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Developing a Model for Recycling Plastic Bottle into Synthetic Fiber Developing a Model for Recycling Plastic Bottle into Synthetic Fiber Submitted by Mohammed Milad Bhuiya Student ID: 14207012 Program: BSME Kazi Simon Hasan Student ID: 14207066 Program: BSME This Thesis is Submitted in Partial Fulfillment of the Requirements for the Degree of Bachelor of Science in Mechanical Engineering Department of Mechanical Engineering IUBAT—International University of Business Agriculture and Technology ii SUPERVISOR’S APPROVAL The thesis titled “Developing a Model for Recycling Plastic Bottle into Synthetic Fiber.” Submitted by Mohammed Milad Bhuiya, ID: 14207012 and Kazi Simon Hasan, ID: 14207066, has been accepted as satisfactory in partial fulfillment of the requirement for the degree of Bachelor of Science in Mechanical Engineering. …………………………….. Mafizul Huq Department of Mechanical Engineering, IUBAT iii DECLARATION This thesis has been prepared after eight months of research on “Developing a Model for Recycling Plastic Bottle into Synthetic Fiber”. The thesis is solely for academic requirement of the course MEC 488 and has not been submitted in part or full elsewhere for any other degree, reward or for any other purpose. I do solemnly and sincerely declare that all and every right in the copyright of this thesis belong to IUBAT-International University of Business Agriculture and Technology. Any reproduction or use in any form or by any means whatsoever is prohibited without the written consent of IUBAT. Submitted By: Signature: ................................................. Name: Mohammed Milad Bhuiya Student ID: 14207012 Signature: ................................................. Name: Kazi Simon Hasan Student ID: 14207066 iv ACKNOWLEDGEMENT First of all, praise is due to almighty ALLAH with his compassion and mercifulness to allow us finalizing this undergraduate thesis. We express sincerest gratitude to our supervisor, Mafizul Huq, Associate Professor, Department of Mechanical Engineering, IUBAT, who has supported us throughout our thesis with his patience and knowledge. We attribute the level of our Bachelor degree to his encouragement and effort and without him this thesis would not have been completed and written. Our special thanks to all the lab assistants of IUBAT who participated in maintenance related to experimental setup. We are grateful to IUBAT for funding. It would not be possible to complete this thesis without the financial co-operation of this organization. Finally, we thank our parents for supporting us throughout all our studies at University. We are also grateful to our friends for inspiring us in different stages of the thesis work. The Authors Department of Mechanical Engineering, IUBAT - International University of Business and Agriculture Technology. Uttara model town, Sector: 10, Dhaka-1230, Bangladesh. December, 2019. v Developing a Model for Recycling Plastic Bottle into Synthetic Fiber Candidates Supervisor ………………………. ………………………. Mohammed Milad Bhuiya Mafizul Huq ID: 14207012 Department of Mechanical Engineering ………………………. Kazi Simon Hasan ID: 14207066 vi ABSTRACT This study has been carried out to effectively manage and recycle the PET plastic bottles by identifying practical means and introducing recycling as cleaner production tool to achieve sustainable development goals. We have designed and analyzed a PET bottle recycling machine that turns PET flakes, pellets, granules into synthetic fiber. PET bottle is a thermoplastic resin so it can be melted and reshaped repeatedly. Utilizing plastic extrusion process with our recycling machine we can melt PET bottle flakes and then air is blown using air compressor turning that molten plastic into continual synthetic fiber. At present years the consumption and disposal of polyethylene terephthalate (PET) has increased greatly in Bangladesh. After use, PET products should be disposed in selective waste collection in order to recycle and reinsert the plastic into production chain. We have found out with the abundance in plastic bottle and PET product waste we can make synthetic fiber in a very cheap price. Compering with the imported fiber or felt, flock our synthetic fiber costs less than half of the price. This fiber can be used primarily as the packaging material or stuffing material. It can also be processed at a spinning mill to turn it into polyester yarn and then into polyester thread. As recycling PET bottle has commercial value, employment and income can be generated as a result it will help the economy of our country. Key words: PET recycle, Extrusion, Synthetic fiber, PET bottle, r-pet, plastic recycling, plastic extrusion vii TABLE OF CONTENTS ACKNOWLEDGEMENT ....................................................................................................... v ABSTRACT ............................................................................................................................vii TABLE OF CONTENTS .................................................................................................... viii LIST OF FIGURES ................................................................................................................ x LIST OF TABLES .................................................................................................................. xi LIST OF SYMBOLS AND ABBREVIATION .................................................................xii CHAPTER 1: INTRODUCTION ......................................................................................... 13 1.1 Research Background .................................................................................................. 13 1.2 Problem Statement ....................................................................................................... 14 1.3 Objectives ...................................................................................................................... 17 1.4 Organization of the Report.......................................................................................... 18 CHAPTER 2: LITERATURE REVIEW: ........................................................................... 19 CHAPTER 3: METHODOLOGY ....................................................................................... 24 3.1 Introduction of Extrusion Process .............................................................................. 24 3.1.1 Ram Extrusion ....................................................................................................... 24 3.1.2 Screw Extrusion ..................................................................................................... 25 3.2 Types of Extrusion Process.......................................................................................... 26 3.2.1 Sheet/Film Extrusion ............................................................................................. 26 3.2.2 Blown Film Extrusion ........................................................................................... 26 3.2.3 Over-Jacketing Extrusion ..................................................................................... 27 3.2.5 Co-extrusion ........................................................................................................... 28 3.2.6 Extrusion Coating .................................................................................................. 28 3.3 Materials Used .............................................................................................................. 28 3.3.1 Symbols of plastics ................................................................................................. 29 3.3.2 Properties of Polyethylene terephthalate (PET) ................................................. 29 3.4 Design of Machine ........................................................................................................ 30 3.4.1 Schematic diagram of Machine ............................................................................ 31 3.4.2 Screw Shaft Design: ............................................................................................... 32 3.4.3 Hopper .................................................................................................................... 34 3.4.4 Pipe Barrel.............................................................................................................. 34 3.4.5 Induction Motor..................................................................................................... 34 3.4.6 Circular Band Heater ............................................................................................ 35 viii 3.4.7 Temperature Controller........................................................................................ 35 3.4.8 Thermocouple ........................................................................................................ 36 3.4.9 Air Compressor...................................................................................................... 36 3.4.10 V-Belt and Pulley arrangement .......................................................................... 37 3.5 Working principle ........................................................................................................ 38 CHAPTER 4: DATA COLLECTION AND CALCULATION ........................................ 40 4.1 Calculation of Current consumption .......................................................................... 40 4.1.1 Electricity consumption of Induction Motor....................................................... 40 4.1.1 Electricity consumption of Barrel Heater ........................................................... 40 4.1.3 Electricity consumption of Air Compressor ....................................................... 41 4.2 Calculation of cost of fiber........................................................................................... 42 4.3 Result Analysis ............................................................................................................. 43 CHAPTER 5: CONCLUSION.............................................................................................. 46 REFERENCES ....................................................................................................................... 47 ix LIST OF FIGURES Fig 1. 1: Global PET bottle production .................................................................................... 15 Fig 1. 2: Effect of plastic pollution on animals........................................................................ 16 Fig 1. 3: Global plastic production .......................................................................................... 16 Fig 3. 1: Blown film extrusion ................................................................................................. 27 Fig 3. 2: Symbol for recyclable plastic container .................................................................... 29 Fig 3. 3: Extrusion Machine..................................................................................................... 31 Fig 3. 4: Actual Image of Machine .......................................................................................... 31 Fig 3. 5: Screw Shaft ................................................................................................................ 32 Fig 3. 6: Dimension of hopper ................................................................................................. 34 Fig 3. 7: Circular band heater .................................................................................................. 35 Fig 3. 8: K type thermocouple ................................................................................................. 36 Fig 3. 9: Air compressor .......................................................................................................... 36 Fig 3. 10: Flow chart for PET extrusion .................................................................................. 38 Fig 3. 11: Extrusion process..................................................................................................... 39 Fig 4. 1: Flakes input vs Fiber Output ..................................................................................... 43 Fig 4. 2: Fiber Output vs Power Consumption ........................................................................ 43 Fig 4. 3: Cost of electricity per hour ........................................................................................ 44 Fig 4. 4: Price point of Imported and Recycled Fiber.............................................................. 44 Fig 4. 5: Synthetic fiber from PET flakes per kg ..................................................................... 45 x LIST OF TABLES Table 3. 1: Properties of PET ................................................................................................... 30 Table 3. 2: Dimension of helical screw shaft ........................................................................... 33 Table 3. 3: Specification of Induction Motor........................................................................... 34 Table 3. 