IMPACT OF WEFT YARN TYPE AND FABRIC WEFT DENSITY ON BURNING BEHAVIOR, TEARING STRENGTH AND AIR PERMEABILITY FOR DIFFERENT TYPES OF ANTIBACTERIAL DRAPERY FABRICS

Drapery fabrics are textile products utilized for home and decorative textiles. Recently there have been new functional requirements for the drapery fabrics such as fl ame retardancy, antimicrobial effi ciency, UV protection, etc. This study has been conducted to investigate the eff ect of weft yarn type and weft density on drapery fabrics’ burning behaviour, tearing strength and air permeability properties. “A special inherently fl ame-retardant yarn” was used as the warp and weft yarns of the woven drapery fabrics while “a special inherently and antibacterial yarn” was also used as the weft yarn in some of the sample groups. Two main fabric groups each consisting of 12 woven drapery samples with diff erent weft yarns and weft densities were separately evaluated among themselves by using SPSS Statistical software package and bar graphs. Burning behaviours of the samples in terms of damage length and damage width with the ignition source were satisfying both for the drapery samples with the special inherently fl ame-retardant weft yarn as well as those with the special inherentl y fl ame retardant and antibacterial yarn weft yarns. In other words, usage of inherently fl ame retardant and antibacterial yarn as the weft yarns did not contribute negatively on the fl ame retardancy of drapery fabrics. The results of two-way ANOVA test indicated that weft yarn type was a signifi cant factor for tearing strength in warp and weft wise while weft density and the interaction of weft yarn type and weft density factors were non-signifi cant factors on tear strength values in warp and weft wises at signifi cance level of 0.05. Additionally, correlation analyses revealed that weft yarn tenacity values were highly correlated with the drapery fabrics’ weft tearing strength values. Moreover, weft yarn type, weft density and their interaction were infl uential factors on air permeability of the drapery fabrics at signifi cance level of 0.05.


INTRODUCTION
Drapery fabrics have always been used as important decorative textile products. Due to its superior features, polyester is the most frequently used raw material for drapery fabrics. Although drapery fabrics are expected to provide a decorative aspect, some additional technical properties such as acoustic features, thermal insulation, protection from the ultraviolet effect (UV) of sun ray, fl ame retardancy, etc. should also be considered due to the security requirements for the textiles in big social areas such as theatre halls, show centres, concert areas [1,2].
Fire-retardant fabrics are known to be having more resistivity to the fi re compared to others. Some special features may be transferred to textile products through the fi nishing procedures or by utilizing functional yarns in the textile materials. The methods for reducing the fl ammability of textiles may be explained with 4 ways: Utilizing high performance fi bres such as polyether, ether ketone, polyimides, carbon, glass may be a good alternative as the fi rst method. The second one is the modifying the structures of fibres by copolymerization and chemical modifi cation where the fl ame-retardant monomer is found in chain structures of fi bres. It is also possible to incorporate some fl ame additives during polymer extrusion such as (bisphenol-S-oligomer derivatives from Toyobo, cyclic phosphonates (Antiblaze CU and 1010 from Rhodia or phosphinate salts from Clariant). The other method for fl ame retardant textiles is surface treatment with fi re retardant chemicals. Adding fl ame retardants during polymer processing is the most popular one for polyester fi bres which is very economic and effi cient.
The method of modifi cation of polymer is used on the industrial scale for producing a fl ameproof fi bre. The method of incorporation of comonomeric phosphinic acid into polyester polymeric chain is used for an important example of FR Polyester. Flame retardancy of textile materials are infl uenced by several factors such as raw material, weaving or knitting type, additives in the fi bre, yarn constructions, fabric constructions, treatment type, etc. [3][4][5][6][7][8][9][10][11][12].
Some studies in the literature are related to imparting the fl ame retardancy properties to textile materials. Kotresh et al. performed an investigation about the burning behaviour of commercial fl ame retardant (FR) polyester curtain fabric samples with varying weights in the range of 300-550 g/m 2 by using cone calorimetry. The weight of the fabric per unit area is found to be infl uencing the peak heat release rate, rate of heat release (RHR), smoke release and other parameters [13]. Carosio et al. applied a novel method to improve fl ame retardant properties of textile fabric using multi-layered thin fi lms. PET fabrics were coated with silica nanoparticles using layer-by-layer assembly. Five bilayers of positively and negatively charged colloidal silica (<10 nm average thickness) increased time to ignition and decreased heat release rate peak of PET fabric by 45% and 20%, respectively [14]. Yang et al. conducted a study related to evaluation and analysing of the fl ame-retardant textiles. Micro-scale combustion calorimetry (MCC) was used for the evaluation of fl ammability of diff erent textile fabrics made of cotton, rayon, cellulose acetate, silk, nylon, polyester, polypropylene, Nomex and Kevlar [15]. potke na ponašanje tkanine za draperiju pri gorenju, na čvrstoću pri cepanju i na propusnost vazduha. "Posebno predivo koja usporava plamen" korišćeno je kao osnova i potka prediva od pletenih tkanina za draperije, dok  se "posebna svojstveno i antibakterijsko predivo" takođe koristilo kao predivo potke u nekim od grupa uzoraka.  Dve osnovne grupe tkanina, od kojih se svaka sastojala od 12 uzoraka pletenih draperija sa različitim predivima  potke i gustinom potke zasebno su procenjene uz pomoć softverskog paketa SPSS i stubičastih grafi [16]. The expectations about the decorative textiles have also been focused on their antimicrobial properties beside with their satisfying non-fl ammability features. Textile products provide appropriate conditions for the microorganisms such as bacteria and fungi. Those microorganisms are observed everywhere in the environment and may proliferate easily when the required conditions such as moisture, nutrients and temperature are provided. Those microorganisms' growth on textile may lead to some undesired eff ects on the textile consumers such as unpleasant odour, stains, discoloration, decrement of mechanical strength as well as contamination increment. Hence microorganism generation and their growth on textiles should be minimized by the help of antimicrobial agents or by using antimicrobial fi bres or yarns [17][18][19][20].
A special inherently antibacterial and fl ame-retardant yarn was used within our study where they were used as the weft yarns of drapery fabrics. A comparative analyse was performed in order to investigate some physical and functional properties of drapery fabrics with inherently fl ame retardant and antibacterial weft yarn and the antibacterial treated drapery fabrics with conventional inherently fl ame-retardant weft yarn. The objective of this study is to explore the eff ect of utilizing a special multi-functional yarn in drapery fabrics as weft yarn and the eff ect of a applying a further antibacterial fi nishing process on some fabric properties such as burning behaviour, tearing strength and air permeability at diff erent weft densities. It is aimed to fi ll the gap in the literature by conducting a comparative study about the investiga-tion of the fl ame retardancy, mechanical and air permeability features of the fabrics gained with diff erent ways of antibacterial features. The investigation may provide a valuable approach for the multifunctional fl ame retardant and antibacterial drapery fabrics.

Materials and Preparation
In the study, total of 24 polyester fabrics varying in diff erent yarn count and yarn structure were woven on Dornier Staubli at diff erent weft densities. The weft yarns used for the woven drapery fabrics are staple polyester yarn (Trevira CS), textured polyester yarn (Trevira CS), antibacterial staple polyester yarn (Trevira CS Bioactive), antibacterial textured polyester yarn (Trevira CS Bioactive), respectively. All weft yarns are inherently fl ame retardant. The fl ame-retardant property in the yarns is fi rmly anchored in the fi bre in the form of a comonomer -an organophosphorous compound ( Figure 1).
The antibacterial feature for the drapery fabrics is provided whether with utilizing inherently fl ame retardant and antibacterial weft yarns or provided with an additional surface treatment. The 50 dtex /40 fi l, 600 tpm (S direction), trilobal bright textured inherently fl ame-retardant polyester was utilized as the warp yarn for all fabrics. The 8/1 weft satin Z(3) drapery fabrics having the warp density of 80 threads/ cm were woven on Dornier Staubli Jacquard Machine at diff erent weft densities. Table 1 and Table 2 displays the experimental design of the study where the fabrics with fi ner weft yarns and the fabrics with coarser weft yarns were evaluated separately within the study. Illustration of the 8/1 weft satin Z(3) drapery fabrics is also indicated in Figure 2.    For the treated fabric groups, imparting of antibacterial fi nishing was achieved with the padding system by using antibacterial agent (RucoBac AGP) with the ratio of 4g/l after the fabrics were washed at 70 °C. All antibacterial treated or untreated samples were dried and cured in Stenter after wet processes.

Method
Prior to all tests, all fabrics were conditioned for 24 hours in standard atmospheric conditions (at the temperature of 20 ± 2 °C and relative humidity of 65 ± 2 %). Curtains and drapery fabrics are expected to meet some of the requirements such as fl ame retardancy, windproof feature as well as satisfying mechanical properties. Hence within our study burning behaviour, tearing strength in warp and weft wise and air permeability properties were evaluated. Each section is discussed with the help of the bar graphs and statistical results, respectively.

Burning Behaviour
A testing device of NFP 92-503 was used for measuring the damage length and damage width of fabrics in the warp direction for the fl ammability test. The fabric samples were inclined at 30 o to the horizontal and were subjected to a radiant heat fl ux for 5 minutes and fl aming ignition source was applied to the heated fabrics. Figure 3 displays the NFP 92-503 Electric Burner Testing device [21]. Damage zone at the length and width in warp and weft wise were recorded in millimetres among the fabrics with the help of the test device ( Figure 4).

Tear Strength
Tearing may be described as the consecutive breakage of yarn groups along the fabrics. Tear strength may be defi ned as one of the important mechanical parameters which infl uences the serviceability of drapery fabrics. This property may be infl uenced with several factors such as yarn, fabric structure, fabric treatment type, conditions, etc. Single tear method named as 'Determination of tear force of wingshaped test specimens' was utilized for conducting tear strength tests of fabric samples by utilizing Titan -Uni versal Strength Tester by James H. Heal & Co. Ltd. test machine ( Figure 5). Five samples for weft and fi ve samples for warp tear strength were prepared [23].

Air Permeability
Air permeability of drapery fabrics should be considered to guarantee them they are windproof. Air permeability of woven fabrics may be infl uenced from the yarn type, yarn linear density as well as surface treatment type. Drapery fabrics were subjected to air permeability test with SDL Atlas Digital Air Permeability Tester according to EN ISO 9237 standard [24]. Measurements were performed by application under 100 Pa air pressure per 20 cm 2 fabric surface. Averages of measurements from 10 diff erent areas of fabrics were calculated ( Figure 6).

Statistical Analyses
In order to understand the statistical importance of weft yarn type and weft density on tearing strength and air permeability properties of drapery fabrics, two-way ANOVA test was performed. Student-Newman-Keuls (SNK) were also conducted to compare the means of damage width, damage length for tear strength and air permeability of the drapery fabrics. The treatment levels in SNK tests were marked in accordance with the mean values and levels marked by diff erent letter (a, b, c, d) indicating the signifi cant diff erences. Additionally, Pearson correlation analyses were conducted to obtain the correlation coefficient between yarn tensile properties and fabric tear strength properties. The signifi cance level (α) selected for all statistical tests in the study is 0.05. All statistical procedures were conducted using the SPSS 23.0 Statistical software package.

Analysing of the Burning Behaviour
Damage zone with the ignition source  When the damage zone of the fi rst group fabrics is considered (Figure 7), the highest damage length is obtained from TT150 coded fabrics whereas the highest damage width is obtained from AT150 coded fabrics. There was no damage area observed among the TK144, TT144 and AT144 coded fabrics. It may be generally anticipated that burning behaviours of the drapery fabrics at the weft density of 44 were more satisfying compared to those with the weft density of 38 and 50 threads/cm. Among the second group of fabrics with coarser weft yarns; the highest damage zone length and damage zone width were obtained from the TK234 coded fabric groups with inherently fl ame-retardant staple polyester weft yarn produced at 34 threads/cm weft density (Figure 8). On the other hand, no longitudinal and transverse damages were observed among the AK230, AT230, AT234, AT238 coded fabrics. Regarding to damaged areas, the samples with inherently fl ame retardant antibacterial polyester weft yarns were generally more satisfying compared to antibacterial treated samples with inherently fl ame-retardant polyester weft yarns among the 2 nd drapery groups. Another prominent result was the increasing trend of damage zone at the length and width as the weft density increased among the samples with inherently fl ame-retardant textured polyester weft yarns of 300 denier/128 fi lament.
As a general evaluation, it can be concluded that ensuring the antibacterial feature of the fabric structure by using inherently antibacterial yarn did not have any negative eff ect for the performance of fabrics' fl ame retardancy. Figure 9 and Figure 10 indicates the tear strength of 1 st and 2 nd fabric groups consisting of 12 drapery samples, respectively. According to Figure 9; as the tear strength in warp wise is considered among the 1 st group fabrics, it is observed that the tear strength results seem to be decreasing as the weft density increases except for the AT1 coded fabrics. The maximum tear strength in warp wise was obtained from AT150 coded fabrics while the minimum value was obtained from AK150 coded fabrics. When the tear strength in weft wise is considered, the maximum value was observed among AT150 coded fabrics while the minimum value was obtained from TK144 coded fabrics. The decrease of tear strength with the increasing weft density is more prominent in warp wise among the 1 st fabric groups. The tearing strength of 2 nd drapery fabric groups made of coarser yarns are displayed in Figure 10. it is observed that tearing strength results in warp wise was distinctly lower than tearing strength results in weft wise. The maximum tear strength in warp wise was obtained from AT230 coded fabrics with textured inherently fl ame retardant and antibacterial weft yarn at 30 threads/cm weft density while the minimum value was obtained from AK238 coded fabrics with staple inherently fl ame retardant and antibacterial weft yarn at 38 weft density. As the tear strength in weft wise is evaluated, the maximum tear strength in weft wise was obtained from AT230 coded fabrics while minimum value was observed among AK234 coded fabrics. As the fabric tearing strength values are observed in Figure 9 and Figure 10, it is understood that tearing strength values in weft wise were higher than the tearing strength values in warp wise. This can be attributed to lower fabric density in weft wise compared to warp wise which does not restrict the yarn slippage during tearing process which refers to high tear strength [25]. Considering the both two drapery groups with fi ner and coarser weft yarns, samples made of textured polyester weft yarns provided more satisfying tearing strength results compared to those made of stapel polyester weft yarns. This result can be seen more clearly especially in the weft direction.

