ANIONIC DYEABILITY OF POLYESTER FABRIC BY CHEMICAL …

IJMTES | International Journal of Modern Trends in Engineering and Science ISSN: 2348-3121

ANIONIC DYEABILITY OF POLYESTER FABRIC BY CHEMICAL SURFACE MODIFICATION

Beyene Dumecha1, Nalankilli G2 1(Dept. of Textile Engg., College of Engg. & Tech.,Wolkite University, Wolkite, Ethiopia, [email protected])

2(Ethiopian Institute of Textile & Fashion Tech. Bahir Dar University, Bahir Dar, Ethiopia, [email protected]) ______________________________________________________________________________________________________

Abstract—Polyester fibre, semi-crystalline fibrer is hydrophobic owing to the lack of any hydrophilic groups in its structure. It is necessary to impart desired properties by introducing specific functional groups on the surface of the fiber to make it more practically useful. Alkali and amine treatment with caustic soda and ethylene diamine, respectively were studied in the present work for surface modification. Dyeing of the treated samples with anionic dyes such as reactive dye, acid dye and vat dye as well as disperse dye for a comparison purpose was also studied. Aminolysis reaction of Poly (ethylene terephthalate) (PET) fibers with ethylene diamine gives amino (~NH2) functional groups whereas hydrolysis by sodium hydroxide gives hydroxide (~OH) functional groups on the surface of the polyester fabric as observed by the Fourier Transform Infrared Spectroscopy (FTIR). The effects of temperature, reaction time, ethylene diamine and caustic soda concentration were studied in order to find out the conditions in which best results dyeing could be obtained. The dyeability of treated samples with reactive, acid and vat dye was observed to increase with temperature, reaction time, and reagents concentration at optimum conditions due to significant increase in number of reactive functional groups on the surface of the fiber and considerable decrease in glass transition temperature, Tg which was indicated by Differential Scanning Calorimetry (DSC). The colour strength (K/S) values of all anionic and disperse dyed samples were measured using spectrophotometer and compared with the control samples. There is also a significant improvement in fabric water wettability, hand and comfort ty with good fastness properties (wash, rubbing and light) due to these surface modifications, although there is loss in weight and tensile strength because of chain scission, as the reaction proceeds.

Keywords— Polyester; Reactive Dye; Vat Dye; Acid Dye; Anionic Dyes; FTIR; DSC; Dyeability; Surface Modification _________________________________________________________________________________________________________________

1. INTRODUCTION By nature, polyester fiber is hydrophobic owing to the lack of any hydrophilic groups in its structure. In order to make apparel made from polyester fibers comfortable for consumers, surface modifications are required to make the fabric surface hydrophilic enough for a good moisture management performance. Its hydrophobocity leads to poor performance with regard to moisture management, anti-static properties, etc [1]. The introduction of new functional groups by means of chemical modification reactions is one possible means for altering the physical and chemical nature of the fiber. By choosing the proper experimental conditions, it should be possible to restrict the chemical modification to the surface of the fiber, leaving the interior structure unchanged [2].. Most of the previous research papers on hydrolysis and aminolysis were reported the dyeability of polyester fabric by disperse dyes at low temperature and with basic dyes using attraction of opposite ionic natures of the fabric and dyes. However, this paper focuses on extensions of the current understanding for anionic dyes. This is because of the fact that the treated PET fabric can develop reactive functional groups like ~OH, ~NH2 and COO~ that are responsible for affinity of this fiber towards anionic dyes. The exhaustion and affinity of the cotton like PET (from PET hydrolysis) and wool like PET (from aminolysis) can be increased with optimum dyeing conditions [3]. On commercial polyester fibre, having very compact structure and no dye sites, it is difficult to achieve a satisfactory dye depth without the use of high temperature/pressure (HT-HP) or carrier chemicals. HT-HP dyeing is high energy expensive and the use of carrier chemicals has known disadvantages. It has long been recognized that dyes other than disperse dyes would play a

much larger industrial role if they could be applied to poly(ethylene terephthalate) (PET) fabrics at low temperatures. The selection of dyestuffs is also limited to disperse dyes for polyesters because of their compact structure and high crystallinity. The low and finite water solubility of these dyes is considered a critical factor in determining the leveling properties and the dyeing rate. High-temperature dyeing leads to difficulties for polyester/natural blends, causing damage to the natural fibers during the dyeing process. Polyester fibres have taken the major position in textiles all over the world although they have draw backs such as Low moisture regains (0.4%), low dyeability, tendency to accumulate static electricity, soiling, etc. Therefore, it is very necessary to solve these problems and using surface modification methods can have an effect on hand, thermal properties, wet ability, hydrophilicity and dye-ability at atmospheric condition with minimum energy using anionic dyes (reactive dyes, Acid dyes as well as vat dyes). The scope of this research is from treatment of polyester fabric with two chemicals (caustic soda and ethylene diamine) separately up to dyeing with anionic dyes (namely reactive, vat and acid dye).. A. Reaction of Polyester with Sodium Hydroxides One of the surface modification methods for polyester is hydrolysis reaction using strong alkali under controlled conditions. Polyester undergoes nucleophilic substitution and is hydrolysed by aqueous sodium hydroxide. The hydroxyl ions attack the electron-deficient carbonyl carbons of the polyester to form an intermediate anion. Chain scission follows and results in the production of hydroxyl and carboxylate end-groups [4-7].

Volume: 04 Issue: 09 2017 www.ijmtes.com 3


Fig.1 Reaction of caustic soda with PET A peeling mechanism has been proposed by which alkali attacks PET chains (preferentially from the end groups) and removes hydrolyzed PET material, thus leading to the formation and exposition of new surfaces [8]. Similarly, it was suggested [9] that cleavage of ester linkages by hydrolysis on the fibre surfaces resulted in formation of hydroxyl and carboxylic groups which increases hydrophilic groups on the surface of PET fibers. These leads to improvement of polarity and hydrogen bonding capacity with water molecules, and thus better water wet ability. The number of end groups generated by the caustic treatment was significantly greater than the number present in the untreated fabric, and the number tended to increase with the severity of the conditions. Higher caustic concentrations tended to produce more end groups than lower concentrations. The number of new end groups formed did not appear to be related to the weight loss per second [10,11,4]. These findings also showed that Chain scission follows and results in the production of hydroxyl and carboxylate end-groups:

Fig.2 Reaction of caustic soda with PET Chain scission occurs and results in considerable Weight Loss and hydroxyl and carboxylate end group formation so as to achieve the silk-like effect. However, alkaline hydrolysis is only a surface and local reaction resulting in only a small change in the corresponding molecular weight, density, crystallinity, moisture regain, and so on [12, 5].. By varying the extent of the hydrolysis, modification of the fiber surface wettability alone or improved surface wettability combined with altered fabric pore structure is possible [13]. This is used commercially as the so-called ‘denier reduction’ [10, 14, 4]

1.1 Reaction of Polyester with Amines The other way of the surface modification methods for polyester is aminolysis reaction using amine containing compounds under controlled conditions. These chemicals can introduce the amine functional groups and increases wet ability and anionic dyeability of PET fabric [15]. The introduction of new functional groups by means of chemical modification reactions was one possible mean for altering the physical and chemical nature of the fibre. By choosing the proper experimental conditions, it would be possible to restrict the chemical modification to the surface

of the fibre, leaving the interior structure unchanged. The presence of amine groups would increase wet-ability, and also provide potential sites for the formation of chemical bonds with anionic dyes. Other works also suggested that Polyester undergoes nucleophilic substitution during aminolysis. The amine from ethylene diamine attacks the electron-deficient carbonyl carbon, chain scission occurs at this site and amide formation occurs [12]. Researcher reported the chemical treatment of polyester fibers by amination reaction with multifunctional amines and showed that the tensile properties of the treated fibers were hardly affected [15]. It has been reported that ethylamine treated PET can form wool-like surface structure by reaction of an amine with an ester group of the PET which leads to chain scission at the reaction site and to amide formation [16]:

Fig.3 Formation of Amide by chain scission

Methylamine (CH3NH2) by nature, like methyl alcohol and water, is a good solvent for many organic compounds including polymers. A common way for MA to react is by forming ammonia crystallization with compounds; alternatively, it can react with the carbonyl carbon compounds and transform esters bonds into amides bonds (Graecia Lugito 2014). One findings suggested that PET treated with organic nitrogen compound or multi amine compound selected from the class consisting of diethylene triamine, triethylene tetramine, tetraethylene pentamine could be dyed with acid dyes [17, 18, 4].

2. MATERIALS AND METHODS 2.1 Materials used

Commercially bleached 100% polyester fabric with 70picks/inch, 150ends/inch, and 80 GSM specifications was used. Chemicals used are laboratory grade caustic soda, commercially available ethylenediamine, sodium carbonate, wetting agent, detergent, different types of reactive dyes (C.I Remazol Red RB-133, C.I Reactive blue 19 (bifunctional), vinylsulphone), vat dye (C.I Vat yellow-33), disperse dye (Bemacron Red SE-RDL, C.I disperse yellow 23) and acid dye (Erionyl Red-B) were used. For the experiment purpose Launder O meter, spectrophotometer, Differential scanning calorimetry (DSC), crock meter and Fourier transform infrared (FTIR) spectroscopy were used.

2.2 Experimental methods 2.2.1 Experimental design

As explained above, the aminolysis treatment conditions of PET fabric by ethylene diamine were optimized. The variables for optimization were temperature (T), concentration of ethylene diamine (C) and time of treatment (t). To get best combination of the variables, Minitab17 software was used and the results are shown below. All conditions were taken from different articles where the maximum and minimum values were considered to design these experiments.



Number of factors of the design were three (3), namely concentration, temperature as well as time and the level was five (5). Number of runs or samples treated was twenty five (25) and the details are shown below:- Temperature (T in oC):- 30, 45, 65, 80, 90 Concentration of ethylene diamine (C in %):- 20, 25, 40, 55, 70 Time of treatment (t in min.):- 30, 45, 60, 90, 120 TABLE. 1 TAGUCHI EXPERIMENTAL DESIGN

2.2.2 Treatment of polyester (PET) with chemicals Commercially bleached polyester fabric was pre-treated with 2g/l non-ionic detergent, 0.2 g/l sodium carbonate (pH 8-9) with MLR of 1:30 at temperature of 50-55oC for 45 minute and rinsed with water and air dried without tension to remove any possible impurities which can adversely affect the surface treatments. The concentrations of ethylene diamine taken for the experiments were preparedas (v/v) of 20%, 25%, 40%, 55% and 70% from marketed 95% concentration by dilution with pure water and treated in different temperatures and time according to the experimental design taken from Minitab 17 Taguchi software. The strengths of caustic soda were also adjusted by dilution in water to get 5%, 8%, 10%, 12% and 15% as (w/v) which was first 98% concentrated in the market for hydrolysis of polyester fabric.

2.2.2.1 Alkaline hydrolysis of polyester The required amount of caustic soda solution with 5%, 8%, 10%, 12% and 15% concentration was prepared based on MLR for each sample separately. Then the alkali solution along with fabric sample were immersed in the sealed stainless steel tubes and rotated in the closed bath at 60oC for 60 minutes. The material to liquor ratio was 1:20. After the predetermined durations, the samples were removed from the bath, rinsed repeatedly with cold water, neutralized with a solution of acetic acid and rinsed. The samples are then dried at room temperature, conditioned and weighed to calculate the weight loses.

2.2.2.2 Aminolysis of polyester by ethylene diamine In separate bath, similar treatments were carried out on polyester fabric separately with ethylene diamine in different temperatures, concentrations and times. The polyester fabric was cut, conditioned and weighed accurately after pretreated for removal of any impurities. The

required concentration of ethylene diamine solution was prepared based on MLR for each sample as 20%, 25%, 40%, 55% and 70%(v/v). The fabric along with the solution was placed in the stainless steel tube of HTHP machine and heated in various temperatures and time according to the designed conditions explained above by Minitab 17 software. The result was analyzed using Microsoft excel, 2007 graphing. Then all samples were washed, rinsed and air dried without tension. The dried fabric was conditioned and weighed accurately to calculate the weight loss.

2.2.3 Determination of weight loss after treatment Weight loss occurs after treatment with caustic soda and ethylene diamine because of these chemicals have a tendency to attack the electron deficient carbonyl carbon and then chain scission occurs at this site which is removed during washing and rinsing process. The percentages of weight loss were calculated with the following formula: Weight loss (%) = [(W1 -W2)]/W1 x100. Where, W1 and W2 were the weights of fabric before and after treatment, respectively.

2.2.4 Determination of tensile strength Tensile strength and extension at break can be determined using H5KS universal tensile strength testing machine according to ISO13934/1. The measurements will be carried out for number of samples and average values were reported. For comparison purposes this test was carried out for the untreated polyester fabric also.

2.2.5 Determination of wet-ability AATCC test method No. 79 was used to measure fabric wetting. Wet ability of the treated fabric will be tested using standard absorbency tests. Water drop absorbency test:- a drop of water is placed on the fabric and the time it takes for the drop to penetrate the fabric is recorded. The wettablity is determined by counting the elapsed seconds between the contact of the water drop with the fabric and disappearance of the drop into the fabric. The faster the wetting time, the more absorbent is the fabric. Sinking time test: -four samples were tested and average values were reported. Capillary rise test: - in this test each specimen is cut vertically into 20 x 2 cm strip, hung long ways with the bottom end dipped in water in order to measure the length of the fabric by which water is absorbed in 5 minutes.

2.2.6 Differential scanning calorimetry (DSC) characterization

The differential scanning calorimetry (DSC) for untreated and treated polyester fabrics was carried out using DSC 4000 Perkin-Elmer, USA thermal analyzer and its thermal property such as Tg value and melting temperature were reported.



2.2.7 Fourier transform infrared (FTIR) characterization

In the case of Fourier transform-infrared spectroscopy (FTIR) measurements was done to analyze the types of functional groups introduced or removed after treatments.

2.3 Dyeing with anionic dyes Dyeing was performed using HTHP dyeing machine. The dyeing conditions were: MLR 1:20, at various temperature, time and PH based on the dye types used for dyeing and bond can be formed between functional groups of PET and the dyes. The ethylene diamine treated samples were cut into two and one half was subjected to acid dye while the other half was subjected to reactive dye. In the same manner the caustic treated samples were dyed with reactive and vat dyes.

2.3.1 Dyeing with reactive dyes Reactive dyes for ethylene diamine treated samples were performed using (C.I Reactive blue 19) according to acid dye for nylon fiber. The dyeing conditions were: - MLR 1:20, at 100oC for 60 minutes under acid pH of 4-5 adjusted with acetic acid. Dye bath composition Reactive dye 2 % o.w.f Sodium chloride 30 g/l Ammonium sulphate 2% o.w.f Leveling agent 2% o.w.f Dyeing was started after the samples and all additives other than dyes were heated for 10 minute at 40oC. Then the temperature was raised gradually to boil for better level dyeing. After dyeing the samples were taken out from the sample holder and rinsed with cold water and dried. Reactive dyeing was also applied for caustic treated PET fabric similar to cotton dyeing. The dyeing conditions were: - MLR 1:20 at 100oC for about 90 minute under alkaline pH(9-10) using sodium carbonate. Dye bath composition Reactive dye (C.I Remazol Red RB-133) 2% o.w.f Sodium chloride 50g/l Sodium carbonate 15 g/l Leveling agent 2% o.w.f Dyeing was started with the bath containing dye solution and fabric sample at 30oC. After 20 minute half of the pre-dissolved salt was added and the temperature was raised to 60-65oC. At this point the other half of the salt was added and dyeing continued for about an hour. After dyeing was completed, the samples were washed with 5 g/l standard soap at boiling for 20 minute and rinsed with warm and cold water and dried.

2.3.2 Dyeing with acid dye The ethylene diamine treated polyester fabric was dyed with acid dyes. Due to the formed amine functional groups on the PET fabric there is bond formation between the dyes and the fibers. The dyeing was carried out using HT-HP machines using Erionyl Red-B acid dyes. The dyeing conditions were:- MLR 1:20, at 100oCfor 60 minutes under acid pH of 3-4 adjusted with acetic acid.

Dye bath composition Acid dye 2 % owf Sodium sulphate (glauber’s salt) 30g/l Ammonium acetate 3% o.w.f Leveling agent 2% o.w.f Dyeing was started after the samples and all additives other than dyes were heated for 10 minute at 40oC. Then the temperature was raised gradually to boil for better level dyeing. After dyeing, the samples were taken out from the sample holder and rinsed with cold water and dried.

2.3.3 Dyeing with vat dye In the case of vat dye, the caustic treated fabric samples were subjected to dyeing after the dye was changed into lueco form using sodium hydrosulphite (hydros). Due to the fabrics functional group reactions with the dyes, the insoluble dye can be fixed inside the fiber after oxidation of dye by hydrogen peroxide and acetic acid. C.I vat yellow-33 dye was used. The dyeing conditions were: - MLR 1:20, at 100oCfor 60 minutes under strong alkaline pH of 12-14 adjusted with sodium hydroxide. Dye bath composition Vat dye 2 % owf Sodium hydroxide 10 g/l Sodium hydrosulphite 10 g/l Sodium sulphate 15 g/l Wetting agent 1 g/l Once the actual dyeing process is complete, there was rinsing to remove adhering exhausted dye liquor and chemicals, oxidizing the leuco dye to the pigment form using hydrogen peroxide and acetic acid for neutralization and soaping at or near the boil for five minutes and rinsing with cold water. For comparison purpose disperse dyeing was also performed using C.I Bemacron Yellow SE-RDL disperse dye.

2.4 Color yield measurement The colour yield of a dyeing is the depth of colour that a unit mass of dye is able to impart to the dyed substrate. The colour yield was determined by measurement of K/S value of the dyed samples on Gretag Macbeth colour-eye 3100 spectrophotometer. To measure K/S value, the samples were folded with 4 folds for better opacity and the measurement was done three times for each samples and the average values at wave length of maximum K/S was reported.

2.5 Fastness determination The test was carried out for optimal samples of treated fabric and original untreated PET fabric for washing, rubbing and light fastness. Launder O meter (MESDAN LAB) was used. Samples of size 10cm × 4 cm were cut and covered with a white (bleached) polyester fabric on one side and with white cotton fabric on other side by stitching at the four edges. Then these samples were put in test jars of wash liquor which contains 5 gram per liter standard soap and washed for 45 minute at 50oC according to ISO 3361:79 standard for wash fastness test. The color loss because of washing (on launder O meter) was assessed in terms of change in color and staining. For



determining change in color, the color difference between washed and original sample was compared using ISO 105-A02-1993 BS EN 20105-A02:1995- standard of grey scale for assessing change in color method. Similarly for staining, the color difference between stained and original white polyester fabric was compared using ISO 105 A03;1993 BS EN 20105 A03;1995 of grey scale for assessing staining method.

3. RESULTS AND DISCUSSION 3.1 Introduction of amino functional groups via

aminolysis The method employed to introduce amino functional groups on PET surface is aminolysis reaction with ethylene diamine. This reaction yields formation of a new amide bond and presence of free amino groups on the surface of PET fabric. Five different ethylene diamine concentrations (based on v/v) with different temperature and time were used: (A) 20%, (B) 25%, (C) 40%, (D) 55% and (E) 70%as indicated on the experimental design table 4.1above. These reactions were carried out in stainless steel tubes on HTHP machine. PET fabric samples (precisely weighed) were added to tubes containing ethylene diamine diluted with water. Moderate agitation was used during the reaction. An increase of the degree of functionalization was observed as a consequence of increasing temperature and reaction time. Increasing temperature of reaction increases the rate of reaction but the same degree of functionalization occurs at lower temperature with longer reaction time.

3.2 Optimization of the treatment condition for aminolysis and hydrolysis reaction

Three different variables were used for these treatments as indicated on the experimental design and the values for weight loss, tensile strength loss and the color yield were reported as shown on the Table 2. Optimal conditions for better dye-ability with acid and reactive dye was selected based on maximum possible K/S value at maximum wavelength with minimum possible strength loss. Although there was even higher K/S was obtained at severe conditions, the loss in tensile strength was also very high in which the fabric property was affected. Based on these criteria optimal treatment conditions with ethylene diamine treatment and caustic treatment were reported as follows. TABLE.2 OPTIMAL CONDITIONS FOR EDA AND NAOH TREATMENTS OF PET FABRIC

Samples Treatment condition Strength loss

(%) Warp/weft

K/S value Conc

(%) Temp. (oC)

Time (min.)

EDA treated for acid dye 25 80 120 16.32/20.60 7.45

EDA treated for reactive

dye 25 80 120 16.32/20.60 7.73

NaOH treated for vat dye 10 60 60 7.54/8.53 2.23

NaOH treated for reactive

dye 10 60 60 7.54/8.53 2.12

Dark shade can be obtained with acid and reactive dyes with severity of the condition, but the strength loss was ashighas 30% to 40%and there is degradation of the fabric also.

3.3 Effects of aminolysis and hydrolysis on the weight loss of PET fabric

3.3.1 Effect of aminolysis on weight loss of polyester fabric

First, aminolysis reactions or functionalization reactions were done with ethylene diamine for five samples at temperature of (a) 30oC, (b) 45oC, (c) 65oC, (d) 80oC and (e) 90oCat various concentration and time. The results of all ethylene diamine treated samples were reported in the following design of experiment table. From the result shown on figure 4 it was observed that, at the early stages of the reaction (at temperature of 30oC), a slightly mass increase (samples with plus sign) is observed due to addition of amine fragments. These results are in good agreement with those obtained by Bech et al for chemical modification of PET films with 1, 2-diaminoethane. Weight loss of the samples treated with ethylene diamines occurs as the treating temperature increases from 45oC to 90 oC. This phenomenon happens because of chain scission, formation of oligomers, and other low molar mass fragments which are removed from the fibers during aminolysis reaction and the rinsing process. Fig.4 shows the weight loss of the aminated PET films as a function of the treatment time at 45oC. Time of treatment varied for each sample with EDA concentration. Weight loss has increased mainly with concentration, however at higher temperature there was more reactivity of the chemicals which causes more weight loss as treatment time increases. TABLE.3 EFFECT OF EDA TREATMENT ON WEIGHT LOSS OF PET FABRIC

Sam

ples

Con

c. o

f E

DA

(%)

Tre

atm

ent

tem

p. (0 c)

Tre

atm

ent

time

(min

.)

Wei

ght

loss

/ gai

n (%

)

1 20 30 30 +1.05

2 25 30 45 +0.95 3 40 30 60 +0.44 4 55 30 90 +0.76 5 70 30 120 +0.45 6 20 45 45 0 7 25 45 60 0 8 40 45 90 0.82 9 55 45 120 0.78 10 70 45 30 0 11 20 65 60 0.83 12 25 65 90 1.75 13 40 65 120 2.10 14 55 65 30 1.60 15 70 65 45 1.69 16 20 80 90 1.53 17 25 80 120 0.92 18 40 80 30 0.77 19 55 80 45 - 20 70 80 60 - 21 20 90 120 3.96 22 25 90 30 0.41 23 40 90 45 1.33 24 55 90 60 - 25 70 90 90 -



Fig.4 Plot of EDA concentration vs. weight loss/gain at 30oC. Fig.5 indicated that at higher treatment time with even lower ethylene diamine treatment the weight loss was relatively higher as temperature raised to 80oC. But, there was still minimum weight loss with lesser treatment time although the generated amine group was not satisfactory as observed by acid dye staining later on. Moreover, further increased in concentration of ethylene diamine to 55% and 70 % with time, (Fig.5, 6) causes the polyester (PET) to degrade.

Fig.5 Interaction of a) EDA weight loss vs.concentration and b) weight loss

vs. time of PET at 45oC Generally, the weight loss increases as compared to initial conditions, where no degradation was observed, which were due to an increase in treatment time and especially as temperature raised 90oC. It can be seen that the weight loss increases slowly to 2.1% for treatment times up to 120 minutes. After this period of time, the weight loss still increases at a much slower rate but causes fabric degradation as the conditions have became severe. This decrease in mass has been due to the extracted oligomers and other low molecular weight fragments are removed during the washing process.

3.3.2 Effect of hydrolysis on weight loss of polyester fabric

Hydrolysis of PET twill fabric was performed by using sodium hydroxide. The reaction of polyester with aqueous sodium hydroxide appears to be confined to the fibre surface. As chain scission occurs, the products of the

reaction dissolve in the solution and reveal a fresh surface, which is attacked in turn. Consequently, the fibre diameter becomes progressively smaller. Five different concentration of caustic treatment was selected to analyze its effects on dyeability of PET fabric with reactive and vat dyes. The selected concentration of caustic soda for this work was at 5%, 8%, 10%, 12% and 15% and treatment was done for about 60 minute at temperature of 60oC using HTHP dyeing machine. It was observed that the alkaline treatment of PET fabrics leads to a loss in weight of the fabrics. The weight loss was increased with increasing concentrations of NaOH at constant temperature and time of treatment as shown in the table.

Fig.6 Effect of treatment time and EDA concentration on PET weight loss at 65oC

Fig.7 Interaction of time vs. weight loss of PET at a) 80oC and b) 90oC


IJMTES | International Journal of Modern Trends in Engineering and Science ISSN: 2348-3121 TABLE.4 EFFECT OF CONCENTRATION OF NAOH ON FABRIC WEIGHT LOSS

Sample Caustic conc. (%)

Temp. (oC)

Time (min)

Weight loss ( %)

1 5 60 60 3.73 2 8 60 60 3.97 3 10 60 60 9.27 4 12 60 60 10.03 5 15 60 60 14.7

Sodium hydroxide had an oxidative effect on the surface of the polyester fiber, and destroyed/remove the surface. The alkaline hydrolysis of polyester is well documented in the literature.

Fig.8 Effect of NaOH conc. on weight loss of PET fabric Among the above five sodium hydroxide concentrations, the one with medium weight loss with better dye-abilityfor reactive and vat dye selected was 10% concentration. As concentration of caustic increase, weight loss increases linearly but, the number of ~OH functional group is increased as explained on the literature.

3.4 Effects of aminolysis and hydrolysis on strength and extension loss of PET fabric

3.4.1 Effect of aminolysis on strength loss of polyester fabric

A comparison of the tenacity/molecular-weight relations of polyester fibre has been made for the products of aminolysis by treating twenty five (25) samples in various conditions and the result of all samples were reported in the Table 5. The reaction between the amine and the PET was confined to the fiber periphery. Nevertheless, due to the limited sensitivity of this technique at very low levels of amination, it is possible that some deeper penetration had occurred that could not be detected. Since reaction within the fiber would lead to some deterioration of on tensile strength. The results recorded in table 5 above illustrate the values of the fabric strength loss (N) for different types of samples which was treated with ethylene diamine according to experimental design.

TABLE.5 RESULTS OF AMINOLYSIS ON TENSILE STRENGTH LOSS OF PET FABRIC

Sam

ples

Con

c. o

f ED

A

(%)

Tre

atm

ent

tem

p. (o C

)

Tre

atm

ent

time

(min

.)

Strength loss (%)

Warp/ weft

Extension loss (%)

Warp/weft

1 20 30 30 0.6/1.33 1.27/3.56

2 25 30 45 3.14/5.30 2.57/4.15 3 40 30 60 5.72/8.27 3.20/4.38 4 55 30 90 8.24/11.47 5.75/9.05 5 70 30 120 8.68/12.53 6.79/13.34 6 20 45 45 8.48/9.60 6.51/12.81 7 25 45 60 12.01/9.87 8.17/14.89 8 40 45 90 17.23/11.73 11.31/18.99 9 55 45 120 20.31/21.07 11.26/16.29 10 70 45 30 16.98/17.60 9.86/15.62 11 20 65 60 0.56/2.41 7.23/9.24 12 25 65 90 7.04/8.53 11.20/15.60 13 40 65 120 14.84/16.81 12.75/17.42 14 55 65 30 1.32/2.93 5.34/7.59 15 70 65 45 28.43/31.53 20.05/21.95 16 20 80 90 15.56/17.07 12.13/19.05 17 25 80 120 16.32/19.20 12.73/21.06 18 40 80 30 8.24/14.67 11.34/17.09 19 55 80 45 - - 20 70 80 60 - - 21 20 90 120 13.27/14.13 12.88/22.73 22 25 90 30 14.84/16.53 8.94/21.29 23 40 90 45 32.95/33.61 23.93/25.03 24 55 90 60 - - 25 70 90 90 - -

On all Fig. 9-11, the numbers 1 to 5 at x-axis represented sample numbers which was treated with ethylene diamine at different conditions as indicated on table of experimental design. At lower temperature of 30oC, the strength loss was increased from 0.6% to about 8% as treatment time and EDA concentration raises gradually (Fig. 9). Generally, almost all results from the graph showed that there was a decrease in breaking strength and extension at break. It can be seen that changes in each condition variables have almost linear relationship with loss in tensile property. This was due to aminolysis reaction causes weight loss and formation of pits on the surface which probably act as weak points when fabric is elongated under stress. However, by controlling the concentration, temperature and time of treatment it is possible to minimize these losses. In contrast with hydrolysis, there was less weight loss but higher strength loss for aminolysis and for that of hydrolysis the weight loss was higher and less strength losss. This was because of the fact that caustic soda could not penetrate the fiber structure unlike ethylene diamine.



Fig.9 Effect of time and EDA concentration on strength loss at a) 30oC b) 45oC

Fig.10 Effect of time and EDA concentration on strength loss at c) 65oC d)

80oC For long reaction time (2 hr in 55-70% diamine Fig.10 at 80oC and Fig. 11, at 90oC), complete solubilization of polyester sample was observed which shows penetration of ethylene diamine in the structure of the fiber. This was happening due to the severity of the conditions and literature suggested that by choosing the proper experimental conditions, it would be possible to restrict the chemical modifications to the surface of the fibre, leaving the interior structure unchanged

Fig.11 Effect of time and EDA concentration on strength loss at 90oC

3.4.2 Effect of hydrolysis on strength loss of polyester fabric

There was loss in fabric tenacity as the hydrolysis decreases the weight of the sample. However, the decrease is small at low weight losses by controlling the concentration of caustic soda and temperature of treatment. The tenacity of the hydrolysed products was reduced with increased caustic soda concentrations due to hydrolysis decreases the weight of the sample as observed on the above figures. Hydrolysis effects was explained in detail on number of previous works and this work only focuses on anionic dye ability of hydrolysed fabric. TABLE.6 EFFECTS OF CONCENTRATION OF NAOH ON STRENGTH LOSS OF PET.

Sam

ple

Con

c. o

f N

aOH

(%) Max Force

(N)

Max. Elongation

(%)

Stre

ngth

loss

(%

) W

arp/

wef

t

Ext

ensi

on lo

ss

(%)

War

p/w

eft

Warp Weft Warp Weft

C - 636 410 22.52 16.43 - -

1 5 620 395 21.13 15.28 2.5/3.6 5.2/6.9 2 8 592 377 20.75 14.94 6.9/ 8.1 6.6/9.1 3 10 588 375 20.51 14.67 7.5/8.5 7.5/10.7 4 12 576 367 20.11 14.23 9.4/10.5 8.9/13.4 5 15 563 360 19.79 14.11 11.5/12.2 10.1/14.1

Fig.12 Effect of NaOH concentrations on PET a) Strength loss b) extension loss

3.5 Fabric wettability

Incorporation of hydrophilic amine groups at the PET surface should change its surface energy. The water wettabilities of EDA-treated PET fabric as a function of reaction time, concentration and temperature are shown in table 4.6 below. Water-drop-absorbency time decreases sharply, but it does not achieve the same level with that of wool or related protein fibers. The amount of water retained after immersion of the fabric in water increases after aminolysis, as does the



height to which water is wicked in vertically held fabric sample. Fig.13 shows that as treatment temperature rises from 30oC to 90oC, there was drop in absorbency time. This indicates amount of hydrophilic groups on the fabric surface was increased and the wet-ability of the sample also improved. Some of these effects may be because of the increased porosity of the treated fabric. At least three factors may contribute to the hydrophilicity of ethylene diamine-treated polyester fibre: (a) Increased surface roughness; (b) possible increase in the number of hydrophilic groups on the fibre surface caused by chain scission; and (c) increased accessibility of the available hydrophilic groups on the fibre surfaces owing to aminolysis reaction. The most hydrophilic groups present in polyester are carboxyl and amine functional groups. TABLE.7 AVERAGE WATER ABSORBENCY TIME FOR WETTABILITY

Samples

Con

c. o

f ED

A

(%)

Tre

atm

ent

tem

pera

ture

(c

o )

Tre

atm

ent

time

(min

.)

Wat

er

abso

rben

cy

(sec

.)

Abs

orbe

ncy

rise

(%)

Control - - - 84.6 0

1 20 30 30 22.5 73.40

2 25 30 45 19.94 76.43 3 40 30 60 20.68 75.55 4 55 30 90 19.12 77.39 5 70 30 120 14.28 83.12 6 20 45 45 11.4 86.52 7 25 45 60 10.20 87.94 8 40 45 90 10.60 87.47 9 55 45 120 9.56 88.69 10 70 45 30 9.16 89.17 11 20 65 60 18.12 78.58 12 25 65 90 15.8 81.32 13 40 65 120 14.62 82.71 14 55 65 30 16.80 80.14 15 70 65 45 14.20 83.21 16 20 80 90 7.0 91.72 17 25 80 120 6.36 92.48 18 40 80 30 8.68 89.73 19 55 80 45 16.96 79.95 20 70 80 60 - - 21 20 90 120 5.12 93.94 22 25 90 30 7.52 91.11 23 40 90 45 5.42 93.59 24 55 90 60 - - 25 70 90 90 - -

Fig.13 Effect of EDA treatment on wettability of PET fabric

TABLE.8 WETTABILITY RESULTS FOR HYDROLYZED PET

As more amine groups are introduced by the amination reaction, the wettability of the treated PET changed almost linearly as treatment temperature and time increases with similar EDA concentration. It can be seen that the wicking ability of the EDA treated fabric was increased due to, firstly, the fabric hydrophilicity was improved after the treatment and thus the affinity of the fibre surface to water was improved. Secondly, the fibre fineness was reduced and thus its porosity was improved, increasing the moisture uptake of the fabric for the samples selected for wicking (from 5-10cm) and sinking time test (from 5 to 8 second) of absorbency tests.

3.6 Dyeability The dyeability of PET fabric treated with ethylene diamine was increased for acid dye and reactive dyes whereas that treated with sodium hydroxide have improved dyeability for vat and reactive dyes. The PET fabric samples were dyed using acid dye Erionyl Red-B, C.I Reactive blue 19, C.I Remazol Red RB-133 reactive dye, C.I Vat Yellow-33, disperse dye (Bemacron Red SE-RDL, C.I Disperse Yellow 23). The color strength is expressed in terms of K/S value. The results are shown in table below.

3.6.1 Dyeing with acid dye The K/S values were recorded at the wavelength of maximum value. The wavelengths of maximum K/S for acid dye and reactive dye were 500 nm and 600 nm respectively for dyeing carried out under acidic pH. The results are shown in Table 9 &10. Ethylene diamine treated PET was subsequently dyed with anionic dyes namely, acid dye and reactive dye. Acid dyes develop a negative charge in the dye bath. Aminolysis produces a significant amount of amine groups (NH2) and carboxylic groups on the fibre. Dyeing was done in acidic media using acetic acid (at pH 3-7) to ionize the treated PET fiber surface and changed the NH2group to NH3+ cationic group. During dyeing process the cationic fabric surface attracts anionic dye. The net positive charge on the fibre attracts the negatively charged dye molecules, which get attached to the fibre with the help of ionic or electrovalent bonds. TABLE.9 EFFECT OF PET AMINOLYSIS AND HYDROLYSIS ON STRENGTH OF REACTIVE DYE

Samples Conc. of NaOH

Time of treatment

(min)

Temperature of treatment

(oC)

Average absorbency time (sec.)

Control - - - 84.6 1 5 60 60 26.2 2 8 60 60 21.5 3 10 60 60 18.4 4 12 60 60 13.8 5 15 60 60 12.83

Samples

Treatment

K/S value

Reactive dye Disperse dye

1 Untreated 0.73 4.66 2 EDA treated 7.73 6.86 3 NaOH treated 2.12 9.08



As result of the interaction of generated amine functional group to the acid dye, the dye uptake is improved. For comparison purpose this dyeing was also applied on untreated polyester fabric and EDA treated polyester fabric. TABLE.10 EFFECT OF PET AMINOLYSIS ON STRENGTH OF ACID DYE

Samples

Treatment

K/S value

Acid dye Disperse dye

1 Untreated 1.53 4.66 2 EDA treated 7.45 6.86

The above table showed that acid dyed samples with treated fabric has much better color yield than original untreated fabric. This was due to an improved in dyeability of the treated fabric by ethylene diamine chemical.

3.6.2 Dyeing with reactive dye Reactive dyeing was done in two ways: - one with EDA treated PET sample and the other was with hydrolysed PET fabric. Dyeing of EDA treated sample with reactive dye was done under acidic pH of 3 to 4 by using acetic acid with bifunctional C.I 5 Remazol blue.(similar to dyeing of wool with Reactive/ acid dye).The result obtained was selected after the fabric characteristics was observed during optimization as shown above under optimization and K/S value was measured on three different places and the average values was reported in the following table. Reactive dyeing was also performed for hydrolysed PET fabric under alkaline media of about 9 – 12 pH using bifunctional Reactive dye (C.I Remazol blue) reactive dye. Due to the formation of ~OH functional group by hydrolysis process, there can be formation of covalent bond between the dye and treated fabric surface. The K/S value was taken in three different places and the average value was reported. All control samples dyeing with disperse dyes was done for comparison purpose in the same condition with that of treated samples. Dyeing was performed for about an hour at boil. On the above table, it is clearly shown that EDA treated and NaOH treated samples have more disperse dye uptake when compared with untreated polyester sample. This is because of the treated sample has reduced Tg temperature, improved porosity and improved dye-ability.

3.6.3 Dyeing with vat dye Vat dyeing was done for caustic treated samples on HTHP machine at boil. The result of K/S value at maximum wave length was compared with untreated original polyester fabric dyed with vat dye and shown in the table below. TABLE.11 EFFECT OF PET HYDROLYSIS ON STRENGTH OF VAT DYE

Samples Treatment

K/S value

Vat dye 1 Untreated 0.73 2 NaOH treated 2.51

The dye-ability of polyester with vat dye was also improved due to the generated hydroxyl group by caustic treatment and

formation of some porosity in which the dyes can penetrate into the fiber and dyeing of pale shade was obtained, but medium shade can be possible with severe conditions. However, as treatment condition increases, then the fibers functional property affected adversely.

3.7 Wash fastness of dyed samples Wash fastness was done for all treated optimal samples and untreated samples dyed with Acid, reactive, vat and disperse dyes. Change in color and staining test was done using launder-O-meter as per ISO standard explained above in the methodology and rubbing test was done using crock meter. The results of all dyed samples was reported as follow on the Table. 12 It can be seen that both Acid and reactive dyes showed good wash fastness both in terms of colour change and degree of staining. It is known that acid dye has moderate to good wash fastness for wool and nylon dye. Although dyeing of dark shade was possible with acid dye, there was lesser wash fastness when compared with that of EDA treated reactive dyed samples. The change in color and degree of staining for reactive and vat dyeing of caustic treated sample was inferior to disperse dyed untreated and caustic treated samples. This was due to the amount of active sites (~OH group) developed by caustic treatment was less in number than cotton fabric and hence lesser attraction of dye towards the fabric. The advantage of dyeing this wool-like fabric with reactive dye is, there is no need of dry wash as for that of acid due to its good fastness to washing with water, acid dye has lower fastness to washing than reactive dye. TABLE. 12 RESULTS OF ALL FASTNESS TESTS

Tre

atm

ent

D

yes

Wash

fastness test

Rubbing fastness

Lig

ht

fast

ness

Cha

nge

in c

olor

Stai

ning

on

whi

te

Dry Wet

Cha

nge

in

colo

r

Stai

ning

on

whi

te

Cha

nge

in

colo

r

Stai

ning

on

whi

te

Untreated Disperse 4 5 4/5 4 4/5 4 7

EDA treated

Acid 3/4 4 4 3/4 3/4 3 5

Reactive 4 4/5 4/5 4 4 4 6

Disperse 4/5 5 4/5 4/5 4 4 7

NaOH treated

Reactive 3 4 4 3/4 3/4 3 6

Vat 3/4 4/5 4 4 3/4 3 5

Disperse 4/5 5 5 5 5 4/5 7

3.8 Differential scanning calorimetry (DSC) study

Thermo-physical properties of the PET fabric samples were studied by using differential scanning calorimeter for untreated, NaOH treated, and EDA treated samples to measure glass transition temperature (Tg), the melting temperature (Tm) and the degree of crystallinity as indicated in the Fig.14. There was reduction in glass transition temperature,Tg from 54.67 to 40.91 and slight



change in melting temperature for EDA treated sample which is due to some scission on fiber’s surface and change in melting temperature was very less which shows there was little or no change on the crystallinity of the treated fabric. However, for the treatments at extreme condition there was reduction in crystallinity because of ethylene diamine penetration into the structure of polyester fabric and this indicates the degradation of the fiber in the severe conditions. TABLE.13 DSC RESULTS

Treatment Tm (oC) Tg(oC) △H(J/g) Untreated 254.58 56.64 24.03 EDA treated 250.85 40.91 33.82 NaOH treated 252.85 44.63 59.74

(a) DSC for untreated PET

(b). DSC for EDA treated PET

(c). DSC for NaOH treated PET Fig.14 DSC Spectrograms

The following graph (graph a, b, c), showed the melting temperature (Tm), glass transition temperature (Tg) and enthalpy. The melting temperature and glass transition temperature peak is shown downward due to the heat flow direction was set down which is indicated at y-axis as Heat Flow Endo Down during measurements of DSC of the samples.

3.9 Fourier transform infrared (FTIR) study The structural features of the molecule, whether they are the backbone of the molecule or the functional

groups attached to the molecule, produce characteristic and reproducible absorptions in the spectrum.

Fig.15 FTIR of untreated PET

Fig.16 FTIR of Caustic treated PET

Fig.17 FTIR for EDA treated PET fabric The changes in the infrared spectrum consist of change in the shape, number, position and intensity of the bands and are observed in the regions containing: CH, CH2, C=O, COO and NH bands. On the above graph, there is an increase in number and change in shape at around 2800nm to 3000nm from 2921 to 2953 which shows a change on C-H, =C-H stretch alkenes and O-H stretch carboxylic acid functional groups. TABLE.14 RESULTS OF FTIR FOR UNTREATED, EDA AND NAOH TREATED PET FABRIC

Treatment Basic functional groups Band (cm-1) Untreated C-O-C, C-O and

Benzene 1097-1300

700-900 EDA treated N–H bend,

N–H stretch 1650–1580, 3400–3250

NaOH treated O-H, benzene 2800-3000, 700-900

Sodium hydroxide treated fabric showed reduction of strong peak to weak peaks at around 1097-1700cm-1 which shows the elimination of short chains in the ester linkage and also shows an increased peak at around 3300-2500 cm-1 which attributed to hydroxyl (~OH) group due to hydrolysis of ester linkage. Due to aminolysis process with ethylene diamine, the appearance of one peak at 1630cm-1 corresponding to amide II stretching vibration of carbonyl groups can be



observed. At a time, the spectrum contains the conformation sensitive NH band from ethylene diamine at 3400 cm-1.

4. CONCLUSION In conclusion, the use of ethylene diamine and caustic soda as reagents for modification of polyesters via aminolysis and hydrolysis reactions, respectively are a viable method to modify the surface of these polymers and to incorporate reactive amine and hydroxyl groups. Modification in chemical structure and increased mobility of the main chain in the polymer lead to generation of amine and OH groups and apparent increasing in wettability of the fabric. Surface modification with these two chemicals brought a weight loss of polyester fabric and it doesn’t affect the strength above the optimum value at optimal level of treatment conditions. The optimum conditions using ethylene diamine are treatment with 25% EDA concentration at 80oC for about 2 hour, whereas for that of caustic treatment it is with concentration of 10% (v/v) of sodium hydroxide at 60oC for about an hour. The polyester dyeability can be increased using anionic dyes such as acid, reactive and vat dye with highly improved wet ability as well as comfort of the fabric by sacrificed of about 5-20% tensile strength loss and 1 to 2% weight loss for aminolysis method and 5-10% strength loss and 10-15% weight loss using hydrolysis methods.There is less weight loss by using ethylene diamine, but as the condition of treatment becomes severe it can degrade the fiber while sodium hydroxide can decrease the fabric’s denier with little minus of tenacity. DSC results shows that the fabric exhibits a decrease of glass transition by about 15oc and lower value of heat of fusion compared to the untreated one, leading to higher segmental mobility and slightly decreased in crystallinity of PET, which in turn improves its dye ability at lower temperature. Among dye types used in this work, reactive dye for EDA treated fabric has better wash fastness than acid dyes and vat dyes. Regardless of the amount of loss of fabric mechanical property in treatment, the comforts as well as ease of dyeability at lower temperature is the main advantage of this treatment. This opens the treated polyester functionality to other areas and can act like cotton and protein fiber in industrial and medical applications.

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