**3. Results and discussion**

Complexation of chitosan with cotton cellulose to produce cotton –based new textiles is of paramount concern. To render these new cotton textiles more durable and stable for subsequent treatments such as dyeing and finishing, it is a must to induce strong interactions between chitosan and cotton. One of the approaches to achieve this is to create aldehyde groups in the molecular structure of cotton cellulose. These aldehyde groups undergo coupling with the amino groups of chitosan to form iminic bonds (1) whereby chitosan is fixed to cotton surface through a series of reactions as shown under:

Eco-Friendly Pretreatment of

[NaIO4] mg/100ml

of 1%.

[chitosan] %

concentration.

**3.2 Chitosan concentration** 

Cellulosic Fabrics with Chitosan and Its Influence on Dyeing Efficiency 7

higher amounts of fixed chitosan as evidenced by the higher contents. The chitosan molecules seems to form a film fixed on the cotton cellulose (in the fabric form) through strong interactions thereby compensating for the higher losses in tensile strength expected at higher sodium periodate concentrations. It is also possible that the cotton cellulose undergoes modification during the initial oxidation and such modification makes the cellulose less susceptible for farther oxidation particular via chain scission. On the other hand, elongation at break marginally reduced after oxidation and chitosan treatment

> Carbonyl content Meq/100g S

0.0 0.112 15.122 38.25 11.34 30 0.181 20.098 30.17 11.02 50 0.243 25.105 29.53 10.71 80 0.252 31.167 29.42 10.45

The above findings indicate that modified cotton fabrics which enjoy the presence of chitosan as evidenced by their nitrogen content and acidic properties as evidenced by the carbonyl content while retaining much of their strength properties can be achieved using NaIO4 concentration 30-5- mg/100ml followed by treatment with chitosan at a concentration

Table 2 shows the dependence of the modification effect- expressed as nitrogen content, carboxyl content and strength properties including tensile strength and elongation at break on the chitosan concentration. As is evident the nitrogen content and strength properties of modified fabric increase as the chitosan concentration increases. At higher concentrations, chitosan molecules would be greatly available in the proximity of the macrostructure of cotton and fabric surfaces both containing aldehyde groups thereby leading to Schiff's base formation between aldehyde groups and chitosan amino groups.

> Carbonyl content Meq/100g S

Table 2. Dependence of the magnitude of modification of cotton fabric on chitosan

0.0 0.000 36.231 28.22 10.31 0.5 0.191 32.143 28.52 11.02 1.0 0.243 25.105 29.53 11.71 1.5 0.292 22.125 31.21 12.44 2.0 0.324 20.176 31.51 12.53 Conditions used for cotton fabric oxidation: [NaIO4], 50 mg/100ml; time, 1hr; temp, 60 oC, M/L, 1:50

Tensile strength (Newton)

Tensile strength (Newton)

Elongation at Break (%)

Elongation at Break (%)

regardless of the oxidant concentration used within the range studied.

Conditions used for oxidation of cotton fabric: time,1hr; temperature,60 oC, M/L, 1:50 Condition used for chitosan treatment: [chitosan], 1%; time, 1.5 hr; temp, 60oC; M/L, 1:50. Table 1. Effect of sodium periodate concentration on some chemical and mechanical

Nitrogen content (%)

properties of chitosan-containing cotton fabric.

Nitrogen content (%)

Condition used in chitosan treatment: time, 1.5 hr; temp, 60 oC; M/L, 1:50

Our work involves fixation of chitosan to bleached cotton fabric as per two methods. The fist method is based on oxidation of the fabric with NaIO4 in acidic medium to yield fabric containing 2,3-vicinal diol of the glucose unit of cotton cellulose or what is called dialdehyde cellulose. The so obtained oxidized fabric is then subjected to chitosan treatment where interaction occurs thereby causing fixation of chitosan on the fabric surface. In the second method, the fabric is treated in a bath containing NaIO4 and chitosan where simultaneous oxidation and chitosan fixation take place.

