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Characterization of scrap poly(ethylene terephthalate)
Abstract
The goals of the investigation were: to indicate the methods of characterization of recycled polymers, to show general tendencies in properties deterioration and characterize recyclates on Central Europe and European Community markets. The properties and composition of scrap poly(ethylene terephthalate) from several sources were characterized by: TGA, DSC, FTIR, tensile properties, dynamic viscosity, intrinsic viscosity and thermo-oxidative stability. We found that all PET regrinds contained admixture of other polymers (0.1–5 wt%). The presence of more than 50 ppm PVC makes PET worthless for advanced application as film forming, because it catalyzes the hydrolysis and reduces the strength of material. Although the individual flakes of recycled PET show almost unchanged molecular characteristics and properties, the processed regrinds always exhibit worse properties. Partial restoration of recycled PET properties can be achieved by careful working, removing the dust fraction and by proper drying. The difference between studied PET's results from different applied recycling procedure. Admixtures of polymers without compatibilizer always deteriorate tensile properties. Various levels of stability of polymer viscous flow during film and tape extrusion were observed, depending on composition of recycled PET from various sources. Microgels were observed in all samples during film extrusion.
... PET recycling is becoming increasingly important, especially in recent years. [52,[81][82][83][84][85][86] It has provided a variety of techniques for recycling discarded beverage cans and many other bins comprising PET or PET mixes with other materials. Reprocessing with virgin resin, blending, compatibilization, and recycling through chemical reactions and solutions are a few of them. ...
... The initial stage in the mechanical recycling of PET is to remove as much contaminated material as possible. [67] PET flakes should meet certain basic standards, according to many researchers, [82][83][84]100] to achieve successful PET recycling. Table 3 shows the minimum conditions for PET flakes to be mechanolytically recycled. ...
... Minimum specifications for mechanical recycling of PET flakes[82][83][84]. ...
Most plastic products should be recycled or reused because they do not readily assimilate into the environment owing to their non-biodegradability. One such plastic is polyethylene terephthalate (PET), a versatile polymer with numerous applications and it accounts for a major portion of global plastic consumption. This manuscript is a review of PET recycling and the production of rPET (recycled PET)/polyester composites reinforcing with various natural fibers in the realm of environmental consequences. The focus is on decreasing plastic trash by utilizing it into transforming to secondary usable products, thus fulfilling the need for sustainability. Utilizing rPET as a matrix material minimizes the demand for virgin materials while also addressing the issue of environmental degradation brought on by post-consumer PET waste. This review article summarizes research on post-consumer PET waste recycling and its use in processing and creation of high-performance composites based on rPET/polyester matrix and blend of various natural fibers. Effects of natural fiber size, fiber content, and fiber surface modifications on the mechanical properties of rPET or polyester matrix-based composites along with discussions on the processing techniques have been exclusively described in this review work.
... Consider the case of PET recycling, the source of poor stability in recycled material usually comes from the presence of the contamination such as water content, coloring pigments or acetaldehyde (extracted from printed ink labels) bring a challenge in determining final properties of recycled material which are refined from low molecular weight (M w ) and low crystallinity (Salminen 2013). Meanwhile, Pawlak et al. (2000) emphasized worthless material for advanced application relevant to higher PVC content in rPET. proposed a requirement for rPET to be reprocessed as listed in Table 1. ...
... The processing cycle influenced PET structure, hence reasonably responsible for the reduction in mechanical properties, flow behavior including the melt flow index (MFI) measurement (Baccouch et al. 2017;Lopez et al. 2014;Nait-Ali 2016). The brittleness of rPET also reported by others (Pawlak et al. 2000;Zander et al. 2019). ...
... A comparative study on thermal measurement corresponding to multiple recycling increased the crystallisation temperature (T c ) but reduced the T m for rPET. Degradation of rPET can be detected from the increase in T c , and reduce of T m (Pawlak et al. 2000). As the number of processing cycle increases, increasing amount of imperfect crystal were detected. ...
Plastic production always stands out with the difficulty of recycling after use. Tens of millions of tons of utilized polymeric materials are disposed each year. Polymer recycling is a pathway to diminish ecological obstacles caused by polymeric waste accumulation from daily applications of polymer materials such as packaging and textiles. Yet, the recycling trouble is still a main challenge. Recycling of plastics requires knowledge in four areas. These areas are plastics collection, their separation, rework technology and recycled products. Existing markets will ensure that post-consumer polymer waste has an economic value. These markets are generally textile sector. Recycled thermoplastic polymers take their place in the market after being converted into textile fiber. Recycling of waste plastics into new textile products is very important for ecology and world sustainability. Today, many fashion and sports textile companies use different textile fibers recycled from waste plastics in many different products (from sportswear, from casual wear to textile products used in shoes). In this chapter, information regarding the stages of the recycling processes and recycling types applied to plastic waste materials was given. Furthermore, the important recyclable thermoplastics polymers types such as PET (polyethylene terephthalate), PP (polypropylene), PA (polyamide), and PLA Poly(lactic acid), their recycling processes, and their recent commercial developments were also covered from the textile point of view. In the coming period, it is expected that the interest of textile producers and consumers in recycling and new textile products produced by recycling from plastic wastes will increase day by day.
... (b) Melt reclaiming can produce cyclic and linear oligomers, which can affect the final product's features, such as printability or dyeability [159]. (c) Impurities such as polyvinylidene chloride (PVDC), PVC, glues, paper, ethylene-vinyl acetate (EVA), etc., produce acidic mixtures, which catalyze the hydrolysis of the PET's linkages of ester during thermal reprocessing [160]. (d) The yellowing of recycled post-consumer PET is another disadvantage. ...
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.
... CuO (4.845%), and FE2O3 (4.023%), which were probably from additive agents such as flame retardants, stabilisers, and oxidants during the manufacturing process [5,12,54-57] and also due to the contamination [12,58]. ably from additive agents such as flame retardants, stabilisers, and oxidants during the manufacturing process [5,12,[54][55][56][57] and also due to the contamination [12,58]. Figure 5 illustrates the Fourier transform infrared (FTIR) (TA Instruments, DE, USA) spectra of rPET flakes and the FTIR list of functional groups shown in Table 2. ...
Nowadays, the environmental impact of plastic waste is crucial, and in the energy industry, fly ash, a type of solid waste, has also prompted severe ecological and safety concerns. In this study, we synthesised composite material from two industrial wastes: recycled polyethylene terephthalate (rPET) as the matrix and fly ash as the filler. The effect of different fly ash loadings on the thermal behaviour and microstructure of the composite material using rPET were evaluated. Various loading amounts of fly ash, up to 68%, were added in the rPET mixtures, and composites were made using a single-threaded bar’s barrel extruder. The feeding zone, compression zone, and metering zone made up the three functional areas of the extruder machine with a single-flighted, stepped compression screw. The composite materials were subjected to DSC and SEM equipped with EDX spectroscopy tests to examine their thermal behaviour and microstructural development. It was found that the thermal behaviour of rPET improved with the addition of fly ash but degraded as the fly ash loading increased to 68%, as confirmed by the DSC study. The composites’ microstructural development revealed an even filler distribution within the polymer matrix. However, when the fly ash loading increased, voids and agglomeration accumulated, affecting the composites’ thermal behaviour.
... extruder type, screw speed); residence time; contaminants (e.g. poly(vinyl chloride) (PVC), adhesive residues); the initial molecular weight; initial carboxyl end group content; and the moisture content of the material [10][11][12][13]. The latter is usually controlled by pre-drying of the PET, as even a water content of 50 ppm causes detectable degradation when processed at 280 • C [14]. ...
During melt-processing, the molecular weight of poly(ethylene terephthalate) PET, being prone to hydrolytic degradation, decreases proportionally with its initial moisture content. Therefore, to avoid undesired deterioration of the physical and mechanical properties, PET granules or recyclates are generally dried (the residual moisture must be generally lower than 500 ppm) just prior to melt-processing. In this research, in contrast to the general practice, PET granules with increasing moisture content in the range of 30-3520 ppm, as conditioned in a climate chamber, were melt blended with a constant amount (13%) of ethylene-butyl acrylate-glycidyl methacrylate (EBA-GMA) type reactive terpolymer by twin screw extrusion. It was found that moisture boosts the reactive toughening process, and consequently, the notched Izod impact strength increases by up to 600%. Notched impact strength higher than 50 kJ/m² was reached only by using PET with optimal (1710 ppm) moisture level instead of fully dried granules, as starting material. It is also noteworthy that the tensile strength and stiffness of the blends showed little variation over the examined moisture content range. Scanning electron microscopic (SEM) analyses show that the size of the dispersed phase decreases continuously with the increasing initial moisture content of PET, which is explained by the increasingly effective interfacial compatibilisation with the terpolymer. Compatibilisation reactions are accelerated by the low-molecular-weight PET chains of increased reactivity that are formed in situ in the presence of moisture during melt-processing. The observed phenomenon can be advantageously utilized for upgrading recycling technology.
The synergistic effects of thermoplastic poly(ether-ester) elastomer (TPEE) and bentonite nanoclay on mechanical, morphological, thermal, and dynamic mechanical properties of recycled poly(ethylene terephthalate) (R-PET) were investigated. The efficiency of TPEE as impact modifier for the R-PET was evidenced by a significant increase in the impact strength and elongation at break with increasing TPEE contents (from 10 to 30 wt%), while the tensile strength and Young’s modulus exhibited an opposite trend. The 70/30 (wt%/wt%) R-PET/TPEE blend was selected as an optimum formulation for further blending with a very low loading of bentonite (1−5 parts per hundred of resin, phr) using the same processing techniques (extruding and injection molding). X-ray diffraction and transmission electron microscopy revealed that the 1 phr bentonite nanocomposite exhibited an exfoliated structure with the highest improvement in the mechanical properties compared with other nanocomposites and the unfilled blend. Meanwhile, the nanocomposites with 2, 3, and 5 phr bentonite formed tactoid or agglomerated bentonite morphology. Differential scanning calorimetry, thermogravimetric and dynamic mechanical analyses demonstrated a noticeable increase in the crystallization temperature, a comparable thermal stability, and a slight increase in the glass transition temperature, respectively, of all nanocomposites when compared with those of the neat R-PET.
The low-temperature slow pyrolysis of PET waste was studied. After intensive thermal activation, the waste PET could be completely pyrolyzed at 25°C min−1 to the final temperature of 400°C. The main components of the resulting oil were paraldehyde (54.7 wt.%) and ethylene glycol (23.7 wt.%); further, benzoic acid and benzoates were obtained. Such products represent valuable intermediates for industrial use or other applications. In addition, the pyrolysis produced a solid carbonaceous residue, particularly usable as a low-ash and low-sulfur smokeless fuel (HHV 31.3, LHV 30.4 MJ kg−1). Thus, the low-temperature pyrolysis of PET waste yields products that are easy to put to use with no demands on the purity of the feedstock.
Since the beginning of polymer synthesis, a huge modification and development have taken place in this field which resulted in a world where people cannot think of a single day without a polymer product. They are light in weight, affordable and have the potential to provide a similar strength like the traditional metallic objects. As the demand for polymer products is increasing rapidly, its characterization and evaluation of mechanical properties become essential for making a reliable, scientific and cost-effective product design. Recently the incorporation of biopolymers in the global market has made this industry more attractive to consumers and government bodies. But the main challenge lies in its characterization as plastics and polymers found in nature or synthesized artificially have a wide range of physical and chemical properties. So, a particular set of instruments that can evaluate the properties of a group of polymers, may not be usable for a different group with the same accuracy and technique. Researchers are working incessantly to find out effective methods for this purpose and many of them are successful in finding some crucial properties of polymers like strength, elastic modulus, viscosity, hardness etc. The present work briefly discusses the superiority of polymer materials and the research work that has been carried out so far for the characterization of the same. Study on the biopolymer, its characterization and necessity in the context of environmental sustainability are also included in this literature.
To progress towards a more sustainable plastic system, multiple interventions are required, including the decoupling from fossil feedstock. Biobased plastics therefore have to be integrated in plastic waste management systems. This should, however, not hamper the performance of current recycling systems. Several studies have previously suggested that the uptake of poly lactic acid (PLA) in this system would endanger poly (ethylene terephthalate) (PET) recycling. This study reports the estimated concentration of PLA in recycled PET and the effect of the presence of this impurity on the optical and thermal properties of recycled PET. The current concentrations of PLA in recycled PET in the Netherlands were modelled to vary between 0% and 0.019%. When the PLA consumption rises, the concentration in recycled PET can be kept below 1% with NIR technologies. The impact of 0.1 to 1% PLA in recycled PET on the optical and thermal properties was negligible. Conversely, the negative impact of 0.1% PVC was substantial. Also the impact of 0.1% EVOH on recycled PET was studied and like PLA found to be limited. This study therefore contravenes previous studies on the impact of PLA on the quality of recycled PET. The difference between this study and the previous studies is that within this study, recycled PET has been processed in agreement with industrial methods. Therefore, in case the sorting and recycling facilities maintain their current careful operation, no negative impact of PLA on PET recycling can be foreseen, and further integration of biobased plastics in the plastic waste management system can be pursued.
The effect of Sb2O3, which is used as the main catalyst in the production of poly(ethylene terephthalate) (PET) by melt polymerization, was studied on solid-state postpolycondensation. It was observed that the catalyst works efficiently even in the solid state. The number-average molecular weight of a PET prepolymer with an Sb2O3 content of 2000 ppm was increased from 18,350 to 40,800 after heating at 210°C for 8 h under vacuum (2–3 Pa), whereas when the catalyst was absent, the molecular weight of the same prepolymer under the same conditions was just increased to 22,500. The activation energies and the frequency factors of the esterification and ester interchange reactions, which take place simultaneously during solid-state postpolycondensation, were determined. © 1995 John Wiley & Sons, Inc.
Poly(ethylene terephthalate) (PET) is one of the polymers whose commercial use has grown most rapidly. This is because, besides its traditional use in injection-molded products and fibers, it is more and more used in blowing processes for bottle production. As a consequence, recycling of PET has also grown in importance [1-4] and is interesting from an ecological and sometimes also an economic point of view.
The mechanical properties of blends of isotactic polypropylene and high-density polyethylene with a postconsumer resin (recycled dairy containers) were investigated over the entire composition range. Modification of these blends with an ethylene/propylene/diene copolymer or an ethylene/vinyl acetate copolymer was also investigated. Isotactic polypropylene/postconsumer resin blends have satisfactory impact and tensile properties at postconsumer resin contents of less than 50% for certain applications. At higher postconsumer resin contents, the tensile properties were adversely affected. The impact properties remained satisfactory. Addition of an ethylene/propylene/diene copolymer improved the mechanical properties of these blends to levels equal to or greater than those for neat isotactic polypropylene. Ethylene/vinyl acetate copolymers were also able to improve the mechanical properties, but not as efficiently as did the ethylene/propylene/diene copolymer. Blends of high-density polyethylene and a postconsumer resin had poor impact and tensile properties. Although the ethylene/propylene/diene copolymer and ethylene/vinyl acetate copolymers were able to improve these properties, the improvement was insufficient for general recycling, except at lower (≤25%) postconsumer resin contents. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2081–2095, 1998
A method for recycling mixed PET and PVC wastes is described. Glycolysis of PET leads to oligomers that are polycondensed with caprolactone. The obtained diols are extended with hexamethylene diisocyanate. In certain conditions the polyurethanes are totally miscible with PVC, leading to acceptable mechanical characteristics for the blend. A relation between the structure of the polyurethane and miscibility with PVC is described. The mechanical characteristics of the blend depends on the polyurethane chemical structure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 657–665, 1998
Viscosity–molecular weight characterization of poly(ethylene terephthalate) (PET) in hexafluoroisopropanol (HFIP), pentafluorophenol (PFP), and HFIP/PFP is reported for the first time using size exclusion chromatography-low angle laser light scattering (SEC–LALLS) measurements. These strong solvents are capable of dissolving PET under very mild conditions and therefore minimize polymer degradation. In addition these solvents are capable of dissolving PET samples which have poor solubility in more traditional PET solvents such as orthochlorophenol (OCP) and phenol/tetrachloroethane (PTCE). By combining molecular weight information, obtained without the need of any SEC calibration curves, with intrinsic viscosity measurements, on several broad molecular weight PET samples, the Mark–Houwink coefficients for the five PET–solvent systems mentioned above have been determined. The coefficients correspond to those which would be obtained by using a large number of relatively monodisperse samples of PET covering a molecular weight range of about 2 × 103 to 2 × 105. Data is also provided which shows that intrinsic viscosities for PET in HFIP, PFP, HFIP/PFP, OCP, and PTCE can be determined from a single viscosity measurement at a finite concentration. Data for interconverting intrinsic viscosities determined in any of these five solvents is also given.
In attempts to improve the properties of post-consumer commingled plastics waste a variety of additives that could potentially act as compatibilizers/impact modifiers were evaluated. The feedstock was representative of a model curbside collection program and contained a variety of polymers, mostly polyethylenes with PET, PP, PVC, etc., in smaller amounts. The ground mixed plastics were first compounded and melt filtered in a counter-rotating nonintermeshing twin-screw extruder and then combined with different amounts of additives in a corotating intermeshing twin-screw extruder. Additives included unmodified and maleated polyolefin elastomers and styrene/olefin block copolymers. Blends were analyzed for thermal and mechanical properties, and processability. The most effective modifier in terms of impact strength improvement was a styrenic block copolymer with very similar rheological characteristics to the commingled plastics matrix. The experimental observations were interpreted by considering the complex morphological features of the injection molded multicomponent, multiphase systems. © 1994 John Wiley & Sons, Inc.
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