Oxygen index examples

As an example, a foam prepared from III, alumina trihydrate as a filler, benzoyl peroxide as a curing agent, and azobis formamide as a blowing agent, leads to a material with an oxygen index of 48, a long-term stability to at least 150 °C, and a smoke density about one fifth that of a commercial foam [284]. 

In other halogen-containing systems, such as flexible PVC and polyolefins, it is preferable to use the zinc borate in conjunction with antimony oxide for maximum performance. In flexible PVC, for example, the zinc borate alone is not very effective in the Oxygen Index test (Fig. 6), but a combination of the zinc borate and antimony oxide (1 1 ratio) outperforms equal weight of antimony oxide at a total loading of more than 10 phr (4). In the presence of alumina trihydrate (ATH), the beneficial effect of using a combination of the zinc borate and antimony oxide is dramatically increased (Fig. 7). 

It is well known that char formation during polymer burning is an important mechanism by which polymers resist burning. For example Van Krevelen (1-2) has shown that a correlation exists between the oxygen index (OI) of a polymer containing no heteroelements and the amount of char it forms when pyrolyzed in the absence of air. As shown in Table I, a similar correlation is seen to hold for a number of common engineering thermoplastics. 

There is evidence to show that the particle size of the filler also plays a significant role in flammability resistance. For example, below a certain particle size (about 1-2 pm), in many tests, including oxygen index, aluminum hydroxide shows enhanced fire-retarding performance,34 which may be associated with the rate of filler decomposition and/or with the formation of a more stable ash. However, it has been found that the particle size effect is absent, or less evident, in the cone calorimeter test.35 Similarly, particle size reduction has been shown to enhance fire retardancy in magnesium hydroxide-filled PP in this case, samples were characterized by the UL94 test.36 This raises the question as to whether further reductions in particle size to the nanoscale will lead to an additional increase in flammability performance, and perhaps enable filler overall levels to be significantly reduced. This aspect is considered in a later section. 

Also phosphorus- and nitrogen-containing polyols are shown to be effective in flame retardancy of PU foams24 such as polyols based on phosphonic acid ester or obtained by partial or full substitution of methylol groups of tetrakis(hydroxymethyl)phosphonium chloride with amine several examples of such polyols were reported by Levchik and Weil.15 Rigid PU foam modified with these polyols showed improved oxygen index values moreover better results were achieved with higher functionality polyols. 

Molybdenum compounds are effective in PVC, especially when coupled with zinc compounds. In addition, these compositions are flame-retardant. For example, 1.5 phr. of Sb20s and 1.5 phr. of Kemgard 911 in plasticized PVC raised the oxygen index from 28 to 33.5 % while the mass of solid particles filtered from the combustion products in an Arapahoe smoke chamber (cf. Fig. 4.1 in Section 4.1.1.1) lessened by 32.6 per cent. 4 phr. of the same additives in rigid PVC enhanced the oxygen index from 41 to 58 % and reduced smoke production by 48 per cent. ... 

Small laboratory tests, for example, oxygen index test (OIT) [6], Setchkin test or similar tests under certain circumstances provide a means for production quality control. Their results can only be applied towards the characterisation of fire risk assessment if it can be demonstrated that the test adequately simulates the actual fire situation. 

Jhe parameters used do not correlate. Examples ean be found of attempted eorrelation in whieh parameters of a different nature are compared, sueh as limiting oxygen index value and... 

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