The Extinction Oxygen Index of Polyester-Cotton Blended Fabrics

Limiting and extinction oxygen index techniques have been used to study the effects that fabric variables and blend composition have on the burning be haviour of 20/80, 50/50 and 65/35 polyester-cotton blended fabrics. Whilst LOI values were not dependent on ignition time, they were for a given blend com position dependent on fabric area density. L _o values determined at zero area density were little dependent on blend composition for the blends studied. EOI values, as shown previously for single fibre component fabrics, were de pendent on igniter application times. Derived [EOI] _o values at zero ignition times, like LOI, increased with area density. Zero area density or "free-fibre" ex tinction oxygen index E _o values, like LOI and L _o , varied only slightly with blend composition. However, when compared with respective values for pure polyester and cotton fabrics, the respective magnitudes of blend E _o values pro vide a better indication than do L _o values of the difference of blend from indi vidual component fibre burning behaviour. Thus it is considered that the ex tinction concept provides a better indication of the variations of flammable character of polyester-cotton blends compared to the individual fibre-con taining fabrics.