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.     

The combination of a hydroxy‐functional organophosphorus oligomer and melamine‐formaldehyde as a flame retarding finishing system for cotton

In previous research, it was found that melamine‐formaldehyde resin can be used as a binder for a hydroxy‐functional organophosphorus flame retarding agent (FR) on cotton. The role that trimethylol melamine (TMM) plays in this flame retarding system was studied. When TMM is applied to cotton, it forms crosslinks between cellulose molecules. When TMM is applied to cotton in the presence of FR, it reacts with FR to form a crosslinked polymeric network in addition to reacting with cotton. The formation of the crosslinked network improves the laundering durability of FR and also increases the fabric stiffness. The number of crosslinks among cotton cellulose formed by TMM decreases as the FR concentration in the system is increased. TMM also functions as a nitrogen provider to enhance the flame retarding performance of FR due to phosphorus–nitrogen synergism. Therefore, the amount of TMM used in a FR/TMM formula plays the most critical role in determining the effectiveness of this flame retarding system. The finish bath pH also plays a significant role in influencing the performance of the flame retarding system on cotton. The optimum pH was found to be around 4. Copyright © 2004 John Wiley & Sons, Ltd.     

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 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.     

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 finishing of cotton fleece fabric: Part V. Phosphorus‐containing maleic acid oligomers

The high flammability of cotton fleece makes it necessary to apply a flame retardant system on cotton fleece so that it can meet the federal regulation ‘Standard for the Flammability of Clothing Textiles’ (16 CFR 1610). The objective of this research was to reduce the flammability of cotton fleece using the phosphorus‐containing maleic acid oligomers (PMAO) synthesized by aqueous free radical polymerization of maleic acid. We found that PMAO can be bound to cotton fleece by esterifying with cotton cellulose with sodium hypophosphite as the catalyst. Both the 45^° flammability and limiting oxygen index data indicated that the treatment of cotton using PMAO reduced the flammability of cotton fleece. The micro‐scale combustion calorimetric data revealed that PMAO reduced the peak heat release rate and heat release capacity of the treated cotton woven fabric. The cotton fleece treated with PMAO/NaH₂PO₂ passed the federal flammability test (16 CFR Part 1610) and achieved ‘Class 1’ flammability. The PMAO bound to cotton was durable to multiple home laundering cycles. The treated fleece also showed high strength retention with little change in fabric whiteness. The use of triethanolamine as an additive modestly enhanced the performance of PMAO with no significant changes in fabric physical properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Correlation between limiting oxygen index and phosphorus/nitrogen content of cotton fabrics treated with a hydroxy‐functional organophosphorus flame‐retarding agent and dimethyloldihydroxyethyleneurea

The combination of a hydroxyl‐functional organophosphorus flame‐retarding agent (FR) and dimethyloldihydroxyethyleneurea (DMDHEU) was used as a durable flame‐retardant finish system for cotton fabrics. DMDHEU functions as a binder between FR and cotton cellulose, thus making this flame‐retarding system durable to home laundering. DMDHEU also provides nitrogen to this system, therefore enhances its performance. Limiting oxygen index (LOI) is one of the most commonly used parameters to indicate the flammability of textiles and other polymeric materials. In this research, we investigated the correlation between LOI and phosphorus/nitrogen content on the cotton fabric treated with that durable flame‐retardant system. Phosphorus concentration on the fabric was analyzed by inductively coupled plasma atomic emission spectroscopy, whereas the nitrogen content was determined indirectly by measuring the carbonyl band intensity in the infrared spectra of the treated fabric. We developed a statistical model to predict LOI of the cotton fabric treated with FR and DMDHEU based on the phosphorus concentration and the intensity of carbonyl band of DMDHEU on cotton. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1885–1890, 2003