EFFECT OF THERMAL TREATMENT ON PHYSICAL AND CHEMICAL PROPERTIES OF RECYCLED POLYPROPYLENE
ABSTRACT
Polypropylene is widely used today in industries and also at home and its production has increase drastically over the years making polypropylene products a major contributor in environmental waste. Therefore, instead of throwing away wasted or unusable polypropylene to where it may cause harm to the environment and the whole biodiversity, recycling comes to rescue. The objective of this study is to determine the change in properties of polypropylene with recycling.For this purpose, the mechanical properties of polypropylene using five recycling generation were determined.
The polypropylene materials were cut into flakes and pretreated before recycled mechanically at 180-2100C with fabricated mold.ASTM D638 type II specimen dimensions was chosen for tensile test. Ultimate tensile stress test relates the mechanical properties such as tensile strength, elastic modulus and percent elongation to failure to the recycling generations.
The curves which were generated prove that the polypropylene properties decrease with recycling. FTIR analysis affirmed that the chemical structures of the material were not affected by the recycling process.
However, the slight decrease in properties can be compensated by adding a virgin polypropylene at a ratio before recycling. Conservative safety factors and plastics additives, filler inclusion can also correct the decrement.
Recycling of plastic materials is effective in conserving the environment andenhancing the life cycle of these materials.
TABLE OF CONTENTS
TITLE PAGE i
LETTER OF TRANSMITTAL ii
CERTIFICATION iii
DEDICATION iv
ACKNOWLEDGEMENT v
ABSTRACT vi
TABLE OF CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xi
LIST OF ABBREVIATIONS xiii
CHAPTER ONE: INTRODUCTION 1
1.1 Background……………………………………………………………………...1
1.2 Project objective…………………………………………………………………3
1.3 Justification 4
CHAPTER TWO: LITERATURE REVIEW 5
2.1 Plastics 5
2.2 Plastic recycling 6
2.2.1 Polyethylene Terephthalate …. 8
2.2.2 Polyethylenes 10
2.2.3 Polyvinyl chloride 13
2.2.4 Polystyrene 14
2.3 Polypropylene 15
2.3.1 History of polypropylene 16
2.3.2 Molecular structure of polypropylene 17
2.3.3 Properties of polypropylene 19
2.3.4 Applications of polypropylene 20
2.4 Physical and Chemical Testing 22
2.4.1 Fourier Transform Infrared Spectroscopy (FTIR) 22
2.4.2 Ultimate Tensile Strength (Ultimate tensile stress (UTS)) 24
CHAPTER THREE: METHODOLOGY 26
3.1 Material Selection 26
3.1.2 Material pretreatment 26
3.2.2 Fabrication of Mold 26
3.2 Experimental Procedure 28
3.3 Testing 33
3.3.1 Fourier Transform infrared spectroscopy 33
3.3.2 Mechanical testing 33
CHAPTER FOUR: RESULTS AND DISCUSSION 36
4.1 FTIR Analysis 36
4.2 Mechanical Properties 44
4.1.1 Ultimate Tensile Strength 45
4.1.2 Elasticity Modulus 48
4.1.3 Elongation Percent 48
4.1.4 Tensile Stress and Strain 53
CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS 59
5.1 Conclusion………………………………………………………………………59
5.2 Recommendation……………………….……………………………………….61
REFERENCES…………………………………………………………………………..62
APPENDICES…………………………………………………………………………..69
LIST OF TABLES
Table 2.1: Table of Resin Identification Codes for Different Plastics 9
Table 2.2: The mechanical properties of polypropylene and its values 21
Table 3.1: Calculated pressure summary table 29
Table 4.1: IR table of functional groups according to their range 37
Table 4.2: Summarized Ultimate tensile stress (UTS) data for each generation 46
Table 4.3: Summarized Elasticity Modulus 49
Table 4.4: Elongation Percent data for each recycled generation 51
Table I: Results for 1st Generation……………………………………………………….73
Table II: Results for 2nd Generation……………………………………………..............74
Table III: Results for 3rd Generation…………………………………………………….75
Table IV: Results for 4th Generation…………………………………………………….76
Table V: Results for 5th Generation……………………………………………………..77
LIST OF FIGURES
Figure 2.1: Schematic of the nature of chain branching varieties of polyethylene 11
Figure 2.2: Structure of polypropylene monomer types 18
Figure 3.1a: Waste Polypropylene materials gathered for the experiment 27
Figure 3.1b: Pre-treated polypropylene flakes 27
Figure 3.2: Experimental Set up 30
Figure 3.3: First generation sample from first run 31
Figure 3.4: Typical Dog bone shaped ASTM D638 specimen used for Tensile test 32
Figure 3.5: Typical Stress-Strain diagram 34
Figure 4.1: FTIR spectrum of 1stgeneration sample 38
Figure 4.2: Reference IR polypropylene spectrum 39
Figure 4.3: IR spectrum of 2nd generation 40
Figure 4.3: IR spectrum of 3rdgeneration 41
Figure 4.3: IR spectrum of 4th generation 42
Figure 4.4: FTIR spectrum of 5th generation 43
Figure 4.5: Linear regression of Ultimate tensile stress (UTS) for all generations 47
Figure 4.6: Elastic Modulus vs recycled generation trend 50
Figure 4.7 Elongation percent vs recycling generation 52
Figure 4.8: Tensile stress strain diagram for 1st recycling generations 54
Figure 4.9: Tensile stress strain diagram for 2ndrecycling generations 55
Figure 4.10: Tensile stress strain diagram for 3rdrecycling generations 56
Figure 4.11: Tensile stress strain diagram for 4threcycling generations 57
Figure 4.12: Tensile stress strain diagram for 5threcycling generations 58
Figure A: Comparison of the stress strain for all generation……………………………72
LIST OF ABBREVIATIONS
UTS Ultimate Tensile Strength
UTM Universal Testing Machine
ASTM American Society of Testing and Materials
PET, PETE Polyethylene terephthalate
PE Polyethylene
PP Polypropylene
LPDE Low-density polyethylene
HDPE High-density polyethylene
LLDPE Linear low-density polyethylene
PVC Polyvinyl chloride
PS Polystyrene
