Journal of Engineered Fibers and Fabrics 47 http://www.jeffjournal.org Volume 10, Issue 2 – 2015

Effect of Recycled PET Fibers on the Performance Properties of Knitted Fabrics

Abdurrahman Telli1, Nilgün Özdil2

1Cukurova University, Department of Textile Engineering, Adana TURKEY

2Ege University, Department of Textile Engineering TURKEY

Correspondence to: Abdurrahman Telli email: atelli@cu.edu.tr

ABSTRACT PET (polyethylene terephthalate) is mostly used in textile and packaging industries. PET Bottle wastes are separated from other wastes and after that some processes are applied to obtain PET flakes, such as breaking, washing, drying and etc. r-PET fibers are produced by melt spinning method from these recycled PET flakes. r-PET fibers have already been used for secondary textile products like as carpet bottoms, sleeping bags and insulation materials. In this study usability of recycled PET fibers in apparel industry were researched. Comparative investigations of bursting strength, abrasion resistance, air permeability, surface friction, circular bending rigidity and dimensional stability properties were done to knitted fabrics produced from r-PET and blends with PET and cotton fibers. It was found that, instead of PET, r-PET fibers can be blended in certain amounts without compromising fabrics performance. Keywords: PET bottle, r-PET fibers, recycling, cotton, PET, interlock fabric INTRODUCTION Plastics are divided into two groups as thermosets and thermoplastics. Thermosets become softer structure when heated but they don’t get into liquid form. Because of this, they can’t be used again by simply process. However, thermoplastics can be softened and hardened again. In 1987, Society of Plastics Industry developed descriptive codes for thermoplastics to increase their reusable for a sustainable future. In this way, they have aimed to classify thermoplastics from thermosets and other waste. Plastics have similar densities which changes in a narrow range and they have the same or very similar electrical and magnetic properties. There are too many types of plastic wastes, so separation of them is a difficult process and they are usually used as composites. Plastics can be separated with various chemical and technological processes but they have

to be carried out without causing economic and ecological problems. When the lifecycle analysis of plastics is investigated it is found that PET is rarely used in composites and because of this, they can be recycled easier. Society of Plastics Industry gave PET based products the code “1” because they believe recycling of PET should be prioritized [1-2]. PET (Polyethylene terephthalate) contains ester groups [3]. This polymer is mostly used in textile and packaging industries. About 60% of world’s PET polymer production is used in textile industry for fiber production and about 30% of its production is used in PET bottles industry [4-5]. In textile industry PET fibers are generally used in blends, recycle of PET polymers from them is not possible. Therefore to use PET bottle wastes are the best way to obtain pure PET polymers [6]. PET flakes are gained from PET bottles after a series of processes like breaking, washing, drying and etc. [7]. Recycling wastes into new products is essential in an ecological approach. PET bottle wastes are valuable for environment if they are used as PET bottles again. Because this way, material gets primary raw material status and it will have a longer lifecycle. But because of the contamination content and low intrinsic viscosity values of PET flakes, PET bottle wastes are not used for PET bottle production again. These restrictions do not prevent to usage of PET flakes as a raw material for fiber production, therefore PET flakes are generally utilized in textile industry [8-12]. In 2007, PET bottle consumption in the world was 15 million tons and it is only 8% of the whole plastics consumption. Besides, in 2007 4.5 million tons of PET bottle were recollected and 3.6 million tons of them were broken into PET flakes. 8% of the whole PET fiber production was supplied from PET flakes [12]. 10%-20% increase is expected for upcoming 5-

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10 years in these values [13]. Furthermore, according to new market predicts, global consumption of PET bottle will grow to almost 19.1 million tons by 2017 [14]. PET flakes are converted to PET fibers using chemical or mechanical methods. In mechanical method the filaments are spun from melted PET flakes. PET is degraded into oligomer or monomer form and again a polymerization happens in chemical method. Glycolysis, methanolysis, hydrolysis, ammonoylsis and aminolysis are some of the commercial chemical methods. However, chemical methods do not seem to have economical value for recycling PET wastes at this time [9, 11-12, 15-16]. r-PET fibers are produced by melt spinning process of the PET flakes which obtained from recycled PET wastes. These fibers have economic advantages due to the lower raw material cost. They also have lower energy consumption in production stage and low carbon emission. Because of these factors, it can be said that r-PET fibers are environmentally friendly fibers. However, in mechanical cycling method, PET flakes include too much contamination and during re-heating process molecular weight of the polymer changes. So, it is quite clear that pure PET fibers and recycled PET fibers have different properties [7-8, 17]. The aim of this study to determine the advantage of usage r-PET fibers which have different features from PET fibers, on the product quality in textile and apparel industry without taking into consideration of the cost and environmental factors. r-PET fibers produced low viscosity polymer have different crystalline/amorphous region ratio and there are differences in fiber matrix because of contamination. So, it is thought that, using of r-PET fibers in blending could create advantages for fiber/fiber cohesion and covering capacity. From this point of view, knitted fabrics were produced from r-PET and r-PET blended with PET and cotton yarns and comparative investigations for fabric properties were done.

Most of the studies about PET bottle and its recycling are related with PET flake production phase. Especially, there are a number of studies about classifying PET and PVC wastes [2, 6, 11]. Another topic which gets much attention is comparing ecological effects of recycled PET and raw PET productions [12]. Additionally, there are not many studies about r-PET spinning parameters and yarn production [7, 17-19]. There is no study about fabric properties produced from r-PET and r-PET blended yarns. It is thought that this study can contribute to knowledge about r-PET fiber. MATERIALS AND METHODS r-PET, PET and cotton fibers were used in this study. r-PET fibers were supplied from one of the company (Bozoglu Textile Inc.) that is produced r-PET fibers using PET flakes by mechanical method in Turkey. Fiber properties used in experimental were given in Table I.

TABLE I. Fiber properties.

Fiber Properties Cotton (Co)

Polyester (PET)

Recycled PET

Bottle (r-PET)

Fineness (dtex) 1.78 1.57 1.85 Mean length (mm) 26.51 28.77 32.62 Tenacity (cN/tex) 27.30 50.66 26.92 Elongation at break (%) 7.0 25.74 39.13

Three different types of 100% PET, 100% r-PET and 100% cotton slivers were produced on carding machine. Then two draw frame passages were used. Blending operations were designated on the first draw-frame machine in different ratios as shown in Table II. The blended slivers were regulated using second draw-frame machine. After that the rovings were produced in roving frame and using ring spinning system nine different type of Ne 20 carded yarns in different fiber blending ratio in the twist coefficient of αe= 3.6 were produced. Knitted fabrics in interlock structure were produced using 30 inch circular knitting machine with 16 E gauge and 36 systems.

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TABLE II. Properties of the yarns and fabrics produced in experimental.

Blending Ratio Yarn

diameter (mm)

Yarn tenacity (cN/tex)

Yarn hairiness (H)

Fabric weight (g/m2)

Fabric thickness

(mm)

Fabric porosity

(%) 100%Co 0.258 12.77 5.59 355 1.30 0.82

70% Co / 30% r-PET 0.260 13.57 5.40 392 1.34 0.80

50% Co / 50% r-PET 0.257 13.42 5.45 359 1.36 0.82

30% Co / 70% r-PET 0.255 12.28 5.64 364 1.34 0.81

100% r-PET 0.246 14.91 5.80 350 1.26 0.80

100% PET 0.227 28.66 4.77 369 1.32 0.80

70% PET / 30% r-PET 0.235 23.30 5.09 365 1.35 0.80

50% PET / 50% r-PET 0.243 21.08 5.18 373 1.29 0.79

30% PET / 70% r-PET 0.241 18.60 5.49 356 1.28 0.80

Because of the more stable fabric structure that provides constituent results for laboratory tests, the interlock structure preferred. The same tightness factor was used all type of the fabrics. The properties of the fabrics were given in Table II. All fabrics were applied soda and oil solvents at 90 ºC in 1/20 liquor ratio to remove paraffin and then the fabrics were washed at 40 ºC for one hour, and dried by laying. During the production process of the yarn and fabrics, no important problem was encountered as compared to the production of ordinary product. Performance tests were carried out after all the fabrics were conditioned at standard atmospheric conditions (20±2 ºC temperature and %65±4 relative humidity) according to TS EN ISO 139 [20-22]. Uster Tester 5 S800 was used to determine the yarn evenness, yarn diameter and hairiness values. Thickness values of the fabrics were measured according to TS 7128 EN ISO 5084 by SDL ATLAS Digital Thickness Gauge [19, 23]. Bursting strength values of the fabrics were tested by “Lawson Hemphill Bursting Strength Tester” instrument according to TS 393 EN ISO 13938-1 [24]. Abrasion resistance values of the fabrics were obtained using “Martindale Abrasion Tester” with 9kPa weights according to ISO 12947-3 standard. For observing the first break on the fabric, machine was used up to 20000 rubs but no breakage on fabric surface was encountered. For this reason, results were based on the weight loss at 2500, 5000, 10000, 12500, 15000, 17500 and 20000 rubs [25]. “Nu-Martindale Test Instrument” was chosen to evaluate pilling resistance of the fabrics in compliance with ISO 12945-2 [26]. The tests were carried out at 2000 turns. After this procedure, pilling degrees of the fabrics were determined using with “Pillgrade-3 Dimensional Pilling and Hair grading” instrument [27]. The

