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Blending Nomex® with cotton improves its affordability and serviceability. Because cotton is a highly flammable fiber, Nomex®/cotton blend fabrics containing more than 20% cotton require flame-retardant treatment. In this research, combination of a hydroxyl functional organophosphorus oligmer (HFPO) and 1,2,3,4-butanetetracarboxylic acid (BTCA) was used for flame retardant finishing of the 65/35 Nomex®/cotton blend woven fabric. The system contains HFPO as a flame retardant, BTCA as a bonding agent, and triethenolamine (TEA) as a reactive additive used to enhance the performance of HFPO/BTCA. Addition of TEA improves the hydrolysis resistance of the HFPO/BTCA crosslinked polymeric network on the blend fabric. Additionally, TEA enhances HFPO's flame retardant performance by reducing formation of calcium salts and also by providing synergistic nitrogen to the treated blend fabric. The Nomex®/cotton blend fabric treated with the HFPO/BTCA/TEA system shows high flame resistance and high laundering durability at a relatively low HFPO concentration of 8% (w/w). The heat release properties of the treated Nomex®/cotton blend fabric were measured using microscale combustion calorimetry. The functions of BTCA; HFPO and TEA on the Nomex®/cotton blend fabric were elucidated based on the heat release properties, char formation, and fire performance of the treated blend fabric. [ABSTRACT FROM AUTHOR]

Nylon/cotton blend fabrics have long been used in military protective clothing. Because fire risk has drastically increased in recent warfare, developing flame retarded military nylon/cotton fabrics becomes extremely important for protecting military personnel. It was previously discovered that a hydroxy-functional organophosphorus oligomer (HFPO) was bound to a nylon fabric in the presence of dimethyloldihydroxylethyleneurea (DMDHEU) as a bonding agent. In this research, the bonding mechanism of HFPO/DMDHEU on the nylon/cotton blend fabrics was investigated. HFPO was bound to the nylon/cotton blend fabrics by (1) forming HFPO/DMDHEU crosslinked polymeric networks on both nylon and cotton and (2) forming a DMDHEU bridge between cellulose and HFPO on cotton. The relative quantity of the HFPO/DMDHEU crosslinked networks and that of the DMDHEU-bridging formed on the treated blend fabrics was controlled by the HFPO-to-DMDHEU ratio. The HFPO/DMDHEU system was an effective and durable flame retarding treatment system for nylon/cotton military blend fabrics. The treated fabrics passed the fabric vertical burning test after 50 home laundering cycles. The fire performance and hydrolysis-resistance of different nylon/cotton blend fabrics treated with HFPO/DMDHEU was fully evaluated, and the performance data were analyzed in relation with the bonding mechanism. [ABSTRACT FROM AUTHOR]

Flame retardant nylon/cotton blend fabrics are widely used in the fields of industrial and military protective uniforms. In this research, we investigate the heat release properties and flammability of the 50/50 nylon/cotton blend fabric treated with a self-crosslinkable durable organophosphorus flame retardant system. For the nylon/cotton blend fabric without treatment, the blend has lower total heat release and higher percent char yield than the arithmetic sum of those of cotton and nylon as single fibers. In addition, both the peak heat release rate (PHHR) and the temperature at peak heat release ( T PHRR ) for cotton increases whereas both PHRR and T PHRR decrease for nylon when those two fibers are blended to form a fabric. Thus, the data indicated that interaction takes place between cotton and nylon during the decomposition process of the blend. The presence of the organophosphorus flame retardant system reduces PHRR, T PHRR and increase char formation for both cotton and nylon as single fibers. When the cotton and nylon are blended and then treated with the flame retardant, the PHRR of the blend becomes even lower and the percent char yield of the blend becomes even higher than those of the treated cotton and nylon as single-fiber fabric. The char length for the treated blend decreases compared with that of the treated cotton and nylon as single-fiber fabrics. We conclude that cotton and nylon interact with each other during the degradation process of the treated nylon/cotton blend fabric and such interaction reduces the flammability of the blend fabric. [ABSTRACT FROM AUTHOR]

Abstract: Effective testing methods are critical for developing new flame retardant textiles by the industry. However, the current testing methods all have limitations. In this research, we applied micro-scale combustion calorimetry (MCC) for evaluating the flammability of the cotton woven fabric treated with a traditional reactive organophosphorus flame retardant in combination with a synergistic nitrogen-containing additive and the nylon-6,6 woven fabric treated with a hydroxyl-functional organophosphorus oligomer and crosslinkers. We found that MCC is capable of differentiating small differences among the treated fabric samples with similar flammability. MCC is able to make quantitative measurement of the peak heat release rate, the most important parameter related to fire hazard of materials, of textile whereas such analysis is more difficult using cone calorimetry due to textile fabrics’ low thickness. By using the thermal combustion parameters measured by MCC, we were able to calculate the limiting oxygen index (LOI) of various treated cotton fabric samples with near-perfect agreement between the experimentally measured and the predicted LOI values of treated cotton fabrics. We also compared the capability of MCC and differential scanning calorimetry for analyzing flame retardant cotton textiles. [Copyright &y& Elsevier]

Abstract: In this research, we studied the mechanism of bonding a hydroxy-functional organophosphorus oligomer (HFPO) to nylon 6.6 fabric using the formaldehyde derivatives of urea and melamine, including dimethyloldihydroxyethyleneurea (DMDHEU) and trimethylolmelamine (TMM), as the bonding agents. The nylon fabric treated with HFPO/DMDHEU or HFPO/TMM retained significant amount of phosphorus after multiple launderings. The laundering durability of the HFPO applied to nylon was probably attributed to the formation of a crosslinked polymeric network on the nylon fiber. The nylon fabric treated with HFPO/DMDHEU showed higher percent phosphorus retention than that treated with HFPO/TMM. The percent phosphorus retention of the treated nylon increased as the DMDHEU or TMM concentration was increased, and the nylon fabric''s stiffness follows the same trend. The micro-scale combustion calorimetry and thermal analysis data indicate that the HFPO bound to nylon reduced peak heat release rate and heat release capacity of the nylon fabric, decreased decomposition temperature and promoted the char formation of the treated fabric. The nylon/cotton blend military fabric treated with HFPO/DMDHEO or HFPO/TMM demonstrated flame retardant performance after 10 laundering cycles. [Copyright &y& Elsevier]

Abstract: Flame retardancy is a desirable property for silk textiles, and it becomes necessity when silk textiles are for interior decorative use in building with public access. However, the flame retardant finishing technology available for silk has significant limitations. In this research, we studied the use of the combination of a hydroxyl-functional organophosphorus oligomer (HFPO) and 1,2,3,4-butanetetracarboxylic acid (BTCA) as a formaldehyde-free flame retardant finishing system for silk. When BTCA is applied to silk, most of BTCA reacts with the hydroxyl group on silk by single ester linkage. In the presence of HFPO, BTCA is able to bond HFPO onto silk by either a BTCA “bridge” between silk and HFPO or a BTCA–HFPO–BTCA cross-linkage between two silk protein molecules. We evaluated the flammability and physical properties of the silk fabric treated with HFPO and BTCA. The treated silk fabric demonstrated a high level of flame retardancy with modest loss in fabric tensile strength. The treated silk passed the vertical flammability test after 15 hand wash (HW) cycles. Increasing the HFPO concentration from 20% to 30% does not show significant improvement in the flame retardant performance of the treated silk. The thermal analysis data demonstrated that HFPO reduces silk''s initial thermal decomposition temperature and promotes char formation. [Copyright &y& Elsevier]

Abstract: N-Methylol dimethylphosphonopropionamide (MDPA) is one of the most commonly used durable flame retardant agents for cotton. In our previous research, we developed a new flame retardant finishing system based on a hydroxy-functional organophosphorus oligomer (HFPO) and bonding agents, such as dimethyloldihydroxyethyleneurea (DMDHEU) and trimethylolmelamine (TMM). In this research, we compared the flame resistant performance as well as physical properties of the cotton fabric treated with these two flame retardant finishing systems. The cotton fabric treated with MDPA/TMM has a higher initial limiting oxygen index (LOI) than that of the fabric treated with HFPO/TMM due to higher nitrogen content in the system. The LOI of the cotton fabric treated with the HFPO and MDPA systems becomes identical when the treated fabric contains equal amount of phosphorus and nitrogen. The MDPA/TMM shows higher laundering durability on cotton than HFPO/TMM system. The fabric treated with HFPO/TMM and MDPA/TMM has low wrinkle resistance and low strength loss whereas the fabric stiffness significantly increases when the TMM concentration is increased. [Copyright &y& Elsevier]

