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Physical and dyeing properties of polyethylene poly(ethylene terephthalate)/montmorillonite nanocomposite filament yarns.

INTRODUCTION

It is well known with state-of-art technology that incorporation of nanofillers into polymers enhances mainly physical, mechanical, and barrier properties. Among various kinds of natural and synthetic nanofillers, montmorillonite type of clay has been more widely investigated because of its high aspect ratio, plate morphology, natural abundance, and low cost (l). Natural clays and polymers are incompatible with each other since they show different characters being inherently hydrophilic and organophilic, respectively. In order to increase organophilic characteristics and thus to improve their dispersion in polymeric matrices, raw clays need to be modified beforehand with organophilic surfactants (2-4). Modified clays thus obtained are called organoclays. Among the modifiers, quaternary long-chain ammonium surfactants are commonly used because of their low cost, commercial availability, and enabling miscibility with a broad range of polymer matrices (5-7). Melt intercalation is the method of choice to obtain polymer nanocomposites because of its simple and versatile processing way. The extrusion process has proved to be effective in the dispersion of the clays (8-12).

Poly(ethylene terephthalate) (PET) and its nanocom-posites have a privileged position in plastics industry since they are widely used in packaging, construction, electronics, household, automobile, and textile industries (13), (14). Furthermore, PET/montmorillonite nanocomposite fibers should be given a special attention since PET fibers occupy the leading position among synthetic fibers in textile industry due to their excellent textile properties such as abrasion resistance, good mechanical properties, durability, and good dimensional stability at a reasonable price (15), (16). However, most investigations on PET/clay nanocomposites mainly concern their engineering plastic applications. There have been numerous studies related to the PET/montmorillonite nanocomposites dealing with their synthesis, processing conditions, nanoscale morphology, mechanical and thermal properties, and their relations (1), (17-27). Nevertheless, physical and dyeing properties of PET/clay nanocomposites in filament yarn form have been studied only by Tell and Kale (28) so far, although dyeability of PET and its compatibility with clay are of great importance in fiber production and application. Furthermore, the related study was mainly focused on generation of flame retardant, and thermally stable PET nanocomposite fibers and their dyeing properties were mentioned superficially. Apart from that, Parvinzadeh Gashti and Moradian investigated the dyeing properties of PET/clay nanocomposites. But their nanocomposites were not in filament yarn form (16). Besides, only commercially available organomodified clays were used in both studies. Considering the literature, it is obvious that there has been a lack of related studies concerning physical and dyeing properties of PET/clay nanocomposites in filament yarn form for textile applications. To cover partly this deficit, we have conducted a detailed study in which PET/organoclay nanocomposites in filament yarn form were produced by melt spinning method using different types of clay modified by using our synthesized quaternary ammonium salt and were investigated their physical and dyeing properties in a detailed manner.

EXPERIMENTAL

Materials

Fiber grade super bright PET chips [intrinsic viscosity (IV) value: 0.65 dL/g] were provided from SASA Polyester Sanayi A.S. (Adana, Turkey). Sodium montmorillonite types of clay were used throughout in this study. Raw clays used were Resadiye clay [cation exchange capacity: 70 meg/100 g (supplier data), Karakaya Bentonit San. Tic. A.S., Tokat, Turkey] and Rockwood clay [Nanofil[R] 116, cation exchange capacity: 90-100 meq/100 g (supplier data), Rockwood Clay Additives GmbH, Moosburg, Germany]. Resadiye clay was designated as RK and Rockwood clay as RW. Reagent grade benzyl chloride (BC) (97%, 126.58 g/mol) was purchased from Sigma-Aldrich, and a tertiary amine ethoxylate (TAE) containing 15 ethylene oxide units, based on a primary tallow amine (914 g/mol) was obtained from Akzo Nobel. The commercial dyes used in this study were disperse dyes being Setapers Red P2G (C.I. Disperse Red 167; Seta [section] Kimya A.S., Turkey) and Setapers Blue TFBL-NEW (a mixture of C.I. Disperse Blue 366 and C.I. Disperse Blue 367; Seta [section] Kimya A.S., Turkey). Lyocol RDN lig and Dilatin POE Lig (Clariant, Turkey) are used as anionic dispersing agent and carrier, respectively. All other chemical reagents were of laboratory grade. The chemicals and dyestuffs were used as received.

Details related to clay mineral content, spectroscopic analysis, and thermal stability of the organoclays can be found in our previous study (29).

Preparation of the Organoclays

Quaternary ammonium salt was synthesized by using TAE and BC; 0.5 mol TAE and 1.5 mol BC were added to 1 L distilled water and stirred at 80[degrees]C for 1.5 h. TAE and BC were chosen intentionally since TAE contains 15 ethylene oxide units and BC has a benzen ring, and they are supposed to make the clay and the PET matrix compatible.

Organomodification procedure of the raw clays with synthesized quaternary ammonium salt was as follows: clay-to-salt ratio was 1:0.55 and solid content-to-water 1:10. First, the surfactant and afterward the raw clay were added to the distilled water slowly. After clay incorporation, organophilic modification was carried out at 80[degrees]C for 1 h under reflux and agitation. Afterward, the slurry was cooled down to 50C, and methanol was added to the system (clay-to-methanol ratio, 1:6) and continued to stirring for 15 min. After dewatering using centrifugal dryer, drying in an air-circulating oven (110[degrees]C for 48 h), grinding, and screening, organically modified clays were ready for usage.

Preparation of the PETIOrganoclay Nanoeomposite Filaments

PET/organoclay nanocomposite filaments were prepared by melt intercalation method. Organoclays and PET chips were dried in an air-circulating oven before compounding processes (organoclays at 120[degrees]C for 24 h and PET at 165[degrees]C for 6 h [301). First, PET/organoclay master batches (85/15 wt/wt) were prepared by using a corotating intermeshing twin screw extruder (Leistritz Micro 27 LG 44D, diameter = 27 mm) with a length to diameter ratio of LID = 44. Barrel zone temperatures of the extruder were as follows: 270[degrees]C, 265[degrees]C (X10), and 270[degrees]C. The extrusion process was carried out with a screw rotation speed of 300 rpm and a throughput of 30 kg/h. Before melt spinning, PET/organoclay master batch chips were dried in a vacuum dryer for 24 h at 120[degrees]C to remove traces of moisture. Super bright POY filaments having a linear density of 170 dtex were produced at the pilot plant of KORDSA Global Technology Center (Izmit, Turkey) at a temperature of 283[degrees]C. The content of organoclay in the filaments was ensured to be 0.5, 1, 2, and 5% by weight.

The prepared PET/organoclay nanocomposite filaments and the neat PET filaments were dyed with disperse dyestuffs at 0.5 and 1.5% depths of shade. In order to investigate the effects of organoclay addition on different dyeing conditions, atmospheric (with/without carrier) and high temperature (HT) dyeings were carried out in IR sample dyeing machine (Termal Laboratuvar Aletleri San. ve Tic, Koll, S ti., Turkey) with a liquor ratio of 100:1. After prewashing of the samples at 70[degrees]C for 10 min without using a soaping agent, addition of acetic acid (C[H.sub.3]COOH, 15% vol/vol) (1 g/L), sodium acetate (C[H.sub.3]COONa) (1 g/L), sodium sulfate (N[a.sub.2]S[O.sub.4]) (6 g/L), and Lyocol RDN Liq (2 g/L) was completed, and dyeing was started at a pH value of 4-4.5. The temperature was raised up to 80[degrees]C immediately and then to final dyeing temperature (100[degrees]C for atmospheric dyeing and 122[degrees]C for HT dyeing) by temperature increments of 1 [degrees]C/min. Dilatin POE Liq (2 g/L) was added to the dyebath at atmospheric dyeing with carrier. Dyeing was then continued at this temperature between 30 and 45 min for 0.5 and 1.5% depths of shade, respectively. After cooling the dyebath down to 70[degrees]C with 1.3[degrees]C/min, the dyed samples were subjected to rinsing in distilled water for 5 min, followed by a reductive cleaning conducted at 80[degrees]C for 20 min by using 6 g/L sodium dithionite (N[a.sub.2][S.sub.2][O.sub.4]) and 6 mL/L, 30% caustic soda (NaOH) at a liquor ratio of 100:1. The samples were then neutralized at 60[degrees]C for 20 min with acetic acid.