ABS Acrylonitrile- butadiene-styrene
SAN Styrene-acrylonitrile
SMA Styrene-maleic anhydride
BOPP Biaxially oriented film
FTIR Fourier Transform Infrared Spectroscopy
DTA Differential Thermal Analysis
DSC Differential Scanning Calorimetry
ATR Attenuated Total Reflectance
CHAPTER ONE
INTRODUCTION
1.1 Background
During last decades, the great population increase worldwide together with the need of people to adopt improved conditions of living led to a dramatically increase of the consumption of polymers (mainly plastics). Materials appear interwoven with our consuming society where it would be hard to imagine a modern society today without plastics which have found a myriad of uses in fields as diverse as household appliances, packaging, construction, medicine, electronics, and automotive and aerospace components. A continued increase in the use of plastics has led to increase the amount of plastics ending up in the waste stream, which then becomes a threat to the environment when the wastes are not decomposable(Hamad et al., 2013). Environmental issues are becoming prioritized in most government and community development agendas. This has motivated the search for economically efficient and ecologically effective material and energy recycling technologies (Petts, 2000). For example, the development and use of strategic technologies driven by recycling credit scheme and the imposition of the landfill tax to preserve landfill void for the future disposal of untreatable residues in England(Read et al.,1998). The potential environmental impacts from plastics are categorized under global warming, acidification, eutrophication and photochemical ozone creation(Bos et al., 2007).
Polypropylene account for around 22% of the total production of plastics in 2008, making it the second largest plastic produced beside polyethylene which is 23.7% (Plastic waste Management Institute, 2009).Polypropylene plastics or also known as polypropene, are materials that are used worldwide since the 19th century (Scheirs, 1998). Polypropylene plastics are widely used in our daily life as kitchen utensils, in toy productions, as insulators for electrical devices, and also in industrial sites as safety equipment(Gaurina-Medijumurec, 2014). Since polypropylene is widely used today in industries and also at home, its production has increase drastically over the years with increasing production of polypropylene made products. Therefore, polypropylene products is a major contributor to the pollution in the world today and now acting as a threat to both man and the whole biodiversity(Anthony, 2003). Itsnon-biodegradability makes post-consumer polypropylene a major environmental issue. Disposal of polypropylene waste by burning is not an environmentally friendly as the gases released are toxic.
Several options have been considered to reduce polypropylene waste such as reuse and recycling (Aurrekoetxeaet al., 2011). The most common examples of reuse are with glass containers, where milk and drinks bottles are returned to be cleaned and used again(Hamad et al., 2013). Reuse is not widely practiced in relation to plastic packaging of plastic products in general tend to be discarded after first use. However, there are examples of reuse in the marketplace. For example, a number of detergent manufacturers market refill sachets for bottled washing liquids and fabric softeners. Consumers can refill and hence reuse their plastic bottles at home, but in all of these cases the reusing of the plastic bottles and containers do not continue for long time especially in the food applications which makes recycling the best alternative.
Mechanical recycling and chemical recycling are the most widely practiced of these methods. However, from industrial point of view, the mechanical recycling is the most suitable because its low cost and reliability (Hamad et al., 2013). Mechanical recycling also known as physical recycling, the plastic is ground down and then reprocessed and compounded to produce a new component that may or may not be the same as its original use (Cui and Forssberg, 2003).
As to this, the recycling of post-consumer polypropylene polymer products is one of the factors in reducing the amount of wastes material produced every day (Harold, 2003). However, until today, the research on the mechanical properties of recycled polypropylene is not widely explored in open literature. Besides that, not much input of the properties of the recycled products either in mechanical or physical properties is comparable with the pure polypropylene materials. Thus, the study on the mechanical properties of the recycled polypropylene product is necessary.
1.2 Project objective
The main objective of this project are:
a) To design and fabricate a mold for purpose of this research
b) To determine how physical and chemical properties of polypropylene changes with recycling.
1.3Justification
Polymer recycling is a way to reduce environmental problems caused by polymeric waste accumulation generated from day-to-day applications of polymer materials such as in packaging and construction. The recycling of polymeric waste helps to conserve natural resource because the most of polymer materials are made from oil and gas. Since recycling has been a solution to reduce environmental problem therefore the limit at which the properties of the materials produce through this method is of high importance.
It is proven theoretically that polypropylene materials take a long time for the properties to deteriorate and also reduce cost of production since no or little virgin polymer is required and energy is conserved.
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