When dealing with the second method, mention should be made of the effect of NaIO4 on the chitosan. According to previous reports(9), the chitosan molecule is susceptible to oxidation by sodium periodate at five points: the terminal aldehyde group at C1, the secondary hydroxyl on C4 at the non reducing end of the chain, the secondary hydroxyl on C3, the primary hydroxyl at C6 and the amino group at C2 position. In addition molecular chain scission of chitosan occurs through the attack of the oxidant on the 1-4 glucosidic linkages. When chitosan is oxidized the action takes place chiefly at C3 and C6 hydroxyls, the amino group at C2 and at the 1-4 glucosidic linkage by virtue of the greater abundance of these sites as compared with the two types of terminal groups.

With the above in mind, factors affecting the major technical properties of cotton-based new textile brought about by the first and second methods were thoroughly investigated. Factors studied include concentrations of chitosan and NaIO4 as well as time and temperature of the treatments. On the other hand, the obtained cotton products were monitored for nitrogen content, carbonyl content, tensile strength, elongation at break and dyeability. IR spectra for cotton fabrics-containing chitosan which were processed as per the two methods are also presented.

#### **3.1 Sodium periodate concentration**

Table 1 shows the effect of sodium periodate concentration on the amount of fixed chitosan (expressed as nitrogen content), carboxyl content, tensile strength and elongation at break of the oxidized fabric. Obviously the amount of fixed chitosan on the cotton fabric increases by increasing the oxidant concentration up to 50 mg/100ml. Further increase in the oxidant concentration to 80 mg/100ml causes no significant increase in nitrogen content. This phenomena could be explained by considering the difference in the reaction site of the oxidation and Schiff's base formation in the cellulosic fabric. During the oxidation, the small periodate ion might be able to enter the cellulosic fabric interior and the glucose unit both inside and on the surface of the cellulosic fabric may be oxidized. On the other hand, chitosan is a huge molecule that cannot enter the fabric, and the modification with chitosan occurs on the surface of the fabric. Results of table 1 reveal that the carbonyl content of the fabric in question, i.e. periodate-oxidized fabric containing chitosan, increases by increasing the oxidant concentration. This is rather a manifestation of oxidation of hydroxyl groups of the cotton fabric to aldehydic groups under the progressive action of the oxidant at high concentrations.

Tensile strength decreases substantially after the fabric was subjected to periodate treatment at a concentration of 30 mg/100ml followed by chitosan treatment. Increasing the periodate concentration up to 80 mg/100ml causes no further significant decrease in the tensile strength of periodate oxidized fabric-containing chitosan. While the loss in tensile strength of the fabric upon using sodium periodate at 30 mg/100ml concentration could be interpreted in terms of degradation of cotton cellulose, the no significant change in tensile strength upon using higher concentrations calls for extra strength imported to the fabric by higher amounts of fixed chitosan as evidenced by the higher contents. The chitosan molecules seems to form a film fixed on the cotton cellulose (in the fabric form) through strong interactions thereby compensating for the higher losses in tensile strength expected at higher sodium periodate concentrations. It is also possible that the cotton cellulose undergoes modification during the initial oxidation and such modification makes the cellulose less susceptible for farther oxidation particular via chain scission. On the other hand, elongation at break marginally reduced after oxidation and chitosan treatment regardless of the oxidant concentration used within the range studied.


Conditions used for oxidation of cotton fabric: time,1hr; temperature,60 oC, M/L, 1:50 Condition used for chitosan treatment: [chitosan], 1%; time, 1.5 hr; temp, 60oC; M/L, 1:50.

Table 1. Effect of sodium periodate concentration on some chemical and mechanical properties of chitosan-containing cotton fabric.

The above findings indicate that modified cotton fabrics which enjoy the presence of chitosan as evidenced by their nitrogen content and acidic properties as evidenced by the carbonyl content while retaining much of their strength properties can be achieved using NaIO4 concentration 30-5- mg/100ml followed by treatment with chitosan at a concentration of 1%.

## **3.2 Chitosan concentration**

6 Natural Dyes

Our work involves fixation of chitosan to bleached cotton fabric as per two methods. The fist method is based on oxidation of the fabric with NaIO4 in acidic medium to yield fabric containing 2,3-vicinal diol of the glucose unit of cotton cellulose or what is called dialdehyde cellulose. The so obtained oxidized fabric is then subjected to chitosan treatment where interaction occurs thereby causing fixation of chitosan on the fabric surface. In the second method, the fabric is treated in a bath containing NaIO4 and chitosan where simultaneous

When dealing with the second method, mention should be made of the effect of NaIO4 on the chitosan. According to previous reports(9), the chitosan molecule is susceptible to oxidation by sodium periodate at five points: the terminal aldehyde group at C1, the secondary hydroxyl on C4 at the non reducing end of the chain, the secondary hydroxyl on C3, the primary hydroxyl at C6 and the amino group at C2 position. In addition molecular chain scission of chitosan occurs through the attack of the oxidant on the 1-4 glucosidic linkages. When chitosan is oxidized the action takes place chiefly at C3 and C6 hydroxyls, the amino group at C2 and at the 1-4 glucosidic linkage by virtue of the greater abundance

With the above in mind, factors affecting the major technical properties of cotton-based new textile brought about by the first and second methods were thoroughly investigated. Factors studied include concentrations of chitosan and NaIO4 as well as time and temperature of the treatments. On the other hand, the obtained cotton products were monitored for nitrogen content, carbonyl content, tensile strength, elongation at break and dyeability. IR spectra for cotton fabrics-containing chitosan which were processed as per the two methods are also

Table 1 shows the effect of sodium periodate concentration on the amount of fixed chitosan (expressed as nitrogen content), carboxyl content, tensile strength and elongation at break of the oxidized fabric. Obviously the amount of fixed chitosan on the cotton fabric increases by increasing the oxidant concentration up to 50 mg/100ml. Further increase in the oxidant concentration to 80 mg/100ml causes no significant increase in nitrogen content. This phenomena could be explained by considering the difference in the reaction site of the oxidation and Schiff's base formation in the cellulosic fabric. During the oxidation, the small periodate ion might be able to enter the cellulosic fabric interior and the glucose unit both inside and on the surface of the cellulosic fabric may be oxidized. On the other hand, chitosan is a huge molecule that cannot enter the fabric, and the modification with chitosan occurs on the surface of the fabric. Results of table 1 reveal that the carbonyl content of the fabric in question, i.e. periodate-oxidized fabric containing chitosan, increases by increasing the oxidant concentration. This is rather a manifestation of oxidation of hydroxyl groups of the cotton fabric to aldehydic groups under the progressive action of the oxidant at high

Tensile strength decreases substantially after the fabric was subjected to periodate treatment at a concentration of 30 mg/100ml followed by chitosan treatment. Increasing the periodate concentration up to 80 mg/100ml causes no further significant decrease in the tensile strength of periodate oxidized fabric-containing chitosan. While the loss in tensile strength of the fabric upon using sodium periodate at 30 mg/100ml concentration could be interpreted in terms of degradation of cotton cellulose, the no significant change in tensile strength upon using higher concentrations calls for extra strength imported to the fabric by

oxidation and chitosan fixation take place.

**3.1 Sodium periodate concentration** 

presented.

concentrations.

of these sites as compared with the two types of terminal groups.

Table 2 shows the dependence of the modification effect- expressed as nitrogen content, carboxyl content and strength properties including tensile strength and elongation at break on the chitosan concentration. As is evident the nitrogen content and strength properties of modified fabric increase as the chitosan concentration increases. At higher concentrations, chitosan molecules would be greatly available in the proximity of the macrostructure of cotton and fabric surfaces both containing aldehyde groups thereby leading to Schiff's base formation between aldehyde groups and chitosan amino groups.


Conditions used for cotton fabric oxidation: [NaIO4], 50 mg/100ml; time, 1hr; temp, 60 oC, M/L, 1:50 Condition used in chitosan treatment: time, 1.5 hr; temp, 60 oC; M/L, 1:50

Table 2. Dependence of the magnitude of modification of cotton fabric on chitosan concentration.

