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Properties of sandwich boards with a core made of bio-composite particleboard containing wood particles and walnut shells
AbstractThe aim of the research was to investigate the possibility of producing bio-composite particleboard with a density reduced to 500–550 kg/m3, containing 25% and 50% of walnut shells. In addition, the study also concerned the possibility of using these materials in sandwich systems. Based on the results, it was found that partial replacement of wood particles with ground shells leads to a significant reduction in the strength of the boards bonded with urea-formaldehyde (UF) resin. However, the implementation of a hybrid gluing method consisting of gluing wood particles with UF resin and walnut shells with 4,4′-methylenediphenyl isocyanate (pMDI) caused a significant improvement in the strength of the boards, especially for the variant with the highest shells content. Despite that, the manufactured materials still do not meet the requirements for furniture boards. The next step of the research has shown that these boards can perform well as a core layer in the sandwich boards covered with high-strength HDF boards. Moreover, it was found that increasing the share of walnut shells positively affected the dimensional stability of the resultant boards (thickness swelling and water absorption). However, substitution of wood with shells accelerated the ignition and flameout times of the boards. It increased the heat release without significantly affecting the percentage loss of the boards’ mass during exposure to fire.
Fire Properties of Paper Sheets Made of Cellulose Fibers Treated with Various Retardants
This article presents the results of flame-retardancy tests conducted on cellulose sheets produced using a Rapid Köthen apparatus treated with retardants. The agents used were potassium carbonate (PC) K2CO3 (concentrations of 20; 33.3; and 50% wt/wt), monoammonium phosphate (MAP) NH4H2PO4 (concentrations of 35% wt/wt), diammonium phosphate (DAP) (NH4)2HPO4 (concentrations of 42.9% wt/wt), and bisguanidal phosphate (FOS) C2H10N6 (concentrations of 22.5% wt/wt). The agents were used to improve Kraft cellulose-based sheets’ flame-retardant properties and compare their performances. As part of the study, the flammability of the materials was determined by the following methods: an oxygen index (OI) test, a mass loss calorimeter (MLC) test, and a mini fire tube (MFT) test. All formulations showed an increase in flame retardancy compared to the control test. All protected samples were non-flammable for OI determinations, and DAP-protected samples showed the highest OI index. For the MLC test, DAP-protected and MAP-protected samples showed the best heat-release rate (HRR), total heat release (THR), and average heat-release rate (ARHE) (samples did not ignite for 600 s). In the MFT test, all treated samples had comparably reduced weight loss. The best parameter was achieved for MAP and DAP (15% weight loss).
The strength and fire properties of paper sheets made of phosphorylated cellulose fibers
Phosphorylated cellulose can be an intrinsic flame retardant and a promising alternative for halogenated fire inhibitors. In this study, the mixture of di-ammonium hydrogen phosphate (DAP) and urea (U), containing phosphate and nitrogen groups, was applied to attain fire inhibitor properties. Functional groups of cellulose were grafted with phosphorous by keeping the constant molar ratio of 1/1.2/4.9 between anhydroglucose units of cellulose/DAP/U in different concentrations of bleached kraft pulp. Phosphorus concentrations were determined using the ICP hrOES method, and paper sheets were made using the Rapid Köthen apparatus. The tensile strength of phosphorylated cellulose increased twice compared with unmodified cellulose when the phosphorous concentration increased to 10,000 g/kg. An increase in the tensile index comes from the higher freeness of pulp and cross-linking of the phosphorous group between cellulose fibers. Remarkable fire retardancy effects were achieved in cellulose concentrations above 5 wt%. The raised phosphorous concentration above 10,000 g/kg due to the phosphorylation process caused the formation of a char layer on a cellulose surface and the nonflammable gas emission. That effect was indirectly confirmed by reducing the combustion temperature and HRR by 50 and 45%, respectively. Due to increasing phosphorus concentration in cellulose sheets, cellulose’s fire and strength properties increased significantly.
Środek ochrony drewna i materiałów drewnopochodnych przed działaniem ognia oraz sposób ich zabezpieczania
Bio-production of fire retardant and hydrophobic packaging paperboard with enhanced tensile strength through coating with modified cellulose nanofiber
Impact of Cellulose Modification by Expandable Graphite andCarbon Nanotubes on Flammability and Thermal Properties
The effect of veneer-surface modification with fumed nanosilica on the selected properties of water-resistant plywood
Phosphorus–Nitrogen Interaction in Fire Retardants and Its Impact on the Chemistry of Treated Wood
This work focuses on the changes in the chemical composition of wood caused by impregnation with fire retardants such as guanidine carbonate (GC), urea (U), diammonium phosphate (DAP) and their mixtures. The treated wood was tested using the oxygen index (LOI), Py–GC/MS analysis and FTIR Spectroscopy. The wood was vacuum treated at a pressure of 0.8 MPa for 20 min and then subjected to thermal degradation using the LOI. This way, degraded and nondegraded layers were obtained and ground (0.2 mm). All treatment variants achieved the class of non-flammable materials based on LOI tests; the exception was the 5% urea solution, defined as a flame-retardant material. Using the analytical methods, it was found that cellulose and hemicelluloses undergo the fastest thermal degradation. This study found that the variant protected with a 5% mixture of GC and DAP before and after the degradation process had the best fire-retardant properties regarding cellulose content in the wood. The highest content of anhydrosugars characterised the same variants, the amount of which indicates a slowdown in the degradation process and, consequently, a reduction in the release of levoglucosan during combustion, suggesting potential applications in fire safety.