Poly oxygen index

Antimony Oxide. The effect of antimony trioxide on the oxygen index of flexible poly(vinyl chloride) containing from 20 to 50 parts of plasticizer is shown in Figure 2. The flame resistance as measured by the oxygen index increases with the addition of antimony oxide until the oxygen index appears to reach a maximum at about 8 parts of Sb202. Further addition of antimony oxide does not have any increased beneficial effect. 

Fig. 2. The effect of antimony oxide on the oxygen index of poly(vinyl chloride) plasticized with dioctyl phthalate (DOP), (—...

Alumina Trihydrate. Alumina trihydrate is usually used as a secondary flame retardant in flexible PVC because of the high concentration needed to be effective. As a general rule the oxygen index of flexible poly(vinyl chloride) increases 1% for every 10% of alumina trihydrate added. The effect of alumina trihydrate on a flexible poly(vinyl chloride) formulation containing antimony oxide is shown in Figure 5. 

The limiting oxygen index of Tefzel as measured by the candle test (ASTM D2863) is 30%. Tefzel is rated 94 V-0 by Underwriters Laboratories, Inc., in their burning test classification for polymeric materials. As a fuel, it has a comparatively low rating. Its heat of combustion is 13.7 MJ/kg (32,500 kcal/kg) compared to 14.9 MJ /kg (35,000 kcal/kg) for poly(vinyHdene fluoride) and 46.5 MJ /kg (110,000 kcal/kg) for polyethylene. 

Table 8 Limiting oxygen index (LOI) for selected poly(organophosphazenes)...

Aryloxyphosphazene copolymers can also confer fireproof properties to flammable materials when blended. Dieck [591] have used the copolymers III, and IV containing small amounts of reactive unsaturated groups to prepare blends with compatible organic polymers crosslinkable by the same mechanism which crosslinks the polyphosphazene, e.g. ethylene-propylene and butadiene-acrylonitrile copolymers, poly(vinyl chloride), unsaturated urethane rubber. These blends were used to prepare foams exhibiting excellent fire retardance and producing low smoke levels or no smoke when heated in an open flame. Oxygen index values of 27-56 were obtained. 

Figure 14 shows that the heat loss by radiation becomes insignificant (the oxygen index becomes independent of pressure) at P > 0.3 atm for PMMA, and at P > 2 atm and P > 6 atm for poly(vinyl chloride) and Teflon, respectively. A weak pressure dependence of Y (1/P° ) accounts for extinction of the flame by convective... 

Fig. 14. Effect of pressure on the limiting oxygen index (LOI) of polymers 1) polytetrafluoroethylene. 2) poly(vinyl chloride), 3) polyfmethyl methacrylate) (After Ref. 83>)...

Fig. 2.21 Effect of char yield of polymers on oxygen index The straight line represents the calculated oxygen indices while the points are actual measured values. Notations at the measured points 12,13,22 polyethersulphone 11,20,24 polyphenylene-sulphide 15 polyarylsulphone 18 ABS 17, 25 chlorinated PVC 14, 19 polycarbonate 30, 31 phenolphthalein/polycarbonate copolymer 23 fluorinated polycarbonate/poly(dimethyl siloxane) copolymer 32 poly(vinyl fluoride) 58 poly(vinylidene fluoride) Reprinted from Ref. 40 by permission of Marcel Dekker, Inc. Copyright Marcel Dekker, Inc.,...

The conventional measurement of oxygen index has been further refined by several authors. Isaacs concluded from a round-robin test that the oxygen index of a steadyburning material (such as poly(methyl methacrylate) or polyacetal) was consistent within 1 % as measured in different laboratories, while that of a material burning... 

In the structure of poly(vinyl chloride) (PVC), alternate carbon atoms are linked to a chlorine atom, so that the polymer contains 56 per cent m/m of chlorine. The plasticizer-free rigid PVC burns away in a flame in open air but ceases to burn as soon as it is removed from the direct flame. Its oxygen index is 43 to 48 per cent. 

Stackman [29] carried out a study to find systems suitable for reducing the flammability of polyethylene terephthalate (PET) and poly-1,4-butylene terephthalate (PBT) while retaining the chemical and physical properties of the original polymers. The additives used were phosphine oxides, phosphonates and phosphates and their activity was assessed by means of an oxygen index test. Most of the phosphorus esters were found to be volatile under the blending conditions and both the halogenated phosphorus esters and halogenated derivatives of phosphorus oxide proved to be ineffective as flame retardants. 

Poly(ethylene terephthalate) with the structure given below was obtained when the sodium salt of diethyl phosphite was used as a comonomer [91,92]. The molecular weights of the resin was from 25,000 to 27,000 Da. Introduction of up to 2% P does not have any detrimental effect on the mechanical characteristics of the resin. The oxygen index (01)... 

Figure 14.32 The flame resistance of polymeric materials, indicated by the oxygen index. 1, polyformaldehyde 2, polyethylene, polypropylene 3, polystyrene, poiyisoptene 4, polyamide 5, cellulose 6, poly(vinyl alcohol) 7, poly(ethylene terephthalate) 8, polyactylonitrile 9, poly(phenylene oxide) 10, polycarbonate 11, aromatic nylon 12, polysulfone 13, Kynol 14, polylmide 15, carbon. Polymers producing large values of char residue are more fire resistant.

Few studies have been attempted to systematically relate oxygen index values to known degradation mechanisms. We have attempted to study two cases, nylon 6 and poly (ethylene terephalate) (PET). 

Polysulfones are self-extinguishing resin. Polysulfones with no flame retardant additives has been given 94V-0 under the UL Standards. The value of limited oxygen index (around 0.40) points out their excellent flame retardancy [109]. Furthermore, exposed to flame, polysulfones emit very little smoke or toxic volatiles. However, the high flameproof properties of polysulfones are scanty when they are used as electriccd parts or in an epoxy resins network. Poly(sulfone) (PSF) and p>oly(ether sulfone) (PES) are commonly used for high performance applications such as advanced... 

---