Flame‐retardant finishing of cotton fleece fabric: part I. The use of a hydroxy‐functional organophosphorus oligomer and dimethyloldihydroxylethyleneurea

Cotton fleece has become a popular fashion in recent years. However, most of the 100% cotton fleece fabric is not able to meet the federal flammability standard (‘16 CFR Part 1610: Standard for the Flammability of Clothing Textiles’) without chemical treatment. In this research, we investigated the use of the combination of a hydroxy‐functional organophosphorus oligomer (HFPO) as the flame‐retarding agent and dimethyloldihydroxylethyleneurea (DMDHEU) as the binder to reduce the flammability of cotton fleece. We found that HFPO is effective in reducing the flammability of the cotton fleece whereas DMDHEU enhances the effectiveness of HFPO due to phosphorus–nitrogen synergism. The flammability as well as other properties of the treated cotton fleece is affected by both the concentration of HFPO and that of DMDHEU. The cotton fleece treated with HFPO/DMDHEU passes the federal flammability standard and shows high strength retention with little change in fabric whiteness and hand. We also found that the flame‐retardant finishing system is durable to multiple home launderings. The combination of HFPO and DMDHEU has the potential to become a practical flame‐retardant finishing system to reduce the flammability of cotton fleeces. Copyright © 2006 John Wiley & Sons, Ltd.     

Flame retardant finishing of cotton fleece fabric. II. Inorganic phosphorus‐containing compounds

Cotton fleece is not able to meet the federal flammability standard for general apparels (CFR 1610) without flame retardant treatment. Consequently, cotton fleece is not available in the market in spite of high demands. In our previous research, we studied the application of a hydroxyl‐functional organophosphorus oligomer as a flame retardant finishing agent for cotton fleece. In this research, we investigated the use of aluminum hydroxyphosphate (AHP) formed in situ on cotton by the reaction of aluminum sulfate and sodium phosphates to reduce the flammability of cotton fleece. We found that the AHP formed on cotton is effective in reducing the cotton fleece's flammability from “Class 3” to “Class 1.” Elemental analysis of aluminum and phosphorus in the AHP shows that the mole ratio of Al/P changes as the pH value of the sodium phosphates solution changes. The pH of the sodium phosphate solutions also affect the quantity of AHP formed on the cotton fleece. The treated cotton fleece retains “Class 1” flammability after one home laundering or the combination of dry‐cleaning and hand washing procedures. The treatment increases the whiteness of the cotton fleece whereas it reduces its bursting strength. The cotton fleece thus treated is also investigated using differential scanning calorimetry and scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phosphate and nitrogen-rich polyelectrolyte complex flame retardant treatment for cotton fleece

The soft nap and deep pile that impart comfort and warmth to cotton fleece also amplify its flammability. Using ambient aqueous processing, an environmentally benign polyelectrolyte complex (PEC), consisting of poly(allylamine hydrochloride) and sodium hexametaphosphate, was deposited on cotton fleece. This treatment adds only 12.5% weight, reduces peak heat release by 68% and total heat release by 74%, and protects from fire via intumescence. Without treatment, fleece burns aggressively with long afterburn and afterglow times, leaving no residue. With the applied PEC, the fabric self-extinguishes within a few seconds and exhibits no afterglow. In addition, it withstands at least five simulated laundering cycles in alkaline detergent, maintaining a 57% reduction in fire growth capacity afterward. The original soft surface can be restored to the fleece by manual brushing. This simple and environmentally benign treatment provides an opportunity to effectively protect highly flammable textured cellulosic textiles in a safe way.     

Flame retardant finishing of the polyester/cotton blend fabric using a cross‐linkable hydroxy‐functional organophosphorus oligomer

Blend fabrics of cotton and polyester are widely used in apparel, but high flammability becomes a major obstacle for applications of those fabrics in fire protective clothing. The objective of this research was to investigate the flame retardant finishing of a 50/50 polyester/cotton blend fabric. It was discovered previously that N,N′‐dimethyloldihydroxyethyleneurea (DMDHEU) was able to bond a hydroxy‐functional organophosphorus oligomer (HFPO) onto 50/50 nylon/cotton blend fabrics. In this research, the HFPO/DMDHEU system was applied to a 50/50 polyester/cotton twill fabric. The polyester/cotton fabric treated with 36% HFPO and 10% DMDHEU achieved char length of 165 mm after 20 laundering cycles. The laundering durability of the treated fabric was attributed to the formation of polymeric cross‐linked networks. The HFPO/DMDHEU system significantly reduced peak heat release rate (PHRR) of cotton on the treated polyester/cotton blend fabric, but its effects on polyester were marginal. HFPO/DMDHEU reduced PHRR of both nylon and cotton on the treated nylon/cotton fabric. It was also discovered that the nitrogen of DMDHEU was synergistic to enhance the flame retardant performance of HFPO on the polyester/cotton fabric.     

