Limiting Oxygen Index LOI Test

The effect of different fire retardants and the fibers siuface modification on LOI values of polyester-Grewa optiva composites has been reported in Table 13.5. It can be observed from the table that when reinforced with raw fibers, the UPE matrix exhibits low LOI value in comparison to neat UPE matrix. Similar results have also been reported by Rai et al. during their study on the effect of coagulum on LOI of polyester 

UPE Grewia optiva Ratio (% by weight) Fire Retardant (% by weight of UPE) LOI 

From the table it has also been observed that the EOI value of neat UPE increases on reinforcement with fire-retardant fillers, and this LOI value increases considerably 

It has been observed from the above discussion that mechanical, physico-chemical and fire retardancy properties of UPE matrix increases considerably on reinforcement with surface-modified natural cellulosic fibers. The benzoylated fibers-reinforced composite materials have been found to have the best mechanical and physico-chemical properties, followed by mercerized and raw Grewia optiva fibers-reinforced composites. From the above data it is also clear that polymer composites reinforced with 30% fibers loading showed the best mechanical properties. Further, benzoylated fibers-reinforced composites were also found to have better fire retardancy properties than mercerized and raw fibers-reinforced polymer composites. Fire retardancy behavior of raw and surface-modified Grewia optiva/GPE composites have been found to increase when fire retardants were used in combination with fibers. This increase in fire retardancy behavior of resulted composites was attributed to the higher thermal stability of magnesium hydroxide/zinc borate. 

Kikuchi, Woodfiber-plastic composites for furniture applications, in Seventh international conference on woodfiber-plastic composites proceeding, pp. 159-161, Forest Products Society, Madison, WI (2004). 

---

Limited oxygen index (LOI) test, 10 175 13 380, 384, 385. See also Limiting oxygen index (LOI)... 

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... 

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. 

---