Enhanced Antistatic and Mechanical Properties of Corona Plasma

Article pubs.acs.org/IECR

Enhanced Antistatic and Mechanical Properties of Corona Plasma Treated Wool Fabrics Treated with 2,3Epoxypropyltrimethylammonium Chloride Mohammad Mahbubul Hassan* Food and Bio-based Products Group, AgResearch Limited, Cnr springs Road & Gerald Street, Lincoln, Christchurch 7647, New Zealand ABSTRACT: In this work, wool fabrics were treated in a corona discharge machine at three different corona intensities and at four fabric speeds. The corona-treated fabrics were subsequently treated with a fiber reactive quaternary ammonium compound, 2,3-epoxypropyltrimethylammonium chloride (EPTAC). The electrostatic propensity, tensile strength, wettability, and surface morphologies of the treated fabrics were assessed. The surfaces of modified wool fabrics were characterized by ATR-FTIR and FT-Raman spectroscopies. It was found that corona treatment decreased the electrostatic propensity only to certain levels, but a significant decrease in corona intensity and an increase in hydrophilicity were observed for the corona-treated fabrics further treated with EPTAC. The tensile strength of the corona in combination with EPTAC-treated fabrics considerably increased over the control fabric, but only small differences in tensile strength were observed for the various corona treatments. ATR-FTIR and FT-Raman spectroscopic results confirmed that EPTAC covalently bonded to the wool fiber surface.

■

conductivity of copper-deposited-polyaramide fibers made by electroless method.6 Recently, Lu et al. reported a palladiumfree electroless deposition of copper onto bamboo fabric surfaces,7 but still the process is not industry friendly. Jeong et al. treated wool fabrics with colloidal nanosilver, which improved their antistatic properties only marginally.8 A range of chemical treatments has been investigated to alleviate static electricity generation in textiles, and most of them are based on chemical treatments that promote absorption of water by introducing hydrophilic groups on the fiber surface.7,9 The antistatic effects of quaternary ammonium compounds are already known.10−15 Traditionally, various quaternary ammonium based antistatic agents with different carbon chain lengths are applied on wool to make wool antistatic, but the treatment is not durable and the active compounds wash off during laundering. These exudates can pollute watercourses as they are relatively toxic. Zhu and Sun bonded several cationic quaternary ammonium compounds to the carboxyl groups of wool through ionic bond formation at mild alkaline conditions10 to provide antibacterial properties to wool. However, in aqueous solutions at acidic conditions, they were liberated from wool. Permanent binding of these compounds to wool will provide wash-durable antistatic properties. Plasma treatments are quite attractive as they do not produce any effluent and are also environmentally friendly. Plasma treatments can be used effectively to modify surfaces of various textile substrates with improved dyeability and hydrophilicity.16−18 Plasma-based polymeric grafting was investigated for the improvement of antistatic properties of acrylic fabrics.19 It

INTRODUCTION Static electricity is generated whenever two insulating materials touch and then separate. One material charges positively, and the other changes negatively. The charge which is generated may not be noticed, as it may be small or there is an electrically conductive pathway which can dissipate the static electricity harmlessly away. However, in some cases especially at low humidity conditions a very high voltage can be produced quite rapidly, leading to electrostatic discharge with sparks and shocks, which can instigate fire if it occurs in a gasoline service station. For instance, when we are coming out of a car, we can create body voltage of up to 15 kilovolts (kV). Static electricity causes an estimated US$5 billion worth of damage each year to electronic devices.1 Although wool has better antistatic properties compared to other fibers, it still produces static charge above an acceptable level recommended for electronic industries and gasoline stations. Therefore, wool fabrics need to be treated with an antistatic agent to provide static safety at workplaces. It is possible to reduce static charges below 2 kV, making it harmless for causing fire by incorporating conductive fibers into the carpet pile, but for electronic industries, lower than 1 kV is preferred. Conductive antistatic yarns have traditionally been made by incorporating conductive carbon or carbon-filled nylon or polyester fibers with ordinary textile fibers, or by blending stainless steel or copper fibers into spun yarns, which are then converted to carpets by conventional carpet-making processes,2,3 but for apparel applications they are unsuitable. Electroless deposition of various metals such as nickel, copper, and other noble metals on textiles has been investigated to make fiber antistatic.4,5 However, the process to make such yarns is quite complicated and involves expensive catalysts, such as palladium or platinum, making such yarns impractical for apparel applications. Gasana et al. found that prechemical deposition of polypyrrole significantly increased the electrical © 2014 American Chemical Society

Received: Revised: Accepted: Published: 10954

August 29, 2013 March 11, 2014 June 13, 2014 June 13, 2014 dx.doi.org/10.1021/ie500447p | Ind. Eng. Chem. Res. 2014, 53, 10954−10964

Industrial & Engineering Chemistry Research

Article

Scheme 1. Conversion of (3-Chloro-2-hydroxypropyl)trimethylammonium Chloride to 2,3-Epoxypropyltrimethylammonium Chloride (EPTAC) at Alkaline Conditions

Scheme 2. Reaction of EPTAC with Carboxyl Groups of Corona-Treated Wool

Scheme 3. Reaction of EPTAC with Hydroxyl Groups of Corona-Treated Wool

Figure 1. Schematic diagram of corona-based plasma treatment equipment used for the treatment of wool fabrics.

of the antistatic treatment to washing. To my knowledge, no published article has shown enhancement of the antistatic property of wool by the combined treatment of plasma and fiber reactive quaternary ammonium compound. The study of Briggs and Kendall showed that corona treatment produced carboxyl and hydroxyl groups on the surface of a low density polyethylene.22 It is envisaged that corona discharge treatment of wool will also produce hydrophilic groups, such as hydroxyl and carboxyl groups, onto the surface of wool and therefore should reduce static charge generation. Moreover, reactive quaternary ammonium compounds can be covalently bonded to those hydroxyl groups that may provide durable antistatic properties. In this work, a fiber reactive quaternary ammonium compound was successfully covalently bonded to the surface of a corona-treated wool fabric. The treated fabric showed an excellent antistatic property, and the developed treatment was found to be durable to washing.

was found that grafting of diallyldimethylammonium chloride onto polyacrylonitrile fiber greatly improved their wettability and antistatic property.19 Low temperature plasma treatment has also been investigated for the improvement of antistatic properties of polyester fabrics.20 It was found that, although plasma treatment improved antistatic properties of polyester fabrics especially after grafting with poly(acrylic acid) , this resulted in significant loss of their tensile strength.20 It was reported that atmospheric glow discharge plasma treatment of nylon and polyester increased their antistatic properties.21 Previous investigations mainly showed enhancement of antistatic properties of textile treated with either quaternary ammonium compounds or with various types of plasma. Due to the lack of any reactive functional groups, it is quite difficult to bind quaternary ammonium compounds onto the surface of wool. The exhaustion treatment with quaternary ammonium compounds by ionic bonding also does not provide durability 10955

dx.doi.org/10.1021/ie500447p | Ind. Eng. Chem. Res. 2014, 53, 10954−10964


■

Article

MATERIALS AND PROCEDURES Methods. The wool fabric used was 210 g/m2 2/2 twill woven having 34 ends/cm and 24 picks/cm. (3-Chloro-2hydroxypropyl)trimethylammonium chloride, a reactive quaternary ammonium compound, was supplied by Dow Chemical Co. (USA) as a 65% aqueous solution. At alkaline conditions, (3-chloro-2-hydroxypropyl)trimethylammonium chloride converts to 2,3-epoxypropyltrimethylammonium chloride (EPTAC) (Scheme 1). The corona plasma treatment produces carboxyl and hydroxyl groups on the surface of wool, and EPTAC reacts with those hydroxyl and carboxyl groups as shown in Schemes 2 and 3 by forming covalent bonds.23,24 Teric GN9, a nonionic detergent, was supplied by Huntsman (USA). Sandozin MRN, a nonionic wetting agent, was purchased from Clariant Chemicals (Switzerland). Corona Treatment. The corona treatment machine used was an AVE-100SO-2W-600 (AFS Entwicklungs- und Vertriebs-GmbH, Germany). The machine consists of two sections, a corona generator and a treatment chamber or station, as shown in Figure 1. The corona generator produces a high frequency (up to 35 kHz) output voltage which is fed to the treatment station, where it is stepped up by a transformer to a voltage high enough to ionize the air molecules and produce a plasma discharge. The corona discharge takes place in the corona station in the gap between two rollers through which the fabric is passed. One of the rollers is connected to the output of the high voltage transformer, and the other is connected to the ground. The rollers are fitted with replaceable silicone-rubber dielectric sleeves which produce a gentle plasma discharge when high voltages are applied. Fabrics can be continuously treated in this machine, and this corona machine is suitable for wool fabric treatment. For each treatment, a fabric sample was passed twice in faceup mode and twice in face-down mode through this corona machine at different speeds and power settings as shown in Table 1. After corona treatment, fabric samples were scoured

Sandozin MRN. A 300 g wool fabric sample was wrapped on a perforated sample holder and was placed in the dyeing machine. The required quantity of EPTAC (5% oww) was then added, and the pH was adjusted to 8.5 with ammonia solution. The temperature was raised to 60 °C at 1 °C/min, and the bath was held for 15 min. The bath was then dropped and the fabric was dried. The durability of the treatment to washing was carried out by washing the fabric in a Wascator at 40 °C for one cycle and also five cycles according to the Woolmark 7A wash protocol with Martha Gardener Wool Mix detergent (Pental Products Pty Ltd.), after which it was dried at 60 °C for 15 min. Measurement of Static Propensity. The antistatic properties of the treated fabric samples were assessed by a simulated Stroll-type antistatic testing instrument, Estameter T (Model TPG 09-01, Herbert Stein GmbH & Co., Germany) at 20 ± 2 °C and at two relative humidity (RH) conditions (40 ± 2 and 20 ± 2% RH). The samples were conditioned for 3 days at those conditions prior to testing to ensure that they were in equilibrium with the very dry conditions. These conditions are selected on the basis that they are used to enhance the generation of static electricity on the samples. For each treatment, three samples were tested and the averages are reported here. Scanning Electron Microscopy (SEM). To assess whether a change in surface scales of wool fiber took place during the corona treatment, the treated fabrics were scanned under a scanning electron microscope. The control wool fabric and the wool fabric treated with corona at 10 m/min speed at 2.1 kW power setting followed by treatment with EPTAC were coated with a thin layer of gold in vacuum sputtering equipment to make the surface electrically conductive and then were scanned by a JEOL Model 6100 scanning electron microscope. Mechanical and Chemical Characterization. The tensile strength and elongation properties of the treated wool fabrics were assessed by using an Instron tensile strength tester (Model 4204) at 20 °C and 65% relative humidity according to the ASTM Test Method D5035-06: Standard Test Method for Breaking Force and Elongation of Textile Fabrics (Strip Method).25 The sample size was 25.4 × 152.4 mm, and the gauge length was 100 mm. The samples were conditioned at the above-mentioned temperature and humidity for 3 days. A PerkinElmer Fourier transform infrared (FTIR; Model System 2000) spectroscope with an attenuated total reflectance (ATR) attachment using zinc−selenium crystal was used for infrared studies to characterize the surfaces of the corona and the EPTAC-treated wool fabrics. Fourier transform (FT) Raman spectra were recorded using an Equinox 55 interferometer bench (Bruker Optics, Ettlingen, Germany) equipped with a FRA-106 Raman accessory and a D418-T liquid nitrogen cooled Ge detector. A 1064 nm Nd:YAG laser was used to generate Raman scattering, and 500 scans were performed for each spectrum. The laser spot size used was 1 mm in diameter, and the resolution of the spectra is 4 cm−1. Contact Angle Measurement. The contact angle was measured in dynamic mode by using a KSV CAM 100 contact angle measurement apparatus. For each sample, the contact angle was measured at 10 places and the average contact angle was reported. For each sample, the first measurement was taken immediately after placing the drop of water and then measurements were taken at 10 s intervals until 30 s.

Table 1. Corona Treatment Conditions Used for Various Wool Fabric Samples sample ID

fabric speed (m/min)

power setting (W)

A1 A2 A3 A4 A5 A6 B1 B2 B3 B4 B5 B6

10.5 10.5 10.5 17.5 17.5 17.5 24.5 24.5 24.5 31.5 31.5 31.5

2100 1500 900 2100 1500 900 2100 1500 900 2100 1500 900

with 0.5 g/L Teric GN9 and 0.2 g/L Sandozin MRN at 50 °C for 30 min in a 9 L capacity Vald Henriksen dyeing machine. The fabrics were then washed with warm water and rinsed with cold water. Various treatment conditions used for the corona treatment are listed in Table 1. The fabrics were finally treated with EPTAC. Treatment with EPTAC. All the treatments were carried out in a 9 L capacity Vald Henriksen laboratory dyeing machine. The bath was filled with water and dosed with 0.2 g/L 10956



■

Article

RESULTS AND DISCUSSION Mechanical Properties of Corona-Treated Wool Fabrics Treated with EPTAC. Results of tensile tests on the control (untreated) and various treated samples are listed in Table 2. The effects of fabric speed through the corona

tensile strength. It can be seen that the average tensile strength of the control fabric in the warp and weft directions is 15.3 and 14.8 MPa, respectively. Usually, in any fabric, warp-way strength is higher than the weft-way strength as more highly twisted yarns are used in the warp direction than the yarns used in weft direction and also ends per centimeter is generally greater than picks per centimeter. It can be seen that all the treated fabrics showed higher tensile strength and elongation in both warp and weft directions than the control fabric sample. The effect of fabric speed on the tensile strength shows a kind of trend as the tensile strength increased with increasing fabric speed. As the increase in speed reduces the dwell time of fabrics inside the treatment chamber, less damage in fabrics occurs, resulting in a decrease in tensile strength loss. The highest increase in tensile strength was shown by samples B3 and B6, and the lowest was shown by sample A1. As sample A1 had the most severe treatment, the high loss in tensile strength is not unexpected, but the loss was still considerably less compared to the control. The average tensile strengths shown by samples A1 and B6 were 16.7 and 18.6 MPa, respectively. Changing in the intensity of the corona by changing the power setting showed little effect on the tensile strength of the corona + EPTAC treated fabrics as the variations in tensile strength from treatment to treatment conditions were small. However, the difference in tensile strength between the untreated and the corona + EPTAC treated wool fabric was considerably high. It is evident that all of the treated samples showed higher tensile strengths than the control. Similarly, the control fabric samples showed the least elongation in both warp and weft directions. Although all the treated samples showed higher elongation compared to the control fabric, the increase in corona intensity

Table 2. Tensile Strength and Elongation of Wool Fabrics Treated at Various Corona Plasma Conditions and Then Treated with EPTAC tensile strength (MPa)

elongation (%)

treatment ID

warp direction

weft direction

warp direction

weft direction

control A1 A2 A3 A4 A5 A6 B1 B2 B3 B4 B5 B6

15.3 17.8 18.0 18.4 18.2 18.5 19.2 18.5 19.2 19.5 18.8 19.3 19.6

14.6 15.6 16.4 16.8 16.6 17.0 17.3 17.0 17.3 17.5 17.2 17.4 17.6

45.5 50.5 49.6 51.5 50.9 49.1 51.9 52.8 51.7 52.9 51.0 51.5 53.5

45.1 53.3 50.0 50.2 48.2 49.6 49.8 51.2 50.5 52.0 49.8 51.5 52.7

machine and the corona intensity on the tensile strength of wool fabrics subsequently treated with EPTAC are shown in Figure 2. The decrease in fabric speed through the corona machine increases the severity of the corona’s effect as well as damage to wool fabrics which ultimately results in a decrease in

Figure 2. Effect of fabric speed on tensile strength of corona + EPTAC treated wool fabrics treated at various corona intensities: (a) 0.9 (b) 1.5, and (c) 2.1 kW. 10957



Article

Figure 3. Effect of fabric speed on static charge generation in wool fabric samples treated at 2.1 kV corona intensity and measured at 40% RH.

Figure 4. Effect of increase in corona intensity on static charge generation in wool fabric samples passed through the corona machine at 10.5 m/min speed and measured at 40% RH.

or the fabric speed showed little effect on the elongation of the treated fabrics as the change in elongation was only marginal. A previous study showed that corona treatment considerably decreased the tensile strength of wool fabric due to the damage to wool fiber scales and also the damage to the molecular chains of wool keratin.26 Here we found that the treatment with EPTAC considerably increased the tensile strength of wool fabric. A possible explanation is that EPTAC acted as a crosslinking agent for wool. Other than carboxyl and hydroxyl groups, EPTAC also can react with amino groups of wool.27 EPTAC molecules are small enough to penetrate the interior of the fiber where they covalently bind to the amino groups of wool through the epoxy functional group and the cationic quaternary ammonium group of EPTAC forms ionic bonds with the carboxyl groups of wool. Therefore, the tensile strength of wool was increased by the treatment with EPTAC. Static Propensity of Wool Fabrics. The static propensity of a fabric depends on various factors including its surface

hydrophilicity and also the relative humidity of the environment. Effect of Fabric Speed and Corona Intensity. The decrease in fabric speed through the corona machine increases the severity of the treatment as well as the formation of more hydrophilic groups on the surfaces of wool fabrics compared to the control resulting in the reduction in generation of static charge. The effect of an increase in fabric speed on the static propensity of the treated fabrics is shown in Figure 3. The assessment of generation of static electricity was carried out at 65% RH. The static propensity for the control fabric was 9 kV, but for the fabric treated at 10.5 m/min fabric speed the static propensity was 5.5 kV. The static propensity was proportionally increased with an increase in fabric speed, and it reached 8.3 kV for the fabric speed of 31.5 m/min. The effect of an increase in power setting on the static propensity of the treated fabrics is shown in Figure 4. It can be seen that the static propensity decreased with increasing the 10958



Article

Figure 5. Effect of RH on static charge generation of wool fabrics treated at various fabric speeds at 2.1 kV corona intensity.

Figure 6. Effect of EPTAC treatment on static charge of wool fabrics corona treated at 2.1 kV corona intensity at various fabric speeds and measured at 40% RH.

corona intensity as the severity of the treatment produced more hydrophilic groups on wool fabrics than the less severe treatment. The static propensity in the case of the 0.9 kV power setting was 7.4 kV, but for increasing the power setting to 2.1 kV the static propensity decreased to 5.5 kV. The increase in corona intensity or decrease in fabric speed through the corona machine increases the severity of the treatment, producing more hydrophilic groups on the surface of wool fabrics and resulting in decreased static propensity. Effect of Humidity. The efficiency of an antistatic agent depends on the degree of its hygroscopicity, the distribution of moisture, and its ability to supply mobile ions to the aqueous layer it forms by absorbing water molecules.26 The static propensity was measured at two RH conditions, 20 and 40%, to observe the role of humidity in the static propensity of wool fabrics. The effect of humidity on the static propensity of the corona-treated wool fabric samples is shown in Figure 5. It is

clearly evident that the static propensity depends on the surrounding humidity conditions. It can be seen that the generation of static charge increased with decreasing RH. It is also evident that the corona treatment reduced the static propensity of wool fabrics at both humidity conditions. The static propensity of the control fabric was 15.0 and 9.0 kV at 20 and 40% RH, respectively, but for the fabric samples treated by corona at 10.5 m/min fabric speed and 2.1 kV corona intensity the static propensity reduced to 9.8 and 5.5 kV, respectively. Samanta et al. also found that air-plasma-treated nylon fabric only produced 1.5 kV static charge compared to 2.7 kV produced by the control nylon fabric.22 Effect of Treatment with EPTAC. Figure 6 shows the static propensity of wool fabrics treated by corona alone and also corona plus EPTAC at the 2.1 kV power setting. It can be seen that the wool fabric corona-treated at 10.5, 17.5, 24.5, and 31.5 m/min speeds had static propensity values of 5.5, 7.2, 7.8, and 10959



Article

Figure 7. Static propensity at 40% RH before and after washing of wool fabrics corona treated at various fabric speeds and subsequently treated with EPTAC.

8.3 kV, respectively, compared to the control fabric, but the same corona-treated fabrics after treatment with EPTAC reduced to 1.9, 2.8, 4.0, and 5.6 kV, respectively. The corona treatment reduced the static propensity to certain levels, but the treatment with EPTAC considerably reduced the static propensity compared to the corona treatment alone. Therefore, corona in combination with EPTAC should be the ideal treatment to achieve good antistatic properties. Durability of Treatment to Washing. The durability of the corona + EPTAC treatment of wool fabric to washing was assessed by measuring the static propensity of the fabric before washing and after washing. Figure 7 shows that the static propensity slightly increased after one cycle of washing. The unwashed samples had residual hydrophilic wetting agent (Sandozin MRN) remaining on the surface of the fabric which probably reduced the fabric’s static propensity. However, after one cycle of washing, no further increase in static propensity was observed up to five cycles of washing, which shows that the developed treatment is reasonably durable. Contact Angle. The contact angle is a quantitative measure of the wetting of a solid surface by a liquid. It is defined goniometrically as the angle formed by a liquid at the threephase boundary where a liquid, gas, and solid intersect. It is the measure of wettability of a surface; the higher the contact angle the higher the hydrophobicity. Wool fabrics are naturally hydrophobic because of the presence of 18-methyleicosanoic acid covalently bonded to the wool fiber surface by a thioester bond.28 The contact angles of untreated fabric, fabric treated by corona at 10.5 m/min fabric speed at 2.1 kV power setting, and corona-treated fabric further treated with EPTAC are tabulated in Table 3. Figure 8 shows optical images of droplets of the control and treated wool fabrics immediately after placing the water drop and also at 10 s intervals up to 30 s. It can be seen that the highest contact angle was shown by the untreated fabric, which was 120° and consistent with the results found in published literature.29,30 It can be seen that the contact angle of the untreated fabric was not diminished even 30 s after placing the droplet. On the other hand, in the case of corona-treated fabric sample the contact angle (immediately after placing the water droplet) was 76.1°

Table 3. Contact Angle of Control, Corona-Treated and Corona + EPTAC Treated Samples after Various Times of Placing Water Droplet average contact angle (deg) treatment

0s

10 s

20 s

30 s

control fabric corona (10.5 m/min at 2.1 kV) corona + EPTAC

120.0 76.1 0

120.0 33.5 0

119.6 0 0

120 0 0

and after 10 s decreased to 33.5°. After 20 s, the water droplet completely disappeared. The measurement of the contact angle for the corona + EPTAC treatment was not possible as the water droplet disappeared immediately after placement on the fabric surface and was soaked up by the fabric because of high hydrophilicity induced by the corona treatment in combination with the treatment with EPTAC. It can be seen that the untreated fabric is reasonably hydrophobic but after the corona treatment hydrophobicity decreased. The EPTAC treatment made the fabric surface superhydrophilic as it immediately soaked up the water droplet. Surface Morphology. The SEM images of the control wool fabric and corona-treated wool fabric at two power settings are shown in Figure 9. In the case of the control wool fabric, the characteristic scaly structure of wool is clearly visible, but in the case of corona treatments, the scales were damaged and the surface of the treated wool fibers became almost smooth as shown in the inset images of Figure 9. It is evident that no structural damage other than scale damage occurred during corona treatments. It is evident that corona treatment removed scales of wool fiber but the most severe damage of scales was observed for the wool fabric samples treated at the 2.1 kV power setting, and the samples treated at 1.5 kV showed comparatively smaller damage than the sample treated at the 2.1 kV power setting. ATR-FTIR Analysis. Figure 10 shows the FTIR spectra of the control wool fabric and various corona-treated wool fabrics treated with EPTAC. The spectra of untreated wool shows the absorbency peak at 1620−1630 cm−1 which can be assigned to the elastic vibration peak of the CO bond, and the peak at 10960



Article

Figure 8. Optical images of water droplet after 0, 10, 20, and 30 s. Top, control fabric; bottom, corona-treated fabric.

Figure 9. SEM images of (a) control fabric and fabric samples treated at (b) 2.1 and (c) 1.5 kW power settings. Insets: change in scales of wool fiber after corona treatment.

1510−1520 cm−1 is labeled as the bending deformation peak of the C−N−H bond.30 The FTIR spectra of untreated and corona-treated wool showed similar signal patterns, but the presence of a broad peak at 3100−3400 cm−1 in the case of

corona-treated wool fabric shows the formation of hydroxyl groups by corona treatment.31 The peak height increased with increasing the corona intensity as shown in Figure 10. Results of FTIR study indicate that there are not any structural changes 10961



Article

Figure 10. FTIR spectra of untreated, corona-treated, and corona + EPTAC treated at various corona intensities.

Figure 11. FT-Raman spectra of control, corona-treated, and corona + EPTAC treated wool fabrics.

corona-treated fabrics treated with EPTAC at 794, 1066, 1263, and 2967 cm−1 could be attributed to R2CCHR′, the stretching vibration of C−O, C−O−C, νsym(CH2), and νasym(CH3), respectively.32,33 The FTIR results suggest that EPTAC was successfully bonded to the wool fiber surface. Raman Analysis. Figure 11 shows the Raman spectra of the control, corona-treated, and also corona + EPTAC treated wool fabric samples. The band positions observed for the different wool fabric samples and the band assignments according to the literature34−38 are summarized in Table 4. The spectrum of the untreated wool is typical of the Raman spectrum of wool. The positions of the amide I band at 1655 cm−1, and the C−C stretching vibrations of the skeletal backbone at 934 cm−1, indicate the high content of α-helix in native wool.34,35 Notable features include the cysteine (Cys) S−S stretch at 508−514 cm−1, the sharp phenylalanine (Phe) stretch at 1002 cm−1, and the amide I and amide B bands at 1650 and 3060 cm−1. The

in the molecular chain wool before and after the corona treatment, but the peak intensity of the groups containing oxygen and nitrogen in the treated samples increased. This shows that the hydroxyl groups on the surface of wool increased after corona treatments. The presence of an absorption peak around 1039 cm−1 in the case of coronatreated wool fabric is because of the formation of SO3 by the breaking and oxidation of S−S bonds in the surface of wool. All of the corona + EPTAC treated fabrics samples showed a strong ester band at 1740 cm−1 which is absent in the coronatreated control wool fabric. Confirmation of the deposition of EPTAC onto the wool fabric surfaces was determined by monitoring the following peaks in the spectra: 2967 cm−1 indicating the presence of aliphatic hydrocarbons, 2872 cm−1 indicating the presence of NH3+Cl−, and 1715 and 1748 cm−1 demonstrating the presence of −CH2NH2 groups in the outer surface of wool fiber. The new bands visible in the case of 10962



Article

angle of the treated surface, because when a water droplet was placed on the surface of wool, it immediately vanished. Similarly, we can see that the antistatic property of the same treated fabric also correspondingly improved. Moreover, it can be seen that the static charge buildup on the surface of wool dropped when the antistatic test was carried out at high relative humidity (Figure 5). The results obtained here indicate that there is a relationship between the hydrophilicity and the static propensity of a fabric.

Table 4. Position and Assignments of the Raman Bands of Control and Treated Wool Fabrics band positions (cm−1) control wool

corona treated

corona + EPTAC

508 643 746 − 852 934 1003 − 1125 − 1208 1318 1338 1450 1615 1655 2932 3061

514 643 754 − 852 938 1002 1032 − − − 1319 1339 1450 1610 1652 2932 3063

508 644 752 769 852 936 1002 1033 − 1086 − 1316 1339 1448 1614 1653 2931 3062

band assignment Cys S−S stretch g−g Tyr residues Trp residues (CH3)3N+ sym stretch Phe, Tyr residues C−C stretch Phe residues C−OH str vibr C−N str vibr C−O−C str vibr CH def C−H bend CH def CH2, CH3 bending modes Tyr, Trp residues amide I CH2 asym stretch amide B, C−N−H bend overtone

■

CONCLUSIONS Wool fabric surface was modified by corona discharge treatment followed by treatment with EPTAC. The tensile strengths of wool fabric samples treated with the various corona treatments and the subsequent treatment with EPTAC were greatly increased compared to those of the control fabric, but the effect of changing corona intensity and fabric speed had little effect on their elongation. Corona treatment alone only marginally improved the static propensity of wool fabric, but the further reaction of corona-treated wool fabrics with EPTAC significantly improved their static propensity. The combined treatment also considerably increased the hydrophilicity of the treated fabrics. The FTIR and FT-Raman spectra analyses confirmed that EPTAC was successfully bonded to the wool fiber surface. Therefore, this combined treatment could be a commercially feasible antistatic treatment for wool.

■

spectrum of corona-treated wool was slightly different from the spectrum of the untreated wool. The bands shown for the untreated wool at 1125 and 1208 cm−1 are absent in the spectrum of the corona-treated wool, which shows that a new band at 1032 cm−1 could be attributed to the C−OH stretching vibration. The corona + EPTAC treated wool also showed the C−OH stretching band at the same position. In the Raman spectra of corona + EPTAC treated wool fabric sample the expected bands of the trimethylammonium group of the substituent can be observed. New bands appeared at 769 and 3030 cm−1; those are not present in the case of control and corona-treated wool and could be attributed to the (CH3)3N+ symmetrical stretch vibration. The Raman spectral results confirm the presence of EPTAC on the surface of wool. Relationship between Hydrophilicity and Static Charge. The triboelectric charge generation by a textile is believed to be dependent on the surface resistivity of that textile material and also is related to the surface hydrophilicity. For instance, hydrophobic polyester produces 6 times more static charge compared to the static charge produced by a hydrophilic regenerated cellulose.39 Corona treatment produces many hydrophilic groups as mentioned earlier,22 and therefore it can be expected that the water absorption capacity of the treated wool fabric would increase. Figure 4 shows that static charge generation decreases with an increase in corona intensity. It is known that hydrophilicity of wool fabric increases with the increase in corona intensity. Figure 8 proves that the contact angle of corona-treated wool was considerably lower than the contact angle shown by the untreated wool; i.e., corona treatment improved the hydrophilicity of wool. ATRFTIR results are also consistent with the results of contact angle data shown in Table 3 and the static charge data shown in Figure 4, as the intensity of the broad peak of hydroxyl at 3100−3400 cm−1 increased with an increase in corona intensity. It can be seen that the hydrophilicity of the surface of the corona-treated wool further treated with EPTAC improved so much that it was difficult to measure the contact

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors acknowledge the financial support received from the Ministry of Business Innovation and Employment (MBIE) of the New Zealand Government thorough Grant C10X0824. We also acknowledge help received from Gail Krsinic of Advantage Networking Ltd. (Lincoln, New Zealand) for SEM scanning and Corrine Bailey of AgResearch for the measurement of static charge.

■

REFERENCES

(1) Antistatic Technology in Performance Apparel; Report: Technical Textile Markets; Textiles Intelligence Ltd., Wilmslow, U.K., 2005. (2) Lowell, J.; McIntyre, J. E. Antistatic fibers in fabrics and carpets. J. Electrost. 1978, 4, 267−282. (3) Leach, J.; Woods, H. J. Process for preparing textiles without static charge accumulation and resulting product. U.S. Patent 3,987,613, Oct 26, 1976. (4) Guo, R. H.; Jiang, S. X.; Zheng, Y. D.; Lan, J. W. Electroless nickel deposition of a palladium-activated self-assembled monolayer on polyester fabric. J. Appl. Polym. Sci. 2013, 127, 4186−4193. (5) Li, Y.; Guo, R.; Lan, J.; Jiang, S.; Lin, S.; Chen, S.; Shang, J. Preparation and magnetic properties of electroless Ni-Fe 3 O 4 composite plating on polyester fabric. Adv. Mater. Res. 2012, 557− 559, 1950−1953. (6) Gasana, E.; Westbroek, P.; Hakuzimana, J.; Clerck, K. D.; Priniotakis, G.; Kiekens, P.; Tseles, D. Electroconductive textile structures through electroless deposition of polypyrrole and copper at polyaramide surfaces. Surf. Coat. Technol. 2006, 201, 3547−3551. (7) Lu, Y.; Liang, Q.; Xue, L. Palladium-free catalytic electroless copper deposition on bamboo fabric: Preparation, morphology, and electromagnetic properties. Appl. Surf. Sci. 2012, 258, 4782−4787. 10963



Article

(31) El-Shafey, E. I. Behavior of reduction-sorption of chromium (VI) from an aqueous solution on a modified sorbent from rice husk. Water, Air, Soil Pollut. 2005, 163, 81−102. (32) Bradley, R. H.; Mathieson, I.; Byrne, K. M. Spectroscopic studies of modified wool fiber surfaces. J. Mater. Chem. 1997, 7, 2477−2482. (33) Carter, E. A.; Fredericks, P. M.; Church, J. S.; Denning, R. J. FTRaman spectroscopy of wool. I. Preliminary studies. Spectrochim. Acta, Part A 1994, 50, 1927−1936. (34) Hogg, L. J.; Edwards, H. G. M.; Farwell, D. W.; Peters, A. T. FT Raman spectroscopic studies of wool. J. Soc. Dyers Colour. 1994, 110, 196−199. (35) Church, J. S.; Corino, G. L.; Woodhead, A. L. The effect of stretching of wool fibers as monitored by FT-Raman spectroscopy. J. Mol. Struct. 1998, 440, 15−23. (36) Jones, D.; Carr, C. M.; Cooke, W.; Lewis. Investigating the photo-oxidation of wool using FT-Raman and FT-IR spectroscopies. Text. Res. J. 1998, 68, 739−748. (37) Shaleb, T.; Gopin, A.; Bauer, M.; Stark, R. W.; Rahimipour, S. Non-leaching antimicrobial surfaces through polydopamine bioinspired coating of quaternary ammonium salts or an ultrashort antimicrobial lipopeptide. J. Mater. Chem. 2012, 22, 2026−2032. (38) Benaki, D. C.; Aggeli, A.; Chryssikos, G. D.; Yiannopoulos, Y. D.; Kamitsos, E. Y.; Brumely, E.; Case, S. T.; Boden, N.; Hamodrakas, S. J. Laser-Raman and FT-IR spectroscopic studies of peptide analogues of silkmoth chorion protein segments. Int. J. Biol. Macromol. 1998, 23, 49−59. (39) Firgo, H.; Schuster, K. C.; Suchomel, F.; Männer, J.; Burrow, T.; Abu-Rous, M. The functional properties of Tencel®A current update. Lenzinger Ber. 2006, 85, 22−30.

(8) Kim, H. Y.; Kim, J. H.; Kwon, S. C.; Jeong, S. H. A study of multifunctional wool textiles treated with nano-sized silver. J. Mater. Sci. 2007, 42, 8020−8024. (9) Lowell, J.; McIntyre, J. E. Antistatic fibers in fabrics and carpets. J. Electrost. 1978, 4, 267−282. (10) Infante, M. R.; Diz, M.; Manresa, A.; Pinazo, A.; Erra, P. Microbial resistance of wool fabric treated with bis-Quats compounds. J. Appl. Microbiol. 1996, 81, 212−213. (11) McKinnon, A. J.; Vivian, A. J.; Rankin, D. A. Antistatic composition. U.S. Patent 4,671,884, June, 1987. (12) Zhu, P.; Sun, G. Antimicrobial finishing of wool fabrics using quaternary ammonium salts. J. Appl. Polym. Sci. 2004, 93, 1037−1041. (13) Hong, J. W.; Kim, H. K.; Yu, J. A.; Kim, Y. B. Characterization of UV-curable reactive diluents containing quaternary ammonium salts for antistatic coating. J. Appl. Polym. Sci. 2002, 84, 132−137. (14) Brown, D. M.; Pailthorpe, M. T. Antistatic wool. Part II: Quaternary polyethoxylated amines as antistatic agents for wool. J. Text. Inst. 1988, 79, 349−355. (15) Brown, D. M.; Pailthorpe, M. T. Antistatic wool. Part I: Polyethylene oxides and polyethoxylated amines as antistatic agents for wool. J. Text. Inst. 1988, 79, 272−280. (16) Ke, G.; Yu, W.; Xu, W.; Cui, W.; Shen, X. Effects of corona discharge treatments on the surface properties of wool fabrics. J. Mater. Process. Technol. 2008, 207, 125−129. (17) Sun, D.; Stylios, G. K. Fabric surface properties affected by low temperature plasma treatment. J. Mater. Process. Technol. 2006, 173, 172−177. (18) Wakida, T.; Niu, S.; Lee, M.; Uchiyama, H.; Kaneko, M. Dyeing properties of wool treated with low-temperature plasma under atmospheric pressure. Text. Res. J. 1992, 63, 438−442. (19) Bai, G.; Liu, Y. Antistatic property of polyacrylonitrile fiber by plasma-grafting treatment. Text. Res. J. 2010, 80, 1658−1664. (20) Chongqi, M.; Shulin, Z.; Gu, H. Anti-static charge character of plasma treated polyester filter fabric. J. Electrost. 2010, 68, 111−115. (21) Briggs, D.; Kendall, C. R. Derivatization of discharge-treated LD-PE: an extension of XPS analysis and a probe of specific interactions in adhesion. Int. J. Adhes. Adhes. 1982, 2, 13−17. (22) Samanta, K. K.; Jassal, M.; Agrawal, A. K. Antistatic effect of atmospheric pressure glow discharge cold plasma treatment on textile substrates. Fibers Polym. 2010, 11, 431−437. (23) Mijovic, J.; Fishbain, A.; Wijaya, J. Mechanistic modelling of epoxy-amine kinetics: Model compound study. Macromolecules 1992, 25, 979−985. (24) Song, J.; Jin, Y.; Fu, G.; He, A.; Fu, W. A Facile approach toward surface sulfonation of natural cotton fibers through epoxy reaction. J. Appl. Polym. Sci. 2012, 124, 1744−1750. (25) Standard Test Method for Breaking Force and Elongation of Textile Fabrics (Strip Method); ASTM Test Method D5035-06; ASTM International: West Conshohocken, PA, USA, 2006. (26) Mirjalili, M.; Nasirian, S. S.; Karimi, L. Effects of corona discharge treatment on some properties of wool fabrics. Afr. J. Biotechnol. 2011, 10, 19436−19443. (27) Zhao, S. H.; Wu, X. T.; Guo, W. C.; Du, Y. M.; Yu, L.; Tang, J. N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride nanoparticle as a novel delivery system for parathyroid hormonerelated protein 1-34. Int. J. Pharm. 2010, 393, 268−272. (28) Hassan, M. M.; McLaughlin, J. R. Formation of Poly(methyl methacrylate) Thin Films onto Wool Fiber Surfaces by Vapor Deposition Polymerization. ACS Appl. Mater. Interfaces 2013, 5, 1548−1555. (29) Tang, B.; Wang, J.; Xua, S.; Afrin, T.; Taoa, J.; Xua, W.; Sun, L.; Wang, X. Function improvement of wool fabric based on surface assembly of silica and silver nanoparticles. Chem. Eng. J. 2012, 366− 373, 185−186. (30) Valko, E. I.; Tesoro, G. C. Ginilewicz. Elimination of Static Electricity from Textiles by Chemical Finishing. Am. Dyest. Rep. 1958, 47, 403−407. 10964


Enhanced Antistatic and Mechanical Properties of Corona Plasma

Recommend Documents