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Obtaining Flame-Resistant Fiberboards Using Phosphoramide FKM

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A.A. Leonovich, A.V. Sheloumov

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Efficiency of flame retardants can be improved by increasing the share of working elements in their composition while excluding the possibility of any negative effect on the properties and technology of fiberboards. The research aimed to, instead of the well-known flame retardant amidophosphate KM (phosphoric acid and carbamide), use a product with high content of phosphorus, obtained by condensation of ammonium dihydrogen phosphate with urea in the presence of phosphoric acid, – phosphoramide code-named FKM (ammonium dihydrogen phosphate, phosphoric acid and carbamide). KM and FKM are stable designations of products in branch of industry and abroad. The goal was to optimize the parameters of FKM fixing in fiberboard while improving the quality of the board. Synthesized FKM contained a ratio of phosphorus and nitrogen matched by synergy and had optimal acidity for board formation and high concentration of the working solution. No synthetic binder was used; interfiber interaction was provided by heat treatment of the pressed boards immediately after hot pressing. Hardwood fiber, generated on the defibrator at LLC “Sheksninsky KDP”, was treated by spraying two flame retardants: phosphoramide FKM and amidophosphate KM. The flowrate of 50 % aqueous solution of fire retardants was determined on the basis of the calculated 3 % mass fraction of phosphorus in absolutely dry fiber. 3.2 mm thick hardboard was pressed at a temperature of 200 °C with a maximum pressure of 5.5 MPa for 4.5 min, followed by heat treatment at 160 °C for 30–210 min. The ground boards were extracted by either cold or hot water or by ethyl ether. Bending strength of sample fiberboards with FKM was 74.8–78.4 MPa; swelling in water 17.5–20.0 %; mass loss during fire tests 13.3–14.5 % without self-combustion. It was found that phosphoramide FKM can be used to produce dry processed flame-resistant fiberboard without synthetic binders. The boards have high density and strength and do not contain free formaldehyde. Keeping the boards warm after hot pressing by immediate 30-minute heat treatment is sufficient to achieve the physical and mechanical properties conforming to the regulatory requirements for water-resistant boards with strongly bound flame retardant complex.


A.A. Leonovich, Doctor of Engineering, Professor; A.V. Sheloumov, Candidate of Engineering, Senior Researcher

St. Petersburg State Forest Technical University named after S.M. Kirov
Institutsky pereulok, 5, 194021St. Petersburg, Russia


St. Petersburg State Forest Technical University named after S.M. Kirov


amidophosphate, flame retardant, flammability, hardboard, modification, phosphoramide, formaldehyde emission.


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Obtaining Flame-Resistant Fiberboards Using Phosphoramide FKM


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