The effects of weathering and atmospheric pollutants on cotton fabric and cotton fabric treated with selected flame retardants. I. Physical,chemical, and flammability properties

The effects of weathering and atmospheric pollutants on the physical, chemical, and flammability properties of cotton fabric treated with Pyrovatex 3805 and with THPOH-NH₃ flame retardant finishes and untreated controls were determined. The fabrics were exposed to SO₂, NO₂, and ozone singly and in combination for 50, 100, and 150 hr in a 2500-watt xenon arc Weather-Ometer using gas controls with and without light at a temperature of 35°C and a relative humidity of 90%. Excessive strength losses and large changes in D.P. for the untreated control occurred under all exposure conditions after 150 hr. Changes in the physical and chemical properties of the treated fabrics were moderated by the finishes, with Pyrovatex 3805 providing better protection to the cellulose than THPOH-NH₃. Elemental analysis and oxygen index measurements indicate that the Pyrovatex 3805 finish was severely degraded under these exposure conditions, with a resultant loss in flammability properties of the treated fabric after weathering. The THPOH-NH₃ finish was not appreciably affected by these exposure conditions and the treated fabric retained most of its flammability properties after weathering.     

Improvement in the flame retardancy of cotton fabric by admicellar polymerization of 2‐acryloyloxyethyl diethyl phosphate using an anionic surfactant

The phosphorus‐containing acrylate monomer, 2‐acryloyloxyethyl diethyl phosphate (ADEP), was synthesized and applied to cotton fabric by using admicellar polymerization. Sodium dodecylbenzene sulfonate was used as the anionic surfactant. The film of polymerized monomer (PADEP) formed on the cotton surface was characterized by FTIR‐ATR spectroscopy and SEM. Thermal and flame retardant properties of PADEP‐coated cotton were investigated by TGA and flammability tests. Results showed that PADEP polymer film was successfully formed on the cotton fabric. The TGA and DTG analyses showed that the phosphorus‐containing PADEP lowered the decomposition temperature of the treated fabric resulting in a higher char yield than in the case of untreated cotton. The flammability tests showed that the treated cotton had much improved flame retardancy property after the treatment. The treated fabric also retained its good pliability and soft touch with good air permeability. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermogravimetric Analysis of a Cellulosic Fabric Incorporated by Synthetic Ammonium Magnesium Phosphate as a Flame-Retardant

We have investigated the effect of synthetic struvite (MgNH₄PO₄·6H₂o) on the flammability of a cellulosic fabric. It was synthesized by means of the multiple-bath method and deposited onto a cotton fabric. Its uniformity was ensured by means of squeeze rolls, obtaining the optimum effective add-on value of ammonium magnesium phosphate to impart flame retardancy to cotton fabric in the range of around 12 g anhydrous salt per 100 g fabric. A thermogravimetric analysis of pure cotton, treated cotton, and the salt was accomplished, and their thermograms were compared and commented upon. The results obtained fortified the chemical theory expressing the promotion of the formation of solid char rather than the formation of volatile pyrolysis products, during the fulfillment of thermal decomposition of the cellulosic substrate.     

Polymeric multifunctional carboxylic acids as crosslinking agents for cotton cellulose: Poly(itaconic acid) and in situ polymerization of itaconic acid

Multifunctional carboxylic acids have been used as nonformaldehyde durable press finishing agents for cotton. In previous research we found that maleic acid (MA) and itaconic acid (IA) polymerize in situ on cotton fabric at elevated temperatures when both potassium persulfate (K₂S₂O₈) and sodium hypophosphite (NaH₂PO₂) are present, thus imparting wrinkle resistance to the treated cotton fabric. We also found that MA and IA polymerize in aqueous solutions in the presence of K₂S₂O₈ and NaH₂PO₂. In this research, we compared the effectiveness of poly(itaconic acid) (PIA) applied to cotton fabric as a polymer and IA applied as a monomer and allowed to polymerize in situ for crosslinking cotton cellulose. We found that IA is more effective in esterifying cotton cellulose and imparting a high level of wrinkle resistance to the fabric as it polymerizes in situ than PIA applied as a polymer. We also found that tensile strength loss of the cotton fabric crosslinked by IA polymerizing in situ as a function of fabric wrinkle recovery angle is practically the same as that crosslinked by PIA applied as a polymer. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 319–326, 2001     

