Poly Ethylene Terephthalate Powder Research Articles

Modulation of PETase active site flexibility and activity on morphologically distinct polyethylene terephthalate substrates by surface charge engineering

Enzymatic hydrolysis of polyethylene terephthalate (PET) waste is a compelling strategy for environmentally friendly recycling of a major pollutant. Here, we investigate the effects of surface charge point mutations both proximal and distal to the active site of the mesophilic PET-degrading enzyme IsPETase and the thermostable V3 variant with superior activity. The vicinal K95A mutation significantly inhibited IsPETase activity on mechanically processed PET powder. Conversely, this mutation significantly increased hydrolysis of PET powder in the V3 PETase. Activity of both enzymes on PET film was inhibited by the K95A mutation, highlighting complex interplay between mutation context and substrate morphology. Further installing the distal R132N and R280A surface charge mutations potentiated activity of V3 on all substrates tested. This variant afforded 100 % degradation of pre-processed bottle-grade PET powder in 3 days at 40°C reaction temperature, a 3-fold improvement over IsPETase. Whilst reduction of positive charge on the PETase surface is known to reduce interaction with PET, molecular dynamics simulations suggest this can be offset by context-dependent modulation of active site flexibility, which differentially impacts both hydrolysis of morphologically distinct PET substrates and the concentration-dependent inhibition phenomenon observed for PETase.

Compressive and Tensile Behavior of High-Ductility Alkali-Activated Composites with Polyethylene Terephthalate Powder

Researchers have been engaged in the study of high-ductility concrete (HDC) due to its excellent ductility and cracking control ability. This study combines the concepts of HDC and alkali-activated composites (AAC) to develop high-ductility alkali-activated composites (HDAAC) using polyethylene terephthalate (PET) powder. Experimental investigations were conducted to assess the compressive and tensile properties of HDAAC, focusing on the impact of varying PET powder content (0%, 15%, 30%, and 45%) and fly ash/slag ratios (FA/GGBS, 6:4, 7:3, and 8:2). The results indicated that the compressive strength of HDAAC ranged from approximately 30 MPa to about 100 MPa, with the specimens maintaining good integrity after axial compression failure due to the bridging action of PE fibers. The replacement of quartz powder (QP) with PET powder slightly decreased the compressive strength and elastic modulus of HDAAC, albeit mitigating its brittleness under compression. An increase in GGBS content enhanced the compressive strength and elastic modulus of HDAAC due to the increased formation of the C-A-S-H reaction products, leading to reduced porosity and a denser microstructure. Under axial tension, HDAAC exhibited typical multiple-cracking behavior with significant pseudo-strain hardening. Increases in the PET content and FA/GGBS ratio resulted in finer cracks, indicating excellent crack control and deformation capabilities. The initial cracking strength, tensile strength, and ultimate tensile strain ranged from 3.0 MPa to 4.6 MPa, 4.2 MPa to 8.2 MPa, and 4.1% to 7.2%, respectively. Despite a decrease in the initial cracking strength and tensile strength with higher PET content, the ultimate tensile strain of HDAAC slightly increased. Observations under a scanning electron microscope revealed a distinct interfacial transition zone near the PET powder, leading to poor bonding with the alkali-activated matrix. In contrast, QP dissolved on the surface in highly alkaline environments, forming better interface properties. These variations in interface properties can be used to interpret the variations in the mechanical performance of HDAAC.

Process development and techno-economic analysis for mechanochemical recycling of poly(ethylene terephthalate)

Chemical recycling of consumer plastics has garnered great attention recently towards achieving circular economy goals. Particularly in the case of PET waste, mechanochemical depolymerization in ball mill reactors has been identified as a very promising technology due to the high conversion rates achieved under mild conditions. While the absence of solvents in the reaction mixture reduces significant separation costs, mechanochemical depolymerization still presents challenges with respect to the efficient separation and purification of monomers. Thus, meticulous experiments, process modeling, and simulations are essential for demonstrating the separation and purification of monomers. In this study, we present the lab-scale separation process flow for the recovery of terephthalic acid (TPA) and ethylene glycol (EG) from mechanochemically depolymerized polyethylene terephthalate (PET). We additionally examine the use recycling of ideal PET powder and commercial samples (e.g., PET fibers, bottles, and food containers) as feedstocks. The process parameters are optimized to achieve 97 %+ of monomer recovery with 99 %+ purity. The complete recovery of EG, and recycling of process water enables a ‘zero-liquid discharge’ process design. Subsequently, we conduct a techno-economic analysis (TEA) to evaluate the economic potential of the proposed sequence, which resulted in a positive net present value (NPV) for the different scenarios and a minimum selling price (MSP) of $0.99/kg. Finally, we compare the economic potential of mechanochemical recycling of PET to fossil-based production and other recycling methodologies based on economic metrics.