related standard gives the pilling values of the fabrics as 1-5 from the worse to the best numeric. Air permeability tests of the fabrics were carried out with “Textest AG FX 3300 Air Permeability Tester” according to TS 391 EN ISO 9237. 20 cm2 measurement area and 100Pa air pressure were used and average value of the 10 tests was taken as a test result [28]. Friction coefficient of fabric surface was tested using Frictorq (Fabric Friction Tester) instrument. In this instrument, a square-like contact sensor which has 3 contact points covered by a number of calibrated steel needles and creates a 3.5 kPa pressure is set on fabric surface. The kinetic friction coefficient (μkin) which is measured via differentiating rotating forces during the complete movement of the sensor was determined [29]. According to ASTM D 4032 standard “SDL Atlas Digital Pneumatic Stiffness Tester” was used to measure fabrics’ circular bending rigidity values [30]. TS 5720 EN ISO 6330 used for testing dimensional stability of the fabrics. Unwashed fabrics were marked 15 cm inside from the edges using a 50cm x 50 cm template. This marking process was repeated 3 times on both lengthwise and widthwise directions and after that, fabrics were washed and dried according to the standard. Percentage changes on the dimensions of the fabrics after drying were determined [31]. RESULTS AND DISCUSSION Mean values of bursting strength, pilling resistance, air permeability, surface roughness, circular bending rigidity and dimensional stability of the fabrics with different blending ratios were summarized in Table III. Test results were statistically evaluated with Post-Hoc techniques and in order to determine the calculation method for comparison of the mean values, firstly whether the variances of the

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parameters are equal or not is checked by using “Levene Homogenity Test” For the situation of equal variances “LSD (Least Significant Difference)” test and for unequal situation “Tamhane T2” method was used. The analysis was carried out according to 95% confidence level. Therefore if the p value is less than 0.05, it means that the difference is statistically significant. A multi-comparison test called LSD was performed for pilling resistance (p=0.102), air permeability (p=0.0504), friction coefficient

(p=0.508), dimensional stability in wale direction (p=0.080) and other multi-comparison test called Tamhane T2 was performed for bursting strength (p=0.0002), circular bending rigidity (p=0.002), dimensional stability in course direction (p=0.042). All the statistical analysis was performed on a computer using the SPSS (Statistical Package of Social Science) program. The result (p values) of multiple comparisons of the fabric properties were given in Tables IV-IX.

TABLE III. Test results of the fabrics.

Material

Bursting Strength

(kPa)

Fabric Surface Roughness

(µkinetic)

Air Permeability

(lt/m²/s)

Mean value

Max value

Min value CV% Mean

value Max value

Min value CV% Mean

value Max value

Min value CV%

100%Co 1287 1482 1133 13.9 0.362 0.367 0.355 1.2 162 179 148 8.1 70%Co

30%r-PET 1379 1508 1283 6.9 0.349 0.358 0.338 2.1 141 154 132 6.9

50%Co 50%r-PET 1230 1325 1151 5.2 0.359 0.368 0.348 2.5 156 171 147 5.7

30%Co 70%r-PET 1232 1280 1129 4.9 0.352 0.359 0.346 1.5 184 202 173 6.2

100%r-PET 1279 1363 1168 5.5 0.360 0.365 0.355 1.3 376 398 349 4.7

100%PET 2110 2387 1902 9.4 0.345 0.353 0.338 1.7 560 600 533 4.9 70%PET

30%r-PET 1765 1916 1701 5.0 0.356 0.364 0.353 1.3 404 442 366 7.5

50%PET 50%r-PET 1694 1810 1556 5.4 0.354 0.361 0.348 1.8 291 326 263 8.3

30%PET 70%r-PET 1475 1547 1382 4.5 0.364 0.369 0.357 1.2 325 362 285 8.8

Material

Pilling (Grade)

Circular

Bending Rigidity (Newton)

Shrinkage in wale

direction (%)

Shrinkage in course

direction

(%)

Mean value

Max value

Min value

CV%

Mean value

Max value

Min value

CV% Mean value

Max value

Min value CV% Mean

value Max value

Min value CV%

100%Co 4.0 4.1 3.9 2.4 5.9 6.6 5.4 7.5 11.6 12.5 10 12.4 11.8 12.5 11 6.5

70%Co 30%r-PET 4.3 4.4 4.2 2.3 7.7 8.4 6.6 10.5 5.2 5.5 5 5.6 10.7 11.5 9.5 9.7

50%Co 50%r-PET 4.3 4.7 4.1 7.2 6.7 7.4 5.9 10.4 4.2 5 4 15.7 10.5 11 10 4.8

30%Co 70%r-PET 3.5 3.6 3.4 2.4 5.8 6.5 5.4 7.5 2.8 3 2.5 10.2 6.5 6.5 6.5 0

100% r-PET 2.5 2.8 2.4 8.8 3.7 4.2 3.1 11.0 3.8 4.0 3 15.7 5.2 5.5 5 5.9

100%PET 2.7 3 2.4 11.6 2.4 2.6 2.2 7.5 3.0 3.5 2 18.2 6.8 7.5 5.5 16.9

70%PET 30%r-PET 2.8 3.3 2.5 9.7 3.0 3.2 2.7 6.7 5.8 6.5 5.5 9.9 5.5 6.5 5 15.7

50%PET 50%r-PET 2.8 3.1 2.5 10.5 4.9 5.4 4.1 14.4 2.3 3.0 2.5 12.8 7.0 7.5 6.5 7.1

30%PET 70%r-PET 2.6 2.7 2.4 3.2 3.2 3.4 2.6 10.8 0.8 1.0 0.5 43.3 6.3 7 5.5 12.1

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Bursting Strength Figure 1 shows bursting strength results of the fabrics. Table IV provides the result of multiple comparisons for bursting strength. According to the results 100% PET fabrics have the highest value and the PET/r-PET blended fabrics have higher bursting strength than 100% cotton and r-PET/Co blended fabrics. Differences between r-PET fabrics blended with PET and cotton are statistically significant. As shown in Figure 1, 100% r-PET fabrics have lower bursting strength than 100% PET fabrics. The

increase of r-PET content cause decrease in bursting strength of the PET/r-PET blended fabrics, but this change is not significant as compared with 100% PET fabrics according to Table IV. All of the PET/r-PET blended fabrics have higher bursting strength than 100% r-PET fabrics. This result is mainly because of the higher fiber and yarn strength values of the PET fibers (Table I and Table II) as compared with r-PET fibers and yarns. Moreover, in cotton/r-PET blended fabrics, the amount of the r-PET content have not affected bursting strength of the fabrics.

TABLE IV. The result of multiple comparisons for bursting strength.

100%

Co

70%Co

30%r-PET

50% Co

50%r-PET

30% Co

70%r-PET

100%

r-PET

100%

PET

70% PET

30%r-PET

50% PET

50%r-PET

30% PET

70%r-PET

100%Co ----- 1.000 1.000 1.000 1.000 0.013* 0.067 0.139 0.948

70%Co 30%r-PET

1.000 ----- 0.572 0.577 0.977 0.041* 0.006* 0.025* 0.983

50%Co 50%r-PET

1.000 0.572 ----- 1.000 1.000 0.026* 0.000* 0.001* 0.013*

30%Co 70%r-PET

1.000 0.577 1.000 ----- 1.000 0.028* 0.000* 0.001* 0.011*

100%r-PET 1.000 0.977 1.000 1.000 ----- 0.031* 0.001* 0.002* 0.068*

100%PET 0.013* 0.041* 0.026* 0.028* 0.031* ----- 0.643 0.399 0.099

70%PET 30%r-PET

0.067 0.006* 0.000* 0.000* 0.001* 0.643 ----- 1.000 0.019*

50%PET 50%r-PET 0.139 0.025* 0.001* 0.001* 0.002* 0.399 1.000 ----- 0.103

30%PET 70%r-PET 0.948 0.983 0.013* 0.011* 0.068 0.099 0.019* 0.103 -----

* The mean difference is significant at the 0.05 level

FIGURE 1. Bursting strength results. Abrasion Resistance

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Abrasion resistance test results of the fabrics can be seen in Figure 2. At the lower number of rubs, the weight values of the all synthetic fabrics increased because of the static electricity of the these fibers that causes collecting the fuses from abradant fabric and environment. For all of the fabrics, as the number of rubs increase the mass loss increases. 100% cotton fabrics have the highest mass loss for every rubs whereas the 100% PET fabrics have the lowest values. This result is attributed to the higher tenacity values of the PET fibers than cotton and r-PET fibers. Co/r-PET blended fabrics have the lower mass loss values for each number of rubs than pure cotton

fabrics and as the r-PET ratio increase the mass loss decrease. Results of the fabrics produced from blended yarns revealed that, cotton blends have higher mass loss than PET blends and the result of 100% r-PET fabrics is in between them. But for the higher than 10000 rubs, 100% r-PET fabrics displayed higher tendency to be abraded as compared with Co/r-PET blended fabrics. When the abrasion resistance of the r-PET/PET blended fabrics examined 70% PET / 30% r-PET fabrics have the lowest mass loss comparing to the other blended fabrics up to 17500 rubs and 50% PET / 50% r-PET fabrics have the highest (Figure 2).

FIGURE 2. Abrasion resistance- % mass loss chart.

Pilling Resistance Figure 3 displays the pilling resistance results of the fabrics and Table V presents the result of multiple comparisons for pilling properties. According to test results 100% r-PET fabrics have the lowest pilling degree that means higher pilling tendency and there were no significant differences between 100% r-PET, 100% PET and r-PET/PET fabrics (Table V). This study produced results which corroborate the findings of a great deal of the previous work in this field. The pilling tendency of the fabrics knitted 100% r-PET, 100% PET and r-PET/PET blended fibers are higher than the fabrics produced cotton and blends. It is a well-known fact that the reason of that circular cross section with a smooth surface of the synthetic fibers allows the fiber to come to the surface and

form pills [33] and high tensile strength causes difficulty of the pills do not wear away quickly [32]. The results, as shown in Table V, indicate that the differences between 100% Co and Co / r-PET blended fabrics and between 100% PET and PET / r-PET blended fabrics were found statistically insignificant. The most important finding was that all cotton / r-PET blended fabrics have similar results to 100% Co fabrics and these pilling results are in “merely pilling” category. It was noticed that the lower blending ratio of the r-PET fibers to the yarn does not cause any significant differences on the pilling degree of fabrics. But the ratio is increased (%70) the pilling tendency of the fabric increases for both cotton and polyester fabrics.

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TABLE V. The result of multiple comparisons for pilling properties.

100%

Co

70%Co

30%r-PET

50% Co

50%r-PET

30% Co

70%r-PET

100%

r-PET

100%

PET

70% PET

30%r-PET

50% PET

50%r-PET

30% PET

70%r-PET

100%Co ----- 0.162 0.091 0.026* 0.000* 0.000* 0.000* 0.000* 0.000* 70%Co

30%r-PET 0.162 ----- 0.749 0.001* 0.000* 0.000* 0.000* 0.000* 0.000*

50%Co 50%r-PET

0.091 0.749 ----- 0.001* 0.000* 0.000* 0.000* 0.000* 0.000*

30%Co 70%r-PET

0.026* 0.001* 0.001* ----- 0.000* 0.002* 0.006* 0.006* 0.000*

100%r-PET 0.000* 0.000* 0.000* 0.000* ----- 0.271 0.122 0.122 0.873

100%PET 0.000* 0.000* 0.000* 0.002* 0.271 ----- 0.632 0.632 0.343

70%PET 30%r-PET 0.000* 0.000* 0.000* 0.006* 0.122 0.632 ----- 1.000 0.162

50%PET 50%r-PET 0.000* 0.000* 0.000* 0.006* 0.122 0.632 1.000 ----- 0.162

30%PET 70%r-PET 0.000* 0.000* 0.000* 0.000* 0.873 0.343 0.162 0.162 -----

* The mean difference is significant at the 0.05 level

FIGURE 3. Pilling Resistance Results. Air Permeability As the Figure 4 and Table VI examined, it was noticed that 100% PET fabrics displayed the highest air permeability result among the nine different fabrics. Because of the similar fabric thickness and porosity values of the PET fabrics with the others, this result can be attributed to the lower cover factor of the PET fabrics which is caused by lower hairiness and yarn

diameter values of the 100% PET yarns (Table II). Air permeability differences between 100% cotton and cotton/r-PET blended fabrics are statically insignificant (Table VI). But it was explored that increased r-PET ratio caused increased air permeability. Cotton blended yarns have higher hairiness and the fabrics have slightly higher thickness values, so fabrics produced from them have lower air permeability than PET blended fabrics.

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TABLE VI. The result of multiple comparisons for air permeability.

100%

Co

70%Co

30%r-PET

50% Co

50%r-PET

30% Co

70%r-PET

100%

r-PET

100%

PET

70% PET

30%r-PET

50% PET

50%r-PET

30% PET

70%r-PET

100%Co ----- 0.122 0.640 0.112 0.000* 0.000* 0.000* 0.000* 0.000* 70%Co

30%r-PET 0.122 ----- 0.274 0.003* 0.000* 0.000* 0.000* 0.000* 0.000*

50%Co 50%r-PET

0.640 0.274 ----- 0.043* 0.000* 0.000* 0.000* 0.000* 0.000*

30%Co 70%r-PET

0.112 0.003* 0.043* ----- 0.000* 0.000* 0.000* 0.000* 0.000*

100%r-PET 0.000* 0.000* 0.000* 0.000* ----- 0.000* 0.036* 0.000* 0.000*

100%PET 0.000* 0.000* 0.000* 0.000* 0.000* ----- 0.000* 0.000* 0.000* 70%PET

30%r-PET 0.000* 0.000* 0.000* 0.000* 0.036* 0.000* ----- 0.000* 0.000*

50%PET 50%r-PET 0.000* 0.000* 0.000* 0.000* 0.000* 0.000* 0.000* ----- 0.015*

30%PET 70%r-PET 0.000* 0.000* 0.000* 0.000* 0.000* 0.000* 0.000* 0.015* -----

* The mean difference is significant at the 0.05 level

FIGURE 4. Air permeability results.

Fabric Surface Friction Fabric surface friction coefficient results of the fabrics can be observed in Figure 5. It can be seen from Table VII and Figure 5 that difference between the groups of cotton / r-PET blended fabrics and PET / r-PET blended fabrics have been found statically insignificant. In terms of surface friction coefficient, there is no significant difference between PET / r-PET blends and 100% r-PET fabrics. r-PET fiber presence in PET / r-PET

fabrics influenced surface friction properties negatively as compared with 100% PET fabrics (Figure 5). This result is related to the higher yarn hairiness values of the r-PET blended yarns that cause to increase protruding fibers from yarn and fabric surface. The 100% cotton fabrics gave the highest kinetic friction coefficient among the r-PET/cotton blended fabrics. But it was found that the presence of the r-PET fibers in the structure caused lower friction values.

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TABLE VII. The result of multiple comparisons for fabric surface friction.

100%

Co

70%Co

30%r-PET

50% Co

50%r-PET

30% Co

70%r-PET

100%

r-PET

100%

PET

70% PET

30%r-PET

50% PET

50%r-PET

30% PET

70%r-PET

100%Co ----- 0.001* 0.411 0.017* 0.674 0.000* 0.137 0.057 0.519 70%Co

30%r-PET 0.001* ----- 0.011* 0.331 0.004* 0.377 0.055 0.135 0.000*

50%Co 50%r-PET

0.411 0.011* ----- 0.101 0.686 0.001* 0.496 0.263 0.147

30%Co 70%r-PET

0.017* 0.331 0.101 ----- 0.044* 0.068 0.326 0.589 0.003*

100%r-PET 0.674 0.004* 0.686 0.044* ----- 0.000* 0.280 0.131 0.290

100%PET 0.000* 0.377 0.001* 0.068 0.000* ----- 0.007* 0.020* 0.000*

70%PET 30%r-PET 0.137 0.055 0.496 0.326 0.280 0.007* ----- 0.655 0.037*

50%PET 50%r-PET 0.057 0.135 0.263 0.589 0.131 0.020* 0.655 ----- 0.013*

30%PET 70%r-PET 0.519 0.000* 0.147 0.003* 0.290 0.000* 0.037* 0.013* -----

* The mean difference is significant at the 0.05 level

FIGURE 5. Fabric surface friction coefficient results. Circular Bending Rigidity As it can be seen Figure 6, PET and PET blends tend to have lower bending rigidity than cotton and cotton blended fabrics. The present findings seem to be consistent with other research which found that cotton fibers have higher flexural rigidity than PET fibers [34]. From the figures it is apparent that 100% PET and 100% r-PET fabrics have significantly different bending rigidity results. The r-PET blended fabrics have higher bending rigidity than 100% PET fabrics. It was observed that there were no significant differences between PET / r-PET blended fabrics and 100% r-PET fabrics.

