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Cotton fleece does not meet the federal flammability standard (16 CFR Part 1610: `Standard for the Flammability of Clothing Textiles') without chemical treatment. In this research, the chemical reactions of maleic acid (MA) on cotton in the presence of sodium hypophosphite (NaH2PO2) and the use of the combination of MA and NaH2PO2as a flame retardant finishing system for cotton fleece are investigated. It has been found that MA esterifies cotton cellulose at relatively low temperatures in the presence of NaH2PO2as catalyst, and that MA esterified to cotton is able to further react with NaH2PO2at higher temperatures (≥150°C), which bonds phosphorus to the cotton cellulose. The reactions between MA and NaH2PO2on cotton also lead to the cross-linking of cotton cellulose. The treatment using the combination of MA and NaH2PO2is effective in reducing the flammability of cotton fleece from `Class III' to `Class I' (16CFR1610). This is a nonformaldehyde and low cost flame retardant finishing system for cotton fleece. The treated cotton fleece still maintains `Class I' flammability after 20 home laundering cycles.

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

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

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

In recent years, extensive efforts have been made to find formaldehyde-free durable press finishes to replace the traditional formaldehyde-based N-methylol compounds. 1,2,3,4-Butane-tetracarboxylic acid (BTCA) has been the most efficient nonformaldehyde crosslinking agent for cotton, with sodium hypophosphite (NaH2PO2) being the most effective catalyst. In our previous research, we found that a polycarboxylic acid esterifies cellulose through the formation of a five-membered cyclic anhydride intermediate by the dehydration of two adjacent carboxyl groups. In this research, we use Fourier transform infrared spectroscopy (FTIR) to study the formation of cyclic anhydride intermediates by BTCA and poly(maleic acid) (PMA) with and without the presence of NaH2PO2. In the absence of NaH2PO2, BTCA forms the cyclic anhydride only when the temperature reaches the vicinity of its melting point. In the presence of NaH2PO2, however, the anhydride forms at much lower temperatures. We have found that NaH2PO2weakens the hydrogen bonding between the carboxylic acid groups of BTCA, contributing to accelerated anhy dride formation at lower temperatures. Sodium hypophosphite also accelerates the for mation of the anhydride intermediates by polycarboxylic acids in an amorphous state. The FTIR spectroscopy data show that there is a chemical reaction between the anhydride intermediate and NaH2PO2when the temperature climbs above 200°C.

Polycarboxylic acids have been used as crosslinking agents for cellulosic materials to replace traditional formaldehyde-based reagents. The literature reports that maleic acid (MA) and itaconic acid (ITA) can copolymerize on cotton fabric in the presence of potassium persulfate, and esterification of cotton by the copolymer imparts wrinkle resistance to the treated cotton fabric. Our previous research found that in-situ copoly merization occurs only when both potassium persulfate and sodium hypophosphite are present on the cotton fabric. In this work, we investigate in-situ homopolymerization of maleic acid and itaconic acid on cotton fabric. We use Fourier transform infrared spectroscopy to study the anhydride carbonyls formed on the cotton treated with MA and ITA. We also use a redox titration technique to determine the quantity of the remaining monomers on the treated fabric. The data indicate that MA and ITA can polymerize on the fabric at elevated temperatures when potassium persulfate is present at concentration levels higher than reported previously. This conclusion is confirmed by the performance of the cotton treated with MA and ITA in the presence of potassium persulfate at different concentration levels.

Citric acid (CA), one of the polycarboxylic acids used as crosslinking agents for cotton, is cost-effective and environmentally friendly, but its tendency to discolor fabric is a major disadvantage for white fabrics. In this research, we investigate cotton fabric yellowing caused by citric acid at elevated temperatures. We find that yellowing increases as curing temperature, curing time, and CA concentration increase. Using sodium hypophosphite as a catalyst causes less fabric yellowing than monosodium phosphate. The wet analysis data demonstrate that an alkene double bond is formed on cotton fabric treated with CA under curing conditions. Nuclear magnetic resonance (NMR) data indicate that CA is partially converted to trans-and cis-aconitic acids on cotton through dehydration. The visible spectra of fabric treated with trans-and cis-aconitic acids and cured at elevated temper atures show strong absorption in the 400-550 nm region. For polymeric multifunctional carboxylic acids, an increased number of hydroxyl groups in their molecules increases fabric yellowing. Therefore, yellowing caused by citric acid and other hydroxyl multi functional carboxylic acids can probably be attributed to the formation of unsaturated polycarboxylic acids.

The photooxidation of a nonwoven polyethylene fabric was investigated using Fourier transform infrared photoacoustic spectroscopy. The infrared spectroscopic data indicated that hydroperoxide, alcohol, aldehyde, ketone, carboxylic acid, and anhydride groups were formed as the products of the photooxidation of the polyethylene fabric and that the relative amount of carboxyl among all carbonyls increased as the photooxidation progressed. The distribution of the photooxidation products was inhomogeneous between the two surfaces of the fabric. The highest degree of photooxidation occurred on the surface of the fabric facing the UV radiation source, whereas the lowest degree of photooxidation was on the back surface of the fabric. We also found that the polyethylene nonwoven fabric showed a slower photooxidation rate than the polypropylene nonwoven fabric. The UV radiation at 254 nm caused photooxidation of polyethylene. No photooxidation was observed in the fabric exposed to the UV radiation at 350 nm under the same conditions.

In recent years, extensive efforts have been made to find nonformaldehyde durable press finishes to replace the traditional formaldehyde-based reagents for producing wrinkle-free cotton fabrics. 1,2,3,4-butanetetracarboxylic acid (BTCA) has been the most effective nonformaldehyde crosslinking agent. Our previous research has indicated that a polycarboxylic acid esterifies cellulose in two steps: the formation of a 5-membered cyclic anhydride intermediate by the dehydration of two adjacent carboxyl groups, and the reaction between cellulose and the anhydride intermediate to form an ester linkage. In this research, we used Fourier transform infrared and Fourier transform Raman spectroscopy to study the formation of cyclic anhydride intermediates by BTCA and other polycarboxylic acids without the presence of a catalyst. We found that BTCA and other polycarboxylic acids in a crystalline state start to form 5-membered cyclic carboxylic anhydrides when the temperature reaches the vicinity of their melting points with the exception of bifunctional acids, which form cyclic anhydrides at temperatures much higher than their melting points. Intermolecular hydrogen bonding between carboxylic acid groups prevents the formation of the cyclic anhydride intermediates at lower temperatures. We also found that polycarboxylic acids in an amorphous state form cyclic anhydrides at much lower temperatures.

Fourier transform photoacoustic spectroscopy (FT-IR/PAS) has proven to be a powerful technique for the near-surface characterization of solid materials. The effective sampling depth of FT-IR/PAS can be varied by using different interferometer mirror velocities, so that nondestructive depth profiling can be performed. In this research, sized cotton yarns, treated glass fibers, chemically modified poly(ethylene terephthalate) fibers, and a naturally weathered poly(vinyl chloride) composite were investigated with the use of FT-IR/PAS at different mirror velocities. Penetration of the chemical additives in these materials was studied. It was demonstrated that FT-IR/PAS has the ability to investigate the changes in chemical nature within the detectable surface layers of solid samples.