A.R. Horrocks

Handbook of technical textiles

Processes: Technical Textiles Market-An Overview. Technical Fibres. Technical Yarns. Technical Fabric Structure: Woven Fabrics. Knitted Fabrics. Non-woven Fabrics. Technical Textile Finishing. Coating. Colouration. Areas of Application: Heat and Flame Protection. Textile-Reinforced Composite Materials. Waterproof/Breathable Fabrics. Textiles in Filtration. Geotextiles/Natural Fibre Geotextiles. Textiles in Medicine. Textiles in Defence. Textiles for Survival. Textiles in Transport. Textiles and the Environment.

Flame-Retardant Treatments of Cellulose and Their Influence on the Mechanism of Cellulose Pyrolysis

Abstract Cellulose, either as a major component in wood or as the prime textile fiber cotton, is most frequently implicated in fire, causing injuries and fatalities [1]. When ignited, cellulose undergoes thermal degradation, form-ing combustible volatile compounds which become involved in the propaga-tion of fire. Fortunately cellulose has a chemical composition which makes it easily amenable to interactive flame-retardant treatments. Because flam-mability is a relative rather than an absolute concept, there are no truly flame-retardant fabrics, and the best that can be attained is some given level of flame resistance. Barker and Drews [2] proposed that with cellulose, the problem of fire can be described as two distinct phenomena, glowing and flaming, which present different potential hazards and should be ap-proached in different ways. Glowing is a direct oxidation of solid cellulose or its degradation products. It is generally a slow combustion and is of great concern for only specific items, such as c...

The influence of carbon black on properties of orientated polypropylene 2. Thermal and photodegradation

Abstract This paper extends previously reported work and describes the effect of carbon black on thermal and photo-oxidative degradation of oriented polypropylene (PP) geotextile tapes. PP tapes containing carbon black with different particle size, structure (or aggregate shape), specific surface volatile content and concentrations have been exposed separately to circulatory air ovens at 130°C and UVB lamps at 60°C respectively. The exposed tapes were studied using tensile tensiometric, IR spectrophotometric and thermal analytical (DSC) techniques. Thermal stabilities of PP tapes filled with carbon blacks having low volatile contents are comparable to those of unfilled PP tapes. At given oven-exposure times, carbon blacks with varying particle sizes and structures, except for volatile content, show only slight influence on thermal stability of the PP tapes. The thermal stability was not significantly affected in tapes containing increased carbon black concentrations from 2.5 to 5% w/w The carbon black with the highest volatile content adversely affected thermal stability possibly because the surface oxygenated groups present act as sensitisers. Dynamic thermal analysis (DSC) shows that the magnitude of shifts to lower temperatures of the post-fusion oxidative exotherm ( T on ) reflect respective losses in tensile properties and supports previous evidence that T on is a sensitive indicator of the degree of polymer oxidation. However, the presence of carbon black significantly increases UV durability of these filled tapes. The UV resistance in terms of tensile properties is inversely proportional to carbon black particle diameter. The carbon black sample with a high concentration of reactive oxygenated groups, measured as volatile content, shows relative inferior UV resistance to tapes containing low volatile content blacks with similar particle size. No effect of carbon black structure on UV stability was observed, which agreed with the previous results for carbon black-containing polyethylene films under UVA and UVB exposures. The overall evidence suggests that carbon blacks having smallest particle size, possibly high structure and low volatile contents will yield PP tapes having optimum thermal and UV stabilization behaviours. ©

Use of gas chromatographic analysis of volatile products to investigate the mechanisms underlying the influence of flame retardants on the pyrolysis of cellulose in air

