The Effect of Air, Ar and O2 Plasmas on the Electrical Resistivity And

Article The Eﬀect of Air, Ar and O2 Plasmas on the Electrical Resistivity and Hand-Feel Properties of Polyester/Cotton Blend Fabric

Baye Berhanu Yilma 1,2, Joern Felix Luebben 2,* and Govindan Nalankilli 1

1 Ethiopian Institute of Textile and Fashion Technology [EiTEX], Bahir Dar University, Bahir Dar 644, Ethiopia; [email protected] (B.B.Y.); [email protected] (G.N.) 2 Material and Process Engineering [MPE], Albstadt-Sigmaringen University, 72458 Albstadt, Germany * Correspondence: [email protected]; Tel.: +49-(0)-7571-732-9565

Received: 20 December 2019; Accepted: 13 February 2020; Published: 24 February 2020

Abstract: The conventional chemical-based antistatic agents possess ecological and technological drawbacks, such as altering the bulk characteristics, flammability, and toxicity, but not the cost effective process. Recently, using conductive metal fibers in the woven structure also affects the mechanical properties of the fabric. To overcome these challenges, plasma treatment needs to be quite an effective method. In this study, polyester/cotton (P/C), 65/35%, blend fabric was treated in a vacuum-plasma-chamber using air, argon and oxygen. The electro-physical property of the samples were evaluated by measuring the surface and volume resistivities (ρs, ρv) using textile electrode Tera Ohmmeter (TO-3). Textile Softness Analyzer (TSA) has also been used to investigate hand-feel properties of the fabric. After treatment, the results revealed that the surface resistivity was reduced by 35.5% in the case of O2, 27.3% for air and 18.4% for Ar, and also volume resistivity was decreased by 40.9%, 20.3% and 20% after O2, air and Ar-plasma, respectively, whereas hand-feel properties are slightly affected at a higher power level and treatment time. Out of the three gases, oxygen had less effect on hand-feel properties and highly reduced the fabric resistivity. In addition, the SEM images showed that the surface morphology of the fibers changed to being rough due to the plasma.

Keywords: polyester/cotton; ﬁbers; blend; textiles; resistivity; hand-feel; plasma; surface morphology

1. Introduction The polyester/cotton (P/C) blend, in the textile industry, covers 58.45% of market share worldwide [1]. These blends have attracted more attention in home, furnishing and apparel applications due to their user friendly performance, aesthetic value and low cost [2]. Nowadays, the demand for P/C blend fabric in the apparel industry has increased significantly due to the desired properties of functional performance and aesthetic value, which are more difficult to obtain altogether in both polyester (PET) or cotton fabric products. Despite the outstanding P/C fabric properties, its PET surface hydrophobic character hinders its comfort properties when it is used as an apparel fabric [3]. As is already known, the hydrophobic nature of PET fiber has the potential to develop electrical resistivity in the fabric, which is due to the tendency of synthetic fibers to static electrification [4]. The build-up static charge, under low humidity conditions, does not dissipate for a long time because of the low conductivity of textile fibers. Consequently, accumulated static charges adversely affect the comfort properties of the garments when it rubs against the wearer’s body, and at the same time, dust particles are more attracted towards the fabric surfaces. The term “resistivity (ρ)” refers to the phenomena associated with the incapacity of a material to conduct an electrical current; it is an intrinsic property of a material. Resistivity is used as an indicator of the static propensity of a textile fabric [5–7]. The

Fibers 2020, 8, 17; doi:10.3390/fib8020017 www.mdpi.com/journal/fibers Fibers 2020, 8, 17 2 of 15 relationship between the fabric resistivity and its potential to build-up electrostatic charges is not always a clear-cut point; nevertheless, it is widely agreed that the most static-electrical problems emerging from the use of textile substrate can be reduced to manageable levels if the surface resistivity 11 12 7 8 (ρs) and the volume resistivity (ρv) are dropped to 10 –10 Ω/square and 10 –10 Ω m, respectively. · However, PET fibers are insulators and have a volume resistivity of 1014 Ω m [8]. · Thus, the surface treatment of P/C blend fabric is necessary to reduce its electrical resistivity and to enhance comfort properties, while retaining its outstanding fabric properties. In that regard, several techniques have been applied to fabric surface modification, focusing on the improvement of its static charge dissipation or to eliminate the generation of static electricity. These includes introducing conductive meatal/organic fibers into woven structures [9], radioactive static eliminators [10] and antistatic agents [11]. However, the conventional chemical-based antistatic agents have ecological and technological drawbacks such as altering the bulk characteristics, toxicity and not being cost effective [12]. In addition, introducing conductive metal fibers into the woven structure also affects the mechanical properties of the fabric. To overcome these challenges, plasma treatment has to be quite an effective method [13]. Plasma technology offers numerous advantages over other conventional wet-chemical surface modification techniques. It does not need the consumption of water and chemicals, and therefore is a more ecological and economical process. Moreover, plasma treatment has a unique potential to modify the outermost surface of the fibers, limited to several nanometers in depth, by retaining the bulk properties of a material; it has also been widely used in the area of textile surface modification. In particular, the low-pressure plasma system is usually between 0.01 and 10 mbar, which is more preferred due to the high concentration of reactive species, the uniformity of a large surface area, high controllability, and the superior chemical selectivity and reproducibility of the results [14,15]. Previously, some researchers have used antistatic agents for grafting or coating along with plasma technology on PET [4,16–19] and cotton [4,20,21] fibers to reduce their static charge generation. Additionally, a few studies have been done on PET fibers by using atmospheric pressure plasma alone [12,22]. However, in regards to their static properties by applying plasma treatment, the P/C blend fibers have not been investigated yet. In addition, the fabric hand properties of the plasma treated fabric surface have not been explored to the best of our knowledge so far. In this study, low-pressure plasma (LPP) treatment has been used to enhance the antistatic properties of P/C blend fabric by using air, Ar and O2 gases without the use of antistatic chemicals. The change in surface and volume resistivity (ρs, ρv), with respect to plasma power and exposure time, has been measured by the Tera Ohmmeter. The Textile Softness Analyzer (TSA) has also been used to investigate the hand-feel (HF) properties of P/C blend fabric, including softness, stiffness and smoothness.

