Plastics limiting oxygen index

Elame-spread and smoke-density values, and the less often reported fuel-contributed semiquantitive results of the ASTM E84 test and the limited oxygen index (LOI) laboratory test, are more often used to compare fire performance of ceUular plastics. AH building codes requite that ceUular plastics be protected by inner or outer sheathings or be housed in systems aH with a specified minimum total fire resistance. Absolute incombustibHity cannot be attained in practice and often is not requited. The system approach to protecting the more combustible materials affords adequate safety in the buildings by aHowing the occupant sufficient time to evacuate before combustion of the protected ceUular plastic. 

Limiting oxygen index values (LOI) of a number of plastics are shown in Table IV. The LOI is the concentration of oxygen required to maintain burning. Polyphenylene sulfide has a value of 44, and falls among the least flammable types of plastics. 

Limiting Oxygen Index (LOI) - LOI is defined as the required minimum percentage of oxygen in a mixture with nitrogen, which would allow a flame to be sustained by an organic material such as a plastic. 

Useful for determining the Limiting Oxygen Index of plastics.lt has gone through several modifications. 

Figure 10.36. Limiting oxygen index of PVC compounds containing different plasticizers. Formulation PVC 65 vrt%, plasticizer 35 vrt%. Disflamoll DPO -diphenyl 2-ethylhexyl phosphate, TKP - tricresyl phosphate, DPK - diphenyl cresyl phosphate. [Data from Polymer Additives. Plasticizers, Bayer SP-PMA 8013 E, 2000.

Figure 10.37. Limiting oxygen index of PVC containing variable amounts of Uniplex FRP-45. Formulation PVC 100, Uniplex 546-A decreasing from 60 to 0, lead stabilizer 5, Sb203 15. [Data from Uniplex FRP-45. Flame retardant plasticizer. Unitex Chemical Corporation.]...

Burning time and limiting oxygen index depend on the plasticizer type and the amount. They are not greatly affected by addition of antimony oxide, aluminum trihydrate, or zinc borate. Qjj jjgjjjj addition of antimoity oxide, aluminum... 

In the cable industry, plasticization of CPVC by phthalates and phosphates improves the flexibility and processability of CPVC. However, the addition of plasticizer lowers the limiting oxygen index and increases smoke production. The schematic diagram below illnstrates the mechanism of degradation in the absence (A) and the presence (B) of the smoke-suppressing componnd - basic iron oxide, FeOOH. " ... 

These plastics used in RPs can withstand many of the world s most aggressive chemical environments. Different formulated epoxies permit meeting exceptional corrosion resistance, different performance such as the ability to withstand exothermic stresses that are built up during curing, used in different temperature ranges, low burning rate, and limited oxygen index. 

Table L.4 Limiting Oxygen Index (LOI) Values of Various Polymeric Materials (Ref Schwartz, S.S., and Goodman, S.H., Plastic Materials and Processes, van Nostrand Reinhold, New York, 1982, p. 33)...

Table 2.1 lists the limiting oxygen index values for different plastics [42]. 

The limiting oxygen index (LOI) test is used to measure the minimum concentration of oxygen necessary for candle-like burning for 3 minutes or more. A higher LOI indicates that more oxygen is needed to support combustion. The presence of flame retardants increases the LOI. Unmodified PP has a LOI of 17. The key fire properties of some plastics are compared with PP in Table 20. Suitable flame retarded grades of PP can have a LOI of 28. 

PA6 is one of the most important engineering plastics and is widely used as fibers, molded articles, and binders for composites. However, the applications of PA6 are still restricted in many fields owing to its poor flame retardant property and low limiting oxygen index (LOl) 21, and because it bums easily. Fang et al. [257] synthesized hb polyphosphate bisphenol-S ester to improve the flame retardancy of PA6. Chen et al. [258] synthesized hb polyphosphate ester (Scheme 27) and used it as curing agent and flame retardant in epoxy resins. 

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