Eco-Friendly Pretreatment of

Nitrogen content (%)

Time (hr)

Cellulosic Fabrics with Chitosan and Its Influence on Dyeing Efficiency 9

Tensile strength (Newton)

Tensile strength (Newton)

Elongation at break(%)

Elongation at Break (%)

Carbonyl content Meq/100g S

Table 4. Effect of time of chitosan treatment of oxidized fabric on some chemical and

amount of chitosan on the fabric and the extent of penetration of former in the latter.

Table 4 shows that the tensile strength decreases from ca 31 to ca 29 Newton when the duration of chitosan treatment increases from o.5 to 1.5 hr. This little effect of time of chitosan treatment is also seen with respect to elongation at break. At any event, however, these decrements are considered to be a direct consequence of rigidity conferred on cotton caused by chitosan penetration. As already stated, rigidity is proportionally related to the

In the foregoing sections, innovative modified cotton textiles could be achieved by a twostep method namely, periodate oxidation of cotton fabrics in one step followed by treatment of these fabrics in a second step by chitosan. In order to avoid detrimental effects of oxidation and in order to save time, chemicals and energy the two steps were combined in a single stage process where the cotton fabrics were treated in an aqueous solution containing the periodate oxidant and the chitosan under conditions emanated from the studies of the

The nitrogen content, the carbonyl content and strength properties of cotton fabrics before and after being processed as per the two-step process and the one-step process are set out in table 5. For convenience the untreated cotton fabric and the two-step processed modified cotton fabric and the one-step processed cotton fabrics will be referred to as substrate I,

> Carbonyl content Meq/100g S

I 0.000 17.341 38.32 11.3 II 0.513 18.523 29.53 11.71 III 0.652 16.535 45.12 13.52 Where Substrate I: bleached cotton fabric; substrate II: two-step processed modified cotton; substrate III: one –step processed modified cotton. Two-step process involves oxidation by NaIO4 and treatment with chitosan in two consecutive steps. One-step process involves treatment of the cotton fabric with an

Conditions used for oxidation of cotton fabric: [NaIO4], 50 mg/100ml ;time,1hr; temp,60 oC, M/L, 1:50

Condition used in one -step process: [NaIO4], 50 mg/100ml; [chitosan], 2%; temp, 80 oC ; M/L 1:50

Condition used for chitosan treatment: [chitosan], 2%; temp, 80 oC ; M/L 1:50

Condition used in chitosan treatment: [chitosan], 2%; temp, 80 oC ; M/L 1:50

mechanical properties of the obtained modified fabric

**3.5 One step method for modification** 

substrate II and substrate III, respectively.

Nitrogen content (%)

aqueous solution containing oxidant and chitosan.

Table 5. Comparison among substrates I, II, III.

factors discussed above.

Substrate

0.5 0.237 23.335 31.32 13.14 1.0 0.272 19.812 30.52 12.53 1.5 0.513 18.523 29.53 11.71 Conditions used for oxidation of cotton fabric: [NaIO4], 50 mg/100ml; time, 1hr; temp, 60 oC, M/L, 1:50

It is further observed that the values of the carbonyl content of the modified fabric decrease substantially by increasing chitosan concentration. This indicates that the carboxyl groups of the modified cotton fabric under investigation are involved in chemical reactions with chitosan. Once this is the case, the carbonyl groups are masked and their values decreases by increasing the chitosan concentration where opportunities of interactions are better.

#### **3.3 Temperature of chitosan treatment**

Table 3 discloses the effect of chitosan treatment temperature of oxidized cotton on some chemical and mechanical properties of the modified fabric. The treatment was carried out at different temperatures for 90 minutes using chitosan concentration of 2%. The results signify that the nitrogen content increases by raising the chitosan treatment temperature from 40°C to 80 °C .This could be ascribed to increased amount of incorporated chitosan into the oxidized fabric as a result the favorable effect of temperature on swallability of cotton and mobility of chitosan molecules; both enhance the magnitude of interactions between cotton and chitosan. On the other hand, raising the chitosan treatment temperature adversely affects the tensile strength of the modified fabric. Most probably greater penetration of the highly mobile chitosan at higher temperatures in the fibriller structure of swollen cotton causes rigidity and, in term, decrement in tensile strength. The results of elongation at break are in confirmation with this.


Conditions used for oxidation of cotton fabric: [NaIO4], 50 mg/100ml; time, 1hr; temp, 60 oC, M/L, 1:50 Condition used in chitosan treatment: [chitosan], 2%; time, 1.5 hr; M/L, 1:50

Table 3. Effect of chitosan treatment temperature of the oxidized cotton on major technical properties of the modified fabric

Table 3 depicts that the carbonyl content decreases by raising the chitosan treatment temperature from 40°C to 80 °C. This state of affairs implies that higher temperature acts in favour of the interactions of chitosan with cotton cellulose and that these interactions involve, inter alia, the carbonyl groups of cotton.

#### **3.4 Time of chitosan treatment**

Table 4 shows the effect of time of chitosan treatment on major technical properties of the obtained modified cotton fabrics. It is seen that the nitrogen content increases by prolonging the time of chitosan treatment within the range studied. Provision of better contact and intimate association of chitosan with cotton cellulose at longer duration period would account for this. On the other hand, results of carboxyl content, feature that the carbonyl content decreases by increasing the time of chitosan treatment. This is rather similar to the effect of chitosan treatment temperature discussed above and could be explained on the same basis.

It is further observed that the values of the carbonyl content of the modified fabric decrease substantially by increasing chitosan concentration. This indicates that the carboxyl groups of the modified cotton fabric under investigation are involved in chemical reactions with chitosan. Once this is the case, the carbonyl groups are masked and their values decreases by increasing the chitosan concentration where opportunities

Table 3 discloses the effect of chitosan treatment temperature of oxidized cotton on some chemical and mechanical properties of the modified fabric. The treatment was carried out at different temperatures for 90 minutes using chitosan concentration of 2%. The results signify that the nitrogen content increases by raising the chitosan treatment temperature from 40°C to 80 °C .This could be ascribed to increased amount of incorporated chitosan into the oxidized fabric as a result the favorable effect of temperature on swallability of cotton and mobility of chitosan molecules; both enhance the magnitude of interactions between cotton and chitosan. On the other hand, raising the chitosan treatment temperature adversely affects the tensile strength of the modified fabric. Most probably greater penetration of the highly mobile chitosan at higher temperatures in the fibriller structure of swollen cotton causes rigidity and, in term, decrement in tensile strength. The results of elongation at break

> Carbonyl content Meq/100g S

Condition used in chitosan treatment: [chitosan], 2%; time, 1.5 hr; M/L, 1:50

40 0.196 24.116 34.21 13.13 60 0.324 20.176 31.51 12.53 80 0.513 18.523 29.53 11.71 Conditions used for oxidation of cotton fabric: [NaIO4], 50 mg/100ml; time, 1hr; temp, 60 oC, M/L, 1:50

Table 3. Effect of chitosan treatment temperature of the oxidized cotton on major technical

Table 3 depicts that the carbonyl content decreases by raising the chitosan treatment temperature from 40°C to 80 °C. This state of affairs implies that higher temperature acts in favour of the interactions of chitosan with cotton cellulose and that these interactions

Table 4 shows the effect of time of chitosan treatment on major technical properties of the obtained modified cotton fabrics. It is seen that the nitrogen content increases by prolonging the time of chitosan treatment within the range studied. Provision of better contact and intimate association of chitosan with cotton cellulose at longer duration period would account for this. On the other hand, results of carboxyl content, feature that the carbonyl content decreases by increasing the time of chitosan treatment. This is rather similar to the effect of chitosan treatment temperature discussed above and could be explained on the

Tensile strength (Newton)

Elongation at Break (%)

of interactions are better.

are in confirmation with this.

properties of the modified fabric

**3.4 Time of chitosan treatment** 

Nitrogen content (%)

involve, inter alia, the carbonyl groups of cotton.

Temp. oC

same basis.

**3.3 Temperature of chitosan treatment** 


Conditions used for oxidation of cotton fabric: [NaIO4], 50 mg/100ml; time, 1hr; temp, 60 oC, M/L, 1:50 Condition used in chitosan treatment: [chitosan], 2%; temp, 80 oC ; M/L 1:50

Table 4. Effect of time of chitosan treatment of oxidized fabric on some chemical and mechanical properties of the obtained modified fabric

Table 4 shows that the tensile strength decreases from ca 31 to ca 29 Newton when the duration of chitosan treatment increases from o.5 to 1.5 hr. This little effect of time of chitosan treatment is also seen with respect to elongation at break. At any event, however, these decrements are considered to be a direct consequence of rigidity conferred on cotton caused by chitosan penetration. As already stated, rigidity is proportionally related to the amount of chitosan on the fabric and the extent of penetration of former in the latter.

### **3.5 One step method for modification**

In the foregoing sections, innovative modified cotton textiles could be achieved by a twostep method namely, periodate oxidation of cotton fabrics in one step followed by treatment of these fabrics in a second step by chitosan. In order to avoid detrimental effects of oxidation and in order to save time, chemicals and energy the two steps were combined in a single stage process where the cotton fabrics were treated in an aqueous solution containing the periodate oxidant and the chitosan under conditions emanated from the studies of the factors discussed above.

The nitrogen content, the carbonyl content and strength properties of cotton fabrics before and after being processed as per the two-step process and the one-step process are set out in table 5. For convenience the untreated cotton fabric and the two-step processed modified cotton fabric and the one-step processed cotton fabrics will be referred to as substrate I, substrate II and substrate III, respectively.


Where Substrate I: bleached cotton fabric; substrate II: two-step processed modified cotton; substrate III: one –step processed modified cotton. Two-step process involves oxidation by NaIO4 and treatment with chitosan in two consecutive steps. One-step process involves treatment of the cotton fabric with an aqueous solution containing oxidant and chitosan.

Conditions used for oxidation of cotton fabric: [NaIO4], 50 mg/100ml ;time,1hr; temp,60 oC, M/L, 1:50 Condition used for chitosan treatment: [chitosan], 2%; temp, 80 oC ; M/L 1:50

Condition used in one -step process: [NaIO4], 50 mg/100ml; [chitosan], 2%; temp, 80 oC ; M/L 1:50

Table 5. Comparison among substrates I, II, III.

Eco-Friendly Pretreatment of

Fig. 1. IR spectrum of substrate II

Fig. 2. IR spectrum of substrate III

**4. Conclusion** 

Cellulosic Fabrics with Chitosan and Its Influence on Dyeing Efficiency 11

Chemical modification of cotton cellulose in the fabric form was effected through periodate oxidation treatment and chitosan treatment in the consecutive steps under different conditions. A single-step process was also devised for preparation of the same modified cotton. The idea in both cases was to create functional groups in the molecular structure of cotton such as aldehyde and carboxyl groups to expedite strong interactions with chitosan. Modified cotton fabrics processed as per the two processes were monitored, nitrogen content, carbonyl content, tensile strength and elongation at break in addition IR spectra.

A comparison among the substrates I , II and III with respect to nitrogen content, tensile strength and elongation at break and carbonyl content as shown in table 5 would reveal that substrate II exhibits the carbonyl content and the lowest tensile strength as compared with substrates I and III; indicating the determinal effect of oxidation prior to chitosan treatment. On the contrary, substrate III acquires the highest nitrogen content and the highest tensile strength and elongation at break while retaining a carboxyl content which is equal to that of substrate I. This, indeed, signifies the advantages of the one-step process in avoiding prior oxidation entailed in the two-step process.

Presence of chitosan during oxidation of the cotton fabric with NaIO4 seems to protect the cotton against oxidation. At the same time NaIO4 oxidizes chitosan to produce chitosan products with better solubility and more uniform structure and, in turn, better filmforming properties. Such properties will be reflected on strength of the film and the extra strength brought about thereof when the cotton fabric is coated with this film. Achieving substrate III with its potential properties is regarded to be the most salient output of the current work.

#### **Dyeability**

Substrate I, substrate II and substrate III were dyed independently with reactive and acid dyes. The results obtained are shown in table 6. It is observed that regardless of the dye used. Substrate III exhibits colour strength which is higher than those of substrate II. This again signifies the superiority of substrate III which, indeed, together with its other properties (table 5) advocate the one-step process for preparation of innovative modified cotton fabrics-containing chitosan.


Substrate 1: Bleached cotton fabric

Substrate II: processed as per the two-step process

Substrate III: processed as per the one-step process

Table 6. Dyeing of the different substrates under investigation with reactive and acid dyes

#### **IR analysis**

The IR spectrum of substrate II, as shown in figure 1, discloses the presence of a broad band at 3300-3500 cm-1 attributable to the NH2 and OH groups , a weak absorption band appeared at nearly 1730 cm-1 due to the stretching vibration of the C=O double bond of the aldehydic group and a strong absorption band at 1641 cm-1 which is assigned to the C=N group was formed between the aldehydic group and chitosan. Also the IR spectrum of substrate III, as shown in figure 2 reveal the presence of a broad band at 3300-3500 cm-1 attributable to the NH2 and OH groups , a strong absorption band at 2644 cm-1 which is assigned to the C=N group and a weak absorption band at nearly 1730 cm-1 foe C=O group.. These IR spectrums confirm the presence of chitosan in both substrates. That is, chitosan interacted with preoxidized cotton fabric as well as with cotton fabric subjected to concurrent oxidation and chitosan treatments.

Fig. 1. IR spectrum of substrate II

A comparison among the substrates I , II and III with respect to nitrogen content, tensile strength and elongation at break and carbonyl content as shown in table 5 would reveal that substrate II exhibits the carbonyl content and the lowest tensile strength as compared with substrates I and III; indicating the determinal effect of oxidation prior to chitosan treatment. On the contrary, substrate III acquires the highest nitrogen content and the highest tensile strength and elongation at break while retaining a carboxyl content which is equal to that of substrate I. This, indeed, signifies the advantages of the one-step process in avoiding prior

Presence of chitosan during oxidation of the cotton fabric with NaIO4 seems to protect the cotton against oxidation. At the same time NaIO4 oxidizes chitosan to produce chitosan products with better solubility and more uniform structure and, in turn, better filmforming properties. Such properties will be reflected on strength of the film and the extra strength brought about thereof when the cotton fabric is coated with this film. Achieving substrate III with its potential properties is regarded to be the most salient output of the

Substrate I, substrate II and substrate III were dyed independently with reactive and acid dyes. The results obtained are shown in table 6. It is observed that regardless of the dye used. Substrate III exhibits colour strength which is higher than those of substrate II. This again signifies the superiority of substrate III which, indeed, together with its other properties (table 5) advocate the one-step process for preparation of innovative modified

Substrate 1 Substrate II Substrate III

Dye Colour strength ( K/S )

Reactive dye 16.4 22.78 23.05 Acid dye 2.8 4.47 4.49

Table 6. Dyeing of the different substrates under investigation with reactive and acid dyes

The IR spectrum of substrate II, as shown in figure 1, discloses the presence of a broad band at 3300-3500 cm-1 attributable to the NH2 and OH groups , a weak absorption band appeared at nearly 1730 cm-1 due to the stretching vibration of the C=O double bond of the aldehydic group and a strong absorption band at 1641 cm-1 which is assigned to the C=N group was formed between the aldehydic group and chitosan. Also the IR spectrum of substrate III, as shown in figure 2 reveal the presence of a broad band at 3300-3500 cm-1 attributable to the NH2 and OH groups , a strong absorption band at 2644 cm-1 which is assigned to the C=N group and a weak absorption band at nearly 1730 cm-1 foe C=O group.. These IR spectrums confirm the presence of chitosan in both substrates. That is, chitosan interacted with preoxidized cotton fabric as well as with cotton fabric subjected to concurrent oxidation and

oxidation entailed in the two-step process.

cotton fabrics-containing chitosan.

Substrate 1: Bleached cotton fabric

**IR analysis** 

chitosan treatments.

Substrate II: processed as per the two-step process Substrate III: processed as per the one-step process

current work. **Dyeability** 

Fig. 2. IR spectrum of substrate III