Flame‐retardant finishing of cotton fabrics using polyamino carboxylic acids and sodium hypophosphite

The purpose of this research was to use polyamino carboxylic acids (PACAs) and their combination with sodium hypophosphite (NaH₂PO₂) as a flame‐retardant finishing system for cotton fabrics. Flammability of cotton fabric was evaluated by 45° flammability test, differential scanning calorimetry and measuring the char yield. The combination of polyamino carboxylic acids and sodium hypophosphite as a phosphorus‐containing catalyst reduces the flammability of cotton. The pyrolysis properties and the results of char yield of the finished cotton show that with increasing amount of catalyst, the flame retardancy increases. Fastness against multiple laundering, whiteness and tensile strength of the cotton finished with PACAs/NaH₂PO₂ to multiple standard laundering have been studied, too. The flame retardancy effect has an acceptable washing fastness. Whiteness and tensile strength of the finished cotton do not change significantly. Copyright © 2012 John Wiley & Sons, Ltd.     

Flame‐retardant fabric systems based on electrospun polyamide/boric acid nanocomposite fibers

To examine the feasibility of developing flame‐retardant‐textile coated fabric systems with electrospun polyamide/boric acid nanocomposites, fiber webs coated on cotton substrates were developed to impart‐fire retardant properties. The morphology of the polyamide/boric acid nanocomposite fibers was examined with scanning electron microscopy. The flame‐retardant properties of coated fabric systems with different nanoparticle contents were assessed. The flame retardancy of the boric acid coated fabric systems was evaluated quantitatively with a flammability test apparatus fabricated on the basis of Consumer Product Safety Commission 16 Code of Federal Regulations part 1610 standard and also by thermogravimetric analysis. The 0.05 wt % boric acid nanocomposite fiber web coated on pure cotton fabric exhibited an increment in flame‐spreading time of greater than 80%, and this indicated excellent fire protection. Also, the coated fabric systems with 0.05% boric acid nanocomposite fiber webs exhibited a distinct shift in the peak value in the thermal degradation profile and a 75% increase in char formation in the thermooxidative degradation profile, as indicated by the results of thermogravimetric analysis. The results show the feasibility of successfully imparting flame‐retardant properties to cotton fabrics through the electrospinning of the polymer material with boric acid nanoparticles. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Combination of a hydroxy‐functional organophosphorus oligomer and a multifunctional carboxylic acid as a flame retardant finishing system for cotton: Part II. Formation of calcium salt during laundering

Multifunctional carboxylic acids, such as 1,2,3,4‐butanetetracarboxylic acid (BTCA), were used to bond a hydroxy‐functional organophosphorus oligomer (FR) to cotton fabric in the presence of a catalyst, such as sodium hypophosphite (NaH₂PO₂). Previously, it was found that the cotton fabric treated with FR and BTCA showed a high level of phosphorus retention after one home laundering cycle. However, the flame retardant properties quickly deteriorated as the number of home laundering cycles was increased. In this research, it was found that the free carboxylic acid groups bound to the cotton fabric form an insoluble calcium salt during home laundering, thus diminishing the flame retardant properties of the treated cotton fabric. It was also found that the free carboxylic acid groups on the treated cotton fabric were esterified by triethanolamine (TEA), and that the formation of calcium salt on the fabric was suppressed by the esterification of the free carboxylic acid groups by TEA. The cotton fabric treated with BTCA and the hydroxy‐functional organophosphorus oligomer significantly improved its flame retardance when a new catalyst system consisting of hypophosphorous acid (H₃PO₂) and TEA was used in the system. Copyright © 2003 John Wiley & Sons, Ltd.     

Crosslinking cotton with poly(itaconic acid) and in situ polymerization of itaconic acid: Fabric mechanical strength retention

Polycarboxylic acids have been used as nonformaldehyde durable press finishing agents for cotton fabrics. Previously, we found that itaconic acid (IA) polymerized in situ on cotton fabric and also in an aqueous solution in the presence of a K₂S₂O₈/NaH₂PO₂ initiation system. Both poly(itaconic acid) (PIA) and the polymer formed by in situ polymerization of IA are able to crosslink cotton cellulose, thus imparting wrinkle resistance to cotton. In this research, we compared the performance of the cotton fabric crosslinked by PIA and that crosslinked by in situ polymerization of IA. The fabric treated with PIA and that treated with IA had similar wrinkle recovery angles. The cotton fabric treated with IA, however, lost more tensile strength than that treated with PIA due to cellulose degradation. We determined the magnitude of the fabric tensile strength loss attributed to crosslinking by separating the tensile strength loss due to cellulose degradation from the total tensile strength loss, and found that the tensile strength loss caused by crosslinking for the fabric treated with PIA was significantly higher than that for the fabric treated with IA. This can probably be attributed to more concentrated crosslinkages formed on the near surface of the PIA‐treated cotton fabric. PIA had poorer penetration into the amorphous cellulose region in fiber interior due to its much larger molecular size, thus increasing its concentration on the fabric's near surface. The data also suggest that more concentrated crosslinkages on the fabric surface reduced fabric abrasion resistance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2023–2030, 2003     

Flame retardant treated flax fibre reinforced phenolic composites: Ageing and thermal characteristics

In this study, flax composites were prepared from flax fabric and phenolic resin. Chemical treatments were imparted to the fabric to improve adhesion between the fabric and the phenolic matrix. Diammonium phosphate was applied to improve the flammability of the composites. The thermal and flammability properties of the untreated, chemically treated, and flame retardant (FR) treated flax fabric reinforced phenolic composites were studied. Ageing studies were carried out by subjecting the composites to varying conditions of temperature and humidity in an environmental chamber for 2 weeks. FR treatment of flax fabric was shown to be very effective in improving flame retardancy of the composites due to decreased peak heat release rate (PHRR) and smoke production rate (SPR). Thermogravimetric analysis (TGA) of composites showed that after FR treatment, the decomposition temperatures shifted to lower temperatures. Ageing studies revealed that the mechanical properties of untreated, chemically treated and FR treated composites decreased with an increase in ageing temperature.     

Microintumescent mechanism of flame‐retardant water‐based chitosan–ammonium polyphosphate multilayer nanocoating on cotton fabric

Layer‐by‐layer (LbL) assembly of nanocoatings on fabric substrates has been very successful in terms of reduction of flammability. In particular, an LbL system comprised ammonium polyphosphate as the polyanion and chitosan as the polycation, applied to cotton fabric, dramatically reduced cotton flammability. At this point, the fire‐retardant (FR) mechanism of action of this system has never been fully elucidated. Sonicated and nonsonicated coated cotton fabrics were evaluated using a vertical flame test and mass loss calorimeter. Coating morphology was investigated before and after burning. Thermal analyses and chemical analyses in the condensed phase (and in the gas phase) were conducted to reveal the FR mechanism of action. At the cotton surface, a combination of both condensed (formation of aromatic char) and gas phase (release of water and highly flammable gases) mechanisms impart the FR behavior, promoting a kind of “microintumescence” phenomenon. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43783.     

Effect of halloysite nanotubes on mechanical properties and flammability of soy protein based green composites

To address the growing emphasis on the use and development of sustainable materials, bio‐based polymers and fibers are processed to prepare entirely bio‐based fiber‐reinforced ‘green’ composites. To enable these new materials to perform in lightweight vehicle and infrastructural applications, they must be characterized both structurally and in terms of their various performance characteristics. The results of preparation and characterization of bio‐based composites comprising jute fabric and soy protein concentrate (SPC) modified with glycerol and/or halloysite nanotubes (HNT) are reported herein as a first look at the flammability of these bio‐based nanocomposites. The results reveal that SPC has lower flammability (heat release capacity) than petrochemical‐based resins, such as epoxies and vinyl esters. In addition, incorporating 5% mass fraction of HNT is found to reduce the composite flammability, while having no negative impact on the mechanical properties. Copyright © 2012 John Wiley & Sons, Ltd.     

