J. Ronald Martin

The Flammability of Polyester-Cotton Mixtures

Polyester-cotton blended fabrics have the reputation of being “difficult to flame retard.” Treatments developed for flame retarding 100% polyester or 100% cotton fabrics do not seem to have the same effect when the two fibers are combined. Quantitative data are presented which pinpoint how the flammability behavior of polyester-cotton blends differs from that of the components. Physical and chemical aspects of pre-ignition and post-ignition phenomena are discussed for mixtures in which one or both of the polymers has been flame retarded, as well as for untreated combinations.

The Thermal and Flammability Behavior of Polyester-Wool Blends

The flammability behavior of a series of polyester-wool fabrics has been investigated in terms of a number of flaming combustioh and thermal-decomposition characteristics. Combustion behavior has been characterized by mass burning rate and heat emission measurements. Decomposition behavior has been studied by dynamic thermogravimetry, pre-ignition kinetics, and analysis of volatile decomposition products. These fiber blends show burning behavior more complex than would be expected from the additive behaviors of the two components. The decomposition data provide evidence for chemical interactions during decomposition, which may be the reason for the anomalous burning behavior.

The Effects of Moisture on the Flammability Characteristics of Textile Materials

The TRI Flammability Analyzer has been used to determine the effects of moisture on the flammability characteristics of textile materials. Both moisture in the fabric and in the test environment have been considered for a number of un treated and flame-retardant-treated fabrics. The results are reported and interpreted in terms of several measurable quantities: mass transformation rate (MTR), oxygen sensitivity (ΔMTR/Δ% O2), and extrapolated oxygen index (O. I.)0. Variations in fabric moisture content appear to have a greater effect on the behavior of relatively hydrophobic fibers (such as polyester), as compared to cotton or nylon.

Fabric Ignition by Flame Impingement

An apparatus has been constructed and data evaluation techniques developed for quantifying the ease of ignition of fabrics exposed to a small flame. The method takes careful account of fabric moisture content, which can have a substantial influence on this form of ignitability. A proposed specific ignition resistance coefficient, obtained from yes-no trials at preset exposure times, is inde pendent of fabric weight and ambient humidity, so that ignitability can be compared on a common basis.

Ignition of Polymers

For a polymer to ignite, it must first decompose. While low-molecular-weight condensed materials may produce volatile combustible species through sublimation or evaporation processes, one of the fundamental characteristics of the genus polymer is the lack of a boiling point. Thus, the only mechanism by which volatiles can be produced from a pure polymer must be some form of partial or complete thermal decomposition.

Design, Calibration, and use of convective air flow dynamic calorimeter

Abstract A new type of calorimeter has been developed that continously monitors the rate of heat emission from a heat source by following the rate of convective air flow induced by the emitted heat. For this purpose a thermistor version of a hot-wire anemometer connected to a strip chart recorder is positioned to measured the flow of incoming air. Details are given for the construction, calibration, and operation of a form of the calorimeter designed for studying the upward burning of unrestrained fabric samples under conditions closely approximating natural burning.

The Quantification of Fabric Extinguishability

A method has been developed for quantifying the extinguishability of burning fabrics which sepa rates extinguishability due to thermal loss from that due to blocking the transport of vaporized fuel and/or oxygen to the combustion zone. The maximum rate of heat emission during upward burning is measured using convective calorimetry for freely-hanging samples having asbestos paper stapled to one side in several arrangements. The mass of the heat sink is varied by using different numbers of asbestos layers; the vapor transport barrier is varied by drilling different numbers of holes in the asbestos. It is found that vapor blockage generally affects extinguishment to a much greater extent than heat loss. In addition, the effectiveness of the barrier is different for different fabrics, so that extinguishability ranking in terms of heat-emission rate depends on whether or not the fabrics are burned in contact with an inert substrate.

The Auto-Ignition of Multicomponent Fiber Systems

Using a simple experimental procedure for determining the time until ignition after a material is plunged into a heated air environment, it is possible to obtain kinetic data for this auto-ignition process. Results on homogeneous polymeric materials show that, while the rate controlling factors in every case are physical rather than chemical, ignition times at any single temperature depend on the basic thermal degradation process of each polymer. The study also includes work on multicomponent systems, including a mixed fiber blend as well as polymers treated with non-polymeric additives. For each combination studied it is possible to detect whether the presence of a second component has had only a physical influence on ignition, or whether thermal degradation has been affected by chemical interaction. Such data can serve to distinguish modifiers of flammability that act on the ignition process from those that are literally flame retardants or accelerators.