Polyethylene Terephthalate Glycol Research Articles

A Study on the Tensile Behavior of Specimens Manufactured by FDM from Recycled PETG in the Context of the Circular Economy Transition

This article presents the results of a study on the influence of 3D printing by Fused Deposition Modeling (FDM) parameters on the tensile behavior of parts made from Everfil recycled Polyethylene Terephthalate Glycol (rPETG). For this study, 27 rPETG tensile specimens with 100% recycled material were manufactured using an Anycubic 4 Max Pro 2.0 3D printer and by varying the printing parameters: height of the deposited layer in one pass, Lh, and filling percentage, Id. The Lh was set to 0.10, 0.15, and 0.20 mm and the Id was set to 50, 75, and 100 %. The two variable parameters, Id and Lh, influenced the tensile characteristics of the rPETG specimens: maximum breaking strength, percent elongation at break, and modulus of elasticity. The ultimate breaking strength and modulus of elasticity of the rPETG specimens were most influenced by Id, whereas the percentage elongation at break was mostly affected by Lh. The optimized FDM parameters for the fabrication of rPETG tensile specimens were found to be Lh = 0.20 mm and Id = 100%.

A Study of the Optimization of FDM Parameters for the Manufacture of Compression Specimens from Recycled PETG in the Context of the Transition to the Circular Economy

The current paper presents the results of a research on the optimization of Fused Deposition Modeling (FDM) parameters, namely the height of the deposited layer in one pass, Lh, and the filling percentage, Id, with the purpose of manufacturing compression specimens from recycled Polyethylene Terephthalate Glycol (rPETG), and thus, aiming the transition to circular economy. A total of 45 compression specimens were manufactured from rPETG on the Anycubic 4Max Pro 3D printer with variable parameters Lh = 0.10 mm, 0.15 mm, 0.20 mm, and Id = 50%, 75%, 100%. All 45 specimens were tested in compression on the Barrus White 20 kN universal testing machine. The considered variable parameters influence the Compressive Strength (CS) of the specimens, with Id being the parameter with overwhelming influence.

Insights into the photosensitivity and photobleaching of dissolved organic matter from microplastics: Structure-activity relationship and transformation mechanism

Revealing the structure-activity relationship between physicochemical properties and photoactivities of microplastic dissolved organic matter (MPDOM) is significant for understanding the environmental fate of MPs. Here, we systematically analyzed the physicochemical properties and molecular composition of DOM derived from MPs including polystyrene (PS), polyethylene glycol terephthalate (PET), polyadipate/butylene terephthalate (PBAT), polylactic acid (PLA), polypropylene (PP), and compared their photosensitivity and photobleaching behaviors. Results indicated that PSDOM and PETDOM had more similar properties and compositions, and showed stronger photosensitivity and photobleaching effects than PBATDOM, PLADOM and PPDOM. The [3DOM∗]SS and [1O2]SS varied in the range of 0.31-13.03 × 10-14 and 1.71-5.49 × 10-13M, respectively, which were within the reported range of DOM from other sources. The SUVA254, HIX, AImodwa, Xcwa and lignin/CRAM-like component showed positive correlation with the [3DOM∗]SS, [1O2]SS and Φ3DOM*. The negative correlation between E2/E3 and [3DOM∗]SS was due to the higher proportion of low-molecular weight components in MPDOM. The lignin/CRAM-like component was identified to be the crucial photobleaching-component. The lignin/CRAM-like in PSDOM showed a deepened oxidation degree, while its change trend in PETDOM was from unsaturated to saturated. These findings provide new insights into the relevant photochemical fate of MPDOM.

Electroreforming of plastic wastes for value-added products.