Infrared spectroscopy studies of cyclic anhydrides as intermediates for ester crosslinking of cotton cellulose by polycarboxylic acids. IV. In situ free radical copolymerization of maleic acid and itaconic acid on cotton

Polycarboxylic acids have been used as crosslinking agents for cotton fabrics and paper to replace the traditional formaldehyde‐based reagents. Previously, we found that a polycarboxylic acid esterifies cotton cellulose through the formation of a five‐membered cyclic anhydride intermediate. Both maleic acid (MA) and itaconic acid (ITA) are extremely difficult to polymerize under conditions normally used for free radical polymerization. It has been reported in the literature that treatment of cotton fabric with a mixture of MA and ITA significantly improved wrinkle‐resistance of the fabric. In this research, we investigated the in situ copolymerization of MA and ITA on cotton fabric. Fourier transform‐infrared spectroscopy was used to study the anhydride carbonyl formed on the cotton fabric treated with the mixtures of MA and ITA. A redox titration technique also was applied to determine the quantity of alkene double bonds on the treated fabric. It was found that free radical copolymerization of MA and ITA does not occur on the fabric at elevated temperatures when potassium persulfate is present as an initiator. It does occur, however, when both potassium persulfate and sodium hypophosphite are present on the fabric. The in situ copolymerization on the cotton fabric probably is initiated by a reduction–oxidation system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 327–336, 2000     

Phthalonitrile-glass fabric composites

Phthalonitrile polymers, under development at the Naval Research Laboratory, offer promise as high temperature, high performance composite matrix materials. A fully cured resin shows outstanding thermal stability with no evidence of a glass transition temperature or T_g up to 450°C, good mechanical properties, and is easily processed into void-free components. Phthalonitrile/glass fabric composite panels have been successfully fabricated by conventional consolidation of prepregged glass and by a more recently developed simplified process, resin infusion molding. Both processes can be used to produce panels with comparable mechanical properties. More important, flammability performance of these composites, evaluated in terms of specific optical density, combustion gases, heat release, and ignitability, excels over other state-of-the-art polymer/glass composites. This finding is significant given that overcoming flammability obstacles has been the main limiting factor for use of composites in marine applications.     

Verification Concerning the Relative Superiority of a Cellulosic Fabric with Regard to Polyester in Terms of Flammability

In order to prove the superiority of cotton fabric to polyester with regard to flammability, we have studied the effect of Graham's salt as a moderate and nondurable finish on the flammability of pure polyester and cotton fabric. The laundered bone-dried, weighed fabrics were impregnated with suitable concentration of aqueous Graham's salt solutions by means of squeeze rolls and drying at 110°C for 30 min. They were then cooled in a desiccator, reweighed with analytic precision, and kept under ordinary conditions before the accomplishment of the vertical flame test. The optimum add-on value to impart flame retardancy was about 43.65% for polyester fabric and 36.78% for cotton fabric. The results obtained comply with the Coating Theory. Moreover, the superiority of cotton fabric to polyester fabric in terms of combustibility has been deduced.     

Studies on the temperature dependence of extinction oxygen index values for cellulosic fabrics. I. Cotton

The concept of extinguishability as a measure of textile flammability is reviewed. Definition and determination of extinction oxygen index enables a parameter to be defined from which the effects of ignition time and fabric structure may be removed. This so-called extinction oxygen index (EOI) and the derived value at zero ignition time [EOI]₀ more exactly define the burning/nonburning fabric boundary than does the more widely used limiting oxygen index (LOI). This first paper reports the determination of EOI and [EOI]₀ values for a series of cotton fabrics in the temperature range 20–200°C. The influence of the various fabric parameters of area density, air permeability, sample thickness, bulk density, and moisture content was investigated. The advantages of using the EOI rather than the LOI concept as a measure of textile flammability is indicated in the discussion of the results of this study with reference to previous work concerned with LOI data for cotton. In particular, the significance that environmental temperature has on EOI and related parameters reported here and previously reported LOI data is discussed in terms of various published models which define the burning/extinction threshold.     

The influence of plasma treatment on the tribological properties of hybrid PTFE/cotton fabric/phenolic composites

In this study, the effects of air‐plasma and N₂‐plasma treatment on the hybrid polytetrafluoroethylene (PTFE)/cotton fabric and a phenolic resin were investigated in detail. The tribological properties of the untreated and plasma‐treated hybrid PTFE/cotton fabric/phenolic composites were investigated. The results indicated that air‐plasma‐treated hybrid PTFE/cotton fabric/phenolic composites exhibited better antiwear and friction reduction properties. The combination of scanning electron microscopy and Fourier transform infrared spectroscopy analysis illustrated that hybrid PTFE/cotton fabric/phenolic composites treated with air‐plasma possessed more integrated structure and more functional groups, which plausibly contributed to the better tribological properties of the hybrid PTFE/cotton fabric/phenolic composites treated with air‐plasma. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers