X-ray photoelectron spectroscopy analysis of cotton treated with the TBCC/H 2 O 2 /NaHCO 3 system

Abstract

N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC) was used as a bleach activator for activation of hydrogen peroxide (H₂O₂) in aqueous solution with the addition of sodium carbonate (NaHCO₃). The TBCC/H₂O₂/NaHCO₃ system was applied for treatment of cotton greige fabric at 60℃ in comparison with the conventional H₂O₂/NaOH system for treatment of cotton greige fabric at 95℃. Experimental results showed that the TBCC/H₂O₂/NaHCO₃ system was effective for improving the degree of whiteness, reducing the fiber damage, and improving the water absorbency of cotton fabric. For understanding the treatment performance of the TBCC/H₂O₂/NaHCO₃ system, X-ray photoelectron spectroscopy (XPS) was applied to analyze the surface elemental composition of cotton greige fabric before and after treatment. C 1s XPS spectra and quantitative analysis revealed that the TBCC/H₂O₂/NaHCO₃ system improved the water absorbency of cotton fabric by removing hydrophobic matters as well as by oxidizing coloring matters and cellulose. The hexane extractions and scanning electron microscopy images indicated that the TBCC/H₂O₂/NaHCO₃ system most likely removed the hydrophobic matters from cotton fabric in a “layer-by-layer” mode, which limited the cellulose backbones exposed for XPS analysis but allowed water to penetrate into cotton fibers.

Keywords

chemical modification dyeing finishing processing bleaching scouring

Cotton cellulose is an ideal material for clothes, bedding, and linens due to its high water absorbency, comfort, and relative ease of dyeing and finishing. However, raw cotton contains natural non-cellulosic impurities (e.g. hydrophobic and coloring matters),¹ which can severely limit the water absorbency and degree of whiteness of cotton fiber. Scouring and bleaching of cotton are commonly required to eliminate these natural non-cellulosic impurities and as such establish a white uniform substrate for further dyeing and finishing. Many impurities can be removed in scouring by boiling cotton in sodium hydroxide (NaOH) solution (2–5%) for 1 hour,² with the exception of natural coloring matters that may be removed by certain oxidants. Hydrogen peroxide (H₂O₂) is the most widely used oxidant for industrial textile bleaching due to its low cost and eco-friendliness. Bleaching of cotton with H₂O₂ is often performed in alkaline medium (normally NaOH) at high temperatures. In practice, scouring and bleaching of cotton are combined in alkaline H₂O₂ solution and carried out at boiling temperature.³ Such a combined cotton treatment consumes extensive energy, and also causes severe fiber damage. In addition, the conventional hot preparation process is environmentally problematic because of it requiring neutralization that generates substantial levels of electrolytes in effluent, and rinsing with a large amount of water to remove the residual un-decomposed H₂O₂.

By adding a so-called bleach activator to a H₂O₂ aqueous solution, a more kinetically active species (e.g. peracid) is in situ generated, as shown in Scheme 1, which makes allowance for low-temperature cotton treatment.⁴ Tetraacetylethylenediamine (TAED) is commonly used as a bleach activator for low-temperature cotton treatment,^5–12 and also used as a benchmark for developing new bleach activators.^13–15 However, TAED has poor water solubility, which limits its application for industrial textile processing. In addition, TAED is not very effective at a temperature below 70℃.

Scheme 1.

Reaction of bleach activators with H₂O₂.

N-[4-(triethylammoniomethyl)benzoyl]lactam chloride (TBLC) is a novel class of bleach activators with the generic structure shown in Scheme 2. The cationic charge of TBLC is intended to provide water solubility as well as fiber substantivity.^16,17 It has been taken for granted for a while that TBLC was applied in the presence of a large excess of H₂O₂ under alkaline (e.g. pH 11–12) conditions.^18–21 However, recent studies reported that TBLC was most effective when used with equimolar H₂O₂ under near-neutral pH conditions.^22–24 This actually inspires the present work with the aim to develop a new approach for cotton treatment with benefits of reducing consumptions of energy and water as well as fiber damage.

Scheme 2.