2. Materials and Methods In this research, a plain weave 65% PET and 35% cotton blend fabric, ready to make shirt cloth, 115 g/m2 in weight and 0.22 mm in height with 144 ends per inch (44 Ne) and 72 picks per inch (72 Ne) was used. The samples were cut into the size of 11 11 cm2 for plasma treatment, according × to the dimension of Tera Ohmmeter and TSA. The fabric samples were conditioned under standard environmental condition (ASTM D 1776) of 65 2% RH and 21 1 C for 24 h prior to plasma treatment, ± ± ◦ resistivity and fabric handle properties measurement [23]. Air, Ar and O2 were used as plasma gases. LPP laboratory system (Tetra 30, Diener Electronic GmbH + Co. KG, Germany) has been used to treat the P/C blend fabric [24]. It consisted of a rectangular vacuum chamber (approx. 34 L) with a movable sample holder floor tray over the ground electrode and capacitive coupled system, which was driven by low frequency (LF) power supply, typically at 40 kHz (0–1000 W capacity), as shown in Figure1. In addition, a vacuum pump and suction from Leybold (approx. 80 m 3/h) were parts of the plasma system. Air, Ar and O2 were used as plasma gases separately. The duration of treatment time (5, 10 and 15 min) and operating power (200, 500 and 800 W) were varied in order to investigate the FibersFibers 2020 2020, 8, ,x 8 FOR, x FOR PEER PEER REVIEW REVIEW 3 of3 15of 15 Fibers 2020, 8, 17 3 of 15 thethe plasma plasma system. system. Air, Air, Ar Ar and and O2 Owere2 were used used as asplasma plasma gases gases sepa separately.rately. The The duration duration of oftreatment treatment timetime (5, (5,10 10and and 15 15min) min) and and operating operating power power (200, (200, 500 500 and and 800 800 W) W) were were varied varied in orderin order to investigateto investigate thetimethe time time and and and power power power eeffectff ecteffect of theof the plasma plasma treatment treatment treatment on on onthe the the electrical electrical electrical resistivity resistivity resistivity and and and hand-feel hand-feelhand-feel properties properties of ofthe the P/C PP/C /Cblend blendblend fabric. fabric.fabric. The The plasma plasma gases gases were were in troduced introducedintroduced into into the the vacuum vacuum chamber chamber at ata working a working pressurepressure of of0.3of 0.3 mbar mbar (the (the base base pressure pressure is 0.005 is 0.005 mbar) mbar) and and at a at constant a constant flow flowflow rate rate of 60 of 60 sccm sccm (standard (standard cubiccubic centimeters centimeters per per minute), minute), as as well well as asat atroom room temperature. temperature. At At Atthe the the end end of ofeach each plasma plasma process, process, air-flushingair-flushingair-flushing and and venting venting was was done done for for 20 20and and 30 30s, respectively. s, respectively. All All plasma plasma process process parameters parameters were were fullyfully PC PC controlled. controlled.

FigureFigure 1. Schematic 1. Schematic diagram diagram of vacuumof vacuum plasma pl plasmaasma system system (Tetra (Tetra 30 30PC). PC).

Tera-Ohmmeter,Tera-Ohmmeter, with withwith a a guarda guard guard ring ring TextileTextile Textile ElectrodeElec Electrodetrode (TO-3 (TO-3 (TO-3 TE TE 50, TE 50, H. 50, -P.H. H. Fischer-P. -P. Fischer Fischer Elektronik Elektronik Elektronik GmbH GmbHandGmbH Co.and and IndustrieCo. Co. Industrie Industrie und Labortechnikund und Labortechnik Labortechnik KG, Germany),KG, KG, Ge Germany),rmany), was usedwas was used to used measure to tomeasure measure the surface the the surface andsurface volume and and volumeresistivitiesvolume resistivities resistivities of the of plasma theof the plasma plasma treated treated treated and and untreated and un untreatedtreated P/C P/C blend P/C blend blend fabrics fabrics fabrics according according according to to AATCC AATCCto AATCC TM76 TM76 TM76 test teststandard,test standard, standard, as as shown asshown shown below below below in in Figure Figurein Figure2[ 252 [25].]. 2 [25].

Key:Key: • • R1:theR1:the outer outer radius radius of ofthe the inner inner electrodeelectrode • • R2:R2: the the inner inner radius radius the the ring ring electrode electrode • • R3:theR3:the outer outer radius radius of theof the ring ring electrode electrode

Figure 2. Surface and volume resistivities (ρs, ρv) measurement conﬁguration of concentric FigureFigure 2. Surface2. Surface and and volume volume resistivities resistivities (ρ s,( ρρsv, ) ρmeasurementv) measurement configuration configuration of ofconcentric concentric ring ring ring electrodes. electrodes.electrodes. Fibers 2020, 8, 17 4 of 15 Fibers 2020, 8, x FOR PEER REVIEW 4 of 15

DueDue to to the the presence presence of of a a concentric concentric ring ring electrode, electrode, the the resistivity resistivity of of specimens specimens was was measured measured in in bothboth the the lengthlength andand width directions directions simultaneously simultaneously.. During During the the surface surface resistivity resistivity measurement, measurement, the theinsulating insulating disk disk was was placed placed between between the the ground ground base base plate plate and thethe specimen.specimen. Finally,Finally, thethe ringring electrodeelectrode and and inner inner electrode electrode were were positioned positioned on on the the specimen, specimen, respectively, respectively, whereas whereas in in the the volume volume resistivityresistivity measurement, measurement, the the insulating insulating disk disk was was not not needed. needed. The The resistivity resistivity was was measured measured at at 60 60 Sec Sec electrificationelectrification time time by by applying applying 100 V.100 For V. each For seteach of experiments,set of experiments, the mean the of themean three of test the specimens three test werespecimens taken [were26]. taken [26]. Softness,Softness, smoothness smoothness/roughness,/roughness, sti ffstiffnessness and overalland ov HFerall value HF ofvalue the plasma of the treated plasma and treated untreated and Puntreated/C fabric samplesP/C fabric were samples measured were bymeasured TSA (Emtec by TSA Electronic (Emtec Electronic GmbH, Germany) GmbH, Germany) [27]. TSA [27]. was TSA an objectivewas an objective measuring measuring device and device it was and capable it was of collecting,capable of simultaneously, collecting, simultaneously, all relevant parametersall relevant thatparameters had an influencethat had onan theinfluence haptic characteristicson the haptic characteristics of P/C blend fabrics. of P/C Theblend haptic fabrics. property The haptic was evaluatedproperty bywas measuring evaluated the by sonicmeasuring waves the produced sonic wave by rotatings produced a set by of rotating blades on a theset of clamped blades blendon the fabricclamped surfaces, blend andfabric at surfaces, the same and time, at the applying same time, a constant applying 100 a mNconstant force 100 on mN the force surface. on the Thus, surface. the vibrationThus, the was vibration captured was by captured the microphone by the andmicrophone recorded and within recorded a few seconds. within a Then, few seconds. the blade Then, applied the 600blade mN applied force, removed600 mN force, it, and removed again applied it, and again a 600 applied mN force a 600 using mN a force constant using loading a constant rate. loading After thisrate. process, After this all variablesprocess, andall variables their values and were their accessible values were by Softwareaccessible “EMS by Software Emtec Measurement “EMS Emtec system”,Measurement which system”, was interfaced which with was TSA. interfaced In the resultingwith TSA. sonic In the spectrum, resulting the sonic fabric spectrum, smoothness the valuefabric (TS750)smoothness was given value at (TS750) 750 Hz was signal given peak at by750 measuring Hz signal thepeak fabric by measuring vibration, the as seen fabric in vibration, Figure3a, whileas seen thein softnessFigure 3a, value while (TS7) the wassoftness obtained value at (TS7) 6500 was Hz throughobtained the at 6500 vibration Hz through of the rotating the vibration blade itself,of the asrotating depicted blade in Figureitself, as3b. depicted The amplitude in Figure of 3b. acoustic The amplitude signal peaks of acoustic was measured signal peaks in the was dBV measured unit. Inin addition, the dBV unit. the sti Inff addition,ness value the (D) stiffness was determined value (D) was by thedetermined measurement by the of measurement the sample deformationof the sample underdeformation a 600 mN under force, a 600 as shownmN force, in Figureas shown3c. Ain combinationFigure 3c. A combination of these parameters, of these parameters, with the blend with fabricthe blend weight, fabric thickness weight, and thickness a number and of a plies, number was of used plies, to calculatewas used the to overallcalculate HF the value overall (HF HF= f (TS7,value TS750,(HF = D,f (TS7, weight, TS750, thickness, D, weight, number thickness, of plies)). number In thisof plies)). experiment, In this experiment, only the bottom only (back) the bottom side of (back) the fabricside of sample the fabric was sample investigated was investigated and the average and th ofe the average three specimensof the three was specimens taken from was onetaken set from of tests one andset reported.of tests and reported.

(a) (b)

Figure 3. Cont. Fibers 2020, 8, 17x FOR PEER REVIEW 55 of of 15

Figure 3. Technical principle of TSA by sound analysis(c) and deformation measurement: (a) Measuring of smoothness; (b) measuring of softness, and (c) measuring of stiffness ("Reproduced/Adapted with Figure 3. Technical principle of TSA by sound analysis and deformation measurement: (a) Measuring permission from [emtec Electronic GmbH, Leipzig, Germany], Alexander Grüner, Emtec TSA – Textile of smoothness; (b) measuring of softness, and (c) measuring of stiffness ("Reproduced/Adapted with Softness Analyzer: A new and objective way to measure smoothness, softness and stiffness of textiles, permission from [emtec Electronic GmbH, Leipzig, Germany], Alexander Grüner, Emtec TSA – emtec Electronic GmbH, 2018".) [27]. Textile Softness Analyzer: A new and objective way to measure smoothness, softness and stiffness of textiles,The surface emtec chemical Electronic analysis GmbH, 2018".) of the P[27]./C blend fabric samples was evaluated by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The ATR-FTIR analysis was carried out The surface chemical analysis of the P/C blend fabric samples was evaluated by attenuated total with Thermo Scientific Nicolet iS10 FTIR spectrometer (Thermo Fisher Scientific Inc., Madison, WI, reflection Fourier transform infrared spectroscopy (ATR-FTIR). The ATR-FTIR analysis was carried USA) powered by the OMNICTM spectraTM Software. It also contains a deuterated triglycine sulfate out with Thermo Scientific Nicolet iS10 FTIR spectrometer (Thermo Fisher Scientific Inc., Madison, (DTGS) detector and KBr beamsplitter. The spectra were collected using 16 scans for each sample with WI, USA) powered by the OMNICTM spectraTM Software. It also contains a deuterated triglycine a 4 cm 1 resolution between 650 and 4000 cm 1. sulfate− (DTGS) detector and KBr beamsplitter.− The spectra were collected using 16 scans for each The surface morphology of the untreated and plasma-treated P/C blend fabrics were studied sample with a 4 cm−1 resolution between 650 and 4000 cm−1. using SEM (Zeiss Sigma VP, Carl Zeiss Microscopy, Germany). The samples were coated (2–3 nm) The surface morphology of the untreated and plasma-treated P/C blend fabrics were studied with gold for 12 min to obtain conductive fiber surfaces before the analysis [28]. X-Max EDS system using SEM (Zeiss Sigma VP, Carl Zeiss Microscopy, Germany). The samples were coated (2–3 nm) (Oxford Instruments, Oxford, UK) analysis of these samples was conducted in Field Emission Scanning with gold for 12 min to obtain conductive fiber surfaces before the analysis [28]. X-Max EDS system Electron Microscopy (FESEM) at the voltage of 5 kV and a magnification of 10,000X for single polyester (Oxford Instruments, Oxford, UK) analysis of these samples was conducted in Field Emission or cotton fiber surfaces in the P/C blend fabric. Scanning Electron Microscopy (FESEM) at the voltage of 5 kV and a magnification of 10,000X for single3. Results polyester and Discussion or cotton fiber surfaces in the P/C blend fabric.

3.3.1. Results Surface and and Discussion Volume Resistivity (ρs, ρv) Behavior of Plasma-treated P/C Blend Fabric

The surface resistivity (ρs) is the resistance to leakage current along the surface of an insulating 3.1. Surface and Volume Resistivity (ρs, ρv) Behavior of Plasma-treated P/C Blend Fabric material, while the volume resistivity (ρv) is the resistance to the leakage current through the whole bodyThe of an surface insulating resistivity material (ρs) underis the resistance standard conditions.to leakage current The electrical along the resistivity surface ofof anyan insulating dielectric material,material mainly while the depends volume on theresistivity applied (ρ voltagev) is the level, resistance relative to humidity, the leakage temperature current through and electrification the whole bodytime. of Insulation an insulating resistivity material is a under function standard of both conditions. the surface The and electrical volume resistivity of of any the substrate.dielectric Thematerialρs changes mainly almost depends instantaneously on the applied with thevoltage change level, in relative relative humidity, humidity, while temperatureρv is particularly and electrificationsensitive to temperature time. Insulation changes. resistivity In this study,is a function both plasma-treated of both the surface and untreated and volume P/C blendresistivity fabrics of s v werethe substrate. conditioned The at ρ 65 changes2% RH almost and 21instantaneously2 C for 24 h with prior the toresistivity change in measurement. relative humidity, The ρ whiles and ρρv ± ± ◦ ismeasurement particularly sensitive were carried to temperature out underabove-mentioned changes. In this study, standard both conditionsplasma-treated at 60 and Sec untreated electrification P/C blendtime by fabrics applying were 100 conditioned V on the backside at 65 ± 2% of RH the and blend 21 fabric. ± 2 °C Thisfor 24 fabric h prior side to wasresistivity directed measurement. towards the wearer’sThe ρs and body. ρv measurement were carried out under above-mentioned standard conditions at 60 Sec electrificationP/C blend time fabric by applying with plasma 100 V treatment on the backside would of develop the blend low fabric. electrical This fabric resistivity. side was During directed the plasmatowards process, the wearer’s a mixture body. of electrons, free radicals, excited species, photons and ions can interact, eitherP/C chemically blend fabric or physically, with plasma with treatment the P/C blendwould fabric develop surface. low electrical Consequently, resistivity. the surface During may the plasmaincorporate process, new a chemical mixture groupsof electrons, and/or free etch radica awayls, the excited surface species, materials. photons In this and experiment, ions can interact, several eitherfactors chemically that remained or physically, constant included:with the P/C set pressureblend fabric of 0.3 surface. mbar, Consequently, gas flow rate ofthe 60 surface sccm and may a incorporate new chemical groups and/or etch away the surface materials. In this experiment, several Fibers 2020, 8, x FOR PEER REVIEW 6 of 15 Fibers 2020, 8, 17 6 of 15

factors that remained constant included: set pressure of 0.3 mbar, gas flow rate of 60 sccm and a temperaturetemperature of of 23 23 ± 2 °C.C. The selection of these parameters was based on previous experience inin orderorder ± ◦ toto obtainobtain thethe optimumoptimum resultresult [[29].29].

3.1.1.3.1.1. EEffectﬀect ofof thethe Dischargedischarge Powerpower

FigureFigure4 4shows shows the the e effectffect ofof dischargedischarge powerpower onon thetheρ ρss andand ρρvv ofof thethe blendblend fabricfabric afterafter 1010 minmin plasmaplasma treatment,treatment, respectively.respectively. TheThe dischargedischarge powerpower waswas variedvaried fromfrom 200200 toto 800800 WW duringduring plasmaplasma treatment.treatment. The meanmean ofof threethree measurementsmeasurements waswas takentaken forfor eacheach datumdatum inin thethe figure.figure. ItIt shouldshould bebe noticednoticed thatthat thethe lowerlower thetheρ ρss andand ρρvv,, thethe lowerlower thethe staticstatic chargecharge ofof thethe sample.sample. However,However, aa testtest resultresult showedshowed thatthat thethe surfacesurface andand volumevolume resistivityresistivity ofof untreateduntreated PP/C/C blendblend fabricsfabrics developeddeveloped 14.0414.04 GGΩΩ//sqsq andand 18.0118.01 GGΩΩ⋅m,m, respectively,respectively, whichwhich inferredinferred thatthat itit wouldwould adverselyadversely aaffectffect thethe wearer’swearer’s bodybody whenwhen · usingusing thethe fabricfabric asas aa garment.garment. IncreasedIncreased dischargedischarge powerpower withwith thethe decreaseddecreased trendtrend ofof resistivityresistivity waswas observedobserved in in Figure Figure4. Di4. Differentfferent active active species species from from the air,the Ar air, and Ar O 2andplasma O2 plasma bombarded bombarded and/or reactedand/or withreacted the with blend the fabric blend surface fabric bysurface activation, by activation etching,, etching, sputtering sputtering and cleaning and cleaning to change to itschange surface its properties.surface properties. As a result As a of result the interaction, of the interaction, carboxyl carboxyl and hydroxyl and hydroxyl groups groups would bewould formed. be formed. These hydrophilicThese hydrophilic functional functional groups groups would promotewould promote the electrical the electrical conductivity conductivity of the blend of the fabric. blend During fabric. theDuring treatment the treatment process, someprocess, low some molecular low molecula organicr materials organic materials would be would removed be byremoved plasma, by resulting plasma, inresulting an eroded in an feature. eroded The feature. rougher The surface rougher would surface offer would space offer for water space molecules, for water molecules, which is conducive which is toconducive dissipate to the dissipate build-up the static build-up charge static in the charge blend in fabric the blend [16]. fabric [16].

(a) (b)

FigureFigure 4.4. EEffectﬀect ofof dischargedischarge powerpower on:on: ((aa)) surfacesurface resistivityresistivity ( ρ(ρss)) andand ((bb)) volumevolume resistivityresistivity ( ρ(ρvv)) ofof PP/C/C blendblend fabric.fabric.

3.1.2.3.1.2. EEffectffect ofof thethe TreatmentTreatment TimeTime FigureFigure5 5 presents presents the the e effectffect ofof treatmenttreatment timetime onon thethe surfacesurface andand volumevolume resistivityresistivity ofof thethe blendblend fabricfabric atat 500500 W W of of discharge discharge power, power, respectively. respectively. The The plasma plasma exposure exposure time time varied varied from from 5 to 5 15to min15 min in thein the experiment. experiment. The The data data point point in the in the figure figure was was the averagethe average of the of threethe three readings. readings. It is noticeableIt is noticeable that thethat less the electrical less electrical resistivity, resistivity, the better the electricalbetter electr conductivityical conductivity of the fabric. of the Thisfabric. implied This implied that the that hazard the potentialhazard potential of the blend of the fabric blend would fabric be lowered.would be The lowered. wearer’s The body wearer’s would body also bewould more also comfortable. be more Surfacecomfortable. and volume Surface resistivity and volume decreased resistivity as the decreased treatment as timethe treatment increased. time This increased. is due to theThis formation is due to ofthe polar formation groups of by polar air andgroups oxygen by air plasmas, and oxygen as well plasmas, as physical as well changes as physical by argon, changes air by and argon, oxygen air plasmasand oxygen on the plasmas surface on of the blend surface fibers, of whichblend fibers, would which affect thewould electrical affectresistivity. the electrical These resistivity. effects would These promoteeffects would the adsorption promote the of moistureadsorption on of the moisture fiber surface on the and fiber reduce surface its resistivityand reduce [4 its]. resistivity [4]. Fibers 2020, 8, 17 7 of 15 Fibers 2020, 8, x FOR PEER REVIEW 7 of 15

(a) (b)

FigureFigure 5. 5. EffectEﬀect of of the the treatment treatment time time on: on: ( (aa)) surface surface resistivity resistivity ( (ρρss)) and and ( (bb)) volume volume resistivity resistivity ( (ρρvv)) of of P/CP/C blend blend fabric. fabric.

3.1.3.3.1.3. Effect Effect of of the the Types Types of of Plasma Plasma Gases Gases As shown in Figures4 and5, two reactive (air and O ) and one inert (Ar) gas were used for As shown in Figures 4 and 5, two reactive (air and O22) and one inert (Ar) gas were used for plasma treatment. Under a discharge power of 800 W and exposure time of 10 min, O -plasma treated plasma treatment. Under a discharge power of 800 W and exposure time of 10 min, O22-plasma treated samples developed a ρ value of 9.2 GΩ/sq, compared to the 14.04 GΩ/sq of the untreated samples samples developed a ρs svalue of 9.2 GΩ/sq, compared to the 14.04 GΩ/sq of the untreated samples with a reduction of 35.5%. In addition, the ρ decreased significantly to 10.21 GΩ/sq for air-plasma and with a reduction of 35.5%. In addition, the sρs decreased significantly to 10.21 GΩ/sq for air-plasma and11.46 11.46 GΩ/ sqG forΩ/sq Ar for plasma-treated Ar plasma-treated samples, samples, resulting inresulting a 27.3% in and a 18.4%27.3% reduction, and 18.4% accordingly, reduction, as depicted in Figure4a. A similar e ffect is also observed after 15 min O , air and Ar-plasma treatment accordingly, as depicted in Figure 4a. A similar effect is also observed2− after 15 min O2-, air and Ar- with a discharge power of 500 W, as shown in Figure5a. The ρ of O -plasma treated sample at 800 W plasma treatment with a discharge power of 500 W, as shownv in 2Figure 5a. The ρv of O2-plasma highly reduced to 10.65 GΩ m, compared to the 18.01 GΩ m produced by untreated samples with a treated sample at 800 W highly· reduced to 10.65 GΩ⋅m, compared· to the 18.01 GΩ⋅m produced by reduction of 40.9%. Air and Ar plasma treated samples also generated a ρv of 14.35 and 14.4 GΩ m. untreated samples with a reduction of 40.9%. Air and Ar plasma treated samples also generated a ·ρv ofThese 14.35 values and correspond14.4 GΩ⋅m. toThese a 20.3% values and 20%correspond reduction, to respectively,a 20.3% and as 20% presented reduction, in Figure respectively,4b. A similar as effect is also noticed in 15 min O , air and Ar-plasma with a discharge power of 500 W, as seen above presented in Figure 4b. A similar2 effect is also noticed in 15 min O2, air and Ar-plasma with a dischargein Figure5 powerb. of 500 W, as seen above in Figure 5b. 3.2. Hand-Feel Properties of Plasma-treated P/C Blend Fabric 3.2. Hand-feel Properties of Plasma-treated P/C Blend Fabric Fabric hand properties, including stiffness, softness, smoothness and hand-feel (HF), are the Fabric hand properties, including stiffness, softness, smoothness and hand-feel (HF), are the fundamental quality parameters of clothing fabric. However, different treatment processes sometimes fundamental quality parameters of clothing fabric. However, different treatment processes affect these properties. Here, plasma treated P/C blend fabric hand properties were evaluated by TSA sometimes affect these properties. Here, plasma treated P/C blend fabric hand properties were after being conditioned for 24 h at 65 2% RH and 21 1 C. During plasma treatment, an operating evaluated by TSA after being conditioned± for 24 h at± 65 ◦± 2% RH and 21 ± 1 °C. During plasma pressure of 0.3 mbar, gas flow rate of 60 sccm and a temperature of 23 2 C remained identical, while treatment, an operating pressure of 0.3 mbar, gas flow rate of 60 sccm± and◦ a temperature of 23 ± 2 °C the discharge power and treatment time varied from 200 to 800 W and 5 to 15 min, respectively. Here, remained identical, while the discharge power and treatment time varied from 200 to 800 W and 5 to only the effect of discharge power was discussed, due to the similar effect of power and treatment time 15 min, respectively. Here, only the effect of discharge power was discussed, due to the similar effect on the fabric hand properties. However, when comparing the two parameters, the effect of discharge of power and treatment time on the fabric hand properties. However, when comparing the two power on the fabric hand was slightly higher than the treatment time. The mean of the three readings parameters, the effect of discharge power on the fabric hand was slightly higher than the treatment was taken on the back (bottom) side of the blend fabric for each datum in the figure. This was because time. The mean of the three readings was taken on the back (bottom) side of the blend fabric for each this side of the fabric was directed towards the wearer’s body. datum in the figure. This was because this side of the fabric was directed towards the wearer’s body.

3.2.1. Stiffness (mm/N) The stiffness values of plasma-treated and untreated P/C blend fabrics are presented in Figure 6. According to the TSA measurement, the lower the value of the stiffness, the stiffer the sample. Fibers 2020, 8, 17 8 of 15

3.2.1. Stiﬀness (mm/N)

Fibers 2020The, sti8, xff FORness PEER values REVIEW of plasma-treated and untreated P/C blend fabrics are presented in Figure8 of 156. According to the TSA measurement, the lower the value of the stiffness, the stiffer the sample. Thus, Thus,it is a directit is a direct indicator indicator of compliance. of compliance. Stiffness Stiffness refers to refers the tendency to the tendency of a fabric of a to fabric keep standingto keep standing without withoutany support any support or resistance or resistance to bend to when bend external when external forces isforces applied is applied on it [30 on]. it The [30]. untreated The untreated fabric fabrichad a had stiff nessa stiffness value ofvalue 1.33 of mm 1.33/N. mm/N. All the All plasma-treated the plasma-treated samples samples showed showed a lower a lower stiffness stiffness value valuethan the than untreated the untreated samples, samples, which demonstratedwhich demonstrated that plasma that plasma treatment treatment caused ancaused increase an increase in stiffness in stiffnessin the P/ Cin blendthe P/C fabrics. blend Infabrics. addition, In addition, the fabric the becomes fabric becomes stiffer when stiffer the when plasma the plasma variables, variables, power powerand treatment and treatment time are time increased. are increased. During plasmaDuring bombardment,plasma bombardment, the PET fiberthe PET was fiber heated was when heated the whenpower the and power treatment and weretreatment increased, were andincreased, it becomes and harderit becomes when harder exposed when to air. exposed As a consequence, to air. As a consequence,the fiber and thethe yarnfiber becomeand the strongeryarn become and thestrong stifferness and of the the stiffness P/C blend of fabricthe P/C was blend enhanced. fabric was The enhanced.small detected The increasesmall detected in stiffness increase after plasmain stiffness treatment after meansplasma that treatment the fabric means becomes that presumably the fabric becomesless comfortable presumably to a sensitiveless comfortable person [to31 ].a sensitive person [31].

FigureFigure 6. 6. EffectEﬀect of of plasma plasma treatment treatment on on the the st stiiffnessﬀness property of P/C P/C blend fabric.

3.2.2. Softness Softness (dBV) (dBV) Softness is aa flexuralflexural propertyproperty of of the the fabric fabric and and it isit oneis one of theof the key key elements elements of clothing of clothing comfort comfort [32]. [32].A lower A lower softness softness value value indicates indicates a softer a softer fabric fabric surface. surface. The The untreated untreated fabric fabric had had a softness a softness value value of of10.293 10.293 dBV. dBV. All All plasma-treated plasma-treated samples samples have have a a higher higher value value than than untreateduntreated blendblend fabric,fabric, as shown inin Figure Figure 77.. After After plasma plasma treatment, treatment, softness softness is is de decreasedcreased due due to to the the etching etching and and sputtering sputtering effect e ffect of theofthe fiber fiber surface. surface. Additionally, Additionally, the softness the softness value value of the offabric the was fabric further wasfurther increased increased when the when plasma the powerplasma and power the and exposure the exposure time were time wereenhanced, enhanced, whic whichh means means that that the the softness softness of of the the blend blend fabric fabric decreases. As As a a result, result, the the fabric fabric comfort comfort property property was was slightly slightly affected affected after after plasma plasma treatment treatment [33]. [33]. In particular, the Ar-plasma treated sample was more affected when compared with air and O -plasma In particular, the Ar-plasma treated sample was more affected when compared with air 2and O2- plasmatreated samples.treated samples. Fibers 2020, 8, 17 9 of 15 Fibers 2020, 8, x FOR PEER REVIEW 9 of 15 Fibers 2020, 8, x FOR PEER REVIEW 9 of 15

FigureFigure 7. 7.E Effectﬀect of of plasmaplasma treatmenttreatment on the so softnessftness property property of of P/C P/C blend blend fabric. fabric. Figure 7. Effect of plasma treatment on the softness property of P/C blend fabric.

3.2.3.3.2.3. Smoothness Smoothness (dBV) (dBV) 3.2.3. Smoothness (dBV) SmoothnessSmoothness is correlatedis correlated to fabricto fabric surface surface slipperiness, slipperiness, as a functionas a function of frictional of frictional property, property, whereas Smoothness is correlated to fabric surface slipperiness, as a function of frictional property, roughnesswhereas isroughness related to is therelated surface to the texture surface of texture the fabric of the [34 ].fabric As TSA [34]. resultsAs TSA depict, results in depict, Figure in8 ,Figure that the whereas roughness is related to the surface texture of the fabric [34]. As TSA results depict, in Figure roughness8, that the value roughness of all plasmavalue of treated all plasma samples treate wered samples greater were than greater untreated than sample.untreated The sample. smoothness The 8, that the roughness value of all plasma treated samples were greater than untreated sample. The ofsmoothness the fabric was of the reduced fabric afterwas reduced plasma treatmentafter plasma due treatment to the formation due to the of formation voids, cracks of voids, and porescracks on smoothness of the fabric was reduced after plasma treatment due to the formation of voids, cracks theand plasma pores treatedon the plasma P/C blend treated fabric P/C blend surface fabric by thesurface etching by the and etchin cleaningg and cleaning effect [33 ef].fect This [33]. gives This an and pores on the plasma treated P/C blend fabric surface by the etching and cleaning effect [33]. This gives an uneven fabric surface and comparatively high surface roughness. Prolonged treatment time unevengives an fabricuneven surface fabric andsurface comparatively and comparatively high surface high surface roughness. roughness. Prolonged Prolonged treatment treatment time time and high and high plasma power produced rougher fabric surfaces. As shown in Figure 8, all gases used have plasmaand high power plasma produced power produced rougher ro fabricugher surfaces.fabric surfaces. As shown As shown in Figure in Figure8, all 8, gases all gases used used have have almost almost similar influence on the increase in surface roughness as a function of the discharge power. similaralmost similar influence influence on the increaseon the increase in surface in surface roughness roughness as a function as a function of the dischargeof the discharge power. power. There is no There is no significant difference between the gases within the accuracy of our measurements. significantThere is no disignificantfference betweendifference the between gases withinthe gases the within accuracy the accuracy of our measurements. of our measurements.

Figure 8. Effect of plasma treatment on the smoothness property of P/C blend fabric. FigureFigure 8. 8. EffectEﬀect of of plasma plasma treatment treatment on onthe the smoothness smoothness property property of P/C of Pblend/C blend fabric. fabric.

3.2.4. Hand-Feel (HF) 3.2.4. Hand-Feel Hand-Feel (HF) (HF) The HF value is the overall effect of stiffness, smoothness, softness, number of plies, thickness and weight of fabric, i.e., HF = f (TS7, TS750, D, weight, thickness, number of plies). A higher HF Fibers 2020, 8, x FOR PEER REVIEW 10 of 15 Fibers 2020, 8, 17 10 of 15 The HF value is the overall effect of stiffness, smoothness, softness, number of plies, thickness and weight of fabric, i.e., HF = f (TS7, TS750, D, weight, thickness, number of plies). A higher HF valuevalue would would be be obtained obtained when when thethe TS7TS7 and TS750 va valueslues were were decreased decreased and and D Dvalue value was was increased. increased. Additionally,Additionally, the the elasticity, elasticity, plasticity plasticity and and hysteresishysteresis properties of of the the fabric fabric were were also also included included in inHF HF valuesvalues through through Emtec Emtec software software within within thethe TSATSA device. As As is is presented presented in in Figure Figure 9,9 all, all plasma-treated plasma-treated samplessamples had had lower lower HF HF values values than than the the untreated untreated sample. sample. In In general, general, the the plasma plasma treatment treatment a affectedffected the hapticthe haptic property property of the of P/ Cthe blend P/C blend fabric fabric [33,35 [33,35].]. The degree The degree of its of eff itsect effect depends depends on the on type the oftype plasma of gas,plasma duration gas, ofduration treatment of treatment and the amountand the amount of plasma of plasma power. power.

FigureFigure 9. 9.E Effectﬀect of of plasma plasma treatmenttreatment in the hand hand-feel-feel property property of of the the P/C P/C blend blend fabric. fabric.

3.3.3.3. Surface Surface Chemical Chemical Analysis Analysis

TheThe ATR-FTIR ATR-FTIR spectra spectra of air,of Ar,air, OAr,2-plasma O2-plasma treated treated and untreated and untreated P/C fabric P/C samplesfabric samples are presented are inpresented Figure 10 in. TheFigure blend 10. The ratio blend of the ratio PET of the fiber PET in fi theber in blend the blend fabric fabric covers covers 65%. 65%. For For this this reason, reason, the developingthe developing peaks peaks of the of Pthe/C P/C blend blend fabric fabric are are similar similar to to the the peaks peaks ofof pure PET PET fabric. fabric. The The peaks peaks 1 emergingemerging in in the the ATR-FTIR ATR-FTIR spectra spectra at at 1712, 1712, 12421242 andand 721 cm−1 cancan be be assigned assigned toto the the chemical chemical nature nature 1 −1 ofof the the PET PET fiber fiber [3, 36[3,36,37],,37], whereas whereas peaks peaks observed observed at at 3330 3330 and and 2902 2902 cm cm− can can be be associated associated to to both both PET andPET cotton and incotton the blend.in the Nevertheless,blend. Nevertheless, the absorption the absorption bands bands and their and functionaltheir functional groups groups of plasma of treatedplasma and treated untreated and untreated P/C blend P/C fiber blend ATR-FTIR fiber ATR-FT spectrumIR spectrum is presented is presente belowd below in Table in1 Table[38]. 1 [38].

TableTable 1. 1.Functional Functional groupsgroups andand theirtheir peaks found in in ATR-FTIR ATR-FTIR spectrum spectrum of of plasma plasma treated treated and and untreateduntreated P /P/CC blend blend fabric. fabric. Absorption Peaks (cm−1) Functional Groups Absorption Peaks (cm 1) Functional Groups 3330 − Hydroxyl O-H 3100–30003330 Aromatic Hydroxyl C-H O-H 3100–30002902 Aliphatic Aromatic C-H C-H 29021712 Carboxylic Aliphatic C=O C-H 17121408 CarboxylicAromatic ring C= O 1408 Aromatic ring 1339 Alkane CH2 1339 Alkane CH 1242 Carboxylic (C-O)2 1242 Carboxylic (C-O) 1098, 1018 Ester (O=C-O-C) 1098, 1018 Ester (O=C-O-C) 872, 721 Aromatic (C-H) 872, 721 Aromatic (C-H) Fibers 2020, 8, 17 11 of 15 Fibers 2020, 8, x FOR PEER REVIEW 11 of 15

FigureFigure 10. 10. ATR-FTIRATR-FTIR spectra spectra of of plasma plasma treated treated and and untrea untreatedted P/C P /blendC blend fabric fabric (plasma (plasma condition: condition: 0.3 mbar0.3 mbar pressure, pressure, 10 min 10 min treatment treatment time, time, 500 500W power W power and and 60 sccm 60 sccm gas gasflow ﬂow rate). rate).

TheThe spectra spectra developed developed from from untreated untreated and and plasma plasma treated treated P/C P/C samples are are very similar. It It does does notnot depict depict any any considerable considerable difference diﬀerence on the surf surfaceace chemistry chemistry of of the the fabric. fabric. However, However, the the intensity intensity 1 1 ratioratio was was calculated calculated by normalizing the peaks at 17121712 andand 12421242 cmcm−−1 withwith respect respect to that at 721 cm−1. . The intensity ratios of A /A and A /A are shown in Table2. In regards to the Ar-plasma The intensity ratios of A17121712/A721721 and A12421242/A721721 are shown in Table 2. In regards to the Ar-plasma treatedtreated sample, sample, the the absorbance absorbance ratio ratio is is very very slightly slightly decreased, decreased, as as compared compared to to other other plasma plasma treated treated and control samples. In the case of O and air plasma treatment, the normalized peak intensity ratio is and control samples. In the case of O22 and air plasma treatment, the normalized peak intensity ratio isbetter better than than that that of of the the untreated untreated sample. sample. This This probably probably indicates indicates the the formation formation hydrophilic hydrophilic groups groups on the surface of the fabric during O and air plasma treatment [39,40]. on the surface of the fabric during2 O2 and air plasma treatment [39,40].

TableTable 2. TheThe Absorbance Absorbance ratio ratio of of the the peaks peaks in in ATR-FTIR ATR-FTIR spectra spectra of of plasma plasma treated treated and and untreated untreated P/C P/C blendblend fabric. fabric.

SampleSample AA17121712//AA721721 AA12421242/A/A721721 UntreatedUntreated P /P/CC 0.62 0.62 0.706 0.706 OO2-plasma2-plasma treated treated 0.622 0.622 0.708 0.708 Ar-plasmaAr-plasma treated treated 0.617 0.617 0.695 0.695 Air-plasmaAir-plasma treated treated 0.647 0.647 0.717 0.717 1 Peak Peakintensity intensity at 721 at 721 cm cm−1 for− for aromatic aromatic C-H C-H out out of of plane vibrations vibrations was was used used for normalization.for normalization.

InIn general,general, thethe absorbance absorbance ratios ratios measured measured by ATR-FTIR by ATR-FTIR have nothave revealed not revealed a signiﬁcant a significant diﬀerence differenceamong samples. among As samples. is already As known, is already the known, plasma treatmentthe plasma only treatment changes only theoutermost changes the surface outermost layers surfaceof a textile layers substrate of a textile at the substrate depth ofat the a few depth nanometer of a few rangesnanometer (5–50 ranges nm). (5–50 However, nm). theHowever, ATR-FTIR the ATR-FTIRtechnique istechnique very limited is very in detecting limited ain thin detecting layer in a athin nano-level. layer in Ina ordernano-level. to get moreIn order accurate to get surface more accuratechemistry surface of plasma chemistry treated of sample, plasma more treated sophisticated sample, more techniques sophisticated are required techniques [3,12]. are required [3,12].

3.4. Surface Morphology Analysis Fibers 2020, 8, 17 12 of 15

3.4.Fibers Surface 2020, 8, x Morphology FOR PEER REVIEW Analysis 12 of 15

The SEM images of (a) untreated, (b) air, (c) Ar and (d) O2 plasma treated P/C blend fabric samples The SEM images of (a) untreated, (b) air, (c) Ar and (d) O2 plasma treated P/C blend fabric are shown in Figure 11. The single fiber was scanned at the size of 1 µm and a magnification of 10000 samples are shown in Figure 11. The single fiber was scanned at the size of 1 μm and a magnification× with 5 kV to present the surface characteristics. It can be seen on SEM images that untreated PET and of 10000× with 5 kV to present the surface characteristics. It can be seen on SEM images that untreated cotton fibers, in the P/C blend fabric, have relatively flat and smooth surfaces, whereas after 10 min PET and cotton fibers, in the P/C blend fabric, have relatively flat and smooth surfaces, whereas after plasma treatment, some new features develop on the fiber surface according to the types of plasma 10 min plasma treatment, some new features develop on the fiber surface according to the types of gases [12]. plasma gases [12].

FigureFigure 11.11. SEM images: ( a) untreated; (b) air; (c) Ar and (d)O) O2 plasma treated PP/C/C blend fabric at LPP conditionsconditions (60(60 sccm,sccm, 500500 W,W, 0.30.3 mbarmbar andand 1010 min).min).

TheThe morphologicalmorphological changeschanges ofof the fiberfiber surfaces were producedproduced byby ionion bombardment withwith highhigh energeticenergetic particlesparticles duringduring thethe plasma process. In particular, air-plasma (Figure 1111b)b) created porosity andand voidsvoids onon cottoncotton fibers,fibers, asas wellwell asas solidifiedsolidified nano-spotsnano-spots on the PET fiberfiber surfaces [[13].13]. However, Ar-plasmaAr-plasma (Figure(Figure 1111c)c) producedproduced groovesgrooves andand ribbon-likeribbon-like featuresfeatures onon thethe cottoncotton surfacesurface andand erodederoded surfacessurfaces onon thethe PETPET fibersfibers [[19,41].19,41]. In addition, O2-plasma-plasma (Figure 11d)11d) also developed a similar feature toto thatthat ofof thethe air-plasma treatment.treatment. The effect effect of air-plasma treatment is more pronounced compared toto OO22-plasma [[20].20]. Ar-plasmaAr-plasma producedproduced stronger stronger and and harder harder micro micro surfaces surfaces due due to to the the cross-linking cross-linking of of polymers. In all plasma treatments, some solidified particles are observed on the plasma-treated PET fiber surfaces [16].

4. Conclusions Fibers 2020, 8, 17 13 of 15 polymers. In all plasma treatments, some solidiﬁed particles are observed on the plasma-treated PET ﬁber surfaces [16].

4. Conclusions

This study concerned the effect of air, Ar and O2 plasma gases on the electrical resistivity and fabric hand properties of P/C blend fabrics under the LPP system. After plasma treatment, the ρs and ρv of the fabric was reduced. However, the fabric softness, smoothness, stiffness and overall HF properties were slightly affected by plasma treatment, as the TSA results revealed. The O2-plasma had a higher resistivity reduction and lower hand-feel effects due to its chemical nature, whereas Ar-plasma had a lower resistivity reduction and higher hand-feel effects due to its stronger sputtering effect. In addition, the SEM images have shown the voids, grooves and micro-pits feature on the plasma treated P/C blend fabric surfaces that correspond to the types of plasma gases. As a result, the plasma treated fabric surface became relatively rougher and stiffer than untreated fabric surfaces. In general, cold plasma treatment had a unique potential to modify and alter the outermost surface of the fibers by less than a few nanometers in depth; it has also been widely used in the area of textile substrate modification in order to change its surface properties.

Author Contributions: J.F.L. and G.N. were supervisors for the research work; B.B.Y. proposed the research idea and designed the experiment together with J.F.L.; J.F.L. offered the laboratory access; B.B.Y. undertook the plasma treatment, resistivity, hand-feel testing, analysis of the result and wrote the draft of the manuscript; J.F.L. and B.B.Y. carried out SEM and ATR-FTIT work; J.F.L., B.B.Y. and G.N. edited the manuscript together. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by Engineering Education Capacity Building Program of Ethiopia (EECBP) together with the German Academic Exchange Service (DAAD) by providing scholarship under section ST32 and the APC was funded by Albstadt Sigmaringen University. Acknowledgments: Authors are very grateful to Groz-Beckert KG (Albstadt-Ebingen, Germany) for giving the opportunities to use SEM and ATR-FTIR. The authors also would like to thank Ziad Heilani and Paul-Gerhard Ringwald for their support during the experiments. Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

References

1. Sarker, F.; Prasad, R.K.; Howlader, M.R.; Abir, N.; Nurunnabi; Akter, R. Scope of Dyeing Polyester Cotton (PC) Blended Fabric in Single Bath Process for Water, Energy and Time Saving. IOSR J. Polym. Text. Eng. 2015, 2, 12–16. [CrossRef] 2. Abou-Nassif, G.A. Blending Behavior of Cotton and Polyester Fibers on Diﬀerent Spinning Systems in Relation to Physical Properties of Blended Yarns. IJSRET 2017, 6, 1–11. 3. Kale, K.; Palaskar, S.; Hauser, P.J.; El-shafei, A. Atmospheric pressure glow discharge of helium-oxygen plasma treatment on polyester/cotton blended fabric. Indian J. Fibre Text. Res. 2011, 36, 137–144. 4. Bhat, N.V.; Benjamin, Y.N. Surface Resistivity Behavior of Plasma Treated and Plasma Grafted Cotton and Polyester Fabrics. Text. Res. J. 1999, 69, 38–42. [CrossRef] 5. Gonzalez, J.A. Electrostatic protection. In Textiles for Protection, 1st ed.; Scott, R.A., Ed.; Woodhead Publishing Limited: Cambridge, UK; CRC Press LLC: New york, NY, USA, 2005; pp. 503–528. 6. Sello, S.B.; Stevens, C.V. Antistatic Treatment. In Handbook of Fiber Science and Technology Part B, 1st ed.; Lewin, S.B., Sello, M., Eds.; Marcel Dekker, INC.: New york, NY, USA; Basel, Switzerland, 1984; pp. 291–299. 7. Bhattacharya, S.S.; Amin, H.N. Analysis of Surface resistivity behavior of Conductive Woven fabrics made from Copper Jari & SS/Polyester yarns for ESD control. IRJET 2015, 2, 1007–1012. 8. Hersh, S.P. Surface Characteristics of Fibers and Textiles, Part 1; Marcel Dekker: New York, NY, USA, 1975. 9. Cullough, M.; Francis, P.; Hall, J.; David, M. Nonlinear Aromatic Polyamide Fiber or Diber Assembly and Method of Preparation. Patent 4869951, 1989. 10. Henry, P.S.H. Radioactive Static Eliminators for the Textile Industry. In Radioisotope Techniques. Volume II; M.H. Stationary Oﬃce: London, UK, 1952; pp. 150–161. Fibers 2020, 8, 17 14 of 15

11. Shyr, T.; Lien, C.; Lin, A. Coexisting antistatic and water-repellent properties of polyester fabric. Text. Res. J. 2011, 81, 254–263. [CrossRef] 12. 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. [CrossRef] 13. Rashidi, A.; Moussavipourgharbi, H.; Mirjalili, M.; Ghoranneviss, M. Effect of low-temperature plasma treatment on surface modification of cotton and polyester fabrics. Indian J. Fibre Text. Res. 2004, 29, 74–78. 14. Morent, R.; Geyter, N.D.; Verschuren, J.; Clerck, K.D.; Kiekens, P.; Leys, C. Non-thermal plasma treatment of textiles. Surf. Coatings Technol. 2008, 202, 3427–3449. [CrossRef] 15. Jelil, R.A. A review of low-temperature plasma treatment of textile materials. J. Mater. Sci. 2015.[CrossRef] 16. Chongqi, M.; Shulin, Z.; Gu, H. Anti-static charge character of the plasma treated polyester filter fabric. J. Electrostat. 2010, 68, 111–115. [CrossRef] 17. Meng, L.; Wei, Q.; Li, L. Influence of oxygen plasma treatment on properties of polyester fabrics coated with copper films. Appl. Mech. Mater. 2012, 189, 193–196. [CrossRef] 18. Haji, A.; Rahbar, R.S.; Shoushtari, A.M. Plasma assisted attachment of functionalized carbon nanotubes on poly(ethylene terephthalate) fabric to improve the electrical conductivity. Polimery 2015, 60, 337–342. [CrossRef] 19. Wang, C.X.; Lv, J.C.; Ren, Y.; Zhi, T.; Chen, J.Y.; Zhou, Q.Q.; Lu, Z.Q.; Gao, D.W. Surface modification of polyester fabric with plasma pretreatment and carbon nanotube coating for antistatic property improvement. Appl. Surf. Sci. 2015, 359, 196–203. [CrossRef] 20. Rani, K.V.; Sarma, B.; Sarma, A. Plasma treatment on cotton fabrics to enhance the adhesion of Reduced Graphene Oxide for electro-conductive properties. Diam. Relat. Mater. 2018, 84, 77–85. [CrossRef] 21. Mojtahed, F.; Shahidi, S.; Hezavehi, E. Influence of plasma treatment on CNT absorption of cotton fabric and its electrical conductivity and antibacterial activity. J. Exp. Nanosci. 2016, 11, 215–225. [CrossRef] 22. Kan, C.W. Evaluating antistatic performance of plasma-treated polyeste. Fibers Polym. 2007, 8, 629–634. [CrossRef] 23. ASTM International. ASTM D1776-04: Standard Practice for Conditioning and Testing Textiles; West Conshohocken: Philadelphia, PA, USA, 2004; pp. 1–4. 24. Low-pressure plasma laboratory system (Tetra 30, S. No. 114275). Operating Instructions, Diener Electron; GmbH + Co. KG: Ebhausen, Germany, 2018; pp. 1–102. 25. AATCC Test Method 76. Electrical Surface Resistivity of Fabrics; AATCC Standard: Research Triangle Park, NC, USA, 2005. 26. ASTM standard D 257. Standard Test Methods for DC Resistance or Conductance of Insulating Materials; West Conshohocken: Philadelphia, PA, USA, 2007. 27. Emtec TSA—Textile Softness Analyzer—Techtextil & Texprocess. Available online: https://techtextil- texprocess.messefrankfurt.com/frankfurt/en.html (accessed on 18 November 2019). 28. Nezhad, H.Y.; Thakur, V.K. Effect of morphological changes due to increasing carbon nanoparticles content on the quasi-static mechanical response of epoxy resin. Polymers (Basel) 2018, 10, 1106. [CrossRef] 29. Yilma, B.B.; Luebben, J.F.; Nalankilli, G. The Effect of Low Pressure Oxygen Plasma Treatment on Comfort Properties of Polyester/Cotton Blend Fabric. Int. J. Text. Eng. Process. 2018, 4, 1–10. 30. Vasile, S.; Ciesielska-Wróbel, I.L.; Langenhove, L.V. Wrinkle recovery of flax fabrics with embedded superelastic shape memory alloys wires. Fibres Text. East. Eur. 2012, 93, 56–61. 31. Kan, C.W.; Yuen, C.W.M. Influence of Plasma Gas on the Mechanical Properties of Wool Fabric. IEEE Trans. PLASMA Sci. 2009, 37, 653–658. [CrossRef]

32. Hung, O.; Kan, C. Eﬀect of CO2 laser treatment on the fabric hand of cotton and cotton/polyester blended fabric. Polymers (Basel) 2017, 9, 609. [CrossRef][PubMed] 33. Naebe, M.; Tester, D.; Mcgregor, B.A.; Wang, X. The eﬀect of plasma treatment and loop length on the handle of lightweight jersey fabrics as assessed by the Wool HandleMeter. Text. Res. J. 2015, 85, 1190–1197. [CrossRef] 34. Mao, N.; Wang, Y.; Qu, J. Smoothness and Roughness: Characteristics of Fabric-to-Fabric Self-Friction Properties. In Proceedings of the 90th Textile Institute World Conference, Poznan, Poland, 25–28 April 2016. Fibers 2020, 8, 17 15 of 15

35. Murakami, M.; Mori, M.; Fujimoto, T.; Murata, C. Influence of Plasma Treatment on Total Hand Value and Adhesion Properties of Bi-Fabrics of Fused Interlining and Wool Fabrics. In Proceedings of the 5th Kanesi Engineering and Emotion Research, International Conference, Linköping, Sweden, 11–13 June 2014; pp. 1031–1038. 36. Gore, A.V.; Venkataraman, A. Identification of polyester/cellulosic blends using FT-IR spectrometer. Indian J. Fibre Text. Res. 1998, 23, 165–169. 37. Platnieks, O.; Gaidukovs, S.; Barkane, A.; Gaidukova, G.; Grase, L.; Thakur, V.K.; Filipova, I.; Fridrihsone, V.; Skute, M.; Laka, M. Highly Loaded Cellulose/Poly (butylene succinate) Sustainable Composites for Woody-Like Advanced Materials Application. Molecules 2020, 25, 121. [CrossRef][PubMed] 38. Lima da Silva, R.C.; Alves, C., Jr.; Nascimento, J.H.; Neves, J.R.O.; Teixeira, V.; Lima da Silva, R.C.; Alves, C., Jr.; Nascimento, J.H.; Neves, J.R.O.; Teixeira, V. Surface modification of polyester fabric by non-thermal plasma treatment. J. Phys. Conf. Ser. 2012, 406.[CrossRef] 39. Kan, C.; Lam, C. Atmospheric Pressure Plasma Treatment for Grey Cotton Knitted Fabric. Polymers (Basel) 2018, 10, 233. [CrossRef] 40. Caschera, D.; Mezzi, A.; Cerri, L.; Caro, T.D.; Riccucci, C.; Ingo, G.M.; Padeletti, G.; Biasiucci, M.; Gigli, G.; Cortese, B. Effects of plasma treatments for improving extreme wettability behavior of cotton fabrics. Cellulose 2014, 21, 741–756. [CrossRef] 41. Samanta, K.; Jassal, M.; Agrawal, A.K. Atmospheric pressure glow discharge plasma and its applications in textile. Indian J. Fibre Text. Res. 2006, 31, 83–98.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).