An investigation has been undertaken of the influence of temperature, in the range 300–1000°C, and flame retardant type, on the yields of volatile products and char from flame retardant treated cotton fabrics. The flame retardants studied at commercial levels of application were the three condensed phase active products, ammonium polyphosphate (Amar TR), a phosphonium salt-urea-polycondensate (Proban CC) and a phosphonopropionamide (Pyrovatex CP) and two vapour phase active materials, ammonium polyphosphate-ammonium bromide (Amgard CD) and an antimony (III) oxide-aliphatic bromide (Flacavon H14/587) formulation. H14/587) formulation. Gas chromatographic analysis was restricted to 30 ‘model’ volatile products selected as representative of the pyrolysis process. For clarity, the data are presented in terms of total yields of each of the various generic groups investigated; namely, furans, aldehydes, etc. It was found that the untreated cotton fabric gave no char, with furan yields very much greater than those for the flame retardant treated fabrics. The two vapour phase active flame retardant treatments resulted in low char yields coupled, as was to be expected, with the highest yields of volatiles and CO. The condensed phase retardants, Proban, Pyrovatex and Amgard TR produced large amounts of char, Proban giving most. Significant yields of aromatic species were obtained from the fabrics with the char consolidating Proban and Pyrovatex treatments but Amgard TR, which has a strong dehydration function, gave none. In contrast to the other untreated and flame retardant treated fabrics studied, the antimony/aliphatic bromide treatment (Flacavon) showed two maxima on its yield/temperature profiles. A model for the pyrolytic degradation of cellulose in air has been proposed on the basis of current information concerning char and volatile product formation. This envisages the degradation as two competing series of reaction paths. Volatile flame retardants enhance the decomposition via levoglucosan to form volatile products whilst condense phase active retardants encourage the alternative route to char formation.

Smoke, CO, and CO2 Measurements and Evaluation using Different Fire Testing Techniques for Flame Retardant Unsaturated Polyester Resin Formulations

Smoke is considered to be the main fire hazard but its production depends on major variables, principally the chemical character and the burning rate of the polymer plus the availability of oxygen and hence ventilation. The main aim of this work is to study the effect of smoke suppressants on flammability and smoke production of flame retarded unsaturated polyester resin-nanocomposites using four different testing regimes representing different fire scenarios. Samples containing zinc borate, zinc stannates, ammonium polyphosphate with and without nanoclay are analyzed for smoke generation using cone calorimetry (well-ventilated fire), a tube furnace (fully developed fire), and a smoke density chamber (under-ventilated fire). Carbon monoxide (CO) and carbon dioxide (CO2) measurements using thermogravimetry-evolved gas analysis (TG-EGA), cone calorimetry, and tube furnace have also been analyzed and compared. Results have confirmed that the production of smoke, CO, and CO2 depend upon smoke suppressants and fire conditions used during testing samples. From this study it is evident that tin additives have very little influence on flammability of unsaturated polyester resin but they reduce smoke formation. The slight flame retardant action of the Res/APP/ZB sample is due to enhanced cross-linking of APP in the presence of zinc borate, whereas zinc stannates do not promote cross-linking of APP and hence show no improvement in flame retardancy. Finally, the presence of nanoclay in flame retarded resin shows significant reduction in smoke formations in both well-ventilated and under-ventilated fire condition. However, in the presence of smoke suppressants used in this study, the nanoclay is not instrumental in further suppressing smoke formation.

Effect of carbon black on the oxidation of polyolefins: An overview

Abstract The use of carbon black in polyolefins is widespread. Two to three per cent of finely divided carbon black provides an effective light screen protecting the polymer against exposure to light. In geotextile applications, use of carbon black is widespread due to demands for higher durability. Types of carbon black, their usage and interaction with thermal antioxidants are reviewed. Current understanding of the effects of carbon black on the oxidation reaction shows conflicting evidence. Some workers have reported that carbon black accelerates oxidation due to surface catalysis of peroxide decomposition to form free radicals, adsorption of antioxidants from the polymer and increased accessibility of oxygen. Others have produced evidence of the inhibition of oxidation by carbon black because of its activity as a radical scavenger and its ability to decompose peroxides to form stable products. The role of reactive chemical groups on the carbon black surface, particle size and concentration are reviewed. It is evident that a full understanding of the behaviour of carbon black in polyolefins is currently not available and that it may depend on the balance of competing mechanisms of sensitisation and stabilisation in any specific formulation.

