Suitability of Recycled Polyester in Sportswear and Apparel Application

Suitability of Recycled Polyester in Sportswear and Apparel Application

Shantanu Rajendra Mandhane 
Department of Man-Made Textile Technology
D.K.T.E Society’s Textile and Engineering Institute, Ichalkaranji
Email: mandhaneshantanu5@gmail.com

ABSTRACT

Understanding the suitability of recycled polyester filament yarn in sportswear and apparel application in place of virgin polyester. This study aims to analyse and compare the properties of both recycled polyester and virgin polyester yarns and the fabrics made from the particular yarns. The investigation encompasses several key aspects such as moisture vapor transfer rate of the fabrics, air permeability, wicking, stitch density and pilling of the fabrics.

Two different fabrics are produced: one from recycled polyester and other from virgin polyester. The fabric is produced on knitting machine which is usually used to produce sportswear t-shirts fabrics.

Chapter 1

INTRODUCTION

1.1 General

The growing interest in gymnastics and sports has led to a growing demand for sportswear and active wear. These fabrics are designed to enhance comfort and performance during physical activities, with properties such as light weight, fast drying, stretchability, durability, breathability, and elasticity. Sports fabrics can be water-resistant, spandex-based, or thermal for warmth and cooling. Activewear, on the other hand, is clothing that provides style, comfort, and function, made from sustainable materials. These fabrics must have functional, aesthetic, and comfort properties, such as optimum heat and moisture management, low water absorption, quick drying, pleasant to skin, soft, non-abrasive, dimensionally stable, durable, lightweight, easy-care, and smart fabric structures. Sportswear, or activewear, includes clothing for sports or physical exercise, such as tracksuits, shorts, T-shirts, and Polo shirts. Specialized garments include swimsuits, wet suits, ski suits, and leotards. Sports footwear includes trainers, football boots, riding boots, bikinis, and crop tops. The type of fabric required depends on the intensity of the exercise and the activity. Sports apparel is essential for performing physical exercises like walking, jogging, yoga, and running. It boosts confidence, keeps you fresh, prevents injuries, and promotes recovery. These apparels absorb body sweat, support body movements, boost confidence, prevent injuries, and promote recovery. Recycled polyester, also known as RPET(Recycled Poly Ethylene Terephthalate), is a popular textile material in the fashion world. It is primarily produced from mechanically recycled plastic water battles or chemical recycling, where waste of synthetic products is cleaned and broken down to return them to their original monomers. This approach not only improves performance but also reduces the risk of injury.

1.2 Objectives

1. To study the yarn properties of virgin polyester and recycled polyester.
2. To manufacture knitwear by using recycled and virgin polyester yarn.
3. To evaluate the properties of fabrics manufactured by virgin and recycled polyester

1.3 Scope

Sportswear, or activewear, is clothing and footwear designed for sports and physical exercise, offering practicality, comfort, and safety for athletes. It can be worn as casual fashion or as high-performance sportswear. The demand for functional and stylish sportswear has increased due to growing awareness of fitness and health. Advances in textile technology have led to the development of moisture-wicking, breathable, and high-performance fabrics. The rise of wearable devices like fitness trackers and smartwatches has also increased the demand for sportswear.

Recycled polyester is a sustainable alternative to traditional polyester, reducing greenhouse gas emissions, energy consumption, and water conservation. It reduces the need for virgin petrochemical resources, reduces reliance on fossil fuels, diverts plastic waste from landfills and oceans, and consumes less energy compared to virgin polyester. The process of recycling plastic into polyester emits fewer greenhouse gases and supports a circular economy by reusing materials, reducing waste, and promoting sustainability. Governments and organizations are encouraging the use of recycled materials through policies and regulations, and many companies are adopting sustainability goals and commitments, including using recycled polyester in their products.

