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Polyethylene terephthalate, commonly coded as PET, PETE, is a thermoplastic polymer resin of the polyesters and is used in liquid containers, drinks, food and synthetic fibres. Depending on its processing and thermal conditions, PET may exist both as amorphous and as semi-crystalline. PET may appear opaque, white and transparent depending on its crystalline and amorphous structure. Its crystallinity and consequently its physical and mechanical properties are highly dependent on processing conditions like processing temperature, cooling rate, stretching process etc. In this study, it was tried to summarize all about PET crystallization by referring to all studies carried out before. Crystallization is very significant properties affecting all mechanical and physical properties of PET just as for all kind of polymers. As a result, this subject has taken in very good interest so far and it is believed that this interest will go on increasingly.
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BAÜ Fen Bil. Enst. Dergisi Cilt 13(1) 26-35 (2011)
Crystallization Behavior of PET Materials
Bilal DEMİREL1*, Ali YARAȘ2, Hüseyin ELÇİÇEK3
1* Erciyes University Faculty of Engineering, Department of Materials Science and Engineering, Kayseri.
2Bartin University Faculty of Engineering, Department of Metallurgy and Material Engineering, Bartin.
3Bartin University Faculty of Engineering, Department of Naval Architecture and Marine Engineering,
Polyethylene terephthalate, commonly coded as PET, PETE, is a thermoplastic polymer
resin of the polyesters and is used in liquid containers, drinks, food and synthetic fibres.
Depending on its processing and thermal conditions, PET may exist both as amorphous
and as semi-crystalline. PET may appear opaque, white and transparent depending on
its crystalline and amorphous structure. Its crystallinity and consequently its physical
and mechanical properties are highly dependent on processing conditions like
processing temperature, cooling rate, stretching process etc. In this study, it was tried
to summarize all about PET crystallization by referring to all studies carried out before.
Crystallization is very significant properties affecting all mechanical and physical
properties of PET just as for all kind of polymers. As a result, this subject has taken in
very good interest so far and it is believed that this interest will go on increasingly.
Keywords: Crystallization, material properties, PET
PET Malzemelerin Kristalizasyon Davranıșı
Polyethylene terephthalate, PET veya PETE șeklinde kısaltması yapılan, sıvıların,
yiyecek ve içeceklerin saklanmasında ve tașınmasında, sentetik liflerin yapımında
kullanılan polyester sınıfından termoplastik polimer bir reçinedir. Termal ve proses
șartlarına bağolarak, PET amorf ya da semi-kristal yapıda olabilir. Bu özelliğinden
dolayı PET donuk, beyaz ya da camsı bir yapıda olabilir. PET’in kristal yapısı, buna
bağlı olarak da fiziksel ve mekaniksel özellikleri büyük oranda ișlem sıcaklığı, soğutma
hızı, gerdirme ișlemi gibi proses parametrelerine bağlıdır. Bu çalıșmada, PET’nin
kristalizasyonu ile ilgili daha önce yapılan bütün çalıșmalar özetlenmeye çalıșılmıștır.
Tıpkı bütün polimerlerde olduğu gibi kristalizasyon PET’nin bütün fiziksel ve
* Bilal DEMİREL,
mekaniksel özelliklerini etkileyen çok önemli bir özelliktir. Sonuç olarak, bu konu
șimdiye kadar bir hayli ilgi çekmiștir ve bu ilginin daha da artacağına inanılmaktadır.
Anahtar kelimeler: Kristalizasyon, malzeme özellikleri, PET
1. Introduction
PET has the most application among plastics and is found most commonly in daily life.
It is used especially in containers produced for storing and carrying food and liquids; in
particular carbonated soft drinks (CSDs). However, some cracking problems have been
observed at the bottom of bottles; due to either the geometrical shape of the petaloid
base or the process parameters.
In this literature review the development of the PET bottle was reviewed, followed by a
discussion of physical and chemical properties of PET and the factors that affect these
properties. Then the problem of cracks occurring in the bottle base will be reviewed
and its causes investigated in our following review paper.
2. Development of the PET bottle
PET poly (ethylene terephthalate) was developed in the 1940’s and since then it has
played an important role in the food and beverage packaging industry [1]. Due to its
popularity the use of PET in carbonated soft drinks bottles has been studied extensively
[2]. Initially, PET bottles consisted of two pieces; the blown bottle section, and a
separate ‘cap’ section fitted over the over the hemispherical bottle base. The
polyethylene cap section made the bottle self-standing. In recent times, PET bottles
have been made in one piece with a self-standing petaloid-shaped base [3].
The desirable properties of PET (clear, lightweight, high strength, stiffness, favorable
creep characteristics, low flavor absorption, high chemical resistance, barrier properties
and low price) make it the material of choice for carbonated soft drinks containers,
fibers and films [1]. Due to low cost, better aesthetic appearance, and better handling,
PET is being preferred over polycarbonate (PC) polymers [4].
PET has been also known for many years as a textile fiber forming material. But lately,
it has started to be used in extrusion foam processing for textile fibers because of its
elastic nature [5]. PET is also used as a recyclable polymer, and the markets for
recycled PET (R-PET) are growing by the year.
3. Crystallization behavior of PET
‘Crystalline’ means that the polymer chains are parallel and closely packed, and
‘amorphous’ means that the polymer chains are disordered [8]. Most polymers exist as
complex structures made up of crystalline and amorphous regions. Crystallinity is
usually induced by heating above the glass transition temperature (Tg) and is often
accompanied by molecular orientation [6]. It is impossible to reach 100% crystallinity
with the lowest free energy because polymers do not have a uniform molecular weight.
BAÜ Fen Bil. Enst. Dergisi Cilt 13(1) 26-35 (2011)
Instead, the polymers can only react to produce partly crystalline structures, usually
called "semicrystalline" [7].
The degree of polymer crystallinity depends on both intrinsic and extrinsic factors.
Narrow molecular weight, linear polymer chain structure, and high molecular weight
are very important pre-conditions in terms of obtaining high crystallinity [8].
Crystallinity is also affected by extrinsic factors, like stretch ratio, mode of extension
and crystallization temperature in the preparation of polymer films [9]. Below the glass
transition temperature, polymer chains are rigid; after reaching the glass transition
temperature, the chains become more flexible and are able to unfold under stress. If the
temperature is above Tg and stretching is carried out, the randomly coiled and entangled
chains begin to disentangle, unfold, and straighten and some of them even slide over
their nearest neighbor chains [10].
PET is a crystallizable polymer because of its regularity in chemical and geometric
structures. It is either in the semi-crystalline state or in the amorphous state. The levels
of crystallinity and morphology significantly affect the properties of the polymers
[11]. Even with limitations in its barrier properties and mechanical strength, crystalline
PET is still widely used. Polymers with high crystallinity have a higher glass transition
temperature Tg ( Tg is 67 °C for amorphous PET and 81 °C for crystalline PET ) and
have higher modulus, toughness, stiffness, tensile strength, hardness and more
resistance to solvents, but less impact strength [11,12].
Crystallinity in PET is usually induced by thermal crystallization and/or by stress or
strain induced crystallization. Thermally induced crystallization occurs when the
polymer is heated above Tg and not quenched rapidly enough. In this condition the
polymer turns opaque due to the spherulitic structure generated by thermal
crystallization aggregates of un-oriented polymers [13]. In stress-induced
crystallization, stretching or orientation is applied to heated polymer and the polymer
chains are rearranged in a parallel fashion and become closely packed [14]. The
crystallization process is composed of nucleation and spherulitic crystallization, and
may occur at temperatures above Tg and below the melting point Tm [15]. Quenching
the melt quickly results in a completely amorphous PET [12].
Crystalline polymers have a heterogeneous structure due to the interspersed amorphous
regions while amorphous polymers in all their forms (melts, rubbers, glasses, etc.) have
a homogeneous structure. Polymers are characterized by a glass transition temperature
Tg and a melting temperature Tm [16]. The glass transition behavior of semi-crystalline
polymers are greatly affected by the factors affecting degree of crystallinity such as
molecular weight, amount of crystalline phase and morphology [11, 15, 17]. The glass
transition temperature of semi-crystalline polymer is higher and broader than that of the
amorphous polymer [11].
Crystalline polymers are characterized by a Tm and amorphous polymers are
characterized by a Tg. At the melting point, polymers are like a rubber-liquid. For
crystalline polymers, the relationship between Tg and Tm has been described as follows
mg TT
(for unsymmetrical chains) (Equation 1)
mg TT
(for symmetrical chains) (Equation 2)
PET has a Tg between 340 to 353 K (67 to 80 °C) and a Tm of 540 K (267 °C).
The crystallization of PET has been widely investigated. The Avrami equation was
adopted by [18], with using the density balance method, where the amorphous fraction
was calculated from the final density at that condition, rather than the density of 100%
crystalline PET. X-ray analyses and polarizing microscopy were used to observe
crystalline structures. Different structures could be obtained by adjusting crystallization
temperature or previous melt conditions. The maximum rate of crystallization occurs at
180 °C. Further research in this subject has also been reported [19]. Studies have been
conducted on the kinetics of crystallization of different commercial PET materials in
terms of the Avrami equation with a Differential Scanning Calorimetry (DSC) method
and confirmed that the rate constant k is very sensitive to crystallization temperature
[20]. Different PET samples have different crystallization mechanisms. With
increasing crystallization temperature, spherulite diameter increases [21]. Ozawa
studied the kinetics of dynamic crystallization of PET. He obtained crystallization
curves through DSC at different cooling rates [22]. A modified Avrami equation was
applied to the primary crystallization in a non-isothermal situation. Jabarin compared
the crystallization rate parameters of both isothermal and dynamic processes, and found
that they are similar to each other in terms of mechanisms of crystallization. A method
was developed to predict the minimum cooling rate required to obtain non-crystalline
PET [23]. DSC spectrum of PET is shown in figure 1.
In addition to time and temperature, many other factors such as pressure, the degree of
molecular orientation and environment have influence on crystallization mechanism,
morphology, and final properties of PET [24, 25]. Nucleating agents also affect the
crystallization of PET. Some studies have investigated the effect of the additives on
crystallization behavior [11, 26].
Jiang et al have studied the effects of three kinds of nucleating agents, including talc,
sodium benzoate and an ionomer (Ion., Na+) on the crystallization kinetics of PET by
using DSC. They have used Avrami and Ozawa equations to obtain the parameters of
the isothermal and the nonisothermal crystallization kinetics, respectively. They
concluded that three nucleating agents can increase the crystallization rate of PET, and
sodium benzoate has the most excellent nucleating effect for the crystallization of PET
with the same content of nucleating agent. The crystallization mode of PET might shift
from three-dimensional growth to two dimensional growth by the addition of the
nucleating agents [42].
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Figure 1. DSC spectrum of PET.
The crystallization behavior of PET with and without catalysts has been compared by
[41]. They found that nucleation has a great influence on overall crystallization rate at
low temperatures near Tg. Moisture and molecular weight have a great effect on
crystallization [23, 27]. It is found that the kinetics of crystallization depends on
molecular weight and that with increasing percentage of moisture, the half-time
crystallization and induction time of crystallization decrease. Spherulite growth rate
was independent of water absorbed [20].
In a study with characterization methods for PET, different experimentals methods have
been investigated by Faraj at al. They have used different techniques such as X-ray
diffraction (XRD), energy dispersive X-ray (EDX), differential scanning calorimetry
(DSC), thermogravimetric analysis (TGA), atomic force microscopy (AFM) and UV
spectrophotometer for characterization the structural, thermal and optical properties of
the PET. The surface morphology and optical transmittance of PET substrate have been
reported. They recommend that high quality films on PET substrate give the possibility
to use as alternative substrates to the conventional glasses [43]. XRD patterns of PET,
EDX spectrum of the PET and AFM analysis of PET are shown in figure 2, figure 3 and
figure 4 respectively.
Stress is an important factor, affecting crystallization. The effect of stress-induced
crystallization of PET has been investigated with density measurements, wide-angle X-
ray diffraction and small-angle light scattering measurements [28]. Amorphous PET
films were stretched at constant strain rates below and above Tg. The stress-induced
crystallization has also been analyzed as a function of time and orientation level [29].
Marco et al. focused on the crystallinity induced by stretching PET at temperatures
above the glass transition and on the influence of stretch and blow molding parameters
on the properties of the final product [30].
Figure 2. XRD patterns of PET.
Figure 3. EDX spectrum of the PET.
Figure 4. AFM analysis of PET.
BAÜ Fen Bil. Enst. Dergisi Cilt 13(1) 26-35 (2011)
A study has been conducted with PET material and found that reducing the shot size
(amount of material injected into the mould cavity) will minimize crystallinity while
hold time (length of time the gate remains open allowing more material to be pushed
into the mold cavity) has no effect at the lower shot size. However, with a larger shot
size, a low hold time is necessary to reduce crystallinity. The least crystallinity occurs
with minimum hold time and minimum shot size [31].
In a study conducted by Hanley et al., it was found that the extent of the orientation and
crystallinity depends upon the geometry of the bottle base, and that there is an abrupt
change from the amorphous region to the crystalline regions. The valley and the
transition region to the foot are the most biaxially oriented regions of the base. The
orientation in the middle of the foot is more circular and the crystallization is less. This
shows that the stretch in this region is more uniaxial (or less biaxial) but crystalline
lamellae are still observed [32].
Some experimental works has been conducted on the orientation and crystallization of
PET films subjected to uniaxial or biaxial drawing under industrial processing
conditions [38-40]. The changes in the degree of orientation and crystallinity have been
investigated using the wide-angle X-ray scattering (WAXS) technique [39]. By
analyzing the crystalline diffraction patterns, they found that the orientation of the
developing crystals depends on the relation of the draw rate and temperature to the
chain relaxation process and that the crystallization rate is highly temperature
dependent. Everall et al. used polarized attenuated reflection infrared spectroscopy to
quantify biaxial orientation in PET films and stretch blow molded bottles [41].
Crystallization may be due to many nuclei centres forming small spherulites at low
temperatures. Larger crystal structures may be obtained when the material is
crystallized at higher temperatures or by slow cooling from the melt but 100%
crystallinity is never possible in normal processing conditions [15, 17]. Usually the
percentage crystallinity is lower than 90% [17]. In general, polymeric materials are
semicrystalline with crystalline and amorphous phases co-existing [38]. Mixed
amorphous crystalline macromolecular polymer structure is shown in figure 5 [38].
Figure 5. Mixed amorphous crystalline macromolecular polymer structure [38].
The morphology is described by the spherulite radius, lamellar thickness and long
period; distance between two adjacent lamellae. Small angle light scattering
microscopy and X-ray analyses are usually applied to obtain these parameters [15].
Even at the same crystallinity content, samples crystallized at higher temperature are
more opaque and brittle [18]. Samples with smaller spherulite sizes have higher yield
stress, lower ultimate elongation and high brittleness temperature and higher impact
strength [40].
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... The material appeared to remain in an amorphous state. Polyesters were characterized by a slow crystallization rate [24][25][26] and achieving crystallization may necessitate an annealing process with an elevated temperature and speed to enhance the crystallization rate. ...
... The material appeared to remain in an amorphous state. Polyesters were characterized by a slow crystallization rate [24][25][26] and achieving crystallization may necessitate an annealing process with an elevated temperature and speed to enhance the crystallization rate. Figure 7. Cross-sections using optical microscopy of WF_r-PET fibers and blends with varying Acid-Enz_TC percentages of 1, 2, 5, and 10%, collected at a winding speed of 1000 m/min. ...
... The material appeared to remain in an amorphous state. Polyesters were characterized by a slow crystallization rate [24][25][26] and achieving crystallization may necessitate an annealing process with an elevated temperature and speed to enhance the crystallization rate. Several factors contributed to this phenomenon. ...
Full-text available
Polyester/cotton fabrics with different proportions of Tetron Cotton, TC (35% Cotton/65% PET), and Chief Value Cotton, CVC (60% Cotton/40% PET), were investigated by removing the cotton component under various phosphoric acidic conditions including the use of cellulase enzymes. The remaining polyethylene terephthalate (PET) component was spun using the melt spinning method. Only 85% H3PO4-Enz_TC could be spun into consistent filament fibers. The effects of Acid-Enz TC (obtained from a powder preparation of 85% H3PO4-Enz_TC) at different weight amounts (1, 2, 5, and 10 %wt) blending with WF-rPET powder prepared by white recycled polyester fabric were evaluated for fiber spinnability at different winding speeds of 1000 and 1500 m/min. The results revealed that recycled PET fiber spun by adding Acid-Enz_TC up to 10 %wt gave uniformly distributed filament fibers. A comparative study of the physical, thermal, and mechanical properties also investigated the relationship between the effect of Acid-Enz_TC and the structure of the obtained fibers. Acid-Enz_TC:WF-rPET (5:95) was the optimal ratio. The thermal values were analyzed by DSC and TGA and crystallinity was analyzed by XRD, with mechanical strength closed to 100% WF-rPET. The FTIR analysis of the functional groups showed the removal of cotton from the blended fabrics. Other factors such as the Acid-Enz_TC component in WF-rPET, extraction conditions, purity, thermal, chemical, and exposure experiences also affected the formability and properties of recycled PET made from non-single-component raw materials. This study advanced the understanding of recycling PET from TC fabrics by strategically removing cotton from polyester–cotton blends and then recycling using controlled conditions and processes via the melt spinning method.
Full-text available
A nanogenerator is a device that produces nanoscale electricity, typically using piezoelectric or triboelectric effects. Piezoelectric nanogenerators convert mechanical energy such as vibration or pressure into electrical energy, while triboelectric nanogenerators generate electricity through the friction of two different materials. It is a promising technology that can convert all forms of mechanical energy into electricity for large-scale commercial production. The piezoelectric nanogenerator is based on the nanostructured functional material, while the triboelectric nanogenerator is based on a combination of functional material and flexible polymers with appropriate flexible electrodes, featuring manufacturability, durability, and ability to integrate with other technologies. Nanogenerators have the potential to be used in a variety of applications, such as powering small electronic devices and sensors, harvesting energy from human movement or environmental vibrations, and even generating electricity from the blood flow in the human body. They are also being explored as a potential source of renewable energy. Nanogenerators are still in the early stages of development, and research is ongoing to improve their efficiency and reliability. However, the potential applications of this technology make it an exciting area of research with the potential to revolutionize the way we generate and use electricity. The current work describes the manufacturing technology of highly flexible triboelectric nanogenerators and reports on inexpensive and simple methods for the production of electrodes. The electrical characteristics such as open circuit voltage, short circuit current, and durability test of the device were carried out. The designed devices demonstrated various applications in charging a capacitor, powering LEDs, LCDs, and digital clocks, thus functioning as self-sufficient systems for electronic devices. Motivated by the facts mentioned above, the current work is dedicated to the synthesis and characterization of functional materials based on the ZnS nanosheet structure and its application in the field of nanogenerators. Detailed structural, morphological, compositional, and surface potential analyzes were performed. The thesis consists of eight chapters and the highlights are listed here: Chapter 1 starts with a brief introduction to the importance of green energy, followed by the motivation, the working principle of different nanogenerators, their governing equation, different working modes, and the origin of the problem for the current research work. A detailed review of the literature on piezoelectric and triboelectric nanogenerators based on different functional materials was also presented. Finally, the goals of the work were derived from the review of the literature and the selection of the materials was made. Chapter 2 describes the experimental procedures to prepare the material in nanosheet structure. The simple hydrothermal technique has been discussed at length. This chapter also explains the rationale and the use of sophisticated tools to characterize the synthesized material in detail. Chapter 3 deals with the step-by-step fabrication of nanogenerators, with the basic principle of the instruments for electrical characterization of the fabricated nanogenerators, as well as some standard calculation steps to measure various parameters, e.g., power, charge transferred, efficiency, etc., which is common for all work chapters. Chapter 4 focuses on the synthesis of two-dimensional nanosheets of zinc sulfide (ZnS) on a flexible aluminum (Al) foil substrate using a hydrothermal technique. The synthesis process occurs at a temperature of approximately 140°C for a duration of around 4 hours. A piezoelectric device named PND1 was created using an Indium-doped Tin Oxide (ITO) coated on a Polyethylene Terephthalate (PET) substrate as the top electrode, and ZnS deposited on the Al foil as the bottom electrode. To generate an electric potential, the top ITO electrode was tapped on the ZnS nanosheets. The analysis revealed an open-circuit voltage (VOC) of approximately 400 mV for the ZnS nanosheets-based nanogenerator when gently tapped with a finger. However, applying toe pressure yielded the highest output of around 600 mV for a single nanogenerator. Furthermore, experiments involving polarity switching and superposition were conducted to confirm the nanogenerator's performance. The nanogenerator exhibited an instantaneous output power density of 0.366 mW.m-2. This chapter explores the potential of a ZnS-based energy harvester that efficiently captures biomechanical energy for next-generation flexible self-powered electronic devices. It also suggests that ZnS nanosheets offer advantages over ZnO nanosheets in terms of a simpler single-step production process, lower cost, and higher output gain. Additionally, the impact of increased growth temperature on the morphology and output of the nanogenerator was investigated. The PND2 device, utilizing a larger nanosheet-based substrate grown at a temperature of 160⸰C, yielded approximately 1.5 times more output compared to the PND1 device. In Chapter 5, the focus is on the development of triboelectric nanogenerators (TENGs) using cost-effective inorganic materials. This chapter investigates the fabrication of a TENG based on ZnS nanosheet arrays, marking the first exploration of this approach. The TENG was created by incorporating a ZnS nanosheet film and polydimethylsiloxane (PDMS) as the active tribo-layers. The uniqueness of this research lies in the selection of materials, namely pure ZnS nanosheets and PDMS-aluminum (Al) cover foil. When subjected to manual excitation force, the developed TENG, measuring 5×5 cm2, generated an output voltage of approximately 8 V and a short-circuit current of about 7.12 µA. Additionally, the TENG incorporating pure ZnS nanosheets on an Al substrate produced an output voltage nearly twice that of the TENG utilizing only the Al substrate. By introducing ZnS nanosheets on the Al substrate, the surface area and roughness increased, leading to improved performance. Later in the chapter, the optimized device achieved an instantaneous output power of 4.33 mW.m-2. The TENG's high stability was verified through testing its response over 1000 cycles. Moreover, the TENG successfully powered portable electronic devices such as digital watches, thermometers, calculators, and 64 LEDs when connected to a capacitor. Furthermore, the TENG demonstrated its capability to sense force and pressure, and its output response served as a self-powered clock pulse for digital circuits. The proposed TENG offers ease of handling, simplicity, and affordability, and the performance of the ZnS-based TENG can be enhanced by exploring alternative tribo-materials in place of PDMS. Chapter 6 investigates into comprehensive research on the utilization of triboelectric nanogenerators (TENGs) for converting mechanical energy into electrical energy. One major challenge in TENG development is enhancing charge generation. In this chapter, the potential application of surface-modified aluminum foils using commercially available emery papers with different grit sizes is investigated. The TENG based on these surface-modified Al substrates (SM-TENG) exhibits superior triboelectric performance compared to TENG devices based on plain Al substrates. The SM-TENG device demonstrates a triboelectric open-circuit voltage (Voc) of approximately 138.1 V and a short-circuit current (Isc) of about 27.78 µA, which is around 2.4 times and 2.5 times greater, respectively, than that of plain Albased TENGs. This chapter presents a simple and cost-effective method for modifying any surface. Furthermore, ZnS nanosheets (NSs) arrays are introduced onto the surface-modified aluminum substrate through hydrothermal growth to increase the effective contact area. The modified TENG with ZnS exhibits a Voc of approximately 262 V and an Isc of around 56 µA, which are approximately 4.6 and 5 times greater than the values achieved by plain aluminumbased TENGs. The fabricated TENG demonstrates an impressive output power density of about 1.325 W/m2 when connected to a low load resistance of approximately 2 MΩ. The mechanical durability of the line-patterned ZnS NSs-based TENG device is also tested over approximately 10,000 cycles, showing no significant performance degradation. This simple and affordable surface patterning process offers practical advantages. Additionally, the electrical energy produced by the TENG device successfully powers 40 white LEDs, 56 green LEDs, and 100 red LEDs individually. Thus, the proposed TENG proves to be reliable and suitable for powering low-power electronic devices. Chapter 7 focuses on the use of TENG, which can convert excess kinetic energy into electrical energy and act as a self-sufficient sensor. Herein, a unique technique for modifying contact points by increasing the effective surface area of the tribolayer using a simple and scalable printing method has been carefully examined. In this current chapter, we introduce the morphology of ZnS nanostructure directly on an aluminum electrode as a tribo-positive layer by a hydrothermal process and various line patterns directly on transparent OHP foils by a monochrome laser printer as a tribo-negative layer to increase the effective contact area between two tribolayers. ZnS nanostructures and patterned OHP foils increase the contact points between these tribolayers, resulting in the highest open-circuit pulsed output voltage of ~420 V and a pulsed short-circuit current density of ~83.33 mA.m-2. Furthermore, with the proposed surface modification technique, an ultra-high instantaneous output power density of ~3.9 W.m-2 at a load resistance of 2 MΩ could be easily achieved. The direct power conversion efficiency reached up to 66.67% at a 2 M load, which is very high compared to other traditional TENGs. In addition, the manufactured TENG was demonstrated for novel road safety applications in hilly areas to control vehicle movement and was also tested to light up 130 RGB and 675 red LEDs directly. Therefore, the current idea of surface engineering using laser printers will be helpful for energy harvesting enthusiasts to develop more efficient nanogenerators for higher energy conversion. Chapter 8 summarizes the main achievements of the work and gives general conclusions from the current work as well as suggestions for future work.
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The future is the recovery of the filler and its reuse in hybrid materials. It is important that as a result of recycling, the filler does not lose its properties, but acquires new ones. The aim of this research work was to investigate the effect of filler recovered by pyrolysis on the flammability of poly(ethylene terephthalate) and recycled PET. It was important to obtain a flammability class higher or equal to the pure PET and RPET matrix. Flammability tests carried out using the UL94, LOI, and PCFC methods allowed perform a first characterization of the properties of materials during their combustion. These studies show that it becomes possible to give specific functional properties to recycled fillers.
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This work provides an overview of the importance of recycling PET waste to reduce the environmental impact of plastic waste, conserve natural resources and energy, and create jobs in the recycling industry. Many countries have implemented regulations and initiatives to promote the recycling of PET waste and reduce plastic pollution, such as extended producer responsibility (EPR) systems, bans on certain single-use plastics, and deposit–return systems for plastic bottles. The article further underscores the versatility of recycled PET, as it can be transformed into various products such as fibers, sheets, film, and strapping. These recycled materials find applications in numerous sectors including clothing, carpets, upholstery, and industrial fibers. Recognizing the importance of collaboration among governments, industries, and individuals, we emphasize the need for sustainable PET waste management practices and the promotion of recycled materials. The article also provides information on India’s experiences with PET waste management and regulations in other countries. It is important to note that the global production and consumption of PET have increased significantly in recent years, with the packaging industry being the largest consumer of PET. This has resulted in a significant increase in the generation of PET waste, which poses a significant environmental and health hazard if not managed properly. PET waste can end up in landfills, where it can take hundreds of years to decompose, or it can end up in the oceans, where it can harm marine life and the environment. Therefore, the proper management and recycling of PET waste are essential to mitigate these negative impacts. In terms of India’s experiences with PET waste management, several initiatives have been implemented to promote the recycling of PET waste. For example, the government has launched the Swachh Bharat Abhiyan campaign, which aims to promote cleanliness and sanitation in the country to promote waste segregation and recycling.
Due to the rise of nosocomial infections and the increasing threat of antibiotic resistance, new techniques are required to combat bacteria and fungi. Functional antimicrobial biodegradable materials developed from low-cost renewable resources like polysaccharides would enable greater applications in this regard. Our group has developed and characterized a new antimicrobial polymer using commercially available N-ethyl piperazine and starch via simple one-pot method. The prepared antimicrobial polymer was characterized by FTIR and NMR. In addition, the thermal properties of the synthesized antimicrobial polymer were examined through TGA and DSC. The antimicrobial potential of the prepared material was investigated using the bacteria, Staphylococcus aureus, Escherichia coli, and Mycobacterium smegmatis and a fungi Candida albicans. The result indicates that, as the amount of polymer increases, the antimicrobial activity also increases. SA-E-NPz exhibited a zone of inhibition in the range of 8-13 mm, and the MIC was found to be < 0.625 mg against all four microbes. The antimicrobial activity of polymer coated on fabric was also studied. Furthermore, the cytotoxicity studied against human fibroblast cell lines showed that the prepared polymer is non-toxic to the cells. The study concluded that the synthesized polymer shows good antimicrobial activity, is non-toxic to human fibroblast cells, and thus can be used for wound dressing or textile applications.
The Physics of Polymers presents the elements of this important segment of material science, focusing on concepts above experimental techniques and theoretical methods. Written for graduate students of physics, material science and chemical engineering and for researchers working with polymers in academia and industry, the book introduces and discusses the basic phenomena which lead to the peculiar physical properties of polymeric systems. After more than ten years, with many thousands copies in use, the time has come for a revision and expansion this popular work. The revised and expanded Third Edition includes: A new chapter dealing with conjugated polymers, explaining the physical basis of the characteristic electro-optic response, and the spectacular electrical conduction properties of conjugated polymers created by doping. Polyelectrolyte solutions with their special properties caused by Coulomb forces are newly treated, in chapters of the book dealing with ordering phenomena, the unusually high viscosit and the superswelling of gels. Since basic understanding of melt crystallization has greatly changed during the last decade, the corresponding chapter has.
Structure development in PET film during high strain-rate, constant-force (CF) deformation in the temperature range 80–96°C is compared with structure development during lower strain rate, constant-extension-rate (CER) deformation in a similar temperature range. The higher (maximum) strain rates involved in CF drawing mean that much of the deformation takes place in a regime where the time available for orientational relaxation and crystallization is short. This results in high levels of `non-crystalline orientation' and low levels of crystallinity compared to structures obtained from CER drawing. In CER drawing, due to the lower strain rates, the degree of crystallinity always has time to reach pseudo-equilibrium values corresponding to a given level of non-crystalline orientation, and the amount of orientational relaxation occurring during drawing has the dominant influence on structure development. In CF drawing, pseudo-equilibrium crystallinity values are not reached, except when the deformation approaches the tail-end of the strain-rate spectrum. The results also provide confirmation that microstructure data obtained from rapidly quenched samples are consistent with microstructure data obtained from real-time experiments.
The crystallization behaviour of poly(ethylene terephthalate) (PET) containing different amounts of catalysts as well as of PET without catalysts has been studied. The kinetics of crystallization from the glassy state has been investigated by time-resolved small-angle X-ray scattering employing synchrotron radiation. The degree of crystallinity and Ruland's lattice distortion factork were measured by wide-angle X-ray scattering. The results show that not only calcium acetate but also manganese acetate acts as a nucleating agent in PET. If the crystallization takes place close to the glass transition temperature, the catalysts also influence the amount of lattice distortions: the larger the nucleating effect, the smaller the factork. This is explained by the fact that, due to restricted motion of the molecules, the amount of lattice distortion of the crystals within a spherulite increases with increasing distance from the centre of the spherulite.
Plant tests and finite element (FE) analyses of the injection stretch-blow moulding (ISBM) process of polyethylene terephthalate (PET) bottles have been carried out in this study with a view to optimizing preform designs and process conditions. Plant tests were carefully conducted at first to make bottles in a 330 ml mould from four preform designs under different process conditions. Both a digital handheld thermometer and a FLIR ThermoCAM Imager system were used to measure the initial preform temperature distributions (IPTDs). Comprehensive FE analyses using ABAQUS were then carried out to model the ISBM of these bottles, using a physically based model (Buckley model) to model the complex constitutive behaviour of PET. It was found that the numerical simulations often resulted in free blowing or over-thinning of the bottle bottoms when the measured IPTDs and process conditions were modelled. Parametric studies of the IPTDs, the pre-blowing pressure and the material parameters of the Buckley model were carried out. It was demonstrated that all of them had considerable effects on the effectiveness of FE modelling. In particular, the stress-strain relations modelled by the Buckley model were very sensitive to two parameters used to model the strain-stiffening behaviour. By carefully adjusting the material parameters and process conditions, successful simulations with excellent bottle thickness predictions were then achieved. It is concluded that the model parameters must be obtained by accurately testing the bottle-grade PET with similar process conditions to those in industrial ISBM so that the Buckley model can be confidently used to model the ISBM process. It is also found that good predictions of bottle wall thickness alone do not necessarily justify the numerical modelling. Validation of the deformation process may be equally important.
Effects of three nucleating agents concluding talc, sodium benzoate (SB) and an ionomer (Ion., Na+) on crystal- lization of poly(ethylene terephthalate) (PET) were studied by differential scanning calorimetry (DSC) and polarized opti- cal microscope (POM), the parameters of crystallization kinetics were obtained through Avrami and Ozawa equations. The fold surface free energy σe of pure PET and PET/nucleating agent blends was calculated by Hoffman-Lauritzen theory. The results indicate that the three kinds of nucleating agents increase the crystallization rate constant through promoting their nucleating effect for PET crystallization, among which SB is the best one with the same content. The crystallization mode of PET might shift from three-dimensional growth to two-dimensional growth by the addition of the nucleating agents. The values of σe of PET/nucleating agent blends are much less than that of pure PET, and PET/SB (99:1) blend has the least value of σe (18.2 mJ/m2). The conclusion based on Hoffman theory is similar to the analysis by Avrami and Ozawa equa- tions.
Crystallization kinetics of oriented poly(ethylene terephthalate) have been studied in a temperature range close to Tg. It has been shown that orientation of the amorphous phase promotes a substantial increase in crystallization rate. This effect, in turn, depends on the crystallization temperature: the higher the temperature, the stronger is the effect of orientation. From experimental results it was possible to make an estimation of parameters describing quantitatively the crystallization kinetics in the oriented state.