Thermogravimetric analysis study of the mechanism of pyrolysis of untreated and flame retardant treated cotton fabrics under a continuous flow of nitrogen

Abstract Samples of unmodified cotton fabrics and cotton fabrics finished with various flame retardant treatments at commercial levels of application were subjected to thermogravimetric analysis in a continuous flow of nitrogen. The relative thermal stabilities of the fabric samples were investigated using various heating rates. Each sample was found to give a characteristic TG curve with three distinct regions. This could be interpreted as an indication of the decomposition occurring in three stages, viz. dehydration, volatile evolution (with char formation) and char removal. All the flame retardant treatments lowered the temperature at which volatiles first appeared. Attempts were made to calculate Arrhenius parameters for the volatile evolution processes using a technique developed at Salford. It was found that fabric samples treated with the commercial condensed phase active-flame retardants, namely ammonium polyphosphate (Amgard TR, Albright and Wilson Ltd) a phosphonopropionamide (Pyrovatex CP, Ciba-Geigy Ltd) and a phosphonium salt-urea-polycondensate (Proban CC, Albright and Wilson Ltd) raise the activation energy compared to that of the untreated cotton fabric. Volatile evolution probably occurs via three-dimensional diffusion. Cotton fabrics treated with the commercial vapour phase-active flame retardants ammonium polyphosphate-ammonium bromide (Amgard CD, Albright and Wilson Ltd) and an antimony(III) oxide-aliphatic bromide (Flacavon, Shill and Seilacher) yielded TG curves which were too complex for simple interpretation.

Thermal (heat and fire) protection

This chapter discusses the fire and heat protection and the means of conferring these features into textile products and assemblies and other factors such as comfort, ballistic resistance, chemical, and biological agency resistance will only be commented on if particularly relevant to a particular thermal protective solution or system. The chapter will focus on factors that assist in understanding the nature of the thermal hazards as they apply to textiles and the means of addressing them. Thermal protection relates to the ability of textiles to resist conductive, convective, radiant thermal energy or a combination of two or more. Levels of thermal resistance may be simply defined with respect to maximum temperature of exposure criteria, although time of exposure is a significant parameter as well. Within the area of flammability of all so-called conventional fibers, wool has the highest inherent non-flammability and so is particularly attractive for protective textile end-uses such as uniforms, coveralls, transport seatings, and domestic and contract furnishings, where heavier fabrics may be used and the aesthetic character of wool may be marketed.

Zinc Stannates as Alternative Synergists in Selected Flame Retardant Systems

Zinc stannates, including zinc hydroxystannate, are used components within synergistic fire retardant systems usually in conjunction with halogenated species in a number of polymers. Their behavior is similar to antimony III oxide (ATO) in that they enhance the effectiveness of the halogenated and, principally brominated retardant (Br-FR), present. Unlike antimony III oxide, they are non-toxic but are specific in their synergistic activity. Furthermore, they are effective smoke suppressants. This article reviews the published literature with regard to this synergistic specificity as well as the role of zinc stannates as synergists and smoke suppressants in halogenated polymers exemplified by poly(vinyl chloride), polyolefins exemplified by polypropylene, polyamides, acrylonitrile-butadiene-styrene and polyester and epoxy resins.

The influence of carbon black on properties of oriented polypropylene 3. Thermal degradation under applied stress

Abstract Extending previous studies of the effect of carbon black variables on thermal degradation of oriented polypropylene tapes, it has been shown that level of applied stress and characteristics of carbon black influence the thermal oxidative stability of polypropylene. In particular, retained breaking strain exhibits a higher sensitivity to levels of applied stress than other measurable parameters. No change in carbonyl index occurs throughout the exposures even up to rupture points. Crystallinity values obtained from FTIR crystallinity index measurements are shown to be more reliable than those obtained from DSC and confirm that the applied stress has an orienting effect during oven-ageing. Relative to unfilled tapes, low particle size and low structure appear to enhance oxidation resistance while increased volatiles content reduces oxidation resistance of filled tapes. Even so, all carbon black-filled tapes, especially at ultimate stress loadings >10% showed superior performance to unfilled analogues. These effects and that of black concentration are interpreted in terms of the possible physical and chemical changes occurring.