M. A. Khattab

Thermal studies on paper treated with flame-retardant

Sodium silicate and sodium berate mere tested as dame retardants on two types of paper sheet (100% rice straw pulp paper with a high silica content while the other consisted of 100% wood pulp paper). After addition of inorganic flame retardant salts (sodium silicate and sodium berate) on to the two samples of paper, the thermal behaviour of the treated paper sheets revealed differences in the course of the differential thermal analysis curves. The thermal analysis studies were carried out under an oxidizing atmosphere using differential thermal (DTA) and thermogravimetric (TGA) analysis, The flame retardants used in this study reduced the amount of volatile products formed during decomposition of the paper and increased the weight loss due to formation of char for the treated papers. The thermal degradation of paper can be considered as a first order degradation. Two stages of thermal degradation were kinetically differentiated, namely, a volatilization stage and a decarbonization stage, The activation energy for these two stages were calculated. The addition of flame-retarding salts decreased the activation energy for both stages, Sodium silicate salt showed more reduction of activation energy than sodium berate, especially for the rice straw paper.

Effect of contamination of cotton fabric with linseed oil on the activation energies of pyrolysis and oxidation of the fabric

The spontaneous ignition behaviour of both uncontaminated and oil contaminated cotton fabric has been investigated by using differential thermal analysis (DTA) and evolved gas analysis (EGA) techniques. The temperature, at which the onset of spontaneous ignition T i occurs, was recorded as a function of the oxygen concentration of the flowing oxygen-nitrogen atmosphere to which the fabric materials wer exposed in the DTA furnace, when heated at different heating rates. The activation energy of pyrolysis E p was obtained according to a simple kinetic model derived by Horrocks et al, as follows In(Hr/T 1 2 )=- E p/R(1/Ti)+In A p -In( E p- E ox/R= where E ox is the activation energy of gaseous product oxidation. Plotting of 1/T i vs In [O 2 ] produces true linear regions which intersect at a certain oxygen concentration and have slopes equal to (E ox -E p )/m. Taking the minimum and maximum E p value, and estimating the slopes of the two regions, the value of the molar oxygen concentration m required for the oxidation can be estimated for both untreated and oil contaminated fabrics. The results showed that E p decreased as the oil content in the fabrics was increased. It is probable that the oxidation of the oils generates free radicals, which catalyse the pyrolysis reaction of the cellulose. The movement of the point of intersection of the 1/T i vs In [O 2 ] due to oil concentration increase, and may explain the observed decrease in E ox value with increasing oil concentration. The results also showed a simultaneous increase in the number of oxygen molecules required for combustion as the oil concentration increased, reflecting the sensitivity of the combustion mechanism to oxygen concentration. The evolved gas analysis measurements indicated a diminishing of the dehydration reaction when the fabric was contaminated with oil, therefore suggesting domination of the depolymerization route of reaction.

Evaluation of Thermal Hazard of Azobisisobutyronitrile Using Accelerating Rate Calorimetry

The thermal decomposition of azobisisobutyronitrile (AIBN) has been studied under fully adiabatic conditions in a sealed bomb using an accelerating rate calorimetry technique (ARC). Data relating to temperature, pressure and time have been discussed. AIBN decomposes exothermally and the onset of decomposition occurs at 56.19°C. The reaction reaches its maximum at 112.28°C. During this temperature range, the self-heat rate, and the time to maximum rate of the reaction were evaluated. The experimental data have been also treated to evaluate the activation energy of the potential runaway reaction.

Spontaneous ignition of oil-contaminated cotton fabric

The purpose of this study is to evaluate the effect of different oil contaminants on the spontaneous ignition behavior of cotton fabric. A series of treated fabrics with different oil contamination percentages was investigated and compared. Measurements were designed and carried out to determine the average time-to-ignition and to study the thermal behavior of systems containing cellulose. The results showed that the time-to-ignition of the contaminated samples has notably decreased, particularly at relatively low temperatures (350-450°C). However, at higher temperatures such effects became insignificant. Differential Thermal Analysis measurements were used to explain the mechanism by which the oils affect the thermal behavior of the sample. The heat evolved due to the oxidation of the oil content is sufficient to increase the rate of cotton depolymerization at the expense of the dehydration mechanism. In other words, the heat evolved promotes the formation of volatiles which are not char precursors.