IV Analysis

Solution viscosity measurements of the PET nanocomposite yarn samples were carried out in order to determine the IV. Two grams of sample were dissolved in 25 g o-chlorophenol for 15 min at 125[degrees]C. The solution was then placed in Cannon Fenske Viscometer at 25[degrees]C and viscosity values were recorded. Further details can be found elsewhere (31).

Physical Tests

Tensile tests of the filaments were performed by using a Textechno-Statimat Te, with an extension rate of 50 mm/min and a gauge length of 100 mm. An average of 15 test runs has been reported for each filament. Breaking strength, i.e., tenacity was determined according to ISO 5079 for breaking strength of fiber (32). Boiling shrinkage tests were conducted using Texturmat-ME instrument according to DIN 53866-T2 (33).

X-Ray Diffraction

X-ray diffraction (XRD) experiments were performed in a Bruker AXS Advance D8 diffractometer. Samples were scanned using an incident x-ray of Cu K[alpha] with a wavelength of 1.54 [Angstrom] in 2[theta] ranges from 1[degrees] to 10[degrees] at a rate of 17 min (generator voltage = 40 kV, current = 30 [micro]A). The raw data were transformed into an XRD spectrum using the Bruker Evaluation Software Version 7.0. The distance between clay sheets was calculated using Bragg's law and the 20 peak maximum values from the XRD spectra.

Scanning Electron Microscopy

For morphological analysis, the samples were coated with gold (Au) using Emitech K950X sputter coater to avoid charge buildup and analyzed by LEO 440 scanning electron microscope equipped with a Quartz Xone energy dispersive x-ray analysis system.

Differential Scanning Calorimetry

PerkinElmer PYRIS Diamond[TM] differential scanning calorimeter was used for thermal analysis. Heating scans were performed under nitrogen at 5[degrees]C/min over the temperature range from 30 to 290[degrees]C. First heating scans were used for the evaluation. Crystallinity of the samples was determined by adapting Eq. 1 as follows:

[X.sub.e] = ([DELTA][H.sub.f]-[DELTA][H.sub.c])/[DELTA][H.sub.f.sup.0] (1)

where [x.sub.e] is % degree of crystallinity, [DELTA][H.sub.f] the enthalpy of fusion, [DELTA][H.sub.c], the enthalpy of crystallization, and [DELTA][H.sub.f.sup.0] the heat of fusion of the completely crystalline material at the equilibrium melting temperature, [T.sub.m.sup.0]. The value of 120 J/g has been taken as the enthalpy of melting of 100% crystalline PET (34). The reported results are the average of three samples.

Spectrophotometry

The spectral reflectance measurements of the dyed PET/organoclay nanocomposite filaments were performed using a Konica Minolta 3600d spectrophotometer under D65 illuminant and a 10' standard observer with specular and UV components. Color measurements were carried out using Real-Color v1.3 software. CIELAB color coordinates(L*, a*, b*, C*, and [h.sup.0]) and the corresponding K/S values of the dyed filaments at the wavelength of maximum absorption were determined. The K/S values of the dyed samples, i.e., the color strengths, were calculated using the Kubelka--Munk equation:

K/S = [(1-R).sup.2]/2R (2)

where R is the decimal fraction of the reflectance of the dyed sample, K is the absorption, and S is the scattering coefficient (35) The maximum absorption ([[lambda].sub.max]) was at 630 and 520 tim for the blue and red disperse dyes, respectively. An average of four measurements from different sections of the yarn was obtained.

