PET Particle Size Research Articles

Process Simulation of Terephthalic Acid Using Neutral Hydrolysis of Polyethylene Terephthalate Bottle Waste Method

To mitigate the environment's unique challenges caused by polyethylene terephthalate [PET] bottle litter and to protect the petroleum feedstock. The chemical recycling technology was used to transform PET into practical items with a sizable and successful industrial application. In order to model the chemical neutral hydrolysis depolymerization process of PET plastic wastes utilizing a continuous stir tank reactor for the synthesis of pure terephthalic acid [TPA] and EG for commercial use, this work used ASPEN PLUS V10. The data for the modeling came from an experimental chemical recycling project employing the neutral hydrolysis process to depolymerize PET bottle trash. PET waste was degraded using excess water [H2 O] and zinc acetate [Zn [Ac]2] as the active catalyst. A mean PET particle size of 127.5 m, 1000 kg/h of PET depolymerized at an H2 O: PET [w/w] ratio of 8:1, 513.15 K temperature, 32.0 bar pressure, and 0.5 h residence time were the reaction's ideal working parameters. Regarding PET, it is a first-order reaction. The reaction yielded 782.72 kg/h of TPA, 292.43 kg/h of EG, and a depolymerization of PET of 90.54%. TPA and EG had selectivity of 0.7280 and 0.2720, respectively. Filtration, distillation, and crystallization techniques were used to separate the mixture of components. The heat from the conveyance, reaction, and separation processes was obtained. This effort increased the yield of TPA, the amount of water removed for reuse, the amount of EG generated, and the amount of processing heat required. The procedures and their operating circumstances can be used to scale up commercial processes in the future.

Optimization of PET Particle-Reinforced Epoxy Resin Composite for Eco-Brick Application Using the Response Surface Methodology

Brick is a common building material that is used in society for constructing buildings. A viable environmental strategy to lessen the amount of plastic waste involves the inclusion of plastic trash in building materials. Globally, there is a severe issue with the disposal of plastic garbage in landfills. The primary and secondary carbon bonds that are formed in plastic packaging wastes can severely contaminate the environment. Hence, managing plastic waste to generate new and useful items is essential. One of the most practical ways to safeguard the environment is to manufacture eco-bricks from PET waste and epoxy resin. Additionally, as there is no combustion involved in the production of this eco-brick; it does not harm the environment. Eco-brick can be defined as a novel concept and approach to waste management and recycling. Eco-bricks have many advantages, such as easy availability and being environmentally friendly. This study aimed to improve the composition of the eco-brick using a mixture of epoxy resin and PET particles. In this study, a mathematical modelling technique called the Response Surface Method (RSM) was designed using the Central Composite Design (CCD). Variable input factors were used to develop eco-bricks such as mixture ratio (10–90%), particle size (1–5 mm), and drying time (1–7 days), whereas the variable response included the compressive strength. The complete experimental design was developed using Design Expert 11 software, and simulation experiments with 17 sets of parameters were generated. The microstructural characteristics of the eco-brick were examined using SEM. The results of the experiments indicated that the most optimised parameters that could be used for eco-brick application were: a PET particle size of 1.1 mm, a mixing ratio of 89.9%, and a curing time of 6.9 days. Earlier research that was conducted regarding the production of eco-bricks using a PET particle and epoxy resin mixture showed that these materials had a high potential to boost compressive strength. The quadratic model was used as the basis for the regression analysis for generating the response equations. Since the difference between the experimental and anticipated values was less than 5%, it was concluded that the results of the experimental and predictive tests showed good agreement. The model used in this study yielded noteworthy outcomes. As a result, the suggested statistical model can offer a clear understanding of designing experiments and variables that affect the production of eco-brick using a blend of PET particles and epoxy resin.

Effect of Microplastics on the Removal of Nitrogen and Phosphorus from Synthetic Piggery Digestate by Microalgae.

Microplastics (MPs) have been proven to be one of the major threats to the wastewater treatment system. However, the impact of MPs on microalgae-based wastewater treatment technology are still unknown. In this study, effects of polyvinyl chloride (PVC), polypropylene (PP), and polyethylene (PE) on the removal of nitrogen and phosphorus from synthetic piggery digestate by microalgae were investigated. Results show that the effect of PVC particle size on the growth of microalgae was significant. The effects of PVC content, PP particle size and content, PET particle size and content on the growth of microalgae were all not significant. The removal of ammonia nitrogen by microalgae was influenced significantly by PVC particle size and content, PP particle size and content, the effects of PET particle size and content on the removal of ammonia nitrogen were all not significant. The effects of particle size and content for three MPs on the removal of total phosphorus were all significant. Microalgae cells were bound together after being adsorbed by MPs, which increased the secretion of extracellular polymers and influenced the removal of ammonia nitrogen and total phosphorus.

Particle Size Reduction of Poly(ethylene terephthalate) Increases the Rate of Enzymatic Depolymerization But Does Not Increase the Overall Conversion Extent

Enzymatic depolymerization of poly(ethylene terephthalate) (PET) has emerged as a potential method for PET recycling, but extensive thermomechanical preprocessing to reduce both the crystallinity and particle size of PET is often conducted, which is costly and energy-intensive. In the current work, we use high-crystallinity PET (HC-PET) and low-crystallinity cryomilled PET (CM-PET) with three distinct particle size distributions to investigate the effect of PET particle size and crystallinity on the performance of a variant of the leaf compost-cutinase enzyme (LCC-ICCG). We show that LCC-ICCG hydrolyzes PET, resulting in the accumulation of terephthalic acid and, interestingly, also releases significant amount of mono(2-hydroxyethyl)terephthalate. Particle size reduction of PET increased the maximum rate of reaction for HC-PET, while the maximum hydrolysis rate for CM-PET was not significantly different across particle sizes. For both substrates, however, we show that particle size reduction has little effect on the overall conversion extent. Specifically, the CM-PET film was converted to 99 ± 0.2% mass loss within 48 h, while the HC-PET powder reached only 23.5 ± 0.0% conversion in 144 h. Overall, these results suggest that amorphization of PET is a necessary pretreatment step for enzymatic PET recycling using the LCC-ICCG enzyme but that particle size reduction may not be required.

Hydrolysis of poly(ethylene terephthalate) waste bottles in the presence of dual functional phase transfer catalysts

ABSTRACTThe hydrolysis of poly(ethylene terephthalate) (PET) obtained from waste bottles was studied. The dual functional phase transfer catalyst [(CH3)3N(C16H33)]3[PW12O40] exhibited outstanding catalytic activity to the hydrolysis of PET. Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy were used to confirm the main product terephthalic acid (TPA) of hydrolysis. The effects of temperature, time, particle size of PET and dosage of catalyst on hydrolysis reaction were examined. Under the optimum conditions of reaction temperature 145°C, time 2 h, particle size of PET at 0.5–1 mm and dosage of catalyst at 7 wt %, the conversion of PET and the yield of TPA were almost 100% and 93%, respectively. After easily separated from the product, the catalyst could be reused more than three times without obvious decrease in the conversion of PET and yield of TPA. An economical and convenient process was developed for hydrolysis of PET. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2790–2795, 2013

Recycling of off‐grade pet via partial alcoholysis to synthesize functionalized pet oligomer nanocomposites

AbstractOff‐grade poly(ethylene terephthalate) (PET) of industrial manufacturers was partially depolymerized using excess ethylene glycol in the presence of manganese acetate as a transesterification catalyst to synthesize PET oligomers. Influences of reaction time, Ethylene Glycol (EG)/PET molar ratio, catalyst concentrations, and particle size of off‐grade PET on yield of partial glycolysis reaction were investigated based on Box–Behnken's design of experiment. Thermal analyses of glycolyzed products are examined by differential scanning calorimetry. The optimum samples were also well‐characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy (1H‐NMR and 13C‐NMR). The optimal conditions to synthesize PET oligomer (melting point of about 180°C) for a 120‐min glycolysis reaction time were EG/PET molar ratio of 2 with no catalyst using granule‐shaped PET. The same results were obtained for a 60‐min glycolysis reaction time, including EG/PET molar ratio of 1 with the weight ratio (catalyst to PET) of 0.5% using average particle size of PET. Then, maleated PET as a compatibilizer for preparing PET nanocomposites was produced via reaction between maleic anhydride/phthalic anhydride composition and optimized PET oligomers based on central composite design of experiment. The combination of reaction time of 106 min and PhA/MA molar ratio of 0.85 gave the best results based on d‐spacing and peak shift of nanocomposite samples. Hence, melt mixing of maleated PET with organoclay produced a good intercalation of layered silicate and good dispersion of clay in maleated PET matrix. Analysis of variance (ANOVA) was studied for both glycolyzed products and functionalized PET oligomers. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Kinetics of catalytic glycolysis of PET wastes with sodium carbonate

The kinetics of glycolysis of poly(ethylene terephthalate) wastes with ethylene glycol to give highly pure bis(2-hydroxyethyl terephthalate) was examined in a batch reactor. An excess of ethylene glycol (EG:PET molar ratio of 7.6:1) was used and the reaction was carried out in the presence of sodium carbonate as active catalyst. The influence of several operating conditions covering temperature (165–196 °C), mean particle size (0.14–3 mm), stirring rate (50–800 rpm), reaction time (0–10 h), and catalyst type and concentration was analysed. The selected PET particle size and stirring rate for kinetic calculations were 0.25 mm and 600 rpm, respectively. Using a PET:catalyst molar ratio of 100:1 about 80% BHET yield was attained at 196 °C after 1 h. A simple theoretical power-law model was developed to predict the time evolution of conversion. This kinetic model was found to be consistent with experimental data. The rate constants for both direct and reverse reactions were estimated. Also the values of the activation energy (185 kJ mol −1) and enthalpy of reaction (12 kJ mol −1) were derived.

Influence of High Temperatures on PET‐Concrete Properties

AbstractLightweight aggregate is an important material in reducing the unit weight of concrete and it is essential in the construction of high‐rise buildings; besides, the use of recycled PET bottles as lightweight aggregate in concrete is an effective contribution for environmental preservation. So, the objective of the present work is to study the flexural strength of PET‐concrete and PET thermal degradation in the concrete, when the blends with 10 and 20 vol% of PET are exposed to different temperatures (200, 400, 600 °C). The flexural strength of PET‐concrete exposed to a heat source is strongly dependent on the temperature, the water/cement ratio, as well as on the content and particle size of PET. Furthermore, the activation energy for PET degradation is affected by temperature, location of PET particles on the slabs and the water/cement ratio. A higher content of water gives rise to hydrolytic degradation on PET and a higher vapor pressure that increases the formation of cracks on the concrete. The values of activation energy are higher on the center of the slabs than on the surface, due to the poor heat conduction of concrete.

Effects of crystallinity on solid‐state polymerization of poly(ethylene terephthalate)

AbstractThere has been a widely held assumption that the solid‐state polymerization (SSP) rate of poly(ethylene terephthalate) (PET) decreases with increasing crystallinity. Several published articles that purported to prove this assumption were based on faulty experiments. Therefore, a proper experimental procedure has been used to study the true effects of crystallinity on the SSP of PET. The results show that, for PET in pellet and powder forms, the SSP rate increases with increasing crystallinity. This is because an increase in the crystallinity results in increased end‐group concentration in the amorphous phase, where SSP reactions take place, and decreased concentrations of inactive end groups trapped inside the crystals, thereby increasing the rates of end‐group collision and reactions. These positive effects outweigh the negative effect of the increased byproduct‐diffusion resistance because of the increase in crystallinity. As the particle size of PET is increased beyond a critical value of about 7 mm, the SSP rate actually decreases with increasing crystallinity because of the excessively increased byproduct‐diffusion resistance within the PET particles. However, this critical particle size is far greater than the pellet sizes of commercial PET resins. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 623–632, 2006

Recycling of Waste Poly(Ethylene Terephthalate) with Naphthalene and Neutral Water

The waste poly(ethylene terephthalate) (PET) powder dissolution/reprecipitation was carried out in a batch operation at atmospheric pressure at various temperatures ranging from 180–220°C at temperature intervals of 10°C. Particle sizes of the waste PET ranged from 50–512.5 µm and operation time, which ranged from 30–90 min, were optimized. Dissolution/reprecipitation of the waste PET was carried out in naphthalene (solvent) and neutral water (nonsolvent), respectively. Dissolution/reprecipitation of the waste PET was increased with operation time and temperature. Dissolution/reprecipitation of PET was decreased with increase in the particle size of the waste PET. The waste PET particle size and agitator speed required for complete recycling of the waste PET were also optimized. Analyses of the waste PET and the recycled PET collected after the reprecipitation process was undertaken by determination of various physical properties. The operation applied at lesser time and with cheaper solvent/nonsolvent, resulted in excellent quality of the recycled PET collected after the reprecipitation process. This process of recycling of the waste PET has an industrial significance due to most economical operation for commercialization.

Microkinetics and Mass Transfer in Aqueous Alkaline Depolymerization of Poly (Ethylene Terephthalate)

Depolymerization of poly (ethylene terephthalate) (PET) in aqueous sodium hydroxide solution was undertaken in a batch process at 90–150°C and 1 atm pressure conditions by varying PET particle size in the range of 50–512.5 µm. Process time also was varied from 10–110 min to describe the effect of particle size of PET and mass transfer time on batch reactor performance. The particle size of PET and operation time required were optimized. Operation products consist of terephthalic acid (TPA) and ethylene glycol (EG) as monomers. A comprehensive model for the depolymerization of PET has been developed, taking into account kinetic data and the diffusion operation for the major by-products as monomers from the waste solid PET powder. The model prediction was undertaken by using our own laboratory data. Experimental data with analysis of depolymerized monomeric products (TPA and EG) of PET show good consistency with model results. Acid value as well as carboxyl-group concentrations of TPA significantly increases with operation time. The kinetic parameters for the depolymerization for the formation of monomers were under taken in this study, used for prediction of model results. The mass transport was described by using a classical diffusion equation according to Fick's law and a modified Wilke-Chang diffusion model. Diffusion coefficients were calculated with a change in temperature and charge ratios as a function of operation time to give an explanation of the process phenomena.

Chemical Recycling, Kinetics, and Thermodynamics of Hydrolysis of Poly(ethylene terephthalate) Waste with Nonaqueous Potassium Hydroxide Solution

Poly(ethylene terephthalate) (PET) waste was reacted in a batch process with KOH in nonaqueous ehtylene glycol (EG) solution at 100–180°C for 5–140 min to convert them quantitatively into dipotassium terephthalate (K2-TPA) and EG. Particle size of PET, mol/L of KOH, and reaction time required for depolymerization of complete PET were optimized. Dipotassium terephthalate was precipitated into terephthalic acid (TPA) using HCl from the reaction mixture and separated readily. Other product EG, being the same component as nonaqueous solvent (EG) remains in liquid phase. The EG was recovered completely by using the salting-out method. Rate of hydrolysis was significantly accelerated by addition of another additional solvent, tetrahydrofurane (THF) to EG in the atmosphere of cyclohexylamine (CHA). Moreover, to improve the hydrolysis rate, TPA salt deposited from the unreacted PET surface was removed by introduction of dimethylsulfoxide (DMSO). Analyses of monomers (TPA and EG) and PET were undertaken. Yields of monomers were almost equal to PET conversion. The kinetic model was developed and experimental data were fitted with it. The model showed a good consistency with experimental data. Thermodynamics were also undertaken by determination of activation energy, Arrhenius constant, equilibrium constant, Gibbs free energy, enthalpy, and entropy. The dependence of the rate constant on the reaction temperature was correlated by Arrhenius plot, which shows activation energy of 24.2 kJ/mol and Arrhenius constant of 199.3 min−1.

Chemical Recycling, Kinetics, and Thermodynamics of Alkaline Depolymerization of Waste Poly (Ethylene Terephthalate) (PET)

Depolymerization of PET in aqueous sodium hydroxide solution was undertaken in a batch process at 90–150°C and 1 atm by varying PET particle size in the range of 50–512.5 µm. Reaction time was also varied from 10–110 min to explore effect of particle size of PET and reaction time on batch reactor performance. Particle size of PET and reaction time required were optimized. Disodium terephthalate (TPA salt) and ethylene glycol (EG) remain in liquid phase. EG was recovered by salting‐out technique. Disodium terephthalate was separated by acidification to obtain solid terephthalic acid (TPA). Produced TPA and EG were analyzed qualitatively and quantitatively. Yields of TPA and EG were almost equal to PET conversion. Depolymerization reaction rate was first order to PET concentration as well as first order to sodium hydroxide concentration. Acid value of TPA changes with reaction time. This indicates that PET molecule gets fragmented and hydrolyzes simultaneously with aqueous sodium hydroxide to produce EG and disodium terephthalate. Thermodynamics was also undertaken by determination of activation energy, Arrhenius constant, equilibrium constant, Gibbs free energy, enthalpy and entropy. Dependence of hydrolysis rate constant on reaction temperature was correlated by Arrhenius plot, which shows activation energy of 26.3 kJ/mol and Arrhenius constant of 427.2 L/min/cm2.

Contaminants and levels of occurrence in washed and shredded poly(ethylene terephthalate) from curbside collection. II: Validation of extraction procedures, particle size sampling and crystallinity

Part I of this study showed that washed and dried, shredded poly(ethylene terephthalate) (PET) (flake) obtained from curbside collection when Soxhlet extracted contained 26 semivolatile contaminants below the US FDA threshold of 215 ppb and six above this level. This paper reports the validation of the Soxhlet extraction technique by comparison with total dissolution with trifluoroacetic acid (TFA). The work was carried out for two of the three particle size ranges obtained by grinding the PET flake (300–425 and 425–700 μm) and for the unground flake. Further validation was undertaken by comparison of contaminant levels determined by total dissolution with TFA and sonication with dichloromethane (DCM) using flake ground to the 0–300 μm size range. The levels of contaminants increased with decreasing particle size range, but X-ray diffraction measurements of degrees of crystallinity were similar for each PET particle size range, thus showing that the differences in contaminant levels were not due to variable percentages of the amorphous material from the tops and bottoms of shredded bottles, relative to the amounts of crystalline PET from the mid-sections of the bottles. Hence, it was postulated that the variations in contaminant levels were due to selective grinding of the more highly contaminated surfaces, whilst the larger particles incorporated the less contaminated interior material. The grinding was also strongly selective with respect to the amorphous flake. Analysis of the segregated amorphous and crystalline flake phases indicated that many contaminants were similarly absorbed into both phases, whilst some were preferred by the amorphous PET and others were preferred by the crystalline PET.

Study of poly(ethylene terephthalate)/polypropylene microfibrillar composites. I. Morphological development in melt extrusion

Poly(ethylene terephthalate)/polypropylene (PET/PP) blends of different compositions were extruded through a 2-mm capillary die using a corotating twin-screw extruder. The extrudates were cryogenically fractured and examined using scanning electron microscopy. The viscosity ratio of the constituent polymers alone was found to be unsuitable for explaining the polymer blend morphology. At a PET concentration of 20%, the extrudate consists of three regions. The skin layer, which is about 10 μm thick, has a lower concentration of the dispersed PET phase than the overall concentration. The intermediate region, which is about 400 μm thick, has profuse PET fibers and some small PET particles. The central region, which is approximately 800 μm in diameter, mainly contains PET particles that are generally bigger. A low barrel temperature, low die temperature, and fast cooling rate helped to retain the fibers near the extrudate skin. Meanwhile, the variation of the barrel temperature, die temperature, and cooling media did not produce a significant affect on the PET particle size distribution in the central region of the extrudate. A high screw speed and a high postextrusion drawing speed were very effective in producing fibers in the extrudates through elongation of particles. At a PET concentration of 30%, coalescence of the PET phase was prevalent, leading to the formation of PET platelets near the extrudate skin and irregular PET networks in the central region of the extrudate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1743–1752, 2003

Chemical Kinetics, Simulation, and Thermodynamics of Glycolytic Depolymerization of Poly(ethylene terephthalate) Waste with Catalyst Optimization for Recycling of Value Added Monomeric Products

AbstractReaction of poly(ethylene terephthalate) (PET) waste powder with ethylene glycol (EG) was carried out in a batch reactor at 1 atm pressure and at various temperatures ranging from 100–220 °C at the intervals of 10 °C. Particle size from 50–512.5 μm, reaction time from 30–150 min, amount of catalyst from 0.001–0.009 mol, and type of catalysts required for glycolysis of PET were optimized. To increase the PET weight (%) loss, various external catalysts were introduced during the reaction at different reaction parameters. Depolymerization of PET was increased with reaction time and temperature. Depolymerization of PET was decreased with increase in the particle size of PET. Reaction rate was found to depend on concentrations of liquid ethylene glycol and ethylene diester groups in the polyester. Analyses of value added monomeric products (DMT and EG) as well as PET were undertaken. Yields of monomers were agreed with PET conversion. A kinetic model was proposed and simulated, and observed consistent with experimental data. Comparisons of effect of various amounts of catalysts and type of catalysts on glycolysis rate were undertaken. Dependence of the rate constant on reaction temperature was correlated by Arrhenius plot, which shows activation energy of 46.2 kJ/mol and Arrhenius constant of 99 783 min−1. Arrhenius plot of the rate constant of glycolysis at 1 atm pressure for 127.5 μm PET particle size (KZA = rate constant using zinc acetate as a catalyst, KMA = rate constant using manganese acetate as a catalyst).magnified imageArrhenius plot of the rate constant of glycolysis at 1 atm pressure for 127.5 μm PET particle size (KZA = rate constant using zinc acetate as a catalyst, KMA = rate constant using manganese acetate as a catalyst).