Oxygen Index Method Research Articles

Flame retardancy effect of crosslinking of lignocellulose materials

AbstractDynamic and isothermal thermogravimetry (TG) was used for the study of flame retardancy effects caused by crosslinking of lignocellulose materials. This effect was also checked with the limited oxygen index (LOI) method. It was found that dynamic TG measurements run to 400°C could indicate the decrease of flame retardancy effect when lower residues are observed for samples measured in oxidative in comparison to inert environments. The isothermal TG data of initial reactions are not suitable for the prediction of flame retardancy effects. Epichlorhydrin (E) is a suitable chemical for the flame retardancy of wood. The addition of polyethyleneimine (PEI) decreases the flame retardancy of wood. On the other hand xylan crosslinked with E gives lower LOI values than the xylan crosslinked in the presence of PEI.

Ammoniumphosphate—Decabromobiphenyl oxide synergistic effect in treatment of polyester/cotton blend

AbstractPolyester/cotton blend (87.5:12.5%) was treated with various concentrations of diammonium hydrogen phosphate (DAP)‐Decabromobiphenyl oxide (DBBO) mixture. The flammability of the resulting systems was determined by the limiting oxygen index (LOI) and simultaneous thermal analysis (TA) methods. Evaluation of the results was achieved by plotting the variation of the LOI with the percentage of ammonium phosphate‐‐‐DBBO mixtures at constant total additive loadings on triangular diagrams. The activity of the inorganic salt as a flame retardant was found to be synergistically enhanced by the addition of the DBBO. The maximum interaction between the two additives occurred at bromine‐phosphorus atomic ratio of about 3:1. This corresponds to the stoichiometric ratio for the formation of phosphorus tribromide, PBr3, a species which most probably interacts with the acidic products resulting from the thermal decomposition of the polyester and thus changes their nature so that they become no longer capable of recombination with the other decomposition fragments to produce flammable gases.

The effect of ammonium sulphate—decabromobiphenyl oxide on the flammability of polyester/cotton blend

AbstractA 87.5:12.5 polyester/cotton blended fabric was treated with various concentrations of ammonium sulphate and decabromobiphenyl oxide (DBBO) as well as mixtures of the two additives. The flammability of the resulting systems was determined by the limiting oxygen index (LOI) method and their thermal decomposition by thermogravimetry. Ammonium sulphate was particularly less effective as a flame retardant than the DBBO. Decabromobiphenyl oxide acts in the gas phase to retard the flammability of the polyester while the inorganic salt acts in the condensed phase to decrease that of the cotton. A mechanism for the interaction of ammonium sulphate with cotton was suggested. When a mixture of the two additives containing a high percentage of the bromo‐compound was used a significant increase in the LOI values was observed compared to one having the same total loading but containing a higher percentage of ammonium sulphate. This may be attributed to the stabilizing effect of the released ammonia on the intermediate species formed after the liberation of the bromine radicals from the DBBO.

Measuring Foliar Flammability with the Limiting Oxygen Index Method

Abstract This paper stresses the importance of measuring flammability as a combination of ignitability, sustainability, and combustibility in quantitative terms. The Limiting Oxygen Index (LOI) method is selected and evaluated as a means to measure ignitability and sustainability. The results demonstrated that the technique can distinguish small differences in ignitability and sustainability with good precision. This can be useful for assessing the influence of foliage properties such as chemical composition on these two flammability components. The third component of flammability, combustibility, has to be measured by a different technique. For. Sci. 34(2):523-529.

The oxygen index method in fire retardance studies of polymeric materials

AbstractThe oxygen index test is a fundamental tool in basic research on polymer combustion and on mechanisms of fire retardance. Although the oxygen index should provide an evaluation of intrinsic flammability of polymeric materials, its response may depend on geometry of the specimen. This is shown by comparing the behavior of polypropylene fire retarded with different additive systems. The implication of such in mechanistic studies is discussed. Furthermore, new measurements are proposed to be carried out with the oxygen index apparatus, which give parameters related to ease of ignition, behavior on forced burning, and thermal insulating characteristics of char developed on burning the material.