RESULTS AND DISCUSSION

Main obstacles that arose during spinning operations were sudden clogging of the spinneret and filter packages resulting in sharp pressure increases and high breakage rates especially as of 2 wt% organoclay content. Because of these problems, PET nanocomposite filaments containing 2 and 5 wt% organoclay were not used for further characterizations. Besides, XRD patterns of the PET/organoclay nanocomposites (99.5/0.5 wt/wt) were not shown since only a straight line was observed in their diffractograms because of very low amount of the organoclay.

Physical Properties

The tenacity, elongation at break (%), and boiling shrinkage values of the filaments spun are shown in Table 1. Addition of the organoclay has led to reduced tenacity values. This effect is more pronounced with increased clay concentration. Apparently, addition of 1 wt% organoclay acted as stress concentrators within the nanocomposite fibers and gave rise to reduced physical properties. The decrease in tenacity values was accompanied by an increase in the elongation percentage. Noticable changes were not observed when considered the boiling shrinkage values of the nanocomposite filaments.

TABLE 1. Physical properties of the neat PET and PET/organoclay
nanocomposite filaments.

Sample         Tenacity   Elongation at        Boiling
              (cN/dtex)       break (%)  shrinkage (%)

Neat PET  2.37 [+ or -]  130.3 [+ or -]  63.3 [+ or -]
                   0.14             1.2            0.8

PET/RKOC  2.19 [+ or -]  131.6 [+ or -]  62.7 [+ or -]
99.5/0.5           0.11             0.8            1.1

PET/RKOC  1.85 [+ or -]  140.8 [+ or -]  64.2 [+ or -]
99/1               0.16             2.1            0.7

PET/RWOC  2.17 [+ or -]  137.1 [+ or -]  64.6 [+ or -]
99.5/0.5           0.12             1.4            0.9

PET/RWOC  1.96 [+ or -]  138.1 [+ or -]  64.5 [+ or -]
99/1               0.11             0.9            1.2


IV value is a direct indication whether thermal degradation in polymer matrix takes place. The neat PET and PET nanocomposite filaments showed nearly the same IV values changing between 0.605 and 0.618 dL/g. According to the IV results, thermal degradation in PET was not appreciable, which means that addition of organoclay did not affect PET stability. Considering this fact, it can be said that reduced physical properties of the PET nano-composite filaments were not related to the PET stability.

Morphology

The spacing between clay platelets was determined for the clays and PET/organoclay nanocomposites using the Bragg's law and related XRD patterns were shown in Figs. 1 and 2. Generally, a peak broadening and a decrease of intensity in XRD pattern would be interpreted as a decrease in the degree of coherent layer stacking (i.e., a more disordered system) of the clay. The absence of the signal in XRD pattern would be an indication of clay exfoliation.

RK shows a peak at approximately 2[theta] = 7[degrees] corresponding to the basal interlayer spacing of 12.5 [Angstrom] (Fig. la). After organophilic modification, Resadiye organoclay (RKOC) delivered an increased d-spacing of 18 [Angstrom] (2[theta] = 4.9[degrees]) (Fig. lb). This increase in the intergallery spacing indicates that intercalation occurred and that the interlayer space of the clay increased by 5.5 [Angstrom]. PET master batch containing 15 wt% Resadiye organoclay has two distinctive peaks located at 2[theta] = 2.28 and 5.50[degrees] (d = 38.7 and 16 [Angstrom]), indicating that the intercalation of the PET polymer chains increased the interlayer spacing of RKOC (Fig. 1c). On the other hand, clay platelets were determined to be collapsed to a small extent (16 [Angstrom]) when considered the c/-spacing of the RKOC organoclay being 18 [Angstrom]. PET/RKOC 99/1 nanocomposite showed one single peak at 2[theta] = 6.1[degrees] (d = 14.5 [Angstrom]) (Fig. 1d). But d-spacing of 38.7 [Angstrom] detected at master batch was not observed in the nanocomposite. It can be suggested that RKOC clay platelets were present both stacked in small tactoids and exfoliated within the PET matrix polymer.

RW and organoclay (RWOC) exhibited nearly the same basal spacings as the Resadiye clay being 12.5 and 17.7 [Angstrom], respectively (Fig. 2a and b). PET/RWOC master batch (85/15 wt/wt) delivered two peaks at 2[theta] = 1.7 and (d = 52 and 14.5 [Angstrom]) (Fig. 2c) and PET nanocomposite containing 1 wt% RWOC showed only an indistinctive shoulder located nearly at 2[theta] = 1[degrees] corresponding to a basal interlayer spacing of 43.2 [Angstrom] (Fig. 2d). According to XRD analyses results. RWOC containing samples showed better dispersion of the clay layers, which was attributed to the increased compatibility between PET and RWOC. In our previous study (29), we showed that increased compatibility has arisen from higher organic matter content of the RWOC organoclay.

Scanning electron microscopy images of the PET/organoclay nanocomposite filaments are depicted in Fig. 3. Independent upon the clay type and the clay concentration. PET/organoclay nanocomposite filaments exhibited clay domains varying between 1-2 [micro]m and 8-10 [micro]m (Fig. 3).

Thermal Behavior

Thermal and crystallization behavior of the neat and the nanocomposite filaments are given in Table 2. Differential scanning calorimetry results showed that the addition of organoclay has almost no effect on the melting ([T.sub.m]) and the glass transition temperatures ([T.sub.g]) of the nanocomposite filaments as the [T.sub.m ]and [T.sub.g] values of all nanocomposites are almost the same as the neat PET. However, cold crystallization temperatures ([T.sub.cc]) of the PET nanocomposite yams were determined to be different dependent upon the clay type used. And, a relationship has been observed between cold crystallization temperature and the degree of crystallinity. Both [T.sub.cc] values and corresponding crystallinity values were determined to be higher in PET/RKOC nanocomposite yams when compared with those of the neat PET. But, PET/RWOC nano-composite yarns showed nearly the same [T.sub.cc] and total crystallinity values as the neat PET. Furthermore, PET nanocomposite filaments containing 0.5 wt% showed a slightly reduced degree of crystallinity.

TABLE 2. Thermal behavior of the neat PET and PET/organoclay
nanocomposite filaments.

Sample       [T.sub.g]      [T.sub.cc]       [T.sub.m]   [X.sub.c]
          ([degrees]C)    ([degrees]C)    ([degrees]C)         (%)

Neat     76.9 [+ or -]  106.3 [+ or -]  257.2 [+ or -]  17.6 [+ or
PET                0.3             0.6             0.1      -] 1.4

PET/     77.0 [+ or -]  108.6 [+ or -]  257.7 [+ or -]  24.4 [+ or
RKOC               0.2             0.4             0.1      -] 2.1
99.5/
0.5

PET/     76.7 [+ or -]  108.3 [+ or -]  257.4 [+ or -]  23.8 [+ or
RKOC 99            0.2             0.5             0.2      -] 1.8
/1

PET/     77.0 [+ or -]  106.7 [+ or -]  257.0 [+ or -]  14.5 [+ or
RWOC               0.3             0.5             0.3      -] 2.6
99.5/
0.5

PET/     76.6 [+ or -]  106.5 [+ or -]  256.8 [+ or -]  17.3 [+ or
RWOC 99            0.2             0.3             0.2      -] 1.7
/1


It has been reported that the clay has a dual effect on the crystallization behavior of nanocomposite samples (36), (37). The clay layers can act as a nucleating agent by offering enormous surface area and hence giving rise to higher cold crystallization temperature and greater crystallization rate of PET (1), (27), (38-41). It is also possible that clay layers form of a temporary network structure with the PET chains preventing the development of crystalline order and amorphous orientation, which decreases the degree of crystallinity (23), (28). These effects strongly depend on the state of clay layer dispersion and the interaction between polymeric chains and the clay (37). The greater extent of intercalation in the PET nanocomposite filaments containing RWOC organoclay resulted in nearly the same and/or reduced degree of crystallinity. However, increased total crystallinity values were observed in PET/ RKOC nanocomposite yarns due to the poor dispersion of the RKOC within the PET matrix phase.

Dyeahility

CIELAB color coordinates (L*, a*, b*. C*, and [h.sup.o]) of the neat PET and its nanocomposite filaments dyed with Setapers Red P2G and Setapers Blue TFBL-NEW disperse dyes at 100 and 122[degrees]C are given in Tables 3-6. Corresponding KIS values are depicted in Figs. 4-7. The L* is the color coordinate that represents the lightness of samples. Any decrease in the lightness of samples could be concluded as the more color absorption into the composite. The a* represents the horizontal red--green color axis. The h* stands for the vertical yellow--blue axis. The C* represents brightness or dullness of the samples.

TABLE 3. Color coordinates of the neat PET and PET/organoclay
natiocomposite filaments dyed with 0.5% Setapers Red P2G
at different dyeing conditions.

Dyeing     Sample      L *    a *    b *    c *  [h.sup.o]
condition

Carrier    Neal PET  82.59  10.32  -1.01  10.37     354.41
(-)
           PET/RKOC  80.72   8.04   0.31   8.05       2.21
           99.5/
           0.5

           PET/RKOC  80.30   9.91   0.12   9.91       0.68
           99/1

           PET/RWOC  80.65   8.76   0.09   8.76       0.58
           99.5/
           0.5

           PET/RWOC  80.76   9.17   0.11   9.97       0.66
           99/1

Carrier    Neat PET  80.40  10.24  -0.87  10.28     355.13
(+)
           PET/RKOC  80.52   9.80  -0.78   9.83     355.39
           99.5/
           0.5

           PET/RKOC  79.76  12.97  -1.19  13.03     354.78
           99/1

           PET/RWOC  80.24   8.19  -0.55   8.21     356.13
           99.5/
           0.5

           PET/RWOC  77.94  1 L8i  -0.50  11.82     357.58
           99/1

HT         Neat PET  75.76   5.12   0.78   5.12       8.77

           PET/RKOC  75.45   3.76   0.87   3.86      13.01
           99.5/
           0.5

           PET/RKOC  76.15   4.79   1.59   5.04      18.35
           99/1

           PET/RWOC  76.69   4.34   0.94   4.44      12.18
           99.5/0.5

           PET/RWOC  76.89   4.73   1.79   5,06      20,68
           99/1

TABLE 4. Color coordinates of the neat PET and PET/organoclay
nanocomposite filaments dyed with 1.5% Setapers Red P2G at
different dyeing conditions.

Dyeing     Sample      L *     a *    b *     c *  [h.sup.o]
condition

Carrier    Neat      76.83   13.15  -0.86   13.18     256.26
(-)        PET

           PET/      76.55   14.16  -0.95   14.19     356.17
           RKOC
           99.5/
           0.5

           PET/      76.28  IS. 16  -1.10   18.20     356.53
           RKOC 99
           /1

           PET/      76.76   16.47  -1.18   16.52     355.89
           RWOC
           99.5/
           0.5

           PET/     76.0.1   17.15  -0.73   17.17     357.55
           RWOC 99
           /1

Carrier    Neat      77.32   13.19  -1.24   13.25     354.64
(+)        PET

           PET/      72.69   19.30  -1.14   19.34     356.62
           RKOC
           99.5/
           0.5

           PET/      74.99   16.84  -0.64   16.85     357.88
           RKOC 99
           /1

           PET/      72.12   18.90  -1.14   18.94     356.54
           RWOC
           99.5 /
           0.5

           PET/      72.37   18.66   0.23   18.66       0.72
           RWOC 99
           /1

HT         Neat      71.04   14.22  -1.49   14.29        354
           PET

           PET/      71.53   17.82   0.46   17.82       1.49
           RKOC
           99.5/
           0.5

           PET/      70.56   20.07   0.82  20.(19       2.35
           RKOC 99
           /1

           PET/      71:00  1 1.78   0.42   11.79       2.05
           RWOC
           99.5/
           0.5

           PET/      71.50   13.85  -0.48   13.86     358.03
           RWOC 99

           /1
TABLE 5. Color coordinates of the neat PET and PET/organoclay
nanocmilpife filaments dyed with 0.5% Setapers Blue
TFBL-NEW at different dyeing conditions.

Dyeing     Sample     L *    a *     b *    C *  [h.sup.o]
condition

Currier    Neat     85.15  -2.23   -1.35   2.61     211.23
(-)        PET

           PET/     81.34  -3.98   -2.94   4.95     216.43
           RKOC
           99.5/
           0.5

           PET/     82.79  -4.76   -3.47   5.09     216.11
           RKOC 99
           /1

           PET/     82.92  -3.37   -2.16   4.01     212.64
           RWOC
           99.5/
           0.5

           PET/     83.61  -3.96   -3.09   5.03     218.01
           RWOC 99
           /1

Carrier    Neal     80.20  -4.61   -6.75   8.18     235.65
(+)        PET

           PET/     76.16  -6.58   -7.82  10.22     229.94
           RKOC
           99.5/
           0.5

           PET/     77.28  -5.28   -6.62   8.92     227.93
           RKOC 99
           /1

           PET/     78.07  -6.62   -7.91  10.32     230.07
           RWOC
           99.5/
           0.5

           PET/     77.45  -7.43  -11.48  13.67     237.07
           RWOC 99
           /1

HT         Neat     78.47  -1.40   -0.02   1.40     180.77
           PET

           PET/     81.27  -1.62    1.34   2.10     140.50
           RKOC
           99.5/
           0.5

           PET/     82.49  -1.22    2.74   3.00     114.02
           RKOC 99
           /1

           PET/     80,02  -1.21    1.51   1.93     128.64
           RWOC
           99.5/
           0.5

           PET/     78.86  -1.44    0.02   1.44     179.27
           RWOC 99
           /1


Generally, it can be said that PET nanocomposite yarns containing different amounts of organoclay (either RKOC or RWOC) showed a small decrease in lightness (L*) values especially when dyed at atmospheric (with/without carrier) conditions and almost the same a* and b* values as the neat PET independent upon the dyeing conditions employed. Some exceptional cases observed are as follows: The a* values of the PET/RKOC and PET/RWOC nanocomposite filaments dyed with 1.5% Setapers Red P2G at atmospheric dyeing conditions (with/without carrier) were shifted to higher values meaning more reddish color. Nanocomposite yams dyed with 0.5% Setapers Blue TFBL-NEW at atmospheric conditions (with/without carrier) have more bluish color due to the reduction of the b * values.

TABLE 6. Color coordinates of the neat PET and
PET/organoclay nanocomposite filaments dyed wit
1.5% Setapers Blue TFBL-NEW at different dyeing conditions.

Dyeing     Sample      L *    a *     b *    c *  [h.sup.0]

condition  Neat PET  80.90  -5.42   -7.64   9.37     234.63
Carrier    PET/RKOC  77.90  -5.63   -5.93   8.18     226.50
(-)        99.5/0.5
           PET/RKOC  79.12  -5.14   -4.44   9.79     220.84
           49/1
           PET/RWOC  76.68  -5,86   -6.56   8.80     228.23
           94.5/0.5
           PET/RWOC  79.20  -5.93   -8.15  10,08     233.96
           99/1

Carrier (  Neat PET  71.20  -6.39  -17.01  18.17     249.41
+)         PET/RKOC  71.24  -6.78  -16.11  17.48     247.17
           99.5/0.5
           PET/RKOC  71.28  -6.80  -16.83  18.15     248.00
           99/1
           PET/RWOC  71.87  -6.62  -17.43  18.64     249.20
           99.5/0.5
           PET/RWOC  69.57  -7.03  -17.26  18.63     247.85
           99/1

HT         Neat PET  76.00  -4.98   -8.85  10.16     240.67
           PET/RKOC  75.58  -4.04   -6.32   7.50     237.31
           99.5/0.5
           PET/RKOC  74.84  -4.03   -6.15   9.36     236.75
           99/1
           PET/RWOC  75.32  -4.08   -5.80   7.09     234.91
           99.5/0.5
           PET/RWOC  75.64  -4.51   -6.63  10.02     235.74
           99/1


Independent upon the dyeing conditions employed, the brightness (C *) values showed coherent results. Incorporation of 0.5 wt% organoclay (RKOC or RWOC) reduced the brightness of the nanocomposite filaments dyed with 0.5% Setapers Red P2G or 1.5% Setapers Blue TBFL-NEW, whereas recovery of the brightness was observed when increased the organoclay amount to 1 wt%. All PET/RKOC and PET/RWOC nanocomposite filaments dyed with 1.5% Setapers Red P20 or 0.5% Setapers Blue TFBL-NEW exhibited increased brightness values. According to the color coordinates results, PET/ organoclay nanocomposite filaments could be considered to be absorbed more color then the neat PET. This result could be attributed to the void space generation enabling more disperse dye penetration into the fiber. These results are confirmed by Parvinzadeh Gashti and Moradian (16). Color strength values of the nanocomposite filaments delivered complementary results. KIS values of the PET nanocomposite yarns dyed with 0.5% Setapers Red P2G with/without carrier increased to a small extent while those of the HT dyed samples remained constant (Fig. 4). Increased dye concentration presented similar results being more pronounced in carrier-dyed samples (Fig. 5). The same trend was observed in PET nanocom-posite yarns dyed with Setapers Blue TBFL-NEW (Figs. 6 and 7). It should be noted that achieving high KIS values in carrier-dyed samples using the blue dye is only related to the dye selection when considered also the color strength of the neat PET. According to the KIS values of the dyed samples with Setapers Red P2G, using carrier especially in PET/RWOC (99/1) filaments provided nearly the same color strength as that of the HTdyed neat PET. Furthermore, color strength values of the samples dyed with Setapers Blue TBFL-NEW using carrier surpass that of the HT-dyed neat PET. However, carrier dyeing cannot be an alternative to the HT-dyeing because of environmental concerns. The main idea behind employing different dyeing conditions was to investigate whether dyeing could be realized at atmospheric conditions without carrier addition. But, atmospheric dyeing of the PET nanocomposite yarns containing different amounts of clay without using a carrier resulted in enhanced dyeing properties only to a small extent.

CONCLUSIONS

Clay incorporation led to reduced mechanical properties, which are in accordance with the XRD results. PET/organoclay nanocomposites showed only intercalated structures (not exfoliated). Morphological and thermal analyses delivered complementary results. Better dispersion of the clay layers in the RWOC samples resulted in greater molecular constrain (network formation) and hence had a dominating effect on the decrease of the degree of crystallinity. The lower extent of melt intercalation in the RKOC samples led to increased total crystallinity. Degree of crystallinity of the nanocomposite filaments did not affect the dyeability. Dyeing properties of the PET/organoclay nanocomposite filaments were enhanced due to improvement of the accessibility of PET by clay incorporation for the disperse dye. Carrier usage in PET nanocomposite filaments during atmospheric dyeing provided comparable color strength values with HT dyeing. On the other hand, atmospheric dyeing without using carrier delivered only a slight improvement in terms of dyeability.

ACKNOWLEDGMENTS

The authors would like to thank SASA Polyester Sanayi A.S. for providing materials.

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ilhan Ozen, Servet Gunes

Erciyes University, Textile Engineering Department, 38039 Melikgazi, Kayseri, Turkey

Correspondence to: i. Ozen; e-mail: iozen@erciyes.edu.tr

Contract grant sponsor: Erciyes University Scientific Research Unit; contract grant number: Project FBY-10-3303.

Published online in Wiley Online Library (wileyonlinelibrary.com)

[c] 2012 Society of plastics Engineers

DOI 10.1002/pen.23353
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