The problem of plastic pollution is becoming increasingly serious, and there is an urgent need to reduce the use of plastics and to improve the recovery rate of plastic wastes. Plastic wastes can be transformed into value-added chemicals at the anode through electrocatalytic conversion, while coupling with cathodic reduction reactions to achieve cogeneration of valuable anodic and cathodic products. The plastic electroreforming technology has unprecedented advantages, including a green and decentralizable process, renewable energy storage, ecological benefits, resource recovery, cost-effectiveness, and so on. Herein, we present a mini review about recent advances in this topic. We first discuss the electrooxidation mechanisms of different plastic wastes (such as polylactic acid, polyethylene glycol terephthalate, polyethylene, polyethylene furanoate, polybutylene terephthalate, and polyamides). Then, the progress of plastic waste-assisted electrolysis systems is summarized, including plastic waste-assisted water splitting for hydrogen production and oxygen reduction, as well as plastic electroreforming coupled with CO2 reduction, and the nitrate reduction reaction. Finally, the development prospects and challenges in this field are introduced and discussed. This review aims to provide a concise overview of the emerging plastic electroreforming, thus offering insight on the design of efficient and stable plastic-assisted electrolysis systems.

Can 3D-printed flow electrode gaskets replace CNC-milled graphite current collectors in flow capacitive deionization?

As billions of people suffer from water scarcity, finding sustainable water resources is imperative. Flow capacitive deionization (FCDI) is a highly promising desalination process that can produce clean water from saline streams such as brackish and seawater. Conventional FCDI systems employ Computerised Numerical Control (CNC)-milled graphite plates that serve as current collectors and flow electrode channels. However, they have drawbacks such as high manufacturing costs, waste generation, and the difficulty of producing complex geometries required for efficient flow electrode mixing. Here, we successfully demonstrate that 3D-printed flow electrode gaskets, made of non-conductive polyethylene terephthalate glycol (PET-G) or a carbon black-infused conductive polylactic acid (PLA), are viable alternatives to traditional graphite plates. In specific cases, the desalination and energy efficiency in FCDI cells with 3D-printed conductive gaskets were even 25 % and 10 % higher, respectively, compared to traditional CNC-milled current collectors. The transition to 3D printing offers notable benefits, such as the competence to fabricate complex designs that enhance internal mixing and charge percolation. This innovation represents a change of paradigm in the way FCDI cells should be designed and manufactured, using additive manufacturing, which represents an efficient, scalable, and cost-effective substitute for the conventional approach, contributing therefore for the advancement of FCDI desalination technology.

A critical review of the article: Experimental investigation of the effect of infill parameters on dynamic compressive performance of 3D-printed carbon fiber reinforced polyethylene terephthalate glycol composites

Understanding the dynamic properties of 3D-printed materials subjected to high strain rates enables designers and engineers to obtain engineering data for designing components subjected to dynamic loads. The work of Chili et al., presented in 2023, is the most recent research that evaluates the properties of carbon fiber-reinforced polyethylene terephthalate glycol (CF-PETG) using the Split Hopkinson Pressure Bar (SHPB) test. A detailed analysis and discussion of the results presented in the analyzed document are provided. Finally, the areas for improvement in the research are highlighted to achieve better results.

Effects of industrial solid waste on the generation of PCDD/Fs, dl-PCBs and PAHs tuned by waste pseudo-components during engineering co-combustion

Co-combustion of municipal solid waste (MSW) with industrial solid waste (ISW) is becoming prevailing. But its effects on generation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs) and polycyclic aromatic hydrocarbons (PAHs) remain unclear, hindering their efficient control. Hence, six batches of engineering incineration tests containing diverse blending types and ratios of ISW were designed in an incinerator of 650 t/d. To target the relationship between complex waste components and contaminants, a pseudo-component matrix model was innovatively incorporated, with nine plastic and biomass pseudo-components quantitatively extracted. Compared to raw MSW incineration, co-combustion generally increased generation of 17 PCDD/Fs and 12 dl-PCBs in fly ash up to six-fold, with the highest TEQ concentrations of 843 ng/kg and 68.1 ng/kg, respectively, while exerted less impact on generation of 16 PAHs. Among nine pseudo-components, polyethylene glycol terephthalate (PET), polyvinyl chloride (PVC) and cellulose were identified as the key to generation of PCDD/Fs and dl-PCBs. Combustion of PET and cellulose served to provide benzene derivatives, while PVC contributed more chlorine. Tracking the original waste, blending with waste plastics, polyester textile, artificial leather and paper should be strictly regulated. This study was of significance to optimize co-combustion for source reduction of toxic pollutants.

