Limiting oxygen index polyethylene

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. 

Figure 15.16. Limiting oxygen index of polyethylene vs. concentration of filler. [Adapted, by permission, from Yeh J T, Yang H M, Huang S S, Polym. Degradat. Stabil., 50, No.2, 1995, 229-34.]...

Intumescence of polyethylene (PE) and PP has been reviewed using as intumescent agents zeolites [36], melamine phosphate and pentaerythritol [37]. Ammonium polyphosphate-pentaerythritol [38], zinc borate and ammonium polyphosphate [39], and APP [40], limiting oxygen index (LOI) [36, 37], cone calorimetry [36] and the UL 94 test [25, 36, 37] have all been used in these studies. 

It has been found that magnesium hydroxide appears to have a special synergy with polyethylene vinyl acetate [119], resulting in high levels of flame retardancy as measured by the limiting oxygen index tests (LOI) [120]. The effect of the magnesium hydroxide on the LOI of a polyethylene vinyl acetate (18% of vinyl acetate content) is presented in Table 3.3.1. 

Other binders include polyamide, polyester, and ethylene-propylene-diene rubber (EPDM). From the point of view of safety, binders are expected to be flame retardant. Limiting oxygen flame retardant indexes (LOIs) for some binders are as follows >95% for polytetrafluoroethylene (PEFE), 44-58% for PVDF, 24-29% for polyamide, and 2.8-5.7% for polyethylene (PE). 

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