Chapter 2

LITERATURE REVIEW

2.1 General:

Senthilkumar[1] studies the thermal comfort characteristics of layered knitted fabric for sportswear were compared in the perspective of thermal conductivity, air permeability, water vapour permeability, wicking ability, moisture absorbency, and drying rate. The thermal conductivity and air permeability of bi-layer knitted fabric with one tuck point Type 4 are greatly influenced by thickness and stitch density of the fabric. Water vapour permeability of the bi-layer fabric increases with decrease of thickness and presence of openness of the fabric. Bi-layer fabric Type 4 with lower stitch density and lowest thickness showed higher amount of water take-up compared to other fabrics. It is observed that, moisture absorbency of bi-layer knitted structure increases with increase of stitch density and tightness factor. The frequency of tuck stitch also affects the moisture absorbency of bi-layer knitted fabric.

Hossein Roghani-Mamaqani[2] studies the suitable selection of raw material, fiber morphology, yarn, fabric structure, type of finish, and garment pattern will provide the required functionality. Researchers have engineered advanced polymers, fibers, yarns, and fabrics to meet customer demands and achieved the required performance characteristics. The performance of the sports athlete is directly associated with the proper moisture management property, air permeability property, and thermal insulation properties of the garment, which was worn by the player during sports activity To produce sportswear exhibiting excellent thermal insulation properties, hollow structured thermo-regulated fibers are used. For the summer sportswear exhibiting moisture management properties, different types of functional fibers, yarns, blends of fibers, fabrics, and coatings were used in the structure of textile materials.

Surya Nasrin[3] respaces on fabric drying and how future research can improve the quality of active sportswear clothing by providing comfort to the wearer. Fabric drying performance and moisture management are two important aspects of active sportswear clothing because they help to keep the wearer dry and comfortable during sports-related activities. The literature reviewed in this article has offered a complete overview of the existing knowledge about fabric drying and moisture management. Current state of research on the drying performance of active sportswear fabrics. It also highlights the importance of moisture management in textile fabrics, as it can affect the comfort, functionality, and durability of the fabrics.

ANBUMANI[4] studies the comparative analysis on DER of SBPC and SCCS fabrics was made. It was found that the SBPC fabric has higher DER than that of SCCS fabric for both wale wise and course wise directions at 95% confidence level. This is mainly due to the residual energy of the elastane un raveled from these fabrics. But, the stress values of these fabrics have no significant effect. So, it is concluded that the SBPC fabric is preferable than SCCS fabric with respect to elastic recovery characteristics due to its quick recovery which enhances the power of the performance.

Jefferson M Souza[5] characterizes the functional Single Jersey Knitted Fabrics using non conventional yarns for sportswear the characteristic of the knitted fabrics used in this study are very similar in terms of yarn linear density, course density and wale density, thickness and loop length, the differences observed during the characterization study were mainly attributed to the fabric areal mass, fibre morphology and imbibed materials and not to the fabric structure. All the polyester fabrics in this study have similar thermal conductivity with the exception of the Holofiber yarn probably due to the higher areal mass of this fabric. The knitted fabrics made with Airclo and Finecool yarns display the highest values of thermal resistance and diffusivity and the lowest thermal absorptivity and heat flow because of higher amount of air in the fabric structure that slow the heat transfer process.

Premalatha[6] researches cotton, micro denier filament polyester yarn, spun polyester yarn, and polypropylene have been chosen to enhance the thermal comfort properties of the tri-layer knitted fabrics developed for the purpose of active sportswear. The results evidently showed that the tri-layer knitted fabrics of MDP/MDP/CC combination show exceptionally appreciable thermal comfort properties due to their structural factors such as filamentous nature, lesser thickness, low areal density, and lesser bulkiness. The effect of fiber chosen also plays a major role with respect to the thermal comfort properties of tri-layer fabrics developed. The fabric exhibits exceptionally strong functional qualities, such as moisture absorption, wherein the moisture is absorbed through the body contacting layer of micro denier polyester and it excellently penetrated the water through the middle layer of micro denier polyester, and it evaporates the absorbed moisture to the environment well through the outer layer of cotton, making the sample more suitable for sporting activities.

Elena Onofrei[7] presents a quantitative study of various comfort related properties (thermal and moisture management properties) carried out on different knitted fabric structures containing Outlast and Coolmax yarns, and aiming at the selection the most adequate fabric for sportswear applications. Wicking ability is mainly determined by fabric structure and the drying ability by raw material properties. Fabrics must have high air permeability and low thermal resistance. Fabrics with structures 1 (single jersey), 2 (alternate double oneneedle floats) and 7 (one-needle floats with ribbed surface) fulfill these requirements.

Seval Uyanik[8] studies the factors affecting the bursting strength of the fabrics knitted by blend yarns at different yarn numbers containing rPET, viscose, and virgin PET fibers study show that the most effective factors on bursting strength are the yarn count and tenacity. The decrease in yarn count, which means coarsening from fine to coarse yarns, and the increase in yarn tenacity increases knitted fabrics’ bursting strength, as expectedly.

Damayanti and Ho Shing Wu[9] presents what are the challenges to recycling PET not only from the process but also in the type of PET waste. The water, coloring, acetaldehyde and heavy metal contamination are affected on the recycling process of PET. Furthermore, the degradation of PET had been developing for several methods and technologies, for instance, mechanical and chemical recycling. For mechanical recycling, some recycling materials are downcycling material or limited with recycle time.

Laurianne Viora[10] states the purpose of this comparative study between semi-crystalline virgin and recycled PET was to understand the link between physico-chemical properties, morphological description of crystalline entities, and mechanical behaviour. MFI measurements of the two PET confirm these assumptions with recycled PET having a higher MFI value than the virgin PET, testifying of a less viscous rheological behaviour due to smaller chain lengths. The post-condensation at solid state that is commonly used after the mechanical recycling process might have participated to compensate the effects of degradation that can develop during the re-processing of the resin. To go further in crystallization process understanding, thermal properties using calorimetry analysis have comforted the fact that recycled PET presents significantly faster crystallization kinetics than virgin PET. Regarding the crystal melting of rPET, it takes place for higher temperatures compared to vPET.

Fresia Alvarado Chacon[11] state the influence of recycled content and type of rPET on the particle contamination, IV, optical properties, and ESC of PET bottles has been systematically studied. The particle contamination increases with the recycled content.Colour parameters L* and b* were found to linearly correlate with the recycled content, but the slope of the correlation was different for different types of rPET. The bottles become greyer and yellower with increasing levels of recycled content.

ESİN SARIOĞLU[12] studies v-PET and r-PET yarn properties such as tensile strength, elongation, IPI and hairiness in different spinning systems were investigated. If the fiber type is examined, v-PET yarns have higher tensile strength and lower hairiness values in comparison to r-PET yarns. On the other hand, r-PET yarns have higher elongation and lower IPI values than v-PET yarns.

Tsegaye Sh. Lemmi[13] studies of the thermal aging parameters significantly influence the yarn’s mechanical and surface structural properties when the yarn is subjected to an aging temperature above 220 °C. Additionally, the tenacity and elongation of the yarns are inversely proportional as the aging temperature rises. Further experiments are also in progress related to the effect of thermal aging on the internal structure of high tenacity polyester fibers and on fabrics made from HT polyester yarns for conveyor belt reinforcement purposes.

Mounir Hassan[14] found that 100% polyester fibers showed better physiological responses and performance in athletes compared to other fabric types. This was due to better moisture management, with 68% relative water vapor permeability and lower thermal conductivity. This increased cardiorespiratory fitness and performance. The study also revealed a high correlation between fabric thickness, porosity, air permeability, water vapor permeability, fabric thermal properties, and athletes’ physiological responses. However, the 100% polyester fiber sample exhibited shortcomings in moisture management, such as perspiration being absorbed close to the body, causing post-exercise chill.

Awadhesh Kumar Choudhary[15] discusses effect of independent variables—fibre content and fabric structure—and their interaction is evaluated through moisture management properties and supporting factors like thickness of fabric, porosity and contact angle. All the parameters are significantly affected due to both of the independent variables but little due to their interaction. The overall results indicate towards the fact that moisture management properties are directly proportional to the porosity, i.e. plain single jersey fabric being the most porous structure shows the best results of moisture management among three fabric structures. Also, micro-polyester is better than other two due to more capillary channels available to transport the liquid quickly from the top surface to the bottom surface. On the go, for the sportswear clothing the fabric with good porosity, i.e. lesser areal density or thickness capable of quick moisture transport using micro-polyester single jersey, is projected to prove competent with other alternatives.

Amna Siddique[16] investigates moisture management test (MMT) which evaluates hydro-mobility in fabric. A higher softener concentration impairs fabric moisture management performance due to pore-blocking. Non-ionic softeners like Siligen SIH have minimal dependence on moisture management, but other softners can significantly increase or decrease OMMC values. Solusoft MW with 20 g/L and 15 g/L concentrations is suitable for outdoor activewear and sportswear applications. The selection of an appropriate softener and its concentration are critical for determining the final OMMC of terry fabrics. There is no linear relationship between softener concentration and OMMC, and fabric construction and quality parameters can alter OMMC.

Ivana Salopek Cubric[17] investigates single tuck structure, made of wool, PAN, or wool/PAN blend, offers the highest heat resistance, medium water vapour resistance, and air permeability. This makes it suitable for sportswear, après-sports, and casual wear due to its comfort. However, it can cause pilling and skewness. The double plain knitted structure has the second highest heat resistance and water vapour resistance, making it suitable for outdoor use. The single plain structure has the lowest heat resistance and water vapour resistance, making it ideal for active training. Combining single plain and single tuck structures increases air permeability, making it suitable for active training and rapid body heat loss. The most air permeable knitted structures were made from 100% PAN, which could affect comfort. PA filament yarn, which is stretchy and has high tenacity, is the best suited for sportswear in hot indoor or outdoor climates.

T Sathish Kumar[18] researches findings concluded that the plated interlock knitted fabrics with different raw material combinations of eri silk with bamboo and tencel in top and bottom layers were developed. Fabrics plated with Eri silk in the top layer with either bamboo and tencel in the bottom layer were moisture management fabrics, which showed the potential of liquid moisture transfer to bottom layer keeping active dry. Though both fabrics can be recommended for next-to-skin applications, summer wear, active wear, however the plated interlock knitted fabricseri silk (14.3 tex) with bamboo (14.8 tex) and tencel (14.8 tex) fabrics were found on account of superior moisture management properties in the top layer would be more effective in providing dry feel next to skin. When compare to bamboo combination eri silk/micro denier polyester/tencel fabrics are excellent accumulative one way transport index and excellent overall moisture management capacity observed reason high absorbency and more smooth surface structure present in tencel combination. Hence, seems preferred choice of plated interlock knitted fabrics for the new design/development of products in this field of textiles involves technological approach. The plated interlock knit fabric provides exclusive comfort to evolve rapidly.

Samyuktha V[19] studies the properties of fiber and some physical properties of fabric produced from recycled polyester(r-PET) and recycled cotton(r-Co) were investigated. The results show the fibre strength of recycled cotton is reduced by 4.0% compared to virgin cotton and fibre elongation got reduced by 36% compared to virgin cotton. Similarly for recycled polyester the strength reduction is 10.06% compared to virgin polyester and the reduction in elongation for recycled polyester is 18% compared to virgin polyester. The basic physical properties of recycled polyester(r-PET) and recycled cotton(r-Co) fabrics are analysed and reported. The results indicate that 100% recycled polyester and 100% recycled cotton are having the maximum stitch density. Similarly in case of blends the blend having higher recycled polyester content has higher stitch density followed by 50/50 blend of recycled polyester/recycled cotton and as the content of recycled polyester reduces the stitch density also gets reduced. The corresponding loop shape factor and tightness factors also reported in this paper.

Chapter 3

PLAN OF WORK

3.1 Materials

Polyester filament textured yarn of 150/48 denier and recycled polyester filament textured yarn of 150/48 denier.

3.2 Plan of work

Polyester yarn 150 Denier

↓

Testing Of Yarn

↓

Winding of yarn for knitting

↓

Production of knitted fabric

↓

Testing of knitted fabric properties

&

Recycled polyester yarn 150 Denier

↓

Testing Of Yarn

↓

Winding of yarn for knitting

↓

Production of knitted fabric

↓

Testing of knitted fabric properties

3.3 Methodology

Procurement of both recycled and virgin polyester filament yarn from the spinning mills. After procurement of yarn conducting the appropriate test for the yarn. Further wind the yarn on to bobbins and then knit the suitable double jersey fabric. Test the fabric for different abrasion and moisture properties and compare the results of both recycled and virgin polyester produced fabrics to determine the suitability of recycled polyester in sportswear application.

3.3.1 Sourcing of raw material:

We have acquired the different yarn from following

1. 100% Recycles polyester yarn – Vasupujya Filaments, Silvassa
2. 100 % Virgin polyester yarn – Desai Textile, Ichalkaranj

3.3.2 Testing of material:

a) Yarn Count Testing:

• Instrument: British Wrap Reel and Weighing Balance
• Specimen Size: 120 yards
• Procedure: The conditioned package of yarn to be tested is taken. A lea of 120 yard is prepared using a Wrap reel having circumference of 1.5 yard. The lea is then weighed and Denier of the yarn for staple spun yarn. 5 leas form each package are taken and average count is measured.
• Location: D.K.T.E’s Textile Physics lab

  

…………….Weight in gram X 9000
Denier = —————————————-
…………………Length in meters

b) Tensile and Elongation:

• Instrument: KMI Tensile tester
• Procedure: The sample from well-conditioned package of yarn is taken. The yarn is clamped in jaws with specified specimen length. The machine is started to move the lower jaw and stretch the yarn. The forced present in grams and elongation in yarn at breaking point is noted. 5 such samples from each package are taken and average breaking force and elongation is calculated.
• Location: D.K.T.E’s Textile Physics lab

  

c) Hot Water Shrinkage:

• Procedure: The conditioned package of yarn to be tested is taken. A lea of 10 strands of yarn using a wrap reel and then measure its length with pre tension of 0.2. Then place the lea of yarn into the hot boiling water having temperature of 100º C for 30 minutes. After 30 minutes remove the yarn measure its length with same pre tension of 0.2. Lastly calculate the shrinkage by measurements of length before and after the hot water insertion.
• Location: D.K.T.E’s Textile Man Made Lab

  

——————————–Initial length – Final length X 100
Hot Water Shrinkage % = ————————————————
——————————————Initial length

d) Hot Air Shrinkage:

• Procedure: The conditioned package of yarn to be tested is taken. A lea of 10 strands of yarn using a wrap reel and then measure its length with pre tension of 0.2. Then place the lea of yarn into the hot air oven having temperature of 100º C for 30 minutes. After 30 minutes remove the yarn measure its length with same pre tension of 0.2. Lastly calculate the shrinkage by measurements of length before and after the hot water insertion.
• Location: D.K.T.E’s Textile Man Made Lab

  

…………………………………Initial length – Final length X 100
Hot Air Shrinkage % = ——————————————————–
…………………………………………….Initial length

3.3.3 Winding of yarn for knitting:

After testing the raw material, the 5 kg package of yarn has to be converted into small cones of yarn as per number of feeders in knitting machine; in this case we converted 1- 5 kg of bobbin into 60 bobbins of 83 gm for both recycled as well as virgin polyester.

3.3.4 Knitting of fabric:

a) Cleaning and maintenance of knitting machine:

Before we start producing the fabric we have to check all the machine parts like cams, needles, oiling of the machine parts, and other machine parameters. Then cleaning and preventive maintenance of all the parts of machine has to be done and lastly we have to make sure each and every needle is in working condition and not a lot of wear of the needles have taken place if so the change of needles is required.

b) Selection of design:

The selection of design was done by referring research paper and latest sportswear fabric manufactured in the market. The main requirement of sportswear fabric is it should be more breathable in mature, is property can be obtained by following design.

This above design of knit and miss can provide us with enough strength as well as required breathability in the fabric.

c) Setting of cam design on the knitting machine:

Setting of new cam design on the machine firstly we have to remove all the cams for dial as well as cylinder. Then start fitting the cam according to our design one by one. While setting up the cams on the cylinder one by one the dial is frequently adjusted for proper fitting of cams on the needle.

The cam setting can also be done by an alternating method which is remove one set of needles of cam and change the subsequent cams ahead of the removed set to ensure the cams are fluently passing through the cams. This method is faster and we have used this method.

To remove and replace the cam setting with the new design it took is 3 days as the process is very time consuming and we constantly have to check on needles as they are very brittle and very costly.

d) Checking the design after cam setting:

After completion of the cam setting we check the design with the excess yarn which we have left to ensure the design is proper or not and fluent working of needles in the cam.

e) Creeling of cones:

The bobbins of the yarn form winding are fitted onto the designated creel holder, in this case as there are 60 feeder in the machine we have 60 creel holder (one for each feeder). All the 60 bobbins are placed one by one onto the creel holders and pass passed through suction pipe onto the feeder.

We did this process for recycled polyester 60 bobbing and virgin polyester 60 bobbins separately as we have to produce two different samples.

3.3.5 Production of fabric:

After completion of cleaning, setting up cam, checking design and creeling of the cones then we final check the tension of the yarn we start the production of fabric. The fabric is produced on “Pailung Double jersey circular knitting machine” in the D.K.T.E’s Textile weaving workshop. We produced 2 different samples, first we set up for the production of 100% recycled polyester fabric and produce 10 meters of the fabric. Then we replace the recycled polyester bobbins with 100% virgin polyester bobbins and produce 10 meters of fabric.

Pailung Circular Knitting Machine

• Type : Inter – Rib
• Model : PL-XR2B/CE
• Cylinder Diameter : 30 inches
• Gauge : E-18,24
• Speed : Max – 30 rpm
• Power : 7.5 HP
• Number of feeders : 60
• Oiling : Meminger, Pulsonic

3.3.6 Fabric Testing:

a) Course per inch:
Courses are the loops across the width of the fabric and is measured in courses per inch. It determines the length of the fabric.

b) Wales per inch:
Wales are the loops across the vertical direction of the fabric and is measured in wales per inch.

c) Stitch Density:
Stitch density is the number of stitches per unit area, obtained by multiplying the number of courses per inch by the number of wales per inch.

d) Stitch Length:
The length of yarn required to produce a complete knitted loop is known as stitch length or loop length. Stitch length is a length of yarn which includes the needle loop and half the sinker loop on either side of it. Generally, the larger the stitch length, the more extensible and lighter the fabric and the poorer the cover and bursting strength.

e) GSM:
It is used to determine accurate weight in grams per square meter of the fabric. For calculating GSM a GSM cutter is used. It influences other fabric properties such as thickness, flexural rigidity, bending rigidity, drape, air permeability and thermal properties. For example, the lighter the fabric, the lower its bending rigidity.

f) Thickness:
Thickness of the fabric is measured by placing the fabric in between two parallel plates where the upper plate has known pressure applied and maintained. Fabric thickness also affects the level to which air is permeable in materials, the moisture absorbency and the abrasion resistance. Fabric thickness also determines the material’s stiffness and the extent to which the fabric can be draped or confirm into making specific kind of product.

g) Pilling:
Abrasion resistance is the ability of a fabric to resist surface wear caused by flat rubbing contact with another material. Pilling is the suitable abrasion resistance test applicable in this case.

h) Wicking:
The vertical wicking test measures how well fabric absorbs and transports moisture. In this test a pre marked fabric sample is dipped in a water in order to measure how well it moves moisture from its source, up and through the fabric. It helps to determine whether a fabric will move moisture like sweat away from the wearer.

i) Air Permeability:
Air Permeability is the volume of air in cubic cm passed through 1 sq. cm of fabric in 1 second under the pressure head of 1 cm of water. This parameter influences the thermal comfort properties of fabrics to a large extent. It is generally accepted that the air permeability of a fabric depends on its air porosity, which in turn influences its openness

j) Moisture vapor transfer rate:
It is the amount of water vapour that passes through a fabric over a specific period of time. It is also known as water vapor transmission rate. It helps us to control moisture in the fabric.

Chapter 4

RESULT AND DISCUSSION

4.1 Introduction

In this chapter we are going to discuss on the result and comparison which are been carried out in this project. First we tested the properties of both virgin and recycled polyester yarn and then compare them against each other. Then we tested the properties of both the virgin and recycled fabric and compare them against each other.

4.2 Yarn Testing and discussion

a) Denier:

The study aims at comparing the properties of the fabrics knitted from virgin and recycled polyester filament yarns. Therefore, structural parameters of yarns and fabrics are maintained constant. Denier of both the yarns is selected as 150 for knitting the fabric. Above graph shows that average denier of both the yarns do not differ significantly.

b) Tenacity:

From above graph, it has been observed that yarn strength of virgin and recycled polyester filament do not differ significantly, but slight reduction is observed in recycled polyester.

c) Extension:

In manufacturing of recycled polyester , the molecular weight used i.e. PET bottles will have different molecular weights and properties as compared to that manufacturing virgin polyester. Hence, recycled polyester filaments might be having poor structural development of molecule. Therefore, recycled polyester shows higher value of elongation and less value of tenacity.

d) Hot water shrinkage:

From the above graph we can analyse that the recycled polyester has more hot water shrinkage because the recycled PET bottles have different properties mixed together whereas the virgin polyester is made from specific properties which provides stable results. Also there is no significant change in the hot water shrinkage as seen in above graph.

e) Hot air shrinkage:

The graph represents that the recycled polyester has more hot as shrinkage. As discussed in hot water shrinkage the recycled PET bottles have different shrinkage properties which effects the final yarn properties. Which results in higher hot air shrinkage for recycled polyester tan virgin polyester.

4.3 Fabric Testing and discussion

a) Mass per unit area

For a fair comparison of the fabric made from both recycled and virgin polyester the parameters have to be kept constant throughout the production of the fabric. As seen in above graph there is no significant difference in the GSM of the fabrics produced.

b) Course Per inch:

Course per inch for both the recycled as well as virgin fabrics does not significantly vary.

c) Wales Per inch:

Wales per inch for both the recycled as well as virgin fabrics does not significantly vary.

d) Stitch Density:

Stitch density for both the recycled as well as virgin fabrics does not significantly vary.

e) Stitch Length:

Stitch length for both the recycled as well as virgin fabrics does not significantly vary.

f) Thickness:

Fabric thickness is the property which governs the transmission related to comfort and stiffness related properties of fabric. Fabric thickness mainly depend on linear density of yarn. In present study linear density of virgin and recycled polyester is maintained constant. Therefore there should not be any change in mass per unit area of fabric but fabrics knitted with virgin polyester show slight increase in mass per unit area of fabric which is statically non-significant.

g) Air permeability:

One of the most important factor affecting air, permeability of fabric is thickness of fabric. Thicker fabrics feel have less air permeability fabrics needed with virgin polyester have low air permeability. As these fabrics have more thickness. At the same time stitch density of fabrics knitted with virgin polyester is more, hence they have less cross sectional area for air to pass through.

h) Pill grading:

Both recycled and virgin polyester knitted fabrics show equal pill grading of 5, indicating excellent resistance to pilling and smooth fabric surface after testing.

i) Wicking:

Wicking property of the knitted fabric is linked to fabric thickness, stitch density also air permeability of the fabric. From above properties there is slight difference in the thickness, stitch density and air permeability which results in the wicking property to differ slightly.

j) Moisture vapour transfer rate:

Moisture vapor transfer rate is also dependent on stitch density, air permeability also fabric thickness. The major factor is air permeability which also decides moisture vapour transfer rate of the fabric. From above air permeability graph we can see there is significant difference in the values of recycled and virgin polyester fabrics which further results in change of values for moisture vapour transfer rate of the fabrics.

Chapter 5

CONCLUSIONS

1. While there are some differences observed between virgin and recycled polyester filament yarns in terms of tenacity, extension, and shrinkage properties, the overall findings suggest similarities in denier and minor variations in other characteristics.

2. The comparison between fabrics made from recycled and virgin polyester reveals several similarities and minor differences in various parameters. Mass per unit area, course per inch, wales per inch, stitch density, stitch length, and thickness, pill grading show negligible variation between the two fabric types. However, factors such as air permeability, wicking, and moisture vapor transfer rate demonstrate slight discrepancies, attributed to differences in thickness, stitch density, and air permeability. These findings suggest that while most properties remain consistent, subtle variations exist, particularly in moisture-related characteristics, influenced by fabric composition and structural attributes.

3. In the end we can conclude recycled polyester can replace virgin polyester in sportswear and appeal applications.

Chapter 6

REFERENCES

[1] Suganthi , Senthilkumar (2017) Thermo-physiological comfort of layered knitted fabrics for sportswear.

[2] Hossein Roghani-Mamaqani (2023) Recent developments in materials and manufacturing techniques used for sports textiles.

[3] Surya Nasrin Factors affecting the sweat-drying performance of active sportswear.

[4] N. ANBUMANI,M. SENTHILKUMAR (2011) Dynamics of elastic knitted fabrics for sportswear.

[5] Jefferson M Souza, Sandra Sampaio, Welter C Silva,Sidney G de Lima, Andrea Zille and Raul Fangueiro Characterization of functional single jersey knitted fabrics using nonconventional yarns for sportswear.

[6] C. Premalatha, M. Ramesh Kumar, S.M. Udaya Krithika & C. Prakash (2023) Analysis of thermal comfort properties of tri-layer knitted fabrics.

[7] Elena Onofrei, Ana Maria Rocha, André Catarino The influence of knitted fabrics structure on the thermal and moisture management properties.

[8] Seval Uyanik (2020) The bursting strength properties of knitted fabrics containing recycled polyester fiber.

[9] Damayanti and Ho Shing Wu (2021) Strategic possibility routes of recycled PET.

[10] Laurianne Viora , Marie Combeau , Monica Francesca Pucci, Didier Perrin Pierre-Jacques Liotier ,Jean-Luc Bouvard and Christelle Combeaud A comparative study on crystallisation for virgin and recycled polyethylene terephthalate (PET):multiscale effects on physico-mechanical properties (2023).

[11] Fresia Alvarado Chacon, Marieke T. Brouwer, Eggo Ulphard Thoden van Velzen1 (2019) Effect of recycled content and rPET quality on the properties of PET bottles, part i: optical and mechanical properties.

[12] Sin Sarioğlu, Deniz Vuruşkan, Osman Yayla, Eyüp Ali Satil, Ebru Çelikten (2019) Investigation of yarn properties produced from 100% recycled polyester (r-PET) by different spinning systems.

[13] Tsegaye Sh. Lemmi , Marcin Barburski , Adam Kabziński and Krzysztof Frukacz (2021) Effect of thermal aging on the mechanical properties of high tenacity polyester yarn.

[14] Mounir Hassan Influence of Sportswear Fabric Properties on the Health and Performance of Athletes (2012).

[15] Awadhesh Kumar Choudhary, Ramratan The influence of yarn and knit on moisture management properties of sportswear fabric(2018).

[16] Aman Siddique, Tufail Hassan The effect of softeners application on moisture management properties of polyester/cotton blended sandwich weft-knitted fabric structure (2021).

[17] Ivana Salopek Cubrich, Vesna Marija Potocic Matkovic, Zelijka Pavlovic, Alenka Pavko Cuden Material and structural functionalization of knitted fabrics for sportswear (2022).

[18] T Sathish Kumar, M Ramesh Kumar, C. Prakash & B. Senthil Kumar Study on Moisture Management Properties of Plated Interlock Knitted Fabrics (2021)

[19] Samyuktha V, Dr.G.Ramakrishnan Development of Eco-Friendly Sportswear using Recycled Polyester/Cotton Fibers(Part I) (2020).

Mazharul Islam Kiron

Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.

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