Abstract: N-Methylol dimethylphosphonopropionamide (MDPA), known as “Pyrovatex CP” and “Pyrovatex CP New” commercially, has been one of the most commonly used durable flame retardant agents for cotton for many years. In our previous research, we developed a flame retardant finishing system for cotton based on a hydroxy-functional organophosphorus oligomer (HFPO) in combination with a bonding agent such as trimethylolmelamine (TMM) and dimethyloldihydroxyethyleneurea (DMDHEU). In this research, we investigated the bonding of these two flame retardant finishing agents to cotton. We found that the majority of MDPA is bound to cotton by its N-methylol group and that the use of TMM as a co-reactant modestly increases the fixation of MDPA onto cotton. For HFPO, however, the use of a bonding agent is necessary to form a covalent linkage between HFPO and cotton. Both the fixation of HFPO on cotton and its laundering durability are influenced by the effectiveness and concentration of the bonding agent. The commercial product of HFPO contains approximately 33% more phosphorus than that of MDPA and the percent fixation of HFPO on cotton is also moderately higher than that of MDPA. The bonding between MDPA and cotton is significantly more resistant to hydrolysis during multiple launderings than that between HFPO and cotton. The selection of catalyst also plays a significant role in influencing the bonding of the flame retardant agents to cotton. [Copyright &y& Elsevier]

Abstract: Cotton/nylon blends have been commonly used as the material for protective clothing, but those blend fabrics are not flame retardant finished because of the unavailability of effective flame retardant finishing systems. Previously, we investigated the use of a hydroxyl-functional flame retardant organophosphorus oligomer (FR) in combination with the mixture of dimethyloldihydroxyethyleneurea (DMDHEU) and trimethylolmelamine (TMM) as the binders for flame retardant finishing of cotton. In this study, we investigated the application of FR to the 50/50 cotton/nylon fabric. When the FR/DMDHEU/TMM system is applied to the fabrics of nylon-6,6 and nylon-6, approximately 40% of the FR applied is permanently bound to the nylon fabrics. FR is bound to the nylon fabrics mainly through the formation of a FR/TMM crosslinked polymeric network, thus becoming durable to multiple launderings. The cotton/nylon blend treated with FR shows high levels of flame retardant performance and excellent laundering durability. The treated fabric passes the vertical flammability test even after 50 home laundering cycles. The fabric stiffness as a result of the finishing process is still an obstacle to be overcome for practical use of this finishing system. [Copyright &y& Elsevier]

In our previous research, we developed flame retarding systems for cotton based on a hydroxy-functional organophosphorus oligomer (FR) and a binder, such as 1,2,3,4-butanetetracarboxylic acid (BTCA), dimethyloldihydroxyethyleneurea (DMDHEU) and melamine–formaldehyde (M–F), which are able to form covalent binding between FR and cotton. In this research, we used a factorial experimental design method to study the performance of the flame retarding system based on FR and the mixture of DMDHEU and M–F. We found that an increase in the DMDHEU/(DMDHEU + M–F) ratio in the mixture increases the amount of FR bound to cotton, increases the laundering durability of FR on cotton, and reduces the fabric tensile strength retention. DMDHEU and M–F also function as nitrogen providers and enhance the flame retarding performance of the treated fabric due to phosphorus–nitrogen synergism. M–F is a more efficient nitrogen provider than DMDHEU. The effect of reduced phosphorus–nitrogen synergism as a result of increasing the relative amount of DMDHEU in the mixture (DMDHEU + M–F) outweighs that of the improved bonding of FR to cotton. An increase in FR concentration in a formula increases the amount of FR bound to cotton, whereas it reduces the percent retention of FR on the fabric and also reduces the fabric strength loss. Desirable performance of treated cotton fabrics can be achieved by adjusting the concentrations of FR and the ratio of the two binders in a formula. [Copyright &y& Elsevier]