The Burning Behaviour of Textiles and its Assessment by Oxygen-index Methods

(1988). The Burning Behaviour of Textiles and its Assessment by Oxygen-index Methods. Textile Progress: Vol. 18, No. 1-3, pp. 1-186.

Flame retardant oil modified chlorinated alkyd Resins

Fire retardant oil‐modified alkyd resin based on chlorendic ahnydride (1,4,5,6,7 7‐hexachlorobicyclo‐(2,2,1) hept‐5‐ene‐2,3‐dicarboxylic anhydride) have been synthesized using linseed oil, phthalic anhydride and glycerol. Several paint formulations were designed to study the effect of pigment/binder ratio, antimony trioxide and chlorinated thermosetting and thermoplastic polymers on fire retardancy. Oxygen index method was used to evaluate the fire retardancy of paints. The chlorinated alkyd resin was used as a plasticizer for laroflex MP 35 to improve the fire retardancy of the thermoplastic chlorinated polymer.

New aspects in cationization of lignocellulose materials. IX. Flame retardancy effect of modification with nitrogen and sulfur containing groups

AbstractLignocellulose materials were modified with 3‐chlor‐2‐hydroxypropyltrimethylammoniumchloride, 1,3‐bis(3‐chlor‐2‐hydroxypropyl)imidazoliumhydrogensulphate, and 2‐chlorethyl‐sodiumsulphonate and the flame‐retardant properties of materials obtained were studied. The flame‐retardant effect was proved using the limited oxygen index (LOI) method and values up to 32.8 vol % of oxygen were determined. The LOI values were higher when the modification was done without using NaOH for activation, but in that case the alkylating groups were not chemically bonded to the material. The NaOH activation was necessary to obtain material with flame‐retardant properties stable against washing. No synergistic effects were observed when the material was modified with both nitrogen‐ and sulfur‐containing groups.

Effect of the network structure on the flammability ofcis-1,4-polyisoprene vulcanizates

The combustibilities ofcis-1,4-polyisoprene and its peroxide and sulphur vulcanizates have been investigated by means of the oxygen index method. The temperature distribution in the sample and the molecular weight of the liquid products formed as a result of elastomer destruction in the combustion zone have been measured. It has been found that the combustibility ofcis- 1,4-polyisoprene diminishes as its cross-link density increases. This effect is much stronger for sulphur than for peroxide vulcanizates. The investigations lead to the conclusion that a mechanism of network degradation and volatile sulphur compounds penetrating to the flame are responsible for this difference.

The flame retardance of a natural polymer by a sulphur-aluminium-bromine system

Cellulose (in the form of cotton) was treated with various inorganic sulphur oxyacid salts and the flammabilities of the resulting systems were determined by the limiting oxygen index method. Aluminium sulphate was particularly effective as a flame retardant and its activity was synergistically enhanced by the addition of a suitable organic bromine compound. Flammability studies, by means of triangular diagrams, and simultaneous thermal analyses indicated that the optimum Br:Al atomic ratio was about unity. Furthermore the results showed that the flame-retardant additive system acts mainly in the condensed phase and involves all three elements, sulphur, aluminium and bromine.

Aromatic polyamides. III. Mechanistic studies on the role of substituent chlorine in flame retarding aromatic polyamides

AbstractThe flammability of poly(1,3‐phenylene isophthalamide) and poly(chloro‐2,4‐phenylene isophthalamide) was measured by the oxygen index method. The chloro polyamide had reduced flammability shown by a 10–15 higher oxygen index. Analysis of the chars of the two polymers at 700°C by thermogravimetry (TGA) and elemental analysis showed that the chlorine caused a significant increase in the retention of C, H, N, and O in the pyrolysis residue. Most of the chlorine in the chloro polyamide, however, was lost by 700°C. Based on these results, we have suggested that the chlorine imparts flame retardancy by a combination of vapor‐ and condensed‐phase mechanisms. The origin of condensed‐phase activity is discussed.

Investigations on the flame-retardation of cellulosic fibrous materials

The thermal behaviours of untreated cellulose (cotton) and samples treated with phosphorus and nitrogen-containing flame-retardants have been studied by means of the derivatograph and quantitative DTA, with the aim of revealing the advantageous features of thermal analysis in the investigation of the flame-retardation of cellulose substrates. The complex thermoanalytical method applied proved to be suitable for the investigation of the efficiency of flame-retardation in parallel with the oxygen index method and the determination of the phosphorus content of the sample. The efficiencies obtained with different methods are in correlation.

The effect of the carbon–bromine bond type on the limiting oxygen index. II—Polymethylmethacrylate and polystyrene

AbstractFurther evidence has been obtained to suggest that the fire retardation efficiencies of several organo‐bromine compounds, as measured by the limiting oxygen index method, are independent of the type of carbon‐bromine bond, depending almost entirely upon the bromine concentration. Linear regression analysis has confirmed the linearity of the relationship between the limiting oxygen index method and the bromine concentration. The fire retardation efficiency (as measured by the limiting oxygen index method) of the organo‐bromine compounds does, however, depend to a marked extent upon the substrate.

Flammability characteristics of fiber reinforced organic matrix composites

AbstractThe effect of resin, fiber, and fire retardant additives on flammability characteristics of organic matrix composites was evaluated. Information is presented on the flame spread index, determined by the radiant panel test, the amount of smoke generated, and products of combustion, using the National Bureau of Standards Smoke Density Apparatus, and the amount of oxygen required to support combustion using the Oxygen Index method. These methods were effective in screening the flammability characteristics of organic matrix composites. Of the materials evaluated the polyimide composites were the most resistant to flame spread, exhibited the lowest evolution of smoke and toxic products and had the highest oxygen index. No differences in flame spread and oxygen index were observed for the polyester epoxy glass‐cloth laminates. Addition of antimony trioxide and hydrated alumina to the polyester and epoxy resin systems significantly decreased the flame spread index and increased the oxygen index, but showed a marked increase in smoke evolution. Smoke properties depended on resin content whereas the type of reinforcement did not appear to affect flame spread index or smoke properties. The use of protective barriers in selected shipboard areas can reduce flame spread and lengthen the lime for generation of smoke.

Flammability and smoke measurements on glass reinforced polyester resins

The effects on flammability and smoke production of the amount and orientation of glass fibre in reinforced polyesters, were studied by means of the critical oxygen index ( COI) method (ASTM D2863-770), and a smoke chamber test (Stanton FTB). No significant difference was found between the resins, but the COI value rose linearly as the proportion of fibre increased. Parallel wound fibres had a higher COI than perpendicularly wound fibres. Smoke results were more variable and did not show any difference attributable to the orientation of the fibers.

Fire hazards of organic materials—small scale assessment of flammability and smoke generation

AbstractThe flammability and smoke generation properties of a number of organic materials used in ships, including laminated materials, rigid and flexible cellular polymers, cable insulting materials and adhesives, have been evaluated. The relative flammabilities were determined by the limiting oxygen index method that gives convenient, reproducible, numerical ratings of materials. Smoke generation was assessed photometrically by measuring light attenuation under standard conditions and is reported in terms of the total amount of smoke generated, as well as the times for the smoke density to reach an arbitrary ‘critical’ level and the maximum value. Materials with low flammability and low smoke generation characteristics have been identified, as well as those that would be hazardous in the event of a fire.

Some Effects of Chemical Composition on the Flammability Behavior of Textiles

The oxygen index method is shown to be a valuable tool for the investigation of the flammability of textile samples as a function of their chemical composition. Measurements of limiting oxygen index (LOI) are reported for polyester/cotton blends of varying composition, and for 50/50 polyester/cotton blends in which one component fiber has been selectively treated with flame-retardant additives. LOI values are also reported for cotton fabric treated with nitrogen-containing resins at various levels of nitrogen content, in conjunction with a flame-retardant additive.