Generic structure of N-[4-(triethylammoniomethyl)benzoyl]lactam chloride (n = 1–5).

In this study, N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC) was used a prototype of TBLC (n = 3) to activate H₂O₂ for low-temperature cotton treatment, for which sodium bicarbonate (NaHCO₃) was used to maintain a near-neutral pH. The elemental surface composition of cotton fibers was analyzed by X-ray photoelectron spectroscopy (XPS) to interpret the performance of the TBCC/H₂O₂/NaHCO₃ system for treatment of cotton fabric.^25–32

Experimental details

Materials

One-hundred percent cotton single jersey circular-knitted fabric (178 g/m²) was provided by Hongdou Textile Group (Wuxi, China). TBCC was synthesized and purified according to the previously reported method.¹⁶ A peroxide stabilizer (Prestogen N-D) was purchased from BASF (Shanghai, China). A wetting agent (Penetrant JFC) was purchased from Dymatic Chemicals (Foshan, China). H₂O₂ (30% w/w) and NaHCO₃ were purchased from Sinopharm Group (Shanghai, China). Cupriethylenediamine (1.0 M) was purchased from Fisher Scientific (Shanghai, China), and used for preparing dispersions of cellulose from bleached cotton. All other chemicals were of analytical grade unless otherwise stated.

Treatment methods

The TBCC/H₂O₂/NaHCO₃ system was conducted in a solution with the addition of TBCC (20 mmol/L), H₂O₂ (24 mmol/L), and NaHCO₃ (28 mmol/L), in which the slightly excessive amounts of H₂O₂ and NaHCO₃ with respect to TBCC were deliberately used to drive the reactions to completion. Peroxide stabilizer (Prestogen N-D, 1 g/L) and wetting agent (Penetrant JFC, 1 g/L) were also added to the solution for optimizing the treatment performance. A 5-g sample of cotton greige fabric was immersed in the solution using a liquor-to-goods ratio of 20 : 1. The treatment process was carried out in an Ahiba Nuiance laboratory dyeing machine (Datacolor International, USA) with the following settings: a target temperature of 60℃, a period time of 40 min, a ramp rate of 4℃/min, and a rotate speed of 30 r/min. After completion of the treatment process, cotton fabric was thoroughly rinsed with copious amounts of deionized water and dried under ambient conditions.

For comparison purposes, the H₂O₂/NaOH system was also conducted for treatment of cotton greige fabric. The treatment solution was prepared with the addition of 6 g/L H₂O₂ (30% w/w), 3 g/L NaOH, 1 g/L peroxide stabilizer (Prestogen N-D), and 1 g/L wetting agent (Penetrant JFC). A 5 -g sample of cotton greige fabric was immersed in the solution using a liquor-to-goods ratio of 20 : 1. The treatment process was carried out in the Ahiba Nuiance laboratory dyeing machine using the same settings as described above except for the target temperature of 95℃. The treated cotton fabric was thoroughly rinsed with copious amounts of deionized water and dried under ambient conditions.

Evaluation of water absorbency

The water absorbency of cotton fabric was evaluated by measuring the elapsed time in seconds of a water droplet on cotton fabric according to the AATCC Test Method 79-2007. A shorter elapsed time indicates a better water absorbency.

Determination of degree of polymerization

The degree of polymerization (DP) of cotton fabric was calculated using Equation (1):³³

DP = 2032 \log_{10} (\frac{74.35 + F}{F}) - 573

(1)

where F is the fluidity of a cellulose dispersion that was prepared for measurement by dissolving cotton fabric in a cupriethylenediamine solution according to the AATCC Test Method 82-2007.

Determination of hydrophobic matters in cotton fabric

The hydrophobic matters in cotton fabric were determined by consecutive water and hexane extractions according to the AATCC Test Method 97-2009. The procedure is described in detail below.

A sample of cotton fabric (around 10 g) with the edges folded inside was added to a beaker containing 200 mL of deionized water at 82℃. The beaker was covered with a watch glass and maintained at 82℃ for 2 h. The sample was rinsed with two successive 100 mL portions of deionized water at 82℃, and then dried under ambient conditions. The dried sample from the water extraction was placed in a Soxhlet extractor with a thimble, and was extracted with hexane 15 times. The sample was removed from the extractor and conditioned in a laboratory fume hood, allowing the remaining hexane on the sample to evaporate.

The hexane-extractable content (E) of the cotton fabric is calculated using Equation (2):

E = \frac{W_{water} - W_{hexane}}{W_{0}} \times 100 %

(2)

where W₀ is the dry weight of the sample without any extractions and W_water and W_hexane are the dry weights of the sample after water and hexane extractions, respectively.

Measurement of degree of whiteness

The degree of whiteness of cotton fabric was measured by the CIE whiteness index (WI) using a Datacolor 650 spectrophotometer (Datacolor International, USA) according to the AATCC Test Method 110-2005. Four measurements were performed for each cotton sample with a 90-degree rotation to give an average value.

XPS analysis

A RBD upgraded PHI-5000C ESCA system (Perkin Elmer, USA) with Mg Kα radiation (hν = 1253.6 eV) was used for analysis of the elemental surface composition of cotton fabric. The X-ray anode was run at 250 W, and the high voltage was kept at 14.0 kV with a detection angle at 54°. The base pressure of the analyzer chamber was about 5 × 10^–8Pa. The pass energy was fixed at 23.5 eV to ensure sufficient resolution and sensitivity. A sample of cotton fabric was directly pressed to a self-supported disk (10 mm × 10 mm) and mounted on a sample holder, and then transferred into the analyzer chamber. All the binding energies were calibrated to the containment carbon (C 1s) at 284.6 eV.

Scanning electron microscope

Cotton greige fabric before and after treatment was sputter-coated with gold. Scanning electron microscopy (SEM) was performed on a Zeiss EVO scanning electron microscope.

Results and discussion

Chemical treatment can produce two main effects on cotton fabric: (1) scouring, which aims to remove natural hydrophobic matters and is evaluated by measuring the water absorbency time; and (2) bleaching, which aims to remove natural coloring matters and is evaluated by measuring the degree of whiteness, both potentially causing fiber damage, which is evaluated by measuring the degree of polymerization. Table 1 shows the treatment performance of the TBCC/H₂O₂/NaHCO₃ system in comparison with the H₂O₂/NaOH system for both scouring and bleaching of cotton fabric. As can be seen from the table, the TBCC/H₂O₂/NaHCO₃ system is equivalent to the H₂O₂/NaOH system for improving the degree of whiteness of cotton fabric. This is mainly due to the fact that, when TBCC was added to the solution of H₂O₂ and NaHCO₃, a peracid was in situ generated as demonstrated in Scheme 3, which was capable of effectively eliminating chromophores of natural coloring matters present in cotton at a low temperature. In addition, the degree of polymerization of cotton fabric treated with the TBCC/H₂O₂/NaHCO₃ system was found to be far higher than that of cotton fabric treated with the H₂O₂/NaOH system but only slightly lower than that of cotton greige fabric. This indicates that the TBCC/H₂O₂/NaHCO₃ system was superior to the H₂O₂/NaOH system in protecting cotton fiber from chemical damage. It can hence be concluded that the TBCC/H₂O₂/NaHCO₃ system was more energy-effective and safer than the H₂O₂/NaOH system as an approach to cotton bleaching. However, because of the fact that the natural hydrophobic matters are much more sensitive to a hot treatment in an alkaline solution than to a low-temperature treatment in a near-neutral pH solution, it is a little unexpected that the TBCC/H₂O₂/NaHCO₃ system was found to be considerably effective for improving the water absorbency of cotton fabric.

Table 1.

Degree of whiteness and water absorbency of cotton greige fabric before and after treatments with the N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC)/H₂O₂/NaHCO₃ and H₂O₂/NaOH systems

Treatment system^a	Treatment conditions		WA, s	WI	DP
Treatment system^a	T, ℃	t, min	WA, s	WI	DP
Greige fabric as control			> 60	7.65 ± 0.82	4107 ± 105
TBCC/H₂O₂/NaHCO₃	60	40	7–9	69.59 ± 0.67	3951 ± 78
H₂O₂/NaOH	95	40	<1	69.93 ± 0.93	2165 ± 81

Three replicates of each treatment were performed.

Scheme 3.

Peracid formation from the reaction of N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC) with H₂O₂.

For clearly understanding the performance of the TBCC/H₂O₂/NaHCO₃ system for cotton treatment, XPS was used to analyze the elemental surface composition of cotton fabric before and after treatment. As shown in Figure 1, oxygen and carbon are two dominant elements detected at the cotton fiber surface. Besides, some other elements, such as nitrogen, calcium, and silicon, were also detected in small amounts due to the presence of natural impurities in cotton. The percentages of all detected elements at the cotton fiber surface are shown in Table 2, from which the atomic ratio of oxygen to carbon (O/C) was also calculated as given in the last column.

Figure 1.

X-ray photoelectron spectroscopy survey spectra of cotton greige fabric before and after treatments with the N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride/H₂O₂/NaHCO₃ and H₂O₂/NaOH systems.

Table 2.

Quantitative X-ray photoelectron spectroscopy analysis of cotton greige fabric before and after treatments with the N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC)/H₂O₂/NaHCO₃ and H₂O₂/NaOH systems

Treatment system	C, %	O, %	Other detected elements (N, Ca, and Si), %	O/C^a
Greige fabric as control	84.72	12.67	2.61	0.15
TBCC/H₂O₂/NaHCO₃	79.66	18.31	2.03	0.23
H₂O₂/NaOH	65.67	32.56	1.77	0.50

Pure cellulose has an O/C atomic ratio of 0.83.

Technically, a detailed analysis of carbon (C 1s) is more useful than those of other detected elements. According to the characteristic peaks of binding energies appearing on the XPS spectrum, C 1s can be easily classified into four types:³⁰ C_I referring to un-oxidized carbon (C–C or C–H) at 285.0 eV, C_II referring to carbon with one oxygen bond (C–O) at 286.6 eV, C_III referring to carbon with two oxygen bonds (C = O or O–C–O) at 288.1 eV, and C_IV referring to carbon with three oxygen bonds (O = C–O) at 289.1 eV. Consisting of a chain of glucopyranose units jointed at the 1 and 4 positions through elimination of water, pure cellulose contains only C_II (C–O) and C_III (O–C–O) types of carbons. Hence, a two-component C 1s XPS spectrum is expected for pure cellulose with peaks of binding energies at 286.6 and 288.1 eV. However, raw cotton in fact contains hydrophobic matters, such as waxes, fats, proteins, and pectin, which conceal the cellulose backbone and form laminar layers covering cotton fibers. C_I and C_IV types of carbons in these non-cellulosic materials (for instance, waxes and fats) can be detected at the surface of cotton fibers even after well scouring and bleaching.³⁴ Hence, the two-component C 1s XPS spectrum of pure cellulose would be modified by additional peaks of binding energies at 285.0 eV for the C_I type of carbon and at 289.1 eV for the C_IV type of carbon.

As can be seen in Figure 2, cotton greige fabric exhibited a C 1s XPS spectrum with a relatively strong binding energy at 285.0 eV and a dominant binding energy at 287.8 eV. After treatment with the TBCC/H₂O₂/NaHCO₃ and the H₂O₂/NaOH systems, however, the binding energy at 285.0 eV was significantly reduced and the dominant binding energy was shifted to 288.1 and 289.4 eV, respectively. The C 1s XPS spectrum in Figure 2 indicated that the surface of cotton greige fabric was modified after treatments with the TBCC/H₂O₂/NaHCO₃ and the H₂O₂/NaOH systems, but did not consist of pure cellulose.

Figure 2.

C 1s X-ray photoelectron spectroscopy spectra of cotton greige fabric before and after treatments with the N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride/H₂O₂/NaHCO₃ and H₂O₂/NaOH systems.

The reduction in binding energy at 285.0 eV after cotton treatment in Figure 2 can be attributed to the removal of waxes, which mainly consist of the C_I type of carbon. Waxes are most responsible for the water absorbency of cotton fabric. Hence, the water absorbency of cotton fabric was improved after treatments, as shown in Table 1. It can be seen in Figure 2 that the binding energy at 285.0 eV corresponding to the TBCC/H₂O₂/NaHCO₃ system appears significantly stronger than that corresponding to the H₂O₂/NaOH system. This indicates that the TBCC/H₂O₂/NaHCO₃ system was not as effective as the H₂O₂/NaOH system for removing waxes. This could be an important reason for the result in Table 1 that the TBCC/H₂O₂/NaHCO₃ system was inferior to the H₂O₂/NaOH system for improving the water absorbency of cotton fabric.

The left shift of the dominant binding energy in Figure 2 can be mainly attributed to two oxidative reactions taking place in either the TBCC/H₂O₂/NaHCO₃ or H₂O₂/NaOH systems, as demonstrated in Scheme 4. The oxidation of coloring matters is a desired reaction for cotton bleaching, which may introduce the C_II type of carbon onto the cotton fiber surface, while the oxidation of cellulose is a side reaction that converts the C_II type of carbon into the C_IV type of carbon. As a result, the dominant binding energy of cotton fabric treated with the TBCC/H₂O₂/NaHCO₃ system coincides with the peak of binding energy of the C_II type of carbon, while the dominant binding energy of cotton fabric treated with the H₂O₂/NaOH system is most closely approximating to the peak of binding energy of the C_IV type of carbon. Since both C_II and C_IV types of carbons could impart hydrophilicity to cotton fabric, it is reasonable that the water absorbency of cotton fabric would be improved by oxidations of coloring matters and cellulose to some extent. As indicated in Figure 2, the H₂O₂/NaOH system caused more extensive oxidation of cellulose than the TBCC/H₂O₂/NaHCO₃ system. This could be a possible reason for the fact that the TBCC/H₂O₂/NaHCO₃ system was not as effective as the H₂O₂/NaOH system for improving the water absorbency of cotton fabric.

Scheme 4.

Possible oxidative reactions in cotton treatment: (a) oxidation of coloring matters; (b) oxidation of cellulose.

The O/C atomic ratio can be used as an important indicator of the total treatment performance for scouring and bleaching of cotton.^31,32 A higher O/C atomic ratio generally indicates a better treatment performance. The O/C atomic ratios of cotton greige fabric before and after treatments were calculated from the quantitative XPS analysis data, as shown in Table 2. As expected, pure cellulose has an O/C atomic ratio of 0.83. However, cotton greige fabric was found to have an O/C atomic ratio of 0.15, which is far below the theoretical value of cellulose. Such a low O/C atomic ratio is mainly due to the fact that pure cellulose is embedded under hydrophobic laminar layers. The O/C atomic ratio was considerably increased after treatments because of the removals of hydrophobic matters and two modes of oxidation. However, it is interesting to see in Table 2 that the O/C atomic ratio resulting from treatment with the TBCC/H₂O₂/NaHCO₃ system was remarkably lower than that resulting from treatment with the H₂O₂/NaOH system. Such a great difference in the O/C atomic ratio is not correlated well with the slight difference in water absorbency (Table 1) between the cotton fabrics treated by the two systems.

Table 3 shows the contents of hydrophobic matters determined by hexane extraction. It was found that the cotton fabric treated by the TBCC/H₂O₂/NaHCO₃ system had a slightly higher content of hydrophobic matters than the cotton fabric treated by the H₂O₂/NaOH system, which is roughly in agreement with the water absorbency shown in Table 1. This indicates that the relatively lower value of the O/C atomic ratio of the cotton fabric treated by the TBCC/H₂O₂/NaHCO₃ system was not necessarily caused by a higher content of hydrophobic matters in cotton. It is shown in Figure 3 that the two treated cotton fabrics appeared in different morphologies. It seems that the TBCC/H₂O₂/NaHCO₃ system most likely removed hydrophobic matters in a “layer-by-layer” mode due to the mild process conditions and as such resulted in a relatively smooth surface, while the H₂O₂/NaOH system most likely removed hydrophobic matters by firstly attacking the weak points existing in cotton fibers and as such resulted in a heavily etched surface. Therefore, the cotton fabric treated by the TBCC/H₂O₂/NaHCO₃ system had fewer cellulose backbones exposed for XPS analysis than that treated by the H₂O₂/NaOH system, although the contents of hydrophobic matters in the two cotton fabrics were approximate. This might explain why the TBCC/H₂O₂/NaHCO₃ system could provide cotton fabric with a low O/C atomic ratio but greatly improved water absorbency.

Figure 3.

Scanning electron microscopy images of cotton greige fabric before (a) and after treatments by the N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride/H₂O₂/NaHCO₃ system (b) and the H₂O₂/NaOH system (c).

Table 3.

The contents of hydrophobic matters in treated cotton fabrics determined by hexane extraction

Treatment system	E, %
TBCC/H₂O₂/NaHCO₃	0.145
H₂O₂/NaOH	0.134

TBCC: N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride.

Conclusions

The TBCC/H₂O₂/NaHCO₃ system was applied for treatment of cotton greige fabric at 60℃. In comparison with the conventional H₂O₂/NaOH system for treatment of cotton greige fabric at 95℃, the TBCC/H₂O₂/NaHCO₃ system was capable of providing an equivalent degree of whiteness and caused much less fiber damage, but was slightly inferior in improving water absorbency. C 1s XPS spectra revealed that the C_I type of carbon (un-oxidized) was reduced and the C_IV type of carbon (carboxyl group) was increased to a lesser extent by the TBCC/H₂O₂/NaHCO₃ system than by the H₂O₂/NaOH system. This indicated that the TBCC/H₂O₂/NaHCO₃ system was inferior to the H₂O₂/NaOH system both in removing natural hydrophobic matters, such as waxes that are mainly composed of the C_I type of carbon, and in oxidation of cellulose, which converted the C_II type of carbon into the C_IV type of carbon. This partly explained why the TBCC/H₂O₂/NaHCO₃ system was not as effective as the H₂O₂/NaOH system for improving the water absorbency of cotton fabric. However, the O/C atomic ratio of cotton fabric treated with the TBCC/H₂O₂/NaHCO₃ system was found to be much lower than that of cotton fabric treated with the H₂O₂/NaOH system, which was not correlated well with the water absorbency of cotton fabric achieved by the two systems. The hexane extractions and SEM images indicated that the fact that the TBCC/H₂O₂/NaHCO₃ system provided cotton fabric with a low O/C atomic ratio but greatly improved water absorbency might be due to a “layer-by-layer” removal of hydrophobic matters, which limited the exposure of cellulose backbones to XPS analysis, but allowed water to penetrate into cotton fibers.

Footnotes

Funding

The work was supported by the National Natural Science Foundation of China (Grant No. 21276106) and the Qing Lan Project of Jiangsu Province.

References

Wakelyn

Bertoniere

French

. Cotton fiber chemistry and technology, Boca Raton, FL: CRC Press, 2007, pp. 15–15.

Lewin

Sello

. Handbook of fiber science and technology, New York: Marcel Dekker, Inc, 1984, pp. 193–193.

Zeronian

Inglesby

. Bleaching of cellulose by hydrogen peroxide. Cellulose 1995; 2: 265–272.

Hofmann

Just

Pritzkow

. Bleaching activators and the mechanism of bleaching activation. J Prakt Chem 1992; 334: 293–297.

Scarborough

Mathews

. Using T.A.E.D. in bleaching fiber blends to improve fiber quality. Text Chem Color Am D 2000; 32: 33–37.

El-Shafie

Fouda

MMG

Hashem

. One-step process for bio-scouring and peracetic acid bleaching of cotton fabric. Carbohydr Polym 2009; 78: 302–308.

Hebeish

Hashem

Shaker

. New development for combined bioscouring and bleaching of cotton-based fabrics. Carbohydr Polym 2009; 78: 961–972.

Shao

Huang

Wang

. Cold pad-batch bleaching of cotton fabrics with a TAED/H₂O₂ activating system. Color Technol 2010; 126: 103–108.

Tavcer

. Low-temperature bleaching of cotton induced by glucose oxidase enzymes and hydrogen peroxide activators. Biocatal Biotransfor 2012; 30: 20–26.

