Limiting oxygen index composites

ETFE resins do not support combustion in air and have typical limiting oxygen index (LOI) about 30 to 31. LOI depends on monomer ratio in the polymer and it increases gradually as the fluorocarbon content is increased to the alternating composition and then increases more rapidly to the LOI values for FIFE.68... 

Relative to carbon/carbon composites, the hybrid composites have a reduced thermal stability in air due to the resin content of the matrix. The flammabilities of the hybrid composites, as measured by the limiting oxygen index (LOI) test (63) are given in Figure 36. Pure carbon/carbon composites are not inflammable in... 

Figure 36. Limiting oxygen index (LOI) of flammability resistance for carbon/carbon composites and related hybrid composites with epoxy resin impregnant, as functions of bulk density and resin content (64).

The degree of flammability of a polymeric material may be predicted from its chemical structure. One of the most valuable criteria in fire research, the so-called limiting oxygen index (LOI) may be estimated either from the specific heat of combustion or from the amount of char residue on pyrolysis. Since both quantities can be determined if the chemical structure is known, also the LOI can be estimated. An approximate assessment of the LOI value direct from the elementary composition of the polymer is also possible. 

FIG. 26.9 Correlation between limiting oxygen index and elementary composition. 

Estimate the limiting oxygen index of polycarbonate from its chemical composition. Solution... 

Table 13.5 Effect of fire retardants on limiting oxygen index (LOI) of UPE/Gre v/a opttva/Fire-retardant composites.

The preliminary study on the flammabihty of HUP-MMT compositions was performed by the determination of limiting oxygen indexes (LOI). The flame retardance was affected by styrene content in the resin and the type of clay used (Table 9.3). An additional amount of styrene has been added to some compositions in aim to improve the casting properties on the other hand the excess styrene makes the cured compositions more flammable due to the increased content of polystyrene (LOI = 18) and decreased of HUP (LOI = 24). The cured compositions containing MMT-Na as well as organoclays with DMDTA and ADA, showed... 

The success of graphite in this applications shows that filler with plate like structures should be considered when intumescent materials are being formulated. Recent developments in intumescent paints show that performance can be improved if a layer of organic material is inserted between the layers of the plate like filler. The degradation of this material in the enclosed space increases the expansion rate and the retention of gas inside the degrading material. Based on this principle any plate like filler has the potential to be useful in an intumescent application. The composition of filler is also important. When clay was used as a filler in fire retardant applications, it was found that some of its components interfere with the action of carbonization catalysts and detract fi om the overall performance of the system in terms of limiting oxygen index. ... 

Finally, Figures 4 and 5 show the limiting oxygen index values and char yields (respectively) for several nylon 6,6 compositions. 

Figure 4 Limiting oxygen index (LOI) data for nylon 6,6 compositions with SnCl2-Si (2 3%wt), BaClz-Si (2 3%wt), CaCl2-Si (2 3%wt), MnClz-Si (2 3%wt), ZnClj-Si (2 3%wt), CoClj-Si (2 3%wt), CuClz-Si (2 3%wt).

Flame retardancy effectiveness and the comparison of the exposure to catch fire of the PE-HD/MDH composites were rated in terms of accuracy and repeatability by the test method for measuring the limiting oxygen index (LOI) according to PN-EN ISO 4589-2 2006. 

In this chapter, a flame retardant that contained silicon and phosphoms was grafted onto graphene nanosheet oxide (GNO) and then added to epoxy resin to form a composite. The thermal and flame-retardant properties of the composites were examined by thermogravimetry and determination of the limiting oxygen index (LOI). 

Evaluation of the composite materials in terms of limited oxygen index (LOI) provides first hand information on the effectiveness of fire retardant additives [22]. For LDPE/LDH nanocomposites with up to 16.20 wt% LDH content, the LOI values are shown in Fig. 28. The imfilled LDPE has a LOI value of 18.0 and the addition of a small amoimt of LDH has nearly no effect on the LOI value. Even a small decrease in the LOI value is observed below 5 wt % LDH concentration. However, at higher levels of LDH content (above 5 wt %), the LOI value increases with increasing LDH concentration. The nanocomposites containing 16.20 wt% LDH have a LOI value around 22.0, which is significantly higher than that of unfilled LDPE, but still further improvement is necessary for industrial acceptance. 

---