4: Specification of Induction Motor........................................................................... 35 Table 3. 5: Specification of Air compressor ............................................................................ 37 Table 4. 1: Total Electricity Consumed per hour ..................................................................... 42 xi LIST OF SYMBOLS AND ABBREVIATION PET = Polyethylene Terephthalate V = Voltage R = Resistance I = Ampere R.P.M = Revolutions per minute xii CHAPTER 1: INTRODUCTION 1.1 Research Background Polyethylene terephthalate (PET) is a versatile material and has a broad range of applications such as food packaging, plastic bottle, beverage bottles, clothing, sportswear, agricultural equipment’s, nonwovens, sheets and films, straps, resins, packaging materials, reinforcement in building construction etc. Among these products, bottle grade PET is generally used for water and beverage packaging due to its lightweight, inexpensive price, resistance to microorganisms, and light [1]. Bottles of water, soft drinks, and other beverages constitute 83– 84% of global PET resin requirement. Furthermore, the projected demand for PET packaging materials is forecasted to reach 20 million tons by 2019 with an annual increase of 4.6% [2]. There are two main types of plastics including thermoplastics and thermosets. Thermoplastics are the plastic materials that can be formed into other products by re-melting or reprocessing into different shapes by the application of heat and pressure. These are easily recyclable into other products. These thermoplastics include polyethylene terephthalate (PET), polyethylene, low and high density (LDPE, HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) etc. Thermoset plastic includes components like alkyd, epoxy, ester, melamine formaldehyde, polyurethane, etc. Which upon applying heat can’t be soften thus will not allow the formation of different shapes. At present Bangladesh have a very small amount of work going on about recycling of plastic. There are bulk amounts of plastic wastes and no orderly process is present to recycle it. If there is a methodological way to recycle that waste plastic and manufacture different kinds of products it will create more job opportunity and that it can also help the economy of our country. So, in this study we are implementing extrusion process to recycle PET bottle into synthetic fiber as PET bottles are made of thermoplastic resin. 13 1.2 Problem Statement Since plastic is a non-biodegradable product and cannot be dumped in the ground, plastic recycling is a very important issue in protecting the nature. Use of plastic is increasing and plastic waste becoming a major obstacle to greener technology. Waste plastic is often the most visible component in waste dump and landfill. Recent studies says to us that plastic bottle remains for 450 years long on the earth and since plastic waste is growing rapidly hence the improper disposal of plastics causes problems as distant as breast cancer, reproductive problems in humans and animals, genital abnormalities and much more. Plastics wastes are found in different forms which almost 5% of the municipal solid wastes which is toxic in nature. It is a common sight in both urban and rural areas to find empty plastic bags and other type of plastic packing material littering the roads as well as drains. If current trends continue, our oceans could contain more plastic than fish by 2050. While the United States, Japan and many European countries generate significant amounts of plastic waste, they’re also relatively good at managing it. About half of all of the plastic waste that ends up in the oceans comes from just five countries: China, Indonesia, the Philippines, Thailand and Viet Nam. These countries are experiencing rapid economic growth, which is reducing poverty rates and improving the quality of life for hundreds of millions of people. But as these economies grow, consumption booms — and so does the use of plastic goods [3]. A million plastic bottles are bought around the world every minute and the number will jump another 20% by 2021, creating an environmental crisis some campaigners predict will be as serious as climate change. New figures obtained by the Guardian reveal the surge in usage of plastic bottles, more than half a trillion of which will be sold annually by the end of the decade. The demand, equivalent to about 20,000 bottles being bought every second, is driven by an apparently insatiable desire for bottled water and the spread of a western, urbanized “on the go” 14 culture to China and the Asia Pacific region. Most plastic bottles used for soft drinks and water are made from polyethylene terephthalate (Pet), which is highly recyclable. But as their use soars across the globe, efforts to collect and recycle the bottles to keep them from polluting the oceans, are failing to keep up. Fig 1. 1: Global PET bottle production In the UK 38.5m plastic bottles are used every day – only just over half make it to recycling, while more than 16m are put into landfill, burnt or leak into the environment and oceans each day. “Plastic production is set to double in the next 20 years and quadruple by 2050 so the time to act is now,” said Tag Holm. Animals like birds or fish can mistake plastic in the ocean for food. In addition, because plastic can come in sizes large or small, even the smallest organisms like plankton could be affected. When an animal consumes enough plastic, their digestive 15 systems could get clogged up, eventually starving them to death. Sometimes, the uneven shape of plastic pieces could even choke animals, like sea turtles, to death. Fig 1. 2: Effect of plastic pollution on animals Fig 1. 3: Global plastic production 16 There has been growing concern about the impact of plastics pollution in oceans around the world. Last month scientists found nearly 18 tons of plastic on one of the world’s most remote islands, an uninhabited coral atoll in the South Pacific [4]. Production of Plastic Bottles Requires Fossil Fuels. One big problem with plastic, of course, is that its production requires the use of non-renewable fossil fuels. Plastic bottles are no exception to this. Most plastic bottles are made from a plastic known as PET (polyethylene terephthalate), which is produced using oil. Worse yet, the production of plastic bottles isn’t the only time when energy is wasted. In fact, energy is used during the entire lifespan of a plastic bottle: This includes the energy used for transportation, storage, and the final disposal of the bottle. Plastic bottles are not biodegradable in order to fully understand what this means, it is important to understand the difference between biodegrading and degrading. Biodegrading is when an object gets broken down (digested) by living organisms. This means that the object can be naturally recycled (by decomposers like bacteria and fungi) into new organic molecules and new life. On the other hand, degrading is just the process of breaking down into smaller pieces [4]. So, this paper will concern about, plastic wastes and how plastic waste can be recycled and utilized. 1.3 Objectives 1. To find out how to utilize PET bottle waste. 2. To find out how PET bottles can be recycled. 3. To explore PET recycling situation in Bangladesh. 4. To explore the field of Thermoplastic Extrusion. 5. To explore various PET extrusion process. 6. To assess the need of synthetic fiber in Bangladesh. 17 1.4 Organization of the Report This thesis is organized with five chapters. First chapter is about research background, Problem statement and objective of this study. In chapter 2, elaborated literature review is presented about harmful effect of plastic pollution and how effectively we can recycle plastic bottle. Chapter 3 contains materials, design of machine and methods for this study with detail experimental setup. Chapter 4 includes experimental result, presented with data collection and analysis of obtained results respectively. Conclusion of this research work is drawn in chapter 5 along with our limitation and potential possibilities for further study. 18 CHAPTER 2: LITERATURE REVIEW: Economic and population growth and industrialization in the world together cause an increase in the amount of plastic waste. Plastic pollution is the accumulation of plastic objects and particles (e.g. plastic bottles, bags and microbeads) in the Earth's environment that adversely affects wildlife, wildlife habitat, and humans [5]. As a consequence of all these, while the more intensive use of natural resources is inevitable, the plastic wastes created by the ever-increasing consumption tendency have reached the huge amounts that threaten the environment and human health due to their quantity and harmful contents. For this purpose, plastic waste policies should be developed and waste management studies should also be carried out, especially in the field of recycling these plastic wastes, because of long decomposition time of these wastes in the environment causing landfill and water logging problem [6, 7]. Waste management system enables collection, categorization, reduction, recycling, and reuse of plastic waste. At present, countries’ intensive efforts on waste management are striking. Currently, there is an increasing focus on the importance of recycling and reuse in an effort to save the environment from the harmful substances that result from plastic waste disposal. Many cities have created a new system for waste collection where recyclables go in one bin, non-recyclables in another and food scraps go in a third. Also, in an effort to reduce the disposal of plastic bottle in landfills the city of Toronto, for example, requested all retailers to charge customers a fee for these bottles and have been encouraging retailers to use bottles made from biodegradable material and customers to use reusable bottles [8]. The thought of plastics first came in the late 1950s and early 1960s. The idea of plastic recycling on the other hand began to take shape in the 1990s in United States and elsewhere. At that time this process was run only to destroy the plastic wastes. Between 1960 and 1970, the average person bought between 200 and 250 packaged drinks ever year, Elizabeth Royte reported in her book Bottlemania, citing data from the Container Recycling Institute. Most of those purchases, she added, involved refillable 19 bottles. As of 2017, on a global scale a million plastic beverage bottles were purchased every minute, according to data from Euromonitor International’s global packaging trends report, published in 2017 by The Guardian. Today, plastic bottles and jars represent about 75 percent of all plastic containers, by weight, according to the Plastics Industry Association. Now-a-days many products are coming out of recycling plastic PET bottle. Once bottles have become trash, entrepreneurs around the world are turning them into printer ink cartridges, fence posts, roofing tiles, carpets, flooring, and boats, to name only a few items. Even houses have been constructed from bottles. The latest is a three-story modern on the banks of the Meteghan River in Nova Scotia, promoted as able to withstand a Category 5 hurricane. It only took 612,000 bottles. Waste management, which has an important place among environmental protection policies, should prevent the rapid depletion of natural resources and minimize the potential risks of the wastes to the environment and human health [8]. With the widespread application of PET, large quantities of PET waste were inevitably created. PET has no side effects on the human body and does not pose a direct threat to the environment. On the other hand, it is regarded as a harmful material because of its high volumetric fraction in the waste stream and high resistance to atmospheric and biological agents [9]. Due to poor biodegradation of PET bottle, it is difficult to remove it from our environment. Beverage companies have pledged to use more recycled bottles in manufacturing, a goal that aims to reduce the production of new resin and boosts recycling numbers by adding value to bottle recovery. PepsiCo pledged to increase recycled content in all its plastic packaging 25 percent by 2025. Nestle Waters vowed to make all of its packaging recyclable by 2025 and increase recycled content in bottles to 35 percent by 2025 globally and to 50 percent in the United States, focusing on Poland Spring. Additionally, recycled content for European brands will increase to 50 percent by 2025. Coca-Cola pledged to recycle a used bottle or can for every one the company sells by 2030 and increase recycled material in plastic bottles to 50 percent by 2030. 20 For example, Brazilian team’s total outfit wearing T-shirts made from recycled plastics bottles in the last world cup. There are two acceptable solutions; burning and recycling. Burning method arises releasing toxic fumes into the atmosphere, causing environmental pollution and health risks. As an acceptable solution, the recycling of PET bottles enables the conservation of natural sources such as fossil fuels and energy, solving landfill problem, reducing greenhouse gas emission, lowering carbon footprint, creating new business opportunities as well as a contribution to the national economy [10, 11]. In addition, recycling processes are the best way to economically reduce PET waste [12]. With both reduced energy costs and raw material costs, recycling fiber production has become a form of production with a significant economic advantage [12]. PET flakes are obtained from PET bottle wastes after a series of procedures such as sorting, washing, grinding, drying, etc. Most of the recycled PET flakes produced worldwide are utilized for staple fiber applications in textile sector [13]. Because of environmental reasons initially, the recycling of PET bottles to textile fibers has now become commercially attractive [14]. Worldwide, approximately 7.5 million tons of PET were collected in 2011. This gave 5.9 million tons of flake. In 2009 3.4 million tons were used to produce fibre, 500,000 tons to produce bottles, 500,000 tons to produce APET sheet for thermoforming, 200,000 tons to produce strapping tape and 100,000 tons for miscellaneous applications [15]. Petcore, the European trade association that fosters the collection and recycling of PET, reported that in Europe alone, 1.6 million tonnes of PET bottles were collected in 2011 - more than 51% of all bottles. After exported bales were taken into account, 1.12 million tons of PET flake were produced. 440,000 tons were used to produce fibres, 283,000 tons to produce more bottles, 278,000 tons to produce APET sheets, 102,000 tons for strapping tape and 18,000 tons for miscellaneous applications. (Source: PCI for Petcore and EuPR). In 2008 the amount of post-consumer PET bottles collected for recycling and sold in the United States was approx. 1.45 billion pounds [16]. In 2012, 81% of the PET bottles sold 21 in Switzerland were recycled [17]. In 2018, 90% of the PET bottles sold in Finland were recycled. The high rate of recycling is mostly result of the deposit system in use. The law demands a tax of 0.51 €/ for bottles and cans that are not part of a refund system. Thus encouraged by the law, products are included to have a 10¢ to 40¢ deposit that is paid to the recycler of the can or bottle [18]. Increasing prices may increase the volume of recycling PET bottles [19]. In Europe, the EU Waste Framework Directive mandates that by 2020 there should be 50% recycling or reuse of plastics from household streams [20]. In the United States the recycling rate for PET packaging was 31.2% in 2013, according to a report from The National Association for PET Container Resources (NAPCOR) and The Association of Postconsumer Plastic Recyclers (APR). A total of 1,798 million pounds was collected and 475 million pounds of recycled PET used out of a total of 5,764 million pounds of PET bottles [21]. Furthermore, as petroleum prices increase, recycling of PET becomes more financially feasible rather than a virgin PET. It is expected that the recycling of the PET bottle will be estimated up to annually 13 million tons in 2018 and up to 15 million tons in 2020 [22]. The plastic industry in Bangladesh is relatively new compared with the textile and leather industries. The plastic industry began its journey as a small industry in 1960. The plastic industry in Bangladesh uses imported polymer granules. During the period 1989 to 2007, the import of polymers increased from 10,000 tonnes to 289,000 tonnes per year. At present total consumption of polymers including imported polymers and recycled plastic wastes is 750,000 tonnes in 2010-2011. This corresponds to the per capita consumption of plastics in Bangladesh 5kg per year against the world average 30kg. Per capita consumption in India and ASEAN countries are 8kg and 17kg respectively. There are about 3000 manufacturing units in the plastic sector of which 98% belongs to the Small and Medium Enterprises (SMEs). The plastic sector contributes 1.0percent of GDP and provides employment for half a million people [23]. The PET recycling technology has been developed better and better across the world. There are mainly two methods: chemical 22 recovery and physical recovery. Compared with the method of chemical recovery, the physical recovery has made less secondary pollution on the environment. It is easier to implement the process and start large-scale industrial production. Thus, the method of physical recovery has been widely applied. In thermoplastics, processing techniques can be classified into either batch or continuous process. Batch process includes injection moulding and roto-moulding. Extrusion of plastics is a continuous process. However, blow moulding is available both in batch and continuous process. Extrusion process is the most commonly used process in the world and accounts for ~60% of total consumption by downstream plastic processing industries. Injection moulding is the other popular process accounting for ~25% of the consumption. Blow moulding is used for ~5% while Roto moulding 1% while the rest of the plastic is processed through other processes [24]. At present, many developed countries, such as the United States, Japan and Germany, have made much research on the high-quality precision extrusion recycling technologies like the automatic sorting technology, efficient cleaning and melting equipment, developing "bottle to bottle" technique, and made a great achievement. In 2007, the German Battenfeld Extrusion Technic company developed a new PET single-screw extrusion system. The extruder was equipped with specially developed planetary geared degassing parts which can be directly processed without drying materials. The productivity of the system is 800- 1000kg/h [25]. China is very good at making high capacity recycling machines like Palletizing Machine, High speed Single Screw Extruder, Twin Screw Extruder etc. China once bought about 45 percent of the world’s plastic waste. In 2017, the government started to cut way back on plastic trash imports. Then the big bombshell: In January 2018, it banned almost all imports. Last year, China took in less than 1 percent of its 2016 total. That means a huge amount of plastic is looking for a place to go. So, with rapidly growing textile industry in Bangladesh, recycling plastic bottle into synthetic fiber is very viable. 23 CHAPTER 3: METHODOLOGY 3.1 Introduction of Extrusion Process Plastic extrusion is a manufacturing process in which raw plastic is melted and formed into a continual shape. By feeding plastic material (pellets, granules, flakes) from a hopper into the barrel of the extruder the process can be started. A cylindrical rotating screw shaft is placed inside the barrel which forces out molten plastic through a die in our case we blow the molten plastic with air to make continual fiber. The extruded material takes shape according to the cross-section of die. The material is gradually melted by the mechanical energy generated by turning helical screw shaft and by heaters arranged along the barrel. The molten polymer is then forced into a die, which shapes the polymer into a shape that hardens during cooling. There are two types of plastic extrusion: 1. Ram Extrusion. 2. Screw Extrusion. 3.1.1 Ram Extrusion A ram extruder is an extruder where, instead of extrusion screw, a ram or plunger is used and a plunger goes through a barrel and pushes out the material under pressure. The ram extruder was the earliest extruder to be used in the plastics industry. This typical process is applied for producing profiles, sleeves, rod, block, tubing, lining sheet bars, etc. The ram extrusion process is very effective for specific materials like PTFE which are not extruded successfully using screw extruder because of its low friction. In this process plastic material in powder form is gravity fed into a chamber. In the extraditing chamber the resin powder is heated on sintering temperature. Ultra-high molecular weight polyethylene becomes gelatinous as it melts so it can be extruded with this type of processes. A hydraulic ram pushes the resin materials like PTFE, 24 UHMW, etc. from the chamber to the die. The die actually gives the shape of the desired plastic like a rod, tube or a profile shape with the requisite internal or outer diameter. When the material comes out of the die, it moves the length of the conveyor. The profiles can be manufactured endlessly and cut by the continuous extruding of each length. 3.1.2 Screw Extrusion Screw extrusion involves a helical feed screw that turns inside a barrel. This is often called the feed screw or the extruder screw. The screw is a single shaft with helical flights. Sometimes, when more thorough mixing is needed, two screws are used. The constantly turning screw moves the resin through the heated barrel where it is heated to proper temperature and blended into a homogeneous melt. Extrusion screw design has been improving over the years, with new innovations and ideas. Nowadays, single screws are available that have a secondary flights that improve speed by enabling faster melting. This process of extrusion serves two functions: it heats the plastic material above its melting point and puts the melt under pressure. The molten plastic material can then be forced through an orifice, commonly known as the die. This process is common to all types of extrusion. Most screws have these three zones, Feed zone (also called the solids conveying zone): this zone feeds the resin into the extruder, and the channel depth is usually the same throughout the zone. Melting zone (also called the transition or compression zone): most of the polymer is melted in this section, and the channel depth gets progressively smaller. Metering zone (also called the melt conveying zone): this zone melts the last particles and mixes to a uniform temperature and composition. Like the feed zone, the channel depth is constant throughout this zone. A great advantage of extrusion is that profiles such as pipes can be made to any length. If the material is sufficiently flexible, pipes can be made at long lengths even coiling on a reel. Another advantage is the extrusion of pipes with integrated coupler including rubber seal. 25 3.2 Types of Extrusion Process The extrusion process is broadly classified into seven different types depending upon the specific applications. 3.2.1 Sheet/Film Extrusion In this extrusion process, the molten plastic material is extruded through a flat die. The cooling rolls are used to determine the thickness of sheet/film and its surface texture. The thickness of sheet can be obtained in the range of 0.2 to 15 mm. The thin flat sheet or film of plastic material can be made. Generally, polystyrene plastic is used as a raw material in the sheet extrusion process. 3.2.2 Blown Film Extrusion In the blown film process, the die is like a vertical cylinder with a circular profile. The molten plastic is pulled upwards from the die by a pair of nip rollers. The compressed air is used to inflating the tube. Around the die, an air-ring is fitted. The purpose of an air-ring is to cool the film as it travels upwards. In the center of the die, there is an air inlet from which compressed air can be forced into the center of the circular profile, and creating a bubble. The extruded circular cross section may be increased 2-3 times of the die diameter. The bubbles are collapsed with the help of collapsing plate. The nip rolls flatten the bubble into double layer of film which is called lay flat. The wall thickness of the film can be controlled by changing the speed of the nip rollers. The lay flat can be spooled in the form of roll or cut into desired shapes. Bottom side of the lay flat is sealed with the application of heat, and cut across further up to form opening; hence it can be used to make a plastic bag. The die diameter may vary from 1 to 300 centimeters. Generally, polyurethane plastic is used in this process. 26 Fig 3. 1: Blown film extrusion 3.2.3 Over-Jacketing Extrusion This is also called wire coating process. In this process, a bare wire is pulled through the center of a die. There are two different types of extrusion tooling used for coating over a wire i.e. pressure or jacketing tooling as shown in figure 3. If intimate contact or adhesion is required between the wire and coating, pressure tooling is used. If adhesion is not desired, jacketing tooling is used. For pressure tooling, the wire is retracted inside the die, where it comes in contact with the molten plastic at a much higher pressure. For jacketing tooling, the wire will extend and molten plastic will make a cover on the wire after die. The bare wire is fed through the die and it does not come in direct contact with the molten plastic until it leaves the die. The main difference between the jacketing and pressure tooling is the position of the wire with respect to the die. In this process, the molten plastic is extruded through a die and hollow cross sections are formed by placing a mandrel inside the die. Tube with multiple holes can also be made for specific applications, by placing a number of mandrels in the center of the die. 27 3.2.5 Co-extrusion Co-extrusion is the extrusion process of making multiple layers of material simultaneously. It is used to apply one or more layers on top of base material to obtain specific properties such as ultraviolet absorption, grip, matte surface, and energy reflection, while base material is more suitable for other applications, e.g. impact resistance and structural performance. It may be used on any of the processes such as blown film, over jacketing, tubing, sheet/film extrusion. In this process, two or more extruders are used to deliver materials which are combined into a single die that extrudes the materials in the desired shape. The layer thickness is controlled by the speed and size of the individual extruders delivering the materials. 3.2.6 Extrusion Coating Extrusion coating is used to make an additional layer onto an existing roll stock of paper, foil or film. For example, to improve the water resistant of paper polyethylene coating is used. The applications of extrusion coating are liquid packaging, photographic paper, envelopes, sacks lining for fertilizers packaging and medical packaging. Generally, polyethylene and polypropylene are used. 3.3 Materials Used The different types of plastic materials that can be used in extrusion process are Polyethylene terephthalate (PET), Polypropylene (PP), Acetal, Acrylic, Nylon (Polyamides), Polystyrene, Polyvinyl Chloride (PVC), Acrylonitrile Butadiene Styrene (ABS) and Polycarbonate. 28 3.3.1 Symbols of plastics There are many kinds of plastics. Some of them are recyclable and some of them are not properly recyclable. So, when someone knows about the symbol and the number which is on the products in every item s/he can keep that plastic in right place. Fig 3. 2: Symbol for recyclable plastic container 3.3.2 Properties of Polyethylene terephthalate (PET) Polyethylene terephthalate (sometimes written poly(ethylene terephthalate)), commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids and foods, thermoforming for manufacturing, and in combination with glass fiber for engineering resins. 29 Table 3. 1: Properties of PET IUPAC Name Poly(ethyl benzene-1,4-dicarboxylate) Chemical formula (C10H8O4)n Solubility in water Practically insoluble Melting point > 250 °C; 482 °F; 523 K Boiling point > 350 °C; 662 °F; 623 K 3.4 Design of Machine Our extrusion machine has single screw shaft design with listed below1. Screw Shaft 2. Hopper 3. Barrel 4. Induction Motor 5. Circular Heater 6. Heat Controller 7. Thermocouples 8. Air Compressor 9. Belt and pulley arrangement 30 Different parts of Machine is 3.4.1 Schematic diagram of Machine Fig 3. 3: Extrusion Machine Fig 3. 4: Actual Image of Machine 31 3.4.2 Screw Shaft Design: The design of screw is important for plastic processing. It has mainly three different functions namely, feeding mechanism; uniform melting and mixing of plastic and finally it generates the pressure to push the molten material through die. A screw length (L) is referenced to its diameter (D) as L/D ratio. Generally, L/D ratio is used as 24:1, but for more mixing and output, it may increase up to 32:1. The Screw is made of mild steel. There are three possible zones in a screw length i.e. feed zone, melting zone, and metering zone. (a) Feed zone: In this zone, the resin is inserted from hopper into the barrel, and the channel depth is constant. (b) Melting zone: The plastic material is melted and the channel depth gets progressively smaller. It is also called the transition or compression zone. (c) Metering zone: The molten plastic is mixed at uniform temperature and pressure and forwarded through the die. The channel depth is constant throughout this zone. Fig 3. 5: Screw Shaft 32 In addition, a vented (two-stage) screw has: (a) Decompression zone: In this zone, about two-thirds down the screw, the channel suddenly gets deeper, which relieves the pressure and allows any trapped gases (moisture, air, solvents, or reactants) to be drawn out by vacuum. (b) Second metering zone: This zone is similar to the first metering zone, but with greater channel depth. It serves to re-pressurize the melt to get it through the resistance of the screens and the die. Each zone is equipped with one or more thermocouples in the barrel wall for temperature control. The "temperature profile" i.e., the temperature of each zone is very important to the quality and characteristics of the final product. Table 3. 2: Dimension of helical screw shaft Length 2 feet Major Diameter 1.5 inch Minor Diameter 1 to 1.4 inch Pitch 0.4 inch Helix Angle 15° to 25° Depth 0.5 to 0.1 inch Pulley Diameter 10 inch R.p.m. 110 33 3.4.3 Hopper Our hopper is a pyramidal shaped device used to feed plastic flakes into the screw shaft. Fig 3. 6: Dimension of hopper 3.4.4 Pipe Barrel Barrel houses the screw shaft. The helical screw shaft rotates inside the barrel. The barrel is made of Mild Steel. Has a length of 22.5 inch. 3.4.5 Induction Motor The machine uses an induction motor or an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. It is used to rotate the screw shaft that is housed in pipe barrel. Table 3. 3: Specification of Induction Motor Voltage 220 volt Ampere 4.25 amp R.p.m 1400 Power 0.935 kW 34 3.4.6 Circular Band Heater The circular band heater is an electrical device that converts an electric current into heat energy. There is three circular band heaters placed around the pipe barrel. The diameter of the heater is 2.5 inch and length are 2.8 inch. The resistance of three heater wire is 144 Ω, 136 Ω, 136 Ω accordingly. Fig 3. 7: Circular band heater 3.4.7 Temperature Controller It is widely used for measuring temperature and auto control temperature in different machinery. We are using one temperature controller for three circular band heaters. Table 3. 4: Specification of Induction Motor Input signal K type thermocouple Power supply 110v or 220v Sensitivity range 0º C to 400º C Output Relay 35 3.4.8 Thermocouple A thermocouple produces a temperature-dependent voltage which results in thermoelectric effect, and this voltage can be used to measure temperature. Thermocouples are a widely used temperature sensor. We are using K type thermocouple. It has sensitivity range of -200º C to +1350º C. Fig 3. 8: K type thermocouple 3.4.9 Air Compressor An air compressor is a device that converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed air). An air compressor forces more and more air into a storage tank, increasing the pressure. When tank pressure reaches its engineered upper limit, the air compressor shuts off. The compressed air then, is held in the tank until called into use. Fig 3. 9: Air compressor 36 Specification of air compressor is given belowTable 3. 5: Specification of Air compressor Operating Voltage 220v Power 0.55 kW Speed 2850 r/min Ampere 4.2 amp 3.4.10 V-Belt and Pulley arrangement The belt and pulley arrangement are used to transmit the rotation from motor to helical screw shaft. We have used two v-belt and three pulleys. The motor pulley has a diameter of 3 inch and the other two has 12 inch and 10 inches accordingly. The arrangement is made in a way that it reduces the motor’s 1400 r.m.p into 110 rpm in the screw shaft. 37 3.5 Working principle Before actual extrusion process can take place, the PET bottle is need to be processed for extrusion. Flow chart of the process is given below Fig 3. 10: Flow chart for PET extrusion There are mostly three important steps to be considered before extrusion process: Melting temperature of plastic Speed of the screw Extrusion pressure required In extrusion process, plastic in the form of pellets or granules is gravity fed from the hopper into the barrel. The plastic material enters through the feed throat and comes into contact with the rotating screw, rotating in 110 rpm. The rotating screw pushes the plastic pellets forward into the barrel. The barrel is heated using the circular band heater up to the melting temperature of the plastic, which is 260º C. There are three zones in a rotating screw shaft which are feed zone, melting zone, and metering zone. In the feed zone, the plastic pellets 38 melt gradually as they are pushed through the barrel. In the melting zone plastic pellets are completely melted. A thermocouple is used to maintain the temperature of the mild steel barrel. The overheating of plastics should be minimized which may cause degradation in the plastic properties. At the front of the barrel, the molten plastic leaves the screw shaft and then it is blown with the help of air compressor to make the continual synthetic fiber. Fig 3. 11: Extrusion process 39 CHAPTER 4: DATA COLLECTION AND CALCULATION 4.1 Calculation of Current consumption We are using 3 types of electrical component which are listed below1. Induction Motor. 2. Three Barrel Heater. 3. Air Compressor. 4.1.1 Electricity consumption of Induction Motor From motor specification list we get, Voltage – 220 v Current – 4.25 amp So, Power = V × I =220×4.25 = 935 watt = (935÷1000) kW = 0.935 kW Electricity Consumption = Power × time = (0.935 × 1) kW h = 0.935 kW h 4.1.1 Electricity consumption of Barrel Heater As we have three-barrel heater, measuring heater resistance and ampere with the help of multimeter we get, 40 R1 = 144 Ω, I1 = 0.67 amp R2 = 136 Ω, I2 = 0.56 amp R3 = 136 Ω, I3 = 0.56 amp So, Voltage = I × R So, V1 = 96.48 v , V2 = 76.16 v , V3 = 76.16 v Again, Power = V × I Power consumption of barrel heater B1, B2, B3 is 64.641 watt , 42.649 watt, 42.649 watt accordingly. So, electricity consumption of barrel heater B1, B2, B3 is 0.065 kW h , 0.043 kW h, 0.043 kW h accordingly. 4.1.3 Electricity consumption of Air Compressor From Air Compressor specification list, we get, Power – 0.55 kW Voltage – 220 v Current – 4.2 amp Electricity Consumption = Power × time = (0.55 × 1) kW h = 0.55 kW h 41 Table 4. 1: Total Electricity Consumed per hour Electrical Component Electricity Consumed (kW h) Induction Motor 0.935 Barrel Heater, B1 0.065 Barrel Heater, B2 0.043 Barrel Heater, B3 0.043 Air Compressor 0.55 Total 1.635 kW h 4.2 Calculation of cost of fiber Small industry electricity tariff per unit is 7.66/- tk So, electricity cost per hour to run the machine is = 1.635 × 7.66 = 12.532/- tk per hour At present, our machine can produce up to 936gram synthetic fiber from 1kg PET flakes per hour. PET Flakes costs 35/- tk per kg. So, Cost for making 936g synthetic fiber will be = 12.532+35 = 47.532 tk/As we can see, initially we are making synthetic fiber at a very cheap price excluding any overhead cost. Compering to other synthetic fiber that we import, we can make our synthetic fiber for half of the price. As we improve our machine and bulk production of synthetic fiber will reduce the price furthermore. 42 4.3 Result Analysis 300 250 Fiber output in gram y = 0.978x + 0.419 200 150 100 50 0 0 50 100 150 Flakes input in gram 200 250 300 Fig 4. 1: Flakes input vs Fiber Output 0.6 y = 0.0018x + 0.1023 Power Consumption in kW h 0.5 0.4 0.3 0.2 0.1 0 0 50 100 150 Fiber output in gram 200 Fig 4. 2: Fiber Output vs Power Consumption 43 250 300 1.2 1 Hour 0.8 0.6 0.4 0.2 0 -2 -0.2 0 2 4 6 8 10 Cost of electricity Fig 4. 3: Cost of electricity per hour 250 Taka 200 150 100 50 0 Recycled Fiber Felt/Flock Imported Fiber Cost of different fiber Fig 4. 4: Price point of Imported and Recycled Fiber 44 12 14 1200 1000 Flakes input in gram 800 600 400 200 0 -200 0 -200 200 400 600 800 1000 Fiber output in gram Fig 4. 5: Synthetic fiber from PET flakes per kg From, above graphs and figures we can see the price of fiber production and comparison of foreign fiber. At present, Bangladesh imports the felt, flock and synthetic fiber to fulfill the countries demand. With huge amount of plastic waste already in our environment we can collect and recycle PET bottle with ease. With the advantage of cheap raw material and labour, small or medium enterprise can easily open up recycling plant. As we can produce synthetic fiber for half of price compering to others. Operating a recycling plant will easy and profitable. Our country has a rapidly growing textile industry. We can process this synthetic fiber to make polyester yarn to meet the demand of our textile industry. So, we can see that our recycling machine can help in achieving sustainable environment and also have economic value. 45 CHAPTER 5: CONCLUSION Population growth and rapid pace of urbanization pose several environmental challenges for Bangladesh. One of the challenges is the waste management, and especially plastic waste management. Mechanical recycling of PET bottles is the most preferred recovery route for relatively clean plastic waste stream. It is well suited for developing countries like Bangladesh since it is less cost-intensive. Collection process is the key to successful recycling of PET bottles and plastic waste. It lies on consumers that must become educated and motivated through designed community educational program so that identification and collection of recyclables containers becomes a routine activity. Result shows with the abundance of plastic bottle waste we can make synthetic fiber in a very cheap price compering with the other fiber. Currently we have some limitation in fiber collecting method. The fiber should be collected in a perforated large industry grade bag as the molten plastic is blown with the air compressor. 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