10.

Long

. A critical reinvestigation of the TAED-activated peroxide system for low-temperature bleaching of cotton. Carbohydr Polym 2013; 92: 249–253.

11.

Spicka

Tavcer

. Complete enzymatic pre-treatment of cotton fabric with incorporated bleach activator. Text Res J 2013; 83: 566–573.

12.

Long

. The TAED/H₂O₂/NaHCO₃ system as an approach to low-temperature and near-neutral pH bleaching of cotton. Carbohydr Polym 2013; 95: 107–113.

13.

Cai

Evans

Smith

. Bleaching of natural fibers with TAED and NOBS activated peroxide systems. AATCC Rev 2001; 1: 31–34.

14.

Wang

Washington

. Hydrophobic bleach systems and textile preparation: a discontinuity in fabric care. AATCC Rev 2002; 2: 21–24.

15.

Cai

Evans

. Guanidine derivatives used as peroxide activators for bleaching cellulosic textiles. Color Technol 2007; 123: 115–118.

16.

Lee

Hinks

Lim

. Hydrolytic stability of a series of lactam-based cationic bleach activators and their impact on cellulose peroxide bleaching. Cellulose 2010; 17: 671–678.

17.

Hinks

Shamey . Bleaching cellulosic fibers via pre-sorption of N-[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride. Cellulose 2010; 17: 849–857.

18.

Gursoy

Lim

Hinks

. Evaluating hydrogen peroxide bleaching with cationic bleach activators in a cold pad-batch process. Text Res J 2004; 74: 970–976.

19.

Gursoy

El-Shafei

Hauser

. Cationic bleach activators for improving cotton bleaching. AATCC Rev 2004; 4: 37–40.

20.

Lim

Gursoy

Hauser

. Performance of a new cationic bleach activator on a hydrogen peroxide bleaching system. Color Technol 2004; 120: 114–118.

21.

Lim

Lee

Hinks

. Bleaching of cotton with activated peroxide systems. Color Technol 2005; 121: 89–95.

22.

Shamey

Hinks

. Activated peroxide bleaching of regenerated bamboo fiber using a butyrolactam-based cationic bleach activator. Cellulose 2010; 17: 339–347.

23.

Hinks

Shamey

. Development of a novel bleaching process for cotton. AATCC Rev 2011; 11: 73–77.

24.

Shamey

Hinks

. Cotton bleaching optimization using a butyrolactam-based cationic bleach activator. AATCC Rev 2012; 12: 66–70.

25.

Soignet

Berni

Benerito

. Electron spectroscopy for chemical analyses (ESCA) – a tool for studying treated textiles. J Appl Polym Sci 1976; 20: 2483–2495.

26.

Ahmed

Adnot

Grandmaison

. ESCA analysis of cellulosic materials. Cell Chem Technol 1987; 21: 481–492.

27.

Belgacem

Czeremuszkin

Sapieha

. Surface characterization of cellulose fibres by XPS and inverse gas chromatography. Cellulose 1995; 2: 145–157.

28.

Buchert

Pere

Johansson

. Analysis of the surface chemistry of linen and cotton fabrics. Text Res J 2001; 71: 626–629.

29.

Johansson

Campbell

Koljonen

. On surface distributions in natural cellulosic fibres. Surf Interface Anal 2004; 36: 706–710.

30.

Mitchell

Carr

Parfitt

. Surface chemical analysis of raw cotton fibres and associated materials. Cellulose 2005; 12: 629–639.

31.

Topalovic

Nierstrasz

Bautista

. Analysis of the effects of catalytic bleaching on cotton. Cellulose 2007; 14: 385–400.

32.

Topalovic

Nierstrasz

Bautista

. XPS and contact angle study of cotton surface oxidation by catalytic bleaching. Colloids Surf A 2007; 296: 76–85.

33.

Interox. A bleacher’s handbook. Houston, TX: Solvay Interox, 1981, p.57.

34.

Hartzell-Lawson

Hsieh

Y-L

. Characterizing the noncellulosics in developing cotton fibers. Text Res J 2000; 70: 810–819.