg, Hamburg, Germany
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