Furthermore, 100% Co and cotton / r-PET blends have statistically insignificant difference in terms of bending rigidity results (Figure 6, Table VIII). Cotton / r-PET blends have higher bending rigidity results than 100% r-PET fabrics. Because of the lower bending rigidity of the r-PET fibers than cotton fibers, the increase of the r-PET fiber content cause decrease in bending rigidity for cotton / r-PET blended fabrics.

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TABLE VIII. The result of multiple comparisons for circular bending rigidity

100%

Co

70%Co

30%r-PET

50% Co

50%r-PET

30% Co

70%r-PET

100%

r-PET

100%

PET

70% PET

30%r-PET

50% PET

50%r-PET

30% PET

70%r-PET

100%Co ----- 0.397 0.898 1.000 0.002* 0.000* 0.001* 0.875 0.001*

70%Co 30%r-PET

0.397 ----- 0.995 0.328 0.013* 0.008* 0.013* 0.060 0.004*

50%Co 50%r-PET

0.898 0.995 ----- 0.765 0.004* 0.003* 0.005* 0.197 0.001*

30%Co 70%r-PET

1.000 0.328 0.765 ----- 0.002* 0.000* 0.001* 0.949 0.001*

100%r-PET 0.002* 0.013* 0.004* 0.002* ----- 0.028* 0.400 0.717 0.989

100%PET 0.000* 0.008* 0.003* 0.000* 0.028* ----- 0.027* 0.075 0.557

70%PET 30%r-PET 0.001* 0.013* 0.005* 0.001* 0.400 0.027* ----- 0.213 1.000

50%PET 50%r-PET 0.875 0.060 0.197 0.949 0.717 0.075 0.213 ----- 0.236

30%PET 70%r-PET 0.001* 0.004* 0.001* 0.001* 0.989 0.557 1.000 0.236 -----

* The mean difference is significant at the 0.05 level

FIGURE 6. Circular bending rigidity test results.

Dimensional Stability Dimensional stability was investigated as % shrinkage in both course and wale directions. Lowest shrinkage percent in wale direction belongs to 30% PET / 70% r-PET fabrics and the highest value of this parameter belongs to 100% cotton fabrics as expected. Difference between 100% r-PET and 100% PET fabrics was found statistically insignificant (Table IX).

The test results and statistical evaluations revealed that as the amount of r-PET fibers increase in the fabric, the wale direction dimensional change of the fabrics decrease for cotton/r-PET blended fabrics and it is statistically significant. The differences between the 100% r-PET and r-PET-cotton blended fabrics were found statistically insignificant (Table IX).

Journal of Engineered Fibers and Fabrics 57 http://www.jeffjournal.org Volume 10, Issue 2 – 2015

In course direction, 100% cotton fabrics displayed the highest shrinkage percent same as wale direction. But 100% r-PET fabrics have lower shrinkage values than 100% PET fabrics and this fabric type have the lowest value among the all fabrics. The differences between 100% r-PET and cotton / r-PET blended fabrics were found statistically insignificant. Also,

similarly to the wale direction results, it was found that as the amount of r-PET fibers increase, the dimensional change of the fabrics decreased for Co/r-PET blended fabrics. The differences between 100% r-PET and 100% PET fabrics and between 100% r-PET and PET / r-PET blended fabrics were found statistically insignificant (Table IX).

TABLE IX. The result of multiple comparisons for dimensional stability in wale and course direction.

100%

Co

70%Co

30%r-PET

50% Co

50%r-PET

30% Co

70%r-PET

100%

r-PET

100%

PET

70% PET

30%r-

PET

50% PET

50%r-PET

30% PET

70%r-

PET

100%Co ----- w:0.000*

c:1.000

w:0.000*

c:0.939

w:0.000*

c:0.217

w:0.000*

c:0.059

w:0.000*

c:0.174

w:0.000*

c:0.026*

w:0.000*

c:0.054

w:0.000*

c:0.032*

70%Co 30%r-PET

w:0.000*

c:1.000 ----- w:0.164

c:1.000

w:0.003*

c:0.520

w:0.069

c:0.250

w: 0.006*

c:0.381

w:0.346

c:0.104

w:0.001*

c:0.380

w:0.000*

c:0.185

50%Co 50%r-PET

w:0.000*

c:0.939

w:0.164

c:1.000 ----- w:0.069

c:0.170

w:0.635

c:0.013*

w:0.108

c:0.496

w:0.026*

c:0.087

w:0.016*

c:0.036*

w:0.000*

c:0.087

30%Co 70%r-PET

w:0.000*

c:0.217

w:0.003*

c:0.520

w:0.069

c:0.170 ----- w:0.164

c:0.425

w:0.812

c: 1.000

w:0.000*

c:0.999

w:0.478

c:1.000

w:0.010*

c:1.000

100%r-PET

w:0.000*

c:0.059

w:0.069

c:0.250

w:0.635

c:0.013*

w:0.164

c:0.425 -----

w:0.242

c: 0.991

w:0.010*

c:1.000

w:0.043*

c:0.303

w:0.000*

c: 0.981

100%PET w:0.000*

c:0.174

w: 0.006*

c:0.381

w:0.108

c:0.496

w:0.812

c: 1.000

w:0.242

c: 0.991 ----- w:0.001*

c:1.000

w:0.346

c:1.000

w:0.000*

c:1.000

70%PET 30%r-PET

w:0.000*

c:0.026*

w:0.346

c:0.104

w:0.026*

c:0.087

w:0.000*

c:0.999

w:0.010*

c:1.000

w:0.001*

c:1.000 -----

w:0.000*

c:0.940 w:0.000*

c:1.000

50%PET 50%r-PET

w:0.000*

c:0.054

w:0.001*

c:0.380

w:0.016*

c:0.036*

w:0.478

c:1.000

w:0.043*

c:0.303

w:0.346

c:1.000

w:0.000*

c:0.940 -----

w:0.043*

c:1.000

30%PET 70%r-PET

w:0.000*

c:0.032*

w:0.000*

c:0.185

w:0.000*

c:0.087

w:0.010*

c:1.000

w:0.000*

c: 0.981

w:0.000*

c:1.000

w:0.000*

c:1.000

w:0.043*

c:1.000 -----

* The mean difference is significant at the 0.05 level w: wale direction, c: course direction

Journal of Engineered Fibers and Fabrics 58 http://www.jeffjournal.org Volume 10, Issue 2 – 2015

FIGURE 7. % Shrinkage results in wale direction.

FIGURE 8. % Shrinkage results in course direction

CONCLUSION Important data have been obtained in this study which was focused on r-PET fibers used in textile and apparel industry. The arguments given above prove that fabrics produced with r-PET fibers have not the same properties as well as the fabrics produced with PET fibers. However, these fibers can

be blended with primary raw material (especially cotton) without hardly noticeable changes in quality for textile and apparel industry. For example, adding of % 30 r-PET fibers to the cotton fibers, higher pilling degree and bursting strength can be obtained. Instead of using PET fibers, r-PET fibers can be

Journal of Engineered Fibers and Fabrics 59 http://www.jeffjournal.org Volume 10, Issue 2 – 2015

blended in small amounts without compromising fabrics performance. Significant point here is choosing suitable r-PET ratio in the fabric according to usage area. Furthermore, starting from the results of this paper, producers may gain more advantage from r-PET fiber with a blending at blow-room in place of draw-frame blending. We feel that our study serves as a window to an academic understanding of the r-PET blended fabrics. Nowadays, r-PET fiber have lower price by 20% compared to other fibers (Co and PET) for the same physical characters. It is clear that cost advantage and being ecologically friendly of the fiber is impetus for increasing r-PET fiber consumption. Improvements in PET bottle recycling technology, increase in quality of the recycled polymer because of the waste pureness and performance of cleaning processes will enable high quality r-PET fiber production and also “high quality” products in the future. REFERENCES [1] Sevencan, F and Vaizoglu, S, ”Pet ve Geri

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AUTHORS’ ADDRESSES Abdurrahman Telli Cukurova University Department of Textile Engineering Adana 01330 TURKEY Nilgün Özdil Ege University Department of Textile Engineering TURKEY