Mechanical properties of cement mortar with gamma-irradiated recycled plastic powder, pellet, and fiber

This study aimed to investigate the impact of gamma irradiated recycled polyethylene terephthalate (PET) pellets, powder, and fibers on the mechanical performance and ductility of cementitious mortar. The sensitivity to gamma irradiation was explored by varying the irradiation rate and total dose. The recycled PET additives employed in this experiment consisted of pellets and their different application forms: powder and fiber, containing 30 % recycled raw materials polymerized through a chemically recycled method. For comparison, plain mortar composite and virgin PET mortar composite were used as controls. When PET pellets partially replaced the aggregate, the compressive strength of the composite decreased significantly as the volume fraction of pellets increased. Conversely, specimens partially replaced by PET powder showed an overall increase in compressive strength compared to the control specimens, regardless of the volume fraction of powder, gamma irradiation rate, or total dose, with no change in ductility. To assess changes in tensile strength and ductility of the recycled PET fibers under different gamma irradiation rates and total doses, direct fiber tensile tests were conducted. The gamma-irradiated fiber specimens exhibited a slight increase in strength and ductility. This information allowed for the calibration of the tensile material constitutive relationship of PET fibers, which was subsequently used in nonlinear finite element analysis. The study also investigated the variation in direct tensile, compressive, and flexural strengths with different volume fractions of fiber. The results indicated that the strength enhancement was minimal, but the direct tensile and flexural tensile analyses predicted an enhancement.

An archaeal lid-containing feruloyl esterase degrades polyethylene terephthalate

Polyethylene terephthalate (PET) is a commodity polymer known to globally contaminate marine and terrestrial environments. Today, around 80 bacterial and fungal PET-active enzymes (PETases) are known, originating from four bacterial and two fungal phyla. In contrast, no archaeal enzyme had been identified to degrade PET. Here we report on the structural and biochemical characterization of PET46 (RLI42440.1), an archaeal promiscuous feruloyl esterase exhibiting degradation activity on semi-crystalline PET powder comparable to IsPETase and LCC (wildtypes), and higher activity on bis-, and mono-(2-hydroxyethyl) terephthalate (BHET and MHET). The enzyme, found by a sequence-based metagenome search, is derived from a non-cultivated, deep-sea Candidatus Bathyarchaeota archaeon. Biochemical characterization demonstrated that PET46 is a promiscuous, heat-adapted hydrolase. Its crystal structure was solved at a resolution of 1.71 Å. It shares the core alpha/beta-hydrolase fold with bacterial PETases, but contains a unique lid common in feruloyl esterases, which is involved in substrate binding. Thus, our study widens the currently known diversity of PET-hydrolyzing enzymes, by demonstrating PET depolymerization by a plant cell wall-degrading esterase.

Biodegradation Potential of Polyethylene Terephthalate by the Two Insect Gut Symbionts Xanthomonas sp. HY-74 and Bacillus sp. HY-75.

Polyethylene terephthalate (PET) is a plastic material that is widely used in beverage bottles, food packaging, and other consumer products, which is highly resistant to biodegradation. In this study, we investigated the effects of two insect gut symbionts, Xanthomonas sp. HY-74 and Bacillus sp. HY-75, during PET biodegradation. Both strains degraded PET-containing agar plates, and the sole nutrition source assay showed that HY-74 had different degradation rates depending on the presence of specific carbon and nitrogen sources, whereas HY-75 exhibited comparable degradation across all tested conditions. The two strains biodegraded the PET film with 1.57 ± 0.21% and 1.42 ± 0.46% weight loss after 6 weeks, respectively. Changes in the morphology and structure of the PET films, such as erosion, scratching, and surface roughening, were determined using scanning electron microscopy (SEM). Further, the two strains biodegraded PET powder, broke it into its degradation products, and changed the surface functional groups. This is the first study to investigate the biodegradation of PET by Hymenoptera gut-derived microbes and offers promising insights into the potential applications of insect gut symbionts in PET waste management.

A comparison study of using polyethylene terephthalate and limestone fillers on porous asphalt mixture behaviours

Regardless of their gradations, all varieties of asphalts pavement mixtures are smooth and impermeable, which reduces the safety of cars in different weather situations. Comfort and safety on the roads during various weather conditions are directly influenced by surface layer characteristics. Porous asphalt has quick surface drainage, eliminates splashing, and improves safety. Additionally, because water drains into the asphalt mixture's pores, the desired level of friction between the tire and the pavement will be guaranteed. This necessitates the production of permeable asphalt pavement mixtures for roads and highways that can handle heavy traffic loads. The primary objective of this study is to investigate the enhancement of stability and mechanical properties in porous mixtures by substituting conventional limestone filler with Polyethylene Terephthalate Waste Plastic (PET) powder. Simultaneously, the study aims to mitigate environmental pollution by utilizing PET materials, which take decades to decompose naturally. The PET used in the study was melted at 260 0C and then powdered using 7000, 18000, and 28000 rpm grinders to obtain filler that passed sieve no. 200. The ASTM D7064-based evaluation of the mixture's optimum asphalt content takes into account essential factors, including drain down, percentage of air voids, and optionally, the results of the Cantabro abrasion test, which was calculated to be 4.75%, decreased to 4.5% when polyethylene terephthalate powder was utilized as filler in place of limestone. The optimum limestone filler percentage was 3.0% based on National Asphalt Pavement Association (NAPA) gradation employed the same procedure in the optimum asphalt content evaluation. However, the results showed that the optimum amount when using PET powder reached 3.5%.The criteria used to investigate the newly proposed asphalt pavement mixture are the Marshall method, Drain down of binder, Cantabro loss test, and permeability of porous mixture. This research reveals that adding PET as an alternative filler to limestone reduces permeability, Drain Down, and Cantabro by 22.64%, 29.27%, and 16.33% respectively while increasing the stability by more than 15.5%. It is still promising that the permeability of the mixture stays within the desirable limit for comfort and safe driving. Filler replacement was tied to performance testing and was demonstrated to raise the deformation strength in the KIM test more than twice from 1.54 MPa to 3.63 MPa by employing a specialized head and Marshall loading machine as an alternative method to the wheel tracking test for evaluating rutting in the mixture. The index of retained stability by aging the samples in water bath at 25 °C from one to four days increased from 8.66 MPa by 33.1% to reach 12.57 MPa where filler replaced, and the indirect tensile strength based on ASTM D4867raised by 29.08% from 0.578 to 0.735 MPa for conditions samples and raised from 0.681 to 0.879 MPa to raise the unconditioned samples by 12.9%. It is also worth noting that the use of PET as a waste material has significant environmental benefits.

Discovery and rational engineering of PET hydrolase with both mesophilic and thermophilic PET hydrolase properties

Excessive polyethylene terephthalate (PET) waste causes a variety of problems. Extensive research focused on the development of superior PET hydrolases for PET biorecycling has been conducted. However, template enzymes employed in enzyme engineering mainly focused on IsPETase and leaf-branch compost cutinase, which exhibit mesophilic and thermophilic hydrolytic properties, respectively. Herein, we report a PET hydrolase from Cryptosporangium aurantiacum (CaPETase) that exhibits high thermostability and remarkable PET degradation activity at ambient temperatures. We uncover the crystal structure of CaPETase, which displays a distinct backbone conformation at the active site and residues forming the substrate binding cleft, compared with other PET hydrolases. We further develop a CaPETaseM9 variant that exhibits robust thermostability with a Tm of 83.2 °C and 41.7-fold enhanced PET hydrolytic activity at 60 °C compared with CaPETaseWT. CaPETaseM9 almost completely decompose both transparent and colored post-consumer PET powder at 55 °C within half a day in a pH-stat bioreactor.

Effect of trisilanol isobutyl polyhedral oligomeric silsesquioxane (TPOSS) in recycled PET (rPET) and polypropylene based compound: Investigation on mechanical properties

Recycled polyethylene terephthalate is successfully prepared. This project is involved for “Circular economy” policy. It is successfully prepared into powder form by nano-grinder technique. 10 phr of PP-g-MA and 1 phr to 5 phr of TPOSS are added for compatibilizer and mechanical properties enhancement, respectively. PP-g-MA can form the chemical linkage of the anhydride groups with the polyamide end groups. 20 wt% of recycled polyethylene terephthalate powder and polypropylene based compound is successfully fabricated by melt mixing. Then, it is fabricated by melting spinning technique. Fourier transform infrared presents Si-O-Si linkage in binary blend compound. X-ray diffraction pattern reports that single phase is obtained. Adding TPOSS can be induced to crystallinity enhancement. No significant change of thermal properties was observed from room temperature to 300℃. Scanning electron microscope reports that with the PP-g-MA provides smoothness of surface. Recycled polyethylene terephthalate is uniformly distributed. Melting and crystallization temperatures are reported to be 162℃ to 167℃ and 115℃ to 120℃, respectively. All of throughput rate is reported to be 1.8 g⸳min-1 to 2.3 g⸳min-1. With the existence of TPOSS, the mechanical properties of compound are slightly increased. TPOSS are added for mechanical properties enhancement. The polymer compound presents the excellent properties. It is remarkable to note that recycled polyethylene terephthalate is considered as an excellent candidate for use as raw material for polymer compound production.

Deep learning guided enzyme engineering of Thermobifida fusca cutinase for increased PET depolymerization

A responsible and sustainable circular economy of polymers requires efficient recycling processes with a low CO2 footprint. Enzymatic depolymerization of polyethylene terephthalate (PET) is a first step to make PET polymers a part of a circular economy of polymers. In this study, a structure-based deep learning model was utilized to identify residues in TfCut2 that are responsible for improved hydrolytic activity and enhanced stability. Machine learning guided design identified novel beneficial positions (L32E, S35E, H77Y, R110L, S113E, T237Q, R245Q, and E253H), which were evaluated and stepwise recombined yielding finally the beneficial variant L32E/S113E/T237Q. The latter TfCut2 variant exhibited improved PET depolymerization when compared with TfCut2 WT (amorphous PET film, 2.9-fold improvement // crystalline PET powder (crystallinity > 40%), 5.3-fold improvement). In terms of thermal resistance the variant L32E/S113E/T237Q showed a 5.7 °C increased half-inactivation temperature (T5060). The PET-hydrolysis process was monitored via a quartz crystal microbalance with dissipation monitoring (QCM-D) in real-time to determine depolymerization kinetics of PET coated onto the gold sensor. Finally, conformational dynamics analysis revealed that the substitutions induced a conformational change in the variant L32E/S113E/T237Q, in which the dominant conformation enabled a closer contact between the catalytic site and PET resulting in increased PET-hydrolysis. Overall, this study demonstrates the potential of deep learning models in protein engineering for identifying and designing efficient PET depolymerization enzymes.

ИССЛЕДОВАНИЕ ФОРМИРОВАНИЯ ДЕМПФИРУЮЩИХ ПОКРЫТИЙ ИЗ ПОЛИМЕРОВ И МЕТАЛЛОВ

The processes of obtaining damping polymeric coatings (gas-flame spraying of powders) and composite metal coatings (deformation cladding with a flexible tool) are studied. It is established that coatings applied by the gas-flame method with thermoplastic polymer powders provide a sufficiently high damping efficiency, while the best dissipative characteristics are provided when sprayed with polyethylene terephthalate powder. The maximum adhesion strength (10.5–10.7 MPa) for normal separation of coatings applied with polyethylene terephthalate powder is achieved when using a combustible mixture with a propane/air ratio of 1:26 and subsequent cooling at a rate of no more than 3 deg/s. Based on the results of tribotechnical tests, the composition of sintered bronze-graphite was selected for applying noise-absorbing coatings by the deformation cladding method. The study of the influence of regime parameters of the cladding process on the thickness and continuity of the formed coating layer of bronze-graphite showed that the ratio of the linear speed of movement of the workpiece and the linear speed of rotation of the brush should be within 0.23–0.27, the interference value N — in the range of 0.8–1.5 mm with the number of passes n = 8–12. The microhardness of the clad layer was H0,049 = 1,700 MPa, which exceeded the microhardness of the donor material by 25 %.

Rational redesign of thermophilic PET hydrolase LCCICCG to enhance hydrolysis of high crystallinity polyethylene terephthalates

Polyethylene terephthalate (PET)-degrading enzymes represent a promising solution to the plastic pollution. However, PET-degrading enzymes, even thermophilic PETase, can effectively degrade low-crystallinity (∼8%) PETs, but exhibit weak depolymerization of more common, high-crystallinity (30–50%) PETs. Here, based on the thermophilic PETase, LCCICCG, we proposed two strategies for rational redesign of LCCICCG using the machine learning tool, Preoptem, combined with evolutionary analysis. Six single-point mutants (S32L, D18T, S98R, T157P, E173Q, N213P) were obtained that exhibit higher catalytic efficiency towards PET powder than wild-type LCCICCG at 75 °C. Additionally, the optimal temperature for degrading 39.07% crystalline PET increased from 65 °C in the wild-type LCCICCG to between 75 and 80 °C in the LCCICCG_I6M mutant that carries all six single-point mutations. Especially, the LCCICCG_I6M mutant has a significantly higher degradation effect on some commonly used bottle-grade plastic powders at 75–80 °C than that of wild type. The enzymatic digestion of ground 31.30% crystalline PET water bottles by LCCICCG_I6M yielded 31.91 ± 0.99 mM soluble products in 24 h, which was 3.64 times that of LCCICCG (8.77 ± 1.52 mM). Overall, this study provides a feasible route for engineering thermostable enzymes that can degrade high-crystallinity PET plastic.

The Purification and Characterization of a Cutinase-like Enzyme with Activity on Polyethylene Terephthalate (PET) from a Newly Isolated Bacterium Stenotrophomonas maltophilia PRS8 at a Mesophilic Temperature

A polyethylene terephthalate (PET)-degrading bacterium identified as Stenotrophomonas maltophilia PRS8 was isolated from the soil of a landfill. The degradation of the PET bottle flakes and the PET prepared as a powder were assessed using live cells, an extracellular medium, or a purified cutinase-like enzyme. These treated polymers were analyzed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The depolymerization products, identified using HPLC and LC-MS, were terephthalic acid (TPA), mono(2-hydroxyethyl)-TPA (MHET), and bis(2-hydroxyethyl)-TPA (BHET). Several physicochemical factors were optimized for a better cutinase-like enzyme production by using unique single-factor and multi-factor statistical models (the Plackett–Burman design and the central composite design software). The enzyme was purified for homogeneity through column chromatography using Sephadex G-100 resin. The molecular weight of the enzyme was approximately 58 kDa. The specific activity on para nitrophenyl butyrate was estimated at 450.58 U/mg, with a purification of 6.39 times and a yield of 48.64%. The enzyme was stable at various temperatures (30–40 °C) and pH levels (8.0–10.0). The enzyme activity was significantly improved by the surfactants (Triton X-100 and Tween-40), organic solvent (formaldehyde), and metals (NiCl2 and Na2SO4). The extracellular medium containing the cutinase-type enzyme showed a depolymerization yield of the PET powder comparable to that of Idonella skaiensis IsPETase and significantly higher than that of Humicola insolens thermostable HiCut (HiC) cutinase. This study suggests that S. maltophilia PRS8 is able to degrade PET at a mesophilic temperature and could be further explored for the sustainable management of plastic waste.

Optimization of Concrete Containing Polyethylene Terephthalate Powder and Rice Husk Ash Using Response Surface Methodology

The continuous increase in population, advancement in technology, and affluence have influenced the amount of biodegradable and nonbiodegradable waste generated. Studies have shown that the utilization of different wastes in concrete is imperative to reduce the long-term environmental problems associated with their handling and management. This study evaluates the performance of concrete incorporating polyethene terephthalate powder (PETp) and rice husk ash (RHA) as supplementary cementitious materials varied at 0%, 7.5%, and 15%. Results indicated that the presence of PETp reduces workability while increasing the content of both PETp and RHA decreased the compressive and flexural strengths. A few studies have demonstrated the prediction and optimization of PETp as a fine aggregate. This study explores the central composite design of response surface methodology in optimizing the fresh and hardened properties of concrete incorporating PETp and RHA. The results indicate that workable concrete can be achieved with an RHA content higher than the PETp content. The analysis of variance provided effective models with good prediction capabilities. The simulated values from the models were close to those obtained experimentally. An optimal percentage of 5.76% PETp and 9.45% RHA was obtained for predicted responses and validated with a good level of accuracy. An overview of the different combinations of RHA and PETp indicates that concrete incorporating only RHA had the tendency to absorb the least water and exhibit low voids. However, the combination of 7.5% RHA and 7.5% PETp had a reduced water absorption when compared with a concrete mix containing 15% of either supplementary cementitious material. In general, eco-friendly concrete with improved durability can be produced by incorporating PETp and RHA.

High-strain rate compressive behavior of concrete with two different substituted recycled plastic aggregates: Experimental characterization and probabilistic modeling

This paper presents a pilot study on the characterization of the high-strain rate compressive behavior of a novel concrete with two different substituted recycled plastic aggregates. A reference mix with an average compressive strength of about 55MPa is considered. Recycled PolyEthylene Terephthalate (PET) powder and recycled mixed plastic (composed of PolyPropylene (PP) and PolyEthylene (PE)) granules were adopted to substitute fine and coarse aggregates. Two different substitution strategies are employed. In the first one, the PET powder is used to substitute the fine sand by volume. In the second one, the PET powder is used to substitute the fine sand while the recycled mixed plastic granules are used to substitute the coarse sand and fine coarse aggregates by volume (50% for PET powder and 50% for recycled mixed plastic granules). Four total replacement levels (5%, 10%, 20%, and 30%) by volume were considered. The fresh concrete properties (slump and density) and quasi-static compressive behavior, are investigated. The micro-scale characterization of the material using SEM scans provided a complete understanding of the observed macro-scale behavior. Tests were performed using conventional quasi-static loading with a compressive testing machine and high-strain rate tests with a Φ80-mm Split-Hopkinson Pressure Bar (SHPB) for strain rates up to 200s−1. The dynamic tests revealed the marked strain rate dependency, although specimens with large plastic volume substitution were more sensitive to the strain rate effect. A probabilistic data-driven model for the Dynamic Increase Factor (DIF) is also proposed based on the test data. Ultimately, this study indicates that the proposed material has a good high-strain rate compressive behavior and can be a promising material to be employed for protective techniques against impact and blast loads.

Comparison of the enzymatic depolymerization of polyethylene terephthalate and AkestraTM using Humicola insolens cutinase

The enzymatic depolymerization of synthetic polyesters has become of great interest in recycling plastics. Most of the research in this area focuses on the depolymerization of polyethylene terephthalate (PET) due to its widespread use in various applications. However, the enzymatic activity on other commercial polyesters is less frequently investigated. Therefore, AkestraTM attracted our attention, which is a copolymer derived from PET with a partially biobased spirocyclic acetal structure. In this study, the activity of Humicola insolens cutinase (HiCut) on PET and AkestraTM films and powder was investigated. HiCut showed higher depolymerization activity on amorphous PET films than on Akestra™ films. However, an outstanding performance was achieved on AkestraTM powder, reaching 38% depolymerization in 235h, while only 12% for PET powder. These results are consistent with the dependence of the enzymes on the crystallinity of the polymer since Akestra™ is amorphous while the PET powder has 14% crystallinity. On the other hand, HiCut docking studies and molecular dynamic simulations (MD) suggested that the PET-derived mono (hydroxyethyl)terephthalate dimer (MHET)2 is a hydrolyzable ligand, producing terephthalic acid (TPA), while the Akestra™-derived TPA-spiroglycol ester is not, which is consistent with the depolymerization products determined experimentally. MD studies also suggest ligand-induced local conformational changes in the active site.

Evaluation of Polyethylene Terephthalate Powder in High Speed Sintering

Laser Sintering (LS) was the first Powder Bed Fusion (PBF) method for polymers and it is now quite an established process for rapid prototyping and even for the production of functional parts. High Speed Sintering (HSS) is a variant of PBF which was later developed and it has the potential to be more scalable than LS. Most of the work for HSS and LS has been conducted with polyamide-12 (PA 12). This work reports the first effort to use polyethylene terephthalate (PET) in HSS. Well defined, simple and complex parts could be printed without any build failures. However, limitations were induced by current HSS machines which led to some curvature (warpage) in tensile bars after manufacturing. The reason for this was that all currently available machines for HSS are built for polymers such as polyamide 12, which means their maximum bed temperature is limited to 190 °C. This corresponds to the lower limit of processability of PET in PBF processes. The slightly curved tensile bars were straightened by heating them to 230 °C with a weight on top, and afterwards the mechanical properties were measured. The tensile modulus was similar to what was obtained with PET via LS but the strength and elongation-at-break (EAB) was lower. Microscopy showed that the reason for the lower strength and EAB was the incomplete melting of particles. This arose from the temperature limitation of the current generation of HSS machines. The porosity was established as 2.23% by helium pycnometry which is the same as for LS. The results of the thermal analysis indicated that the PET parts manufactured with HSS were semi-crystalline like the PET parts manufactured via LS.

Metabolic engineering of Yarrowia lipolytica for poly(ethylene terephthalate) degradation

Polyethylene terephthalate (PET) is the most widely used plastic, whose global production scale causes serious problems due to it being highly non-biodegradable. The present work provides a novel approach to plastic degradation studies, which involves direct degradation of PET in the culture of a modified Y. lipolytica yeast strain extracellularly producing cutinase from Fusarium solani. In this study, we successfully accomplished a scale-up of the degradation process in culture, which is promising from the perspective of wider application of the developed method in the future. Additionally, we tested the effect of various supplements, which may increase the PET degradation efficiency in the culture of the Y. lipolytica pAD CUT_FS strain. The ability of PET decomposition was verified by the amount of the released degradation products, such as terephthalic acid (TPA) and mono-(2-hydroxyethyl)-terephthalic acid (MHET), during cultivation. We observed that the quantities of TPA and MHET released during the PET degradation process were increasing daily, and were 1.51 gL−1 and 0.45 gL−1, respectively after 240 h of the bioreactor fermentation. Analysis of the PET film by electron microscopy indicated that there was abundant damage on the surface of the material. This study also demonstrated that the engineered Y. lipolytica strain is able to degrade PET at 28 °C during fermentation. The results obtained in this study using amorphous PET powder provide a wide range of possibilities for application of the cutinase-secreting strain of Y. lipolytica on the more difficult to degrade highly crystalline PET films, PET bottles and PET melts.

Concrete strength analysis using waste plastic as a partial replacement for sand

Plastic got its acceptance as an acceptable-durable material around the globe since late twentieth century. But gradually people understood the issues with plastic that it takes millennia to disintegrate and that this sluggish breakdown rate has a harmful impact on both ocean and terrestrial ecosystems. PET (poly-ethylene terephthalate) is a widely used plastic that is primarily utilized in the production of plastic containers and water bottles. The effect of incorporating carbonated PET plastic wastes into concrete as a fine aggregate alternative, in the achievable concrete strength is investigated in current study. The compressive strength of concrete was determined for five distinct samples with 1%, 2%, 3%, 4%, and 5% substitution of fine aggregates with squashed PET powder. Slump decreased with the enhancement of replacement proportion and binding strength between cement matrix and aggregates improved as the gap at the interfacial transition zone was minimized for all replacements. The unconfined compressive strength of concrete got a thrust. The optimum achievable results were obtained at 3% replacement level.

An experimental investigation and response surface methodology-based modeling for predicting and optimizing the rheological and mechanical properties of self-compacting concrete containing steel fiber and PET

In this study, rheological and mechanical properties of self-compacting concrete containing polyethylene terephthalate (PET) and steel fibers have been investigated experimentally and numerically. A total of 30 mixing schemes are investigated using a response surface (RSM) method. Input variables in the mixtures include PET as a substitute for part of the fine aggregates, steel fibers, stone powder as a substitute for a percentage of cement and superplasticizer. The PET, steel fibers and stone powder quantity in the concrete were in the range of 0–16% of the fine aggregates, 0–0.4% of the concrete volume, and 0–16% of cement weight, respectively. The superplasticizer quantity was 0.5–1.5% of the weight of powder materials. An optimum mixture was determined using RSM optimization technique.To evaluate the rheological specifications, slump flow, T50, V funnel, and l-box tests were used in the experiments. For the mechanical specifications, compressive strength, tensile strength, flexural strength, and stress–strain curve were used. Experimental results show that steel fibers reduce rheological properties while improve mechanical properties, especially ductility. Additionally, PET increases the corresponding strain of maximum compressive strength of concrete (ε0) and ductile fracture. The optimization results indicate that with 4% PET, 0.23% fiber, 6.47% stone powder, and 1.132% superplasticizer, the maximum 28-day compressive strength is obtained, while meeting EFNARC workability indicators.