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.

The Influence of the Accelerated Aging Process on the Compressive Strength of Wood Treated with Components of a Salt Fire Retardant.

This paper presents the results of research on the influence of the components of salt flame retardants on the compressive strength of wood depending on the time of accelerated aging. The effect of the agent was assessed on the basis of the change in the strength of treated wood compared to that of untreated wood. In addition, a statistical analysis of the obtained results was used to determine which of the components most significantly affect the changes in the compressive strength of wood along the fibers, and to what extent. It was found that extending the aging process time in the case of control and boric acid-protected samples did not significantly change the strength properties. It has also been found that some compounds contained in fire retardant have an antagonistic effect related to the compressive strength of wood.