Shigeko Nakanishi

Durable flame-retardant finished cotton fabrics characterized by thermal degradation behaviors

After a series of investigations on the durable flame-retardant finishes, it was thought to be important to study these durable flame-retardant finished materials from the thermal analytical standpoint. Accordingly, cotton fabric was finished with N-methylol dialkyl phosphonopropionamide (Pyrovatex C) by thermofixation and tetrakis (hydroxymethyl) phosphonium sulfate (THPS) precondensate by ammonia cure (Proban), as well as with THPS monomer by heat cure under various conditions, and subjected to the thermogravimetry (TG) to observe thermal degradation behaviors and obtain apparent activation energy (Ea). TG curves of Proban-finished samples showed the largest shift to lower temperatures with a steep slope; thermofixed THPS-finished sample gave a smaller shift with similar steep slope, whereas Pyrovatex-finished samples exhibited a similar shift but with a gradual slope. Ea versus residual ratio curves led us to conclude that CN bond-rich Proban polymer requires the highest Ea and decomposes with considerable rapidity, whereas ethylene-bond-rich Pyrovatex-finished samples with melamine crosslinking decompose gradually with the lowest Ea. As for the relationship between flame retardance and Ea distribution in the process of thermal degradation, typical differences among the above three kinds of finished samples were found, which are compared and discussed.

Flame Retardation of Cellulosic Fibers as Characterized by Thermal Degradation Behavior

Cotton fabric, one of the most flammable materials, is treated with various com pounds containing nitrogen, phosphorus, sulfur, halogens, and boron, individually or in combinations of two components, for a study of flame retardation from the standpoint of thermal decomposition. These samples are subjected to thermogravimetry and ther mal analysis to determine if there is any characteristic difference in the thermal deg radation behavior of flame retardant and untreated samples. The results show that flam mable samples ignite immediately or soon after the onset of thermal degradation, before the degradation rate reaches the maximum point, whereas flame retardant samples ignite considerably above the thermal degradation onset point, after the thermal degradation rate reaches the maximum. The flame retardant samples exhibit characteristic differ ences in thermal degradation behavior compared with those of combustible samples.

Pyrolytic Gas Generation of Cotton Cellulose With and Without Flame Retardants at Different Stages of Thermal Degradation: Effects of Nitrogen, Phosphorus, and Halogens

This study analyzes pyrolytic gases generated at various temperature ranges to observe changes in gas generation behavior dynamically in the process of thermal degradation. Cotton cellulose, a most flammable sample, is treated with compounds containing nitrogen and/or phosphorus as well as halogens with and without nitrogen. Each sample is heated thermogravimetrically, and pyrolytic gases are collected at various selected temperatures on the thermogravimetric curve for gas chromatographic and mass-spectrometric deter minations. The results reveal that flame retardant samples show extremely reduced amounts and fewer numbers of gas products compared with flammable samples, and some gases from flame retardant samples decrease with rising temperature, even disappearing at 500°C in the case of the (NH4)2HPO4-treated sample when flammable samples show further increases. Moreover, there is a considerable amount of toxic acrolein in flammable samples, but it is not detected or the amounts are much smaller in flame retardant samples. Acetonitrile, an effective radical scavenger, is found only in samples exposed to the synergistic effects of nitrogen and phosphorus or bromine. The results confirm that flame retardation works not only to inhibit combustion and subsequent gas generation, but also to scavenge pyrolytic gases already formed, resulting in a reduction or quenching of hazardous gas generation.

Flame Retardation of Cellulosic Fibers Characterized by Apparent Activation Energy of Thermal Degradation

This paper extends previous investigations on the thermal degradation behavior of cotton fabric treated with compounds containing different kinds of elements that con tribute to flame retardation. The apparent activation energy (Ea) is evaluated by Ozawas method at different stages of thermal degradation, represented by the thermal degradation onset point, maximum degradation rate point, and flash point, to observe the variation of Ea in the process of thermal degradation. Ea values of flame retardant samples are generally lower, whereas those of flammable samples are higher than that of untreated cotton fabric at every step throughout thermal degradation. Such results suggest that flame retardant materials decompose more easily than flammable samples, which supports the fact reported in earlier work that the thermal degradation of flame retardant materials is initiated at lower temperatures in comparison with that of flam mable materials.

Gas Chromatographic and Mass Spectrometric Study of the Bromination of Protein Fibers with N-Bromosuccinimide and Triphenylphosphine

Silk fibers were brominated with a 1:1 (mole/mole) mixture of N-bromosuccinimide (NBS) and triphenylphosphine (TPP) in dimethylformamide. β-Bromoalanine (Brala) residues formed by the bromination of serine residues with NBS/TPP were very un stable under acid hydrolysis conditions, and Brala was not detected in the hydrolyzate of the brominated silk by gas chromatography-mass spectrometry of amino acids as their butyl esters of N(Q)-triftuoroacetyl derivatives. The brominated silk fibers were treated with aqueous solutions of ammonia and methyl-, ethyl-, propyl-, and butyl amines. Chromatographic-spectrometric analysis of amino acids of the treated silk samples showed the formation of corresponding β-aminoalanine and β-alkylami noalanines formed by the reaction of Brala residues, by direct condensation, or through the formation of dehydroalanine residues as intermediates. The analysis also showed that monobromotyrosine was formed by the treatment with NBS/TPP. Bromination of tyrosine residues must proceed by electrophilic substitution, probably by the action of free NBS in the reaction mixture.

Effect of Soap-Washing in Hard Water on Flame Retardancy of Flame Retardant Man-Made Fabrics

Reduction of the effect of soap-washing in hard water on flame retardant fabrics is a world-wide problem for any districts where using hard water. In this respect, we attempted a fundamental survey on the effect of soap-washing in hard water on the flame retardancy of flame retardant fabrics. The results are summarized as follows: 1) LOI decreased with increasing hardness of water, and fabrics having rough surface or small openings between threads enhanced the reducing effect by entrapping soap curd deposit. 2) Rinsing with soft water after the wash proved to be considerably effective to recover the reduced flame retardancy. 3) Repeated washing in hard water caused accumulated pickup of soap curd deposit resulting in a considerable reduction of flame retardancy. 4) Addition of dispersing agents of soap, especially nonionic type, was effective in the recovery of LOI. 5) Amount of Ca2+ on the fabrics showed reasonable parallelism to the reduction of LOI through the experimental conditions.

Correlation between Removals of Resins and Soils Observed in Soiled Resin Finished Fabrics during Cleansing Process

It seems probable that the removal of soils from resin finished fabrics occurs simultaneously with the removal of resins during the cleansing process, but the observation for the removal of resin has been ignored so far. Therefore, a simultaneous observation for the removal of resin and soils was carried out in this study to investigate the effect of resin finish on the detergency of soils together with that of stains on the removal of resins. The results disclosed a correlation between the above two effects as follows: 1) Water soluble soils became more removable by resin finish with an increase in the removal of resins from resin finished fabrics. 2) The detergency of oily soils was reduced by resin finish and only a little removal of resin was observed with oily soils on resin finished fabrics. 3) A mixture of hydrophilic and hydrophobic soil as Chinese ink on resin finished fabrics gave a little removal of resins and its detergency was slightly influenced by resin finish. 4) Also dry cleaning showed a tendency that any increase in the removal of resins gave an improved detergency and reduction in detergency showed little removal of resins.