The Heat of Combustion and Oxygen Index of Fibrous Materials

Abstract

Heats of combustion ( Ho), oxygen index (OI), and the differences between their observed and calculated values (Δ Ho) and ΔOI) of various fiberous materials were measured and calculated. Both polyester (where molten mass drips off) and acrylic homo- and copolymers (which leave considerable char in the OI test) have larger values of ΔOI and Δ Ho than those of easily combustible polymers such as polymethyl methacrylate or polypropylene. Cotton or acetates, which show residual carbonaceous materials while burning, have values of ΔOI equal to nylon-6 or polyacrylonitrile, but smaller values of Δ Ho. Oxygen index values from various shapes of samples such as stick-form, film or fabric rolled up into cylinders, and film or fabric in 5 × 10-cm sheets were determined. Oxygen index values of nylon-6, polyester, and acrylic copolymer of 11% methylacrylate decrease rapidly as the test forms change from stick to cylinder to open-width. Such values calculated from observed Ho will be equal to the OI of the material when melting and dripping or char-producing phenomena do not occur. Results of thermogravimetric analysis are also presented.