Assessment of physio-mechanical characteristics of ABS/PETG blended parts fabricated by material extrusion 3D printing

Abstract This study examines the effect of blending acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate glycol (PETG) in various weight percentage ratios (ABS/PETG: 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, 40/60) on the physio-mechanical properties of 3D-printed parts. The result showed that the 3D-printed PETG sample exhibited the highest density of 1.12 ± 0.05 g cm−3 along with the 40ABS60PETG blend displaying similar density value. However, the 40ABS60PETG sample also demonstrated the highest shrinkage, attributed to differences in thermal expansion and cooling rates between ABS and PETG. Moreover, the surface roughness value of the blended samples varied between 8.04 μm–and 9.78 μm, with the 40ABS60PETG sample having a minimal surface roughness of 8.04 ± 0.60 μm. Regarding mechanical performance, the 40ABS60PETG blend showed a notable improvement in flexural modulus, with increases of 6.45% and 60% compared to neat ABS and PETG, respectively. Compression testing revealed that ABS-dominant blends possess higher compression modulus and maximum compressive stress, indicating superior resistance to deformation and enhanced load-bearing capacity. This study highlights the importance of blend ratios to optimize performance, especially for applications requiring a balance between stiffness and flexibility. The results suggest that controlling the ABS/PETG ratio and carefully managing printing parameters can optimize the mechanical and dimensional stability of 3D-printed parts.

Mechanical properties variation of samples fabricated by fused deposition additive manufacturing as a function of filler percentage and structure for different plastics

One of the key factors in manufacturing products by fused deposition molding (FDM) or layer-by-layer printing technology is the material intensity of the product. The task of reducing the amount of material required to manufacture a product without significant loss of mechanical properties is one of the most practically important technological tasks. Material saving in FDM printing of products allows to reduce financial costs and increase the speed of manufacturing of the final product without reducing (or not significantly reducing) the quality properties of the product. In our work it is demonstrated that using Combs filling type and materials of poly lactic acid (PLA) and polyethylene terephthalate glycol (PETG) it is possible to achieve material savings of up to 23% at 50% filling for PLA and 17% at 75% filling for PETG without significant reduction of product strength in comparison with other filling types. Exceptions are PLA samples with 100% fill and Lateral fill. Application of Kruskal-Wallis criterion and Dunn’s criterion with Bonferroni multiple comparison correction showed that there were no statistically significant differences within the strength limits of samples made by FDM printing technology from PLA and PETG plastics (p-value = 0.0514), as well as samples with Triangle and Grid filling type (p-value = 1). Based on this result, three groups of samples statistically significantly differing in ultimate strength were identified by methods of hierarchical cluster analysis; in each group (except for group 1, which included samples made of PLA plastic with Lateral filling type and 100% filling), correlation analysis was performed (Spearman correlation was used). The results of the correlation analysis showed a stable average correlation between the percentage of filling, modulus along the secant 0.05–0.2% strain, ultimate strength and strain corresponding to the yield stress. Analysis of the correlation graph showed that the main parameter correlating with all mechanical properties of the specimen is the 0.05–0.2% strain modulus. Based on this conclusion, robust regression equations predicting the 0.05–0.2% strain modulus as a function of the percentage of specimen filling were constructed for the two selected groups. Analysis of the equations showed that in the third group of specimens, the average modulus of 0.05–0.2% strain is more than twice the modulus of 0.05–0.2% strain in the second group. The detected statistical regularities can be explained by the mechanism of strain hardening, the actual value of which depends on the structure of the macrodefect (type of filling), properties and volume of the material (percentage of filling) used in the fabrication of samples using FDM printing technology.

