Poly Ethylene Terephthalate Flakes Research Articles

More Efficient Chemical Recycling of Poly(Ethylene Terephthalate) by Intercepting Intermediates.

The research presented in this paper offers insight into the availability of intermediates in the depolymerization of polyethylene terephthalate (PET) to be used as feedstock to create value-added products. Monitoring the dispersity, molecular weight, end groups, and crystallinity of reaction intermediates during the heterogeneous depolymerization of PET offers insight into the mechanism by which the polymer chains evolve during the reaction. Our results show dispersity decreases and crystallinity increases while the yield of insoluble PET remains high early in the reaction. Our interpretation of this data depicts a mechanism where chain scission targets amorphous tie chains between crystalline phases. Targeting the tie-chains lowers the Mn of the polymer without changing the amount of recovered polymer flake. Chain scission of tie-chains and isolating highly crystalline PET lowers the dispersity (Đ) of the polymer chains, as the size of the crystalline lamellae guides the molecular weight of the depolymerized oligomers. When sufficient end groups of PET chains are converted to alcohol groups, the PET flakes break apart into highly crystalline and less disperse polymer. Our results also demonstrate that the oligomeric depolymerization intermediates are readily repolymerized, offering new opportunities to chemically recycle PET more effectively and efficiently, from both an energy and purification standpoint.

Influence of polyethylene terephthalate (PET) flakes coating on the microstructure and mechanical properties of alkali activated composites

The objective of this research is the improvement of the mechanical strengths of the alkali activated slag composites with polyethylene terephthalate (PET) flakes content. The main drawback when large PET flakes (2–9 mm) are used in these composites is reduced adhesion between plastic surface and binding matrix. Therefore, the PET flakes were coated with two types of adhesives – based on polyvinyl acetate or sodium silicate solution, and then covered with fly ash, waste glass or slag powders. The microstructure (assessed by scanning electron microscopy) of interfacial transition zone between the PET flakes coated with waste glass and slag powders is denser than for uncoated PET flakes; this explains the improvement of the compressive strength of these mortars especially after longer curing times (28 days). The flexural strengths of the mortars with PET flakes are higher than for reference mortar (with sand aggregate) and the apparent density of the alkali activated composites with PET flakes are in general smaller than for the reference mortar. Thus, the coating of PET flakes improves the mechanical behaviour of mortars, preserving also a low apparent density. These results can lead to a wider recycling of PET waste, slag and waste glass powder, promoting circular economy and reducing the CO2 footprint without compromising the critical mechanical strength of mortars.

Process Parameter Optimization of Waste Polyethylene Terephthalate Bottle Neutral Hydrolysis Depolymerisation Using Process Simulation and Response Surface Methodology

The global surge in plastic production has led to a concerning accumulation of durable plastic waste in landfills and the environment. To address this issue, the depolymerization of waste polyethylene terephthalate (PET) through neutral hydrolysis has been proposed as a chemical recycling solution. Despite its potential environmental benefits, the endothermic nature of this process at high temperatures has raised doubts about its commercial feasibility. In response, this study was conducted to assess optimal conditions for waste PET depolymerization using neutral hydrolysis in a continuous stirred tank reactor with zinc acetate as a catalyst. Process simulation, aimed to manufacture pure terephthalic acid (TPA) and ethylene glycol from pelletized post-consumer PET bottles, was conducted with Aspen Plus Version 11. Sensitivity analysis explored the impact of factors such as reaction temperature, reaction time, PET flake size, and catalyst to PET ratio on both PET conversion and TPA yield. The study found that PET depolymerization increased with decreasing particle size, longer reaction times, increasing catalyst to PET ratio and reaction temperatures within the range of 200–240°C. Optimizing the process through response surface modelling revealed that key parameters for neutral hydrolysis considering a mean particle size of 20 mm were the ratio of water to PET, temperature, pressure, and reaction time with optimal values of 5:1, 225°C, 30 bar, and 67.5 min respectively. The model's reliability was confirmed through variance analysis, emphasizing the significance of main and interaction effects in the regression model.

