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Recycling Plastic Bottle into Synthetic Fiber
Article · December 2019
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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.
Our future work is consisting of adding industry grade air blower, stainless steel barrel to house
helical screw shaft and a breaker plate to get continuous fiber profile.
46
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