A novel 'stop-hole' strategy to extend the fatigue life of orthodontic thermoformed retainers: an in vitro study.

This study aimed to investigate the potential to limit crack propagation in thermoformed retainers (TRs) and extend their fatigue life by placing a 'stop-hole'. Thirty-two TRs, fabricated from 1mm thick, round polyethylene terephthalate glycol (PETG) blanks of ICONIC®, underwent testing within a custom-built fatigue tester. After initial crack growth of 3mm, the TRs were divided into three groups: a control group (C) and two experimental groups based on the stop-hole placement method. In the first experimental group, stop-holes were placed using a 1mm round carbide bur on a slow-speed handpiece (ES), while the second group utilized a heated 1-mm-width ball-ended CPITN probe (EH). Following the placement of a stop-hole at the crack-tip, all 32 TRs resumed testing until the final crack length of 10mm was reached. Stop-hole placement significantly prolonged the delay in crack re-initiation in both experimental groups compared to the control group (P < .001 for both). The mean re-initiation times for the ES and EH groups were 104.50 and 129.50min, respectively, whereas the control group was 28.94min. Consequently, this discrepancy was reflected in the total testing times, with both experimental groups requiring significantly longer time to reach the final crack length (P < .001). There was no significant difference in the testing times between the two experimental groups. This is an in vitro study. The stop-hole methodology significantly extended the fatigue life of a TR in a controlled laboratory environment.

Optimization of Tensile Strength and Cost-Effectiveness of Polyethylene Terephthalate Glycol in Fused Deposition Modeling Using the Taguchi Method and Analysis of Variance.

This paper investigates the optimization of tensile strength, tensile strength per unit weight, and tensile strength per unit time of polyethylene terephthalate glycol (PETG) material in fused deposition modeling (FDM) technology using the Taguchi method and analysis of variance (ANOVA). Unlike previous studies that typically focused on optimizing a single mechanical property, our research offers a multi-dimensional evaluation by simultaneously optimizing three critical quality characteristics: tensile strength, tensile strength per unit weight, and tensile strength per unit time. This comprehensive approach provides a broader perspective on both the mechanical performance and production efficiency, contributing new insights into the optimization of PETG in FDM. The Taguchi method (L16 45) was designed and executed, with the layer height, infill density, print temperature, print speed, and infill line direction as the control factors. Sixteen tensile tests were conducted, and ANOVA was employed to identify the main influencing factors for each quality characteristic. For the tensile strength, the infill density was found to have the greatest impact (48.45%), while the print temperature had the least impact (0.78%). The optimal parameter combination reduced the quality loss to 31.28% and standard deviation to 55.93%. For tensile strength per unit weight, the infill line direction had the greatest impact (87.22%), whereas the print temperature had the least impact (0.77%). The optimal parameter combination reduced the quality loss to 54.09% and standard deviation to 73.54%. Regarding the tensile strength per unit time, the layer height had the greatest impact (82.12%), while the print temperature had the least impact (0.08%). The optimal parameter combination reduced the quality loss to 10.81% and standard deviation to 32.87%.

Fabrication of a PETG-Based Biocarrier Using Additive Manufacturing for Moving Bed Biofilm Reactor (MBBR) Applications

The moving bed biofilm reactor (MBBR) has been identified as a promising method for reducing water pollution. Biocarriers are important in MBBR treatment processes because they provide surface area for biofilm attachment and improve treatment efficiency. These biocarriers use decomposing microorganisms attached to their surface and have been developed in a variety of shapes, materials, and procedures. This study aims to create a biocarrier using an additive manufacturing process and a PETG (Polyethylene Terephthalate Glycol) filament as its material. The biocarrier's pore size plays a crucial role in determining its effectiveness for biofilm attachment and treatment efficiency. By modifying the net diameter of the biocarrier's design, we aimed to investigate the impact of different pore sizes on these factors. We experimented with fabricating three different sizes of the biocarrier's pore by modifying three different sizes of the net diameter of the biocarrier's design: type 1 is 1.8 ± 0.22 mm, type 2 is 1.0 ± 0.29 mm, and type 3 is 0.8 ± 0.27 mm. This research provides insights for the next step: evaluating biofilms' attachment efficiency on each type of biocarrier and comparing their performance.