Morphology control of waste polyesters for enhanced glycolysis reactivity and minimization of side reactions

Effective pretreatment routes using dimethyl sulfoxide (DMSO) as solvent were accomplished to enhance the polyethylene terephthalate (PET) glycolysis rate. Highly ordered structure PET flakes were dissolved in DMSO at high temperatures, followed by solid–liquid separation using two different methods to generate micro-sized powders. Under identical glycolysis conditions, the reaction time of pretreated PET powders was gradually reduced by approximately five times that of PET flakes. During the glycolysis of PET with ethylene glycol (EG), diethylene glycol-containing terephthalate compounds (DCTC) are formed as undesired byproducts at high temperatures. These byproducts significantly affect the overall quality of BHET. Consequently, pretreated PET degradation under mild conditions was employed as a preventive measure against EG dehydration, leading to the production of DCTC. PET powders with controlled morphology exhibit outstanding performance and achieve a 100 % PET conversion at 180 °C to DCTC-free bis(2-hydroxyethyl) terephthalate (BHET). The purity of the obtained BHET was characterized using proton–NMR spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The utilization of this technology presents a potential solution for overcoming the technical and economic challenges associated with current PET upcycling methodologies.

Techno-economic analysis and process optimization of a PET chemical recycling process based on Bayesian optimization

Chemical recycling has gained interest as a promising option to reduce the consumption of fossil feedstocks and relieve environmental issues concerning plastic waste. In this study, we present a preliminary techno-economic analysis of a process design for chemical recycling of polyethylene terephthalate (PET). A conceptual base case design was developed for a continuous catalytic PET depolymerization process. The process design was optimized to minimize total annualized cost (TAC) based on a simulation-based Bayesian optimization approach. A novel interface was utilized to manipulate the process variables, and to retrieve simulation and economic evaluation results. Through five trials of optimization, the process design was improved by about 4.2∼4.4 % in terms of TAC. Sensitivity analyses investigating the effect of process parameters and price variables on the minimum selling price of main product, p-xylene, are presented. The feedstock PET flake price was identified as the most critical factor affecting the economic viability of the process.

In-situ chain extension of polyethylene terephthalate flakes using reactive extrusion as an upcycling approach

To improve recycled PET (rPET) properties, polyethylene terephthalate (PET) flakes were modified with different ratios of 4,4′-methylene diphenyl diisocyanate (MDI) as a chain extender (CE) using in-situ reactive extrusion. Intrinsic viscosity (IV), chemical bonding, thermal properties, and morphology, which strongly depended on MDI content, were investigated. New amide bonds, an indicator of chemical bonds between PET and MDI, were confirmed in the range 1505–1520 cm−1 by FTIR. Additionally, IV values of rPET with MDI (rPET-Ms) increased from 0.42 to 1.08 dL/g. Furthermore, crystallinity and oxygen barrier properties decreased with increasing MDI content. This may have been caused by hindered crystallization from increased random segments with the addition of MDI. There was lower overall migration than the stipulated overall migration limit (OML) in food simulants. These results suggest that in-situ reactive extrusion modification of PET flakes using MDI can provide value-added upcycled PET as an alternative to virgin PET (vPET).

An Innovative Absorption Propagation System Hollow Block Made of Concrete Modified with Styrene-Butadiene Rubber and Polyethylene Terephthalate Flakes to Reduce the Propagation of Mechanical Vibrations in Walls.

This paper discusses an innovative APS hollow block wall with a frame made of concrete modified with recycled materials. The technical data of the hollow block, the percentages of the recycled materials, including SBR rubber granules and PET flakes in the modified concrete, and the composition of the concrete modified with this mixture of recycled additives, are presented. To demonstrate the effectiveness of the solution in reducing mechanical vibrations, the effect of the interaction of different frequencies of the mechanical wave on reducing these vibrations was evaluated for APS blocks and Alpha comparison blocks. The test was carried out on a developed test stand dedicated to dynamic measurements for sixteen frequencies in the range from 8 to 5000 Hz, forcing a sinusoidal course of vibrations. The results are presented graphically and show that the new type of APS hollow block wall was much more effective in reducing mechanical vibrations. This efficiency was in the range from 10 to 51% for 12 out of the tested 16 frequencies. For the frequencies of 8, 16, 128, and 2000 Hz, the values were obtained with a difference of 3.58% in favor of the APS hollow block. In addition, the study of the damping effectiveness of the APS hollow blocks, in relation to the vibrations generated by an M-400 impact mill, showed that the APS block wall had a higher damping efficiency of 16.87% compared to the Alpha hollow block for the signal reading on the floor next to the mill, and 18.68% for the signal reading on the mill body. The modified concrete used in the production of the APS hollow blocks enabled the effective use of two recycled materials, SBR rubber and polyethylene terephthalate, in the form of PET flakes.

Ionothermal synthesis of activated carbon from waste pet bottles for dye waste water treatment

The production and use of poly-ethylene terephthalate (PET) bottles in packaging have increased significantly. Thus, PET bottles have become a significant plastic waste with environmental problems. Currently, the conventional methods for producing activated carbons (ACs) from waste PET are unsustainable, complex, and unfeasible. As a result, ionothermal synthesis (IS) of waste PET bottles impregnated with choline chloride-urea (CU) deep eutectic solvent (DES) was carried out in order to prepare ACs. The obtained ACs were characterized using XRD, CHNS Elemental analysis and FTIR. The as-prepared ACs were effective as adsorbents for dye adsorption from dye waste water. Specifically, the AC obtained from pristine waste PET bottles (956 mgg−1 at 100 ppm) displayed higher adsorptive capacity compared to the ACs obtained from CU-DES impregnated PET flakes (550mgg−1 at 100ppm). Even though it was expected that the use of CU-DES required no post-synthesis washing or higher temperature treatments might be required to improve the adsorptive capacity of the ACs obtained from IS.This research work established that the synthesis of AC from abundant waste PET bottles using a sustainable and facile method could facilitate its commercial application. Also, this work represents the first attempt to produce activated carbons from PET using low temperature annealing in the presence of limited air, instead of the usual pyrolysis.

Polyethylene terephthalate (PET) biodegradation by Pleurotus ostreatus and Pleurotus pulmonarius

The essential properties of polyethylene terephthalate (PET), such as chemical inertness and durability that make it a suitable material for the packaging of mineral and soft drinks, have led to it becoming a major environmental pollutant and a threat to the planet. Ecologically friendly solutions such as bioremediation are now being advocated for by scientists. This paper, therefore, seeks to explore the potential capacity of Pleurotus ostreatus and Pleurotus pulmonarius in biodegrading PET plastic on two different substrates (soil and rice straw). The substrates were combined with 5% and 10% plastic before inoculation with Pleurotus ostreatus and Pleurotus pulmonarius and then left to incubate for 2months. Biodegradation, monitored by FT-IR pointed to the formation of new peaks in the incubated plastics after 30 and 60days unlike in the control. Changes in band intensity and shifts in the wavenumbers caused by stretching of functional groups, C-H, O-H and N-H in the band region of 2898cm-1 to 3756cm-1 are confirmed indicators of successful breakdown caused by contact with P. ostreatus and P. pulmonarius. The FT-IR analysis also gave an indication of N-H stretching at 3338.04cm-1 and 3228.62cm-1 for PET flakes incubated with Pleurotus sp. Furthermore, degradation products like hydrocarbons, carboxylic acids, alcohols, esters, and ketones were also detected in the GC-MS analysis of the decomposed PET plastic after 30 and 60days. These compounds are formed due to chain scission caused by the fungal species. There was a discoloration of the PET flakes caused by an increase in carboxyl-terminated species as a result of enzymes secreted by the fungi in the process of biodegradation.

Study on heat exchangers and industrial absorption column for drying polyethylene terephthalate

This study proposes the use of mass balance and the method of McCabe-Thiele in the absorption column for the removal of drying air humidity with ethylene glycol and energy balances in heat exchangers for the determination of the optimum operating conditions of a factory to produce recycled polyester fibers from polyethylene terephthalate (PET) flakes. The evaluation of these machines involved the combination of variables such as temperature, flow rate, specific heat, and operational efficiency to guarantee the correct adjustment of the physicochemical properties of the fluids and materials of the process. The efficiency of the absorption column was determined at 25%, and a diagram correlating ethylene glycol humidity, the dew point of the drying air, and the efficiency of humidity removal from the PET flake dryer were constructed to define what is the most appropriate configuration for operation. By the graph curves, it was found that the humidity of ethylene glycol for absorption should be inferior to 1% (w/w) to guarantee a dew point < -27?C at 175?C of the drying air introduced in the dryer, which would finally promote a removal with efficiency superior to 91% of the PET flake humidity for values < 0.005% (w/w).

Synthesis of Unsaturated Polyester Resin Based on Pet Waste

Abstract: Polyethylene terephthalate (PET) flakes are widely used as raw material for manufacturing of packaging materials. The worldwide production of PET is 30.5 million metric tons/year. With such a large consumption, the effective application of PET waste is of considerable commercial and technological significance. In this paper we used PET flakes for the synthesis of unsaturated polyester resin to go green. PET flakes were depolymerized by using Neopentyl glycol (NPG) and propylene glycol (PG). Glycolyzed product was reacted with maleic anhydride and phthalic anhydride. Then it was mixed with styrene monomer to get unsaturated polyester (UP) resins. Molecular weight, Hydroxyl value and Acid value of all synthesized UP resins were studied.

Functionalized Waste Plastic Granules to Enhance Sustainability of Bituminous Composites

This paper evaluates the merits of using waste plastic granules made from functionalized polyethylene terephthalate (PET) to enhance bitumen's bond strength to endure extreme environmental conditions such as aging and moisture. The applicability of PET as a modifier for bitumen has been hindered by PET's low compatibility with bitumen, causing phase separation. In this study, to improve PET's compatibility with bitumen, PET flakes were functionalized by grafting bio-oils onto their surface. This study optimized the method of PET functionalization by selecting the optimal time for exposure to microwave irradiation based on the following criteria: PET temperature below the melting temperature of PET, reduction in phase separation of PET-modified bitumen, multiple stress creep recovery, and shear thinning behavior. It was found that the optimized irradiation time for functionalization is 10 minutes. The efficacy of functionalized PET and non-treated PET as modifiers to improve bitumen's bond strength was then studied after exposure to various levels of aging and moisture damage. Bitumen's interaction with siliceous surfaces was evaluated by the bitumen bond strength (BBS) test and the moisture-induced shear-thinning index (MISTI) test. The results of the BBS test, performed on glass substrates , showed that bitumen modified with functionalized PET granules (OTPG) exhibited the highest pull-off tensile strength and the greatest resistance to moisture damage after exposure to adverse environmental conditions. It was found that modifying bitumen with OTPG reduced moisture susceptibility by 25% as measured by the pull-off test. This improvement was also noticed in the results from the MISTI test, which showed that the lowest moisture susceptibility was found for bitumen modified by OTPG. The outcome of this study shows the merits of using functionalized waste plastics in pavements to enhance their durability while promoting sustainability and resource conservation.

Recycling-oriented characterization of PET waste stream by SWIR hyperspectral imaging and variable selection methods

The proposed study was carried out to develop a fast and efficient strategy for plastic waste sensor-based sorting in recycling plants, based on hyperspectral imaging (HSI), combined with variable selection methods, to produce a high-quality recycled polyethylene terephthalate (PET) flakes stream. Variable selection techniques were applied in order to identify a limited number of spectral bands useful to recognize the presence of other plastic materials, considered as contaminant, inside a stream of recycled PET flakes, reducing processing time as requested by sorting online applications. Post-consumer plastic samples were acquired by HSI device working in the short-wave infrared (SWIR) range (1000 - 2500 nm). As a first step, the hypercubes were processed applying chemometric logics to build a partial least squares discriminant analysis (PLSDA) classification model using the full investigated spectral range, able to identify PET and contaminant classes. As a second step, two different variable selection methods were then applied, i.e., interval PLSDA (I-PLSDA) and variable importance in projection (VIP) scores, in order to identify a limited number of spectral bands useful to recognize the two classes and to evaluate the best method, showing efficiency values close to those obtained by the full spectrum model. The best result was achieved by the VIP score method with an average efficiency value of 0.98. The obtained results suggested that the variables selection method can represent a powerful approach for the sensor-based sorting-online, decreasing the amount of data to be processed and thus enabling faster recognition compared to the full spectrum model.

Post-fire residual fracture characteristics and brittleness of self-compacting concrete containing waste PET flakes: Experimental and theoretical investigation

Correct understanding of the fracture mechanism of self-compacting concrete (SCC) after tolerating elevated temperatures plays a big role in the design of SCC mixes and helps better understand the behavior of SCC structures during a fire incident. Besides, to obtain eco-friendly concretes incorporating wastes and be able to employ them in concrete structures, knowing their mechanical characteristics is essential. Therefore, in this research, the three-point bending test was conducted on 240 notched beams to determine the effect of the partial substitution of polyethylene terephthalate (PET) flakes for fine aggregates at volume percentages of 0, 5, 10, and 15% on the fracture characteristics and ductility of SCC in two states: without heat treatment and after the application of 200, 400, and 600 °C. For this purpose, the two methods of size effect method (SEM) and work of fracture method (WFM) were used to analyze and interpret fracture parameters. The analysis of the obtained results demonstrated in the specimens without PET, after the heat treatment, fracture energy values obtained from WFM and SEM, as well as the fracture toughness (KIC) obtained from SEM, declined. Moreover, the results obtained for the effective size of the process zone (cf) parameter in SEM and characteristic length (lch) parameter in WFM demonstrated that the concrete without PET became more brittle and less ductile. On the contrary, in concretes incorporating PET, as the temperature increased, the fracture energy and toughness levels of the SCC declined, but its ductility increased. Moreover, considering the size effect design, the behavior of the SCC approached the linear elastic fracture mechanics (LEFM) criterion as the temperature increased and the substitution percentage of PET for fine aggregate decreased. On average, in all the specimens, the fracture energy values obtained from WFM were 2.35 times those obtained from SEM. Finally, based on the obtained mechanical characteristics and test variables, multivariate models were presented to predict the fracture parameters of SCC incorporating PET after tolerating elevated temperatures and compared with the experimental results of the present research and literature. A proper accuracy was observed for the models.

Circular economy in the brewing chain

The main aim of this review was to check for the applicability of the concept of circular economy to brewing chain. By analyzing the beer brewing process, it was possible to identify the main brewery wastes formed and packaging materials used as well as their range of composition and yields. In order to reduce the contribution of packaging material to the carbon footprint of beer, it would be necessary to replace one-way containers used nowadays with lighter, reusable, or recycled ones. Even if the contribution of beer consumption phase was taken into account, there was no definitive solution about the less environmentally impacting beer packaging format. The direct management of polyethylene terephthalate (PET) packaging for liquid foodstuffs could make available 100% recycled PET flakes to be reconverted into food-grade bottles with minimum downcycling to other non-food usage. The countless potential uses of brewery wastes in nutritional and biotechnological fields were tested in laboratory by disregarding any cost–benefit or market analysis. This was mainly because the estimated market price of dried brewer’s spent grain (BSG) resulted to be about 450% higher than that of conventional lignocellulose residues. All the alternative uses hailed in the literature appeared to be more useful for publishing articles than for defining any economically feasible reusing procedure for all brewery wastes. Owing to their high moisture content, such wastes are so perishable as to prevent their safe usage in the human food chain. Currently, their use as-is in animal feeding is the disposal method not only economically feasible but also able to reduce the greenhouse gas load of beer packed in glass bottles (GB) by about one-third of that associated with packaging materials. Not by chance, it is practiced by most industrial and craft breweries.

Identification of Potential Migrants in Polyethylene Terephthalate Samples of Ecuadorian Market.

Polyethylene terephthalate (PET) is the plastic packaging material most widely used to produce bottles intended for contact with food and beverages. However, PET is not inert, and therefore, some chemical compounds present in PET could migrate to food or beverages in contact, leading to safety issues. To evaluate the safety of PET samples, the identification of potential migrants is required. In this work, eight PET samples obtained from the Ecuadorian market at different phases of processing were studied using a well-known methodology based on a solvent extraction followed by gas chromatography–mass spectrometry analysis and overall migration test. Several chemical compounds were identified and categorized as lubricants (carboxylic acids with chain length of C12 to C18), plasticizers (triethyl phosphate, diethyl phthalate), thermal degradation products (p-xylene, benzaldehyde, benzoic acid), antioxidant degradation products (from Irgafos 168 and Irganox), and recycling indicator compounds (limonene, benzophenone, alkanes, and aldehydes). Additionally, overall migration experiments were performed in PET bottles, resulting in values lower than the overall migration limit (10 mg/dm2); however, the presence of some compounds identified in the samples could be related to contamination during manufacturing or to the use of recycled PET-contaminated flakes. In this context, the results obtained in this study could be of great significance to the safety evaluation of PET samples in Ecuador and would allow analyzing the PET recycling processes and avoiding contamination by PET flakes from nonfood containers.

Effective Recycling Solutions for the Production of High-Quality PET Flakes Based on Hyperspectral Imaging and Variable Selection.

In this study, effective solutions for polyethylene terephthalate (PET) recycling based on hyperspectral imaging (HSI) coupled with variable selection method, were developed and optimized. Hyperspectral images of post-consumer plastic flakes, composed by PET and small quantities of other polymers, considered as contaminants, were acquired in the short-wave infrared range (SWIR: 1000–2500 nm). Different combinations of preprocessing sets coupled with a variable selection method, called competitive adaptive reweighted sampling (CARS), were applied to reduce the number of spectral bands useful to detect the contaminants in the PET flow stream. Prediction models based on partial least squares-discriminant analysis (PLS-DA) for each preprocessing set, combined with CARS, were built and compared to evaluate their efficiency results. The best performance result was obtained by a PLS-DA model using multiplicative scatter correction + derivative + mean center preprocessing set and selecting only 14 wavelengths out of 240. Sensitivity and specificity values in calibration, cross-validation and prediction phases ranged from 0.986 to 0.998. HSI combined with CARS method can represent a valid tool for identification of plastic contaminants in a PET flakes stream increasing the processing speed as requested by sensor-based sorting devices working at industrial level.

Mechanical properties and microstructure of lightweight polymer composites containing mono and hybrid fillers sourced from recycled solid wastes

This paper presents the development of lightweight polymer composites containing various solid wastes as fillers. This research is conducted to formulate mix proportions of polymer composite using unsaturated polyester resin as binder and waste tyre rubber crumb, recycled polyethylene terephthalate (PET) flakes and fly ash as fillers. Effects of various volume fractions of rubber crumb, PET flakes and fly ash and their combinations on 3 days compressive strength and density of the polymer composites are studied and a number of optimum mixes are selected for further study. Compressive strength, flexural strength and toughness of the above optimum mixes are measured at 3, 14 and 28 days. The effect of jute fabric as reinforcing layer on flexural strength and toughness of polymer composite is also studied. Microstructure analysis is conducted to investigate the polymer matrix and matrix-fillers interface of the composites. The optimum mix proportions are developed based on usage of least binder and high volume of filling materials, having lightweight and appreciable compressive strength. Results show that the 28-day density and compression strength of polymer composites are in the range of 1072 to 1616 kg/m3 and 15 to 62 MPa, respectively. These values are well below the American Concrete Institute (ACI)’s lightweight concrete density of 1850 kg/m3 and compressive strength of 17.5 MPa. The combined use of fly ash with rubber crumb or PET flakes improved the compressive and flexural strengths of polymer composites compared to the use of rubber crumb or PET flakes alone. The use of jute fabric increased the flexural strength and toughness of polymer composites. Microstructural analysis revels no additional substance besides binder and fillers, indicating no reaction of fillers with the resin in the composite.

Potential use of PET and PP as partial replacement of sand in structural concrete

ABSTRACT The use of polymeric residues in the civil construction has been the target of many studies aiming to reduce the volume of post-consumer plastics in the environment. This work focuses on the viability to use polyethylene terephthalate (PET) and polypropylene (PP) as partial replacement to sand in concrete. PET and PP flakes from post-consumer packings were used as light aggregate to partially replace, individually, 10% in volume of sand. The effect of adding these polymers was investigated in terms of physical, mechanical, durability and morphological properties of the concrete. Physical properties were measured in terms of water absorption, voids content and specific mass. Mechanical properties were measured in terms of compressive strength and elasticity modulus. Durability properties were measured in terms of capillarity water absorption and electrical indication of the concrete to resist to chloride ion penetration. MEV and EDS were used to carry out morphological analysis. DSC curves were carried out to evaluate thermal properties of the polymeric flakes. Contact anlge test was also performed. The partial addition of PET and PP polymers reduced the compressive strength by 20%, whilst the reduction of the elasticity modulus was 16% for PET samples, and almost insignificant for PP samples. The durability results show that the polymers contributed to increase the resistance of the samples to chloride penetration by 15% and 57%, for PET and PP samples, respectively; however, there was an increase in the voids content and water absorption. In the morphological test it is possible to observe a lower interfacial adhesion between PP and the cementions paste in comparison to PET.

Determination of the residence-time distribution in industrial dryer for the production of recycled polyester

The study proposes the evaluation of the residence-time distribution (RTD) in situ in an industrial dryer for the production of recycled polyester fibers (PES) from colorless polyethylene terephthalate (PET) flakes without interruption of the production. A disturbance of the pulse type was employed, in which the tracer (blue PET flakes) had previously been crystalized and its concentration was obtained according to the time at the dryer outlet. Additionally, analyses of intrinsic viscosity and crystallization percentage of the PET flakes (colorless and blue) and PES intrinsic viscosity and color force were performed. By RTD, the mean residence time (322.8 min), the variance (1305.4 min2), the standard deviation (36.1 min) and the relative error (1.5%) were obtained when compared to the theoretical residence time, indicating the absence of preferred paths or flake agglomerates in the equipment. Finally, the characterization demonstrated that there was no alteration in the parameters of product quality during RTD evaluation, confirming the potential of application of this methodology for diagnoses of continuous industrial processes.