Tear Strength
Additionally, in order to observe the signifi cant eff ect of weft yarn type and weft density on the fabric tear strength in warp and weft wise, two-way ANOVA test was performed. According to ANOVA    (Table 4). Additionally, fabrics produced at diff erent weft density possessed diff erent tear strength in warp wise. According to table 4, lowest tear strength in warp direction was observed among the fabrics made of TK1 and AK1 weft yarn type which were observed under the same subset at signifi cance level of 0.05. The highest tear strength in warp direction was obtained from fabrics with AT1 coded weft yarn type. Positive infl uence of weft yarn type on tear strength was more apparent among the results in weft direction when compared with the warp direction. Highest tear strength value in weft wise was obtained from drapery fabrics with AT1 coded inherently fl ame retardant and antibacterial texture polyester weft yarn while lowest tear strength was obtained from samples with TK1 and AK1 coded staple inherently fl ame retardant and inherently fl ame retardant-antibacterial staple polyester weft yarns. Considering the weft density; drapery fabrics woven at 38 threads/ cm weft density revealed the highest tear strength in warp direction whereas the fabrics produced at 44 and 50 threads/cm weft density were observed under the same subset at signifi cance level of 0.05.
According to SNK results of the second drapery group, Fabrics made of diff erent weft yarn types revealed diff erent tear strength in warp direction at signifi cance level of 0.05. The samples produced with diff erent weft yarn densities revealed diff erent tearing strength in warp wise. The highest tear strength in warp wise were obtained from the fabrics made of TK2, TT2, AT2 coded weft yarns which were observed under the same subset. Fabric sample with AK2 cod-ed inherently fl ame retardant and antibacterial staple weft yarn indicated the lowest tear strength in warp wise. When tear strength in weft direction is evaluated, it is observed that minimum value was obtained from fabrics made of AK2 coded staple inherently fl ame retardant and antibacterial staple weft yarn type while maximum value was obtained from fabrics made of AT2 coded inherently fl ame retardant and antibacterial textured polyester weft yarn type.
Drapery fabrics produced at diff erent threads/ cm weft densities possessed diff erent warp tearing strength. Highest value was obtained from the fabrics produced at 30 threads/cm weft density while the drapery fabrics produced at 34 and 38 threads/ cm weft densities indicated lower value which were observed under the same subset.  The diff erent letters next to the counts indicate that they are signifi cantly diff erent from each other at a signifi cance level of 5 % As a general assessment, tear strength results of the drapery fabrics were consisted with their constituent weft yarns. In order to observe the relation between weft yarn tenacity and drapery samples' tear strength; the correlation analyses between the weft yarn tenacity (provided from Table 1) and the weft tear strength values for the 1 st group drapery fabrics also the correlation analyses between the weft yarn tenacity (provided from Table 2) and warp tear strength for the 2 nd group drapery fabrics were conducted. Table 6 and Table 7 indicates the correlation analyses performed for the 1 st group drapery fabrics and the correlation analyses performed for the 2 nd group drapery fabrics, respectively.
According the correlation analyse results for the 1 st group drapery fabrics indicated in Table 6; weft yarn tenacity was positively correlated with warp tear strength with correlation coeffi cient of 0.58, and weft yarn tenacity was also positively correlated with weft tear strength with the correlation coeffi cient of 0.85. When it comes to 2 nd group, a similar trend was observed for the coeffi cient results where the weft yarn tenacity was positively correlated with warp tear strength with correlation coeffi cient of 0.60 and was positively correlated with weft tear strength with the correlation coeffi cient of 0.95. Our result was also supported with Can and Kirtay's study where a strong correlation was reported between yarn tensile results and fabric tear strength properties of cotton plain fabrics [26].    Figure 11 indicates the air permeability of the 1 st group of drapery fabrics produced from diff erent weft yarns at diff erent weft densities. According to fi gure 11 which reveals the 1 st group drapery fabrics; Maximum air permeability was obtained from fabrics made of TK138 coded weft yarn while minimum air permeability was found among fabrics made of TT150 coded weft yarn. There is a prominent decrement for the air permeability of samples made of inherently fl ame retardant and inherently fl ame retardant-antibacterial polyester weft yarns as the weft density increases. Additionally, as an expected result; the fabrics with staple weft yarns indicated higher air permeability compared to their counterparts with textured fi lament weft yarns which may be attributed to high porosity of the fabrics when staple form is used. Figure 12 reveals the air permeability results of 2 nd group of drapery fabrics with coarser weft yarns. According to fi gure 12; highest air permeability was obtained from TK230 coded fabrics while minimum value was found among the AT238 coded fabrics woven at 38 threads/cm weft density. It is prominently observed that air permeability values decreased as the weft density of the fabrics increased. It may be also anticipated that the antibacterial fi nished fabrics indicated higher air permeability values compared to their untreated counterparts produced from inherently fl ame retardant and antibacterial yarns.

Air Permeability
Additionally, in order to observe the eff ect of weft yarn type and weft density on the air permeability of drapery fabrics, completely randomized two-way ANOVA was performed among the 1 st and 2 nd fabric groups (Table 8). Weft yarn type, weft density and the interaction of weft density and weft yarn type were infl uential factors on the air permeability of 1 st group drapery as well as on the air permeability of 2 nd group of drapery fabrics at signifi cance level of 0.05.   SNK results also revealed that fabrics produced with diff erent weft yarn type and the fabrics produced at diff erent weft densities possessed diff erent air permeability values (Table 9). Considering the 1 st group of drapery fabrics; minimum air permeability was obtained from the fabrics produced with AT1 coded inherently fl ame retardant and antibacterial polyester weft yarn as 96.44 mm/sec while maximum value was obtained from fabrics with TK1 coded inherently fl ame retardant staple weft yarn as 667.55 mm/sec. Considering the weft density the maximum air permeability was observed among the fabrics produced at 38 threads/cm weft density while the minimum air permeability was found among the fabrics produced at 50 threads/cm weft density. When the 2 nd group of drapery fabrics are considered, it is observed that minimum air permeability was found among fabrics woven with AT2 coded inherently fl ame retardant and antibacterial textured weft yarns while maximum air permeability was found among the fabrics with TK2 coded inherently fl ame-retardant staple polyester weft yarns.
Considering the weft density, the maximum air permeability was observed among the fabrics produced at 30 threads/cm weft density while the minimum air permeability was found among the fabrics produced at 38 threads/cm weft density.

CONCLUSIONS
This study aims to evaluate the eff ect of polyester weft yarn type and weft density on burning behaviour, tearing strength and air permeability properties of antibacterial drapery fabrics. Following conclusion can be summarized from the conducted study: 1. Regarding to burning behaviour of the samples, accompanying of antibacterial feature with fl ame retardancy in the yarn did not contribute negatively for the damage zone (mm) results. There was not a clear trend for the eff ect of weft density on fl ame retardancy of the drapery fabrics made of inherently fl ame-retardant warp and weft yarns.
2. Considering the tear strength; weft yarn type was an infl uential factor on tearing strength in warp and weft wise at signifi cant factor of 0.05 among the 1 st group drapery fabrics also among the 2 nd group drapery fabrics. However, weft density was an infl uential factor only on tear strength in warp wise. There is not a prominent diff erence for the tear strength of samples with inherently antibacterial weft yarn and the tear strength of the antibacterial treated samples among the 1 st group drapery fabrics with fi ner weft yarn counts at weft densities of 38, 44, 50 threads/cm. However, the diff erence is much clearer among the 2 nd group drapery fabrics with coarser yarn counts at weft densities of 30, 34 and 38 threads/ cm.
3. It can be anticipated that using textured polyester yarns instead of staple revealed more satisfying tear strength results among both groups. Additionally, Pearson correlation analyses also revealed that there was a strong correlation between the weft yarn tenacity values and the fabric tear strength in weft wise.
4. According to statistical results of air permeability, weft yarn type and weft density and the interaction of these two factors were infl uential on the air permeability property at signifi cance level of 0.05. It may be also observed that drapery fabrics with staple polyester weft yarn indicated higher air permeability values compared to those with textured polyester weft yarn. Hence it may be anticipated that samples with textured polyester yarns seemed to be revealing better windproof property with lower air permeability values. The increment of weft density resulted with lower air permeability values in both 1 st and 2 nd fabric groups.