Effect of Films on In‐Mold Decoration and Microcellular Foaming Injection Molding Parts: Cell Structure, Surface, Warpage, and Mechanical Properties

ABSTRACTThe in‐mold decoration and microcellular foaming injection molding (IMD‐MIM) process was proposed to solve the apparent quality problem of polypropylene in microcellular foaming injection molding. Based on physical experiments and finite element simulation, stainless steel (ST) and polyethylene glycol terephthalate (PET) decorative films were selected for analysis, and the influence of the type and thickness of the decorative films on the cell structure, surface morphology, warpage deformation, and mechanical properties was revealed. The results show that the surface quality of the samples coated is significantly improved, and the asymmetric temperature field caused by the films changes the structure and distribution of the cells. The cell density on the coated side is higher than that on the non‐coated side, and the average cell diameter is smaller, and the foam core layer is shifted to the coated side. The warpage caused by ST film is larger, up to 2.836 mm. With the intervention of ST film and PET film, the impact properties of the samples have little change, but the tensile and flexural properties of the foamed samples have been effectively improved. The tensile strength increased by 28.6% and 25.9%, while the flexural strength increased by 28.6% and 28.1%, respectively. This study provides new insights into the comprehensive optimization of the structure and performance of polypropylene microcellular foaming materials and provides support for the development and application of lightweight materials in the future.

Development of Polymer Composites Using Surface-Modified Olive Pit Powder for Fused Granular Fabrication.

In this study, olive pit agro-waste from the olive oil industry is valorized by incorporating it as an additive in a polyethylene terephthalate glycol (PETG) matrix to develop bio-based composite materials for large format additive manufacturing (LFAM). The olive pits were first ground into olive pit powder (OPP) and then functionalized by polymerizing poly(butylene adipate-co-terephthalate) PBAT on their surface, resulting in a hydrophobic, modified olive pit powder (MOPP) with enhanced compatibility with the PETG matrix. OPP and MOPP composites were compounded and 3D-printed via Fused Granular Fabrication (FGF) using 5, 10, and 15 wt.% concentrations. The PBAT coating increased the degradation temperature and specific heat capacity of the material, contributing to a lower melt viscosity during printing, as confirmed by MFR, MDSC, and TGA analyses. Tensile testing revealed that MOPP composites generally exhibited superior mechanical properties compared to OPP composites, likely due to the improved compatibility between PBAT on the MOPP surface and the PETG matrix. SEM analysis further validated these findings, showing a highly irregular and porous fracture surface in OPP composites, while MOPP composites displayed a smooth surface with well-integrated MOPP in the PETG matrix.

The Mechanical Properties of Orthodontic Aligners of Clear Aligner After Intraoral Use in Different Time Periods.

Although the technique of orthodontic aligners has risen in popularity, their mechanical properties have not been thoroughly investigated. The aim of this study was to evaluate the mechanical properties of the orthodontic aligners Clear Aligner after intraoral use for 7, 10 and 14 days, and to compare them with as-received aligners (0 days). It was also sought to examine the properties of the unprocessed raw material (polyethylene glycol terephthalate) used to manufacture these aligners. Thirty-two aligners by four patients were evaluated and studied at 0, 7, 10, 14 days of use. Each aligner was divided into three segments (two posterior and one anterior), which resulted in 96 samples. Also, 16 samples of unprocessed material were studied. For all samples, elastic modulus, ultimate tensile stress (UTS) and yield stress were calculated by conducting tensile testing. Additionally, material hardness was tested. The two-tailed Mann-Whitney test was performed, having set the level of significance at p = 0.05. Analysis of the measurements indicated a statistically significant decrease in elastic modulus between days 0 and 14 of use, of UTS between days 0 and 7, 7 and 10, and of yield stress between days 0 and 7. For hardness, in every period, posterior segments demonstrated significantly higher values than anterior segments. All properties of the unprocessed material were statistically significantly higher than the processed samples. The unprocessed material presented significant differences in every property tested in comparison to the processed aligners. The processed material showed further deterioration over time during use. The present study provides evidence that thermoforming and ageing affect the mechanical properties of the aligners.

Mechanical and failure behaviors of adhesively bonded dissimilar materials joints incorporating bio-inspired morphological irregularities

Adhesive dissimilar material joints between stainless steel grade 316L and polyethylene terephthalate glycol (PETG) plastic were examined, in which irregular interface morphologies inspired by natural sutures were incorporated. The joint interfaces exhibited various teeth-like, non-repetitive zigzag patterns based on a pseudo-randomization method and sutural interdigitation index. Effects of their irregularities on mechanical and failure characteristics of adhesive butt joints were studied by means of experiments and FE simulations. The cohesive zone model, Drucker-Prager plasticity model and ductile failure criterion were applied for the interface and PETG, respectively. Predicted load-displacement curves of joints with different teeth profiles were well validated. The degree of irregularity became higher to 20 %, 40 %, and 60 %, the joint strengths decreased by 1.47 %, 5.39 %, and 11.95 %, while the total energies to failure increased by 110.74 %, 129.33 %, and 161.23 %, accordingly. More inhomogeneous morphologies led to earlier local damage initiation, but enhanced damage evolution range by impeding abrupt joint separation. Smaller teeth angles provided higher joint strength, whereas significant declines of bonding strength were observed by too acute teeth angle due to excessive stress localization and resulting teeth breakage. The teeth angle of 45° enabled the superior joint performance owing to a proper combination of interlocking and large adhesive force under shear stress state. Finally, a key insight for designing an optimal dissimilar joint with morphological irregularities was provided.

Surface Quality Evaluation of 3D-Printed Carbon-Fiber-Reinforced PETG Polymer During Turning: Experimental Analysis, ANN Modeling and Optimization

This work presents an experimental analysis related to 3D-printed carbon-fiber-reinforced-polymer (CFRP) machining. A polyethylene-terephthalate-glycol (PETG)-based composite, reinforced with 20% carbon fibers, was selected as the test material. The aim of the study was to evaluate the influence of cutting conditions used in light operations on the generated surface quality of the 3D-printed specimens. For this purpose, nine specimens were fabricated and machined under a wide range of cutting parameters, including cutting speed, feed, and depth of cut. The generated surface roughness was measured with a mechanical gauge and the acquired data were used to develop a shallow artificial neural network (ANN) for prediction purposes, showing that a 3-6-1 structure is the best solution. Following this, a genetic algorithm (GA) was utilized to minimize the response, revealing that the optimal combination is 205 m/min speed, 0.0578 mm/rev feed, and 0.523 mm depth of cut, contributing to the fabrication of low friction parts and shafts with a high quality surface, as well as to the reduction of resource waste. A validation study supported the accuracy of the developed model, by exhibiting errors below 10%. Finally, a set of enhanced images were taken to assess the machined surfaces. It was found that 1.50 mm depth of cut is responsible for the generation of defects across the circumference of the specimens. Especially, combined with 150 m/min cutting speed and 0.11 mm/rev feed, more flaws are produced.

Development of Fiber-Reinforced Polymer Composites for Additive Manufacturing and Multi-Material Structures in Sustainable Applications

This study investigates the mechanical properties of carbon and natural fiber-reinforced Polylactic Acid (PLA) and Polyethylene Terephthalate Glycol (PETG) composites produced via Additive Manufacturing (AM), focusