The effect of selected reactive dyes on the flammability behavior of cotton

The flammability behavior cf reactive dyed cotton fabrics was investigated, and the results were compared to the burning behavior exhibited by undyed cotton fabric. A 2 x 3 x 2 factorial design was used to evaluate the effects of dye type, dye color, and dye level on the peak heat transfer rates, time to reach the peak heat transfer rates, total burn time, total heat transfer, heat/time relationship, rate of flame spread, and heat of decomposition of the dyed fabrics. Reactive dyed cotton fabrics included two dye types (Procion H and MX), three dye colors (red, yellow, and blue) and two dye levels (1% and 4%). Testing was carried out on the Mushroom Apparel Flammability Tester (MAFT), 45° angle tester, and Differential Scanning Calorimeter (DSC). In addition, undyed cotton fabric was tested for comparison with the dyed fabric.

The MAFT findings indicated that dye level is the most important factor in the heat transfer rate at the second peak, the time to reach the second heat transfer rate peak, and total heat transfer of the dyed fabrics. No differences were found in the heat transfer rate at the first peak, the time to reach the first heat transfer rate peak, and total burn time for the l3 dyed and undyed fabrics.

The effect of dye level was observed as an increase in the values for the heat transfer rate at the second peak, the time to reach the second heat transfer rate peak, and total heat transfer. The undyed fabric exhibited lower values than the 4% dyed fabrics for these variables but was not significantly different from the 1% dyed fabrics. Heat/time relationship analysis indicated the fabrics had a slow initial rate of heat transfer followed by a rapid acceleration in the rate and finally a leveling off as the total amount of heat transferred by the fabric was reached. The analysis revealed no difference in the flammability hazard of these fabrics during the first minute of burning.

Only dye level affected the 45° angle test measurement of rate of flame spread for the dyed fabrics, with the 4% fabrics exhibiting the longest flame spread times. Dyed and undyed fabrics exhibited no difference in rate of flame spread.

DSC results revealed that both the chemical structure of the dye, including the dye chromophore, and the amount of dye are significant in the decomposition of reactive dyed cellulose. The effect of dye level was observed as a decrease in the values for the temperature at onset of degradation, the degradation peak temperatures, and the peak heights ratio. Dye color was significant for heat of decomposition, the temperature at onset of degradation and the degradation peak temperatures. Heat of decomposition differences were related to dye type and dye level. Yellow fabrics remained relatively constant across dye type and dye level while the red and blue fabrics exhibited contrasting increases and decreases across dye type and dye level.

DSC results for the undyed fabric indicated the fabric begins to degrade at a higher temperature, exhibits only one degradation peak, exhibits a higher degradation peak temperature, and requires less energy for decomposition than the dyed fabrics. Thus, the second

degradation peak for the dyed fabrics may represent the decomposition of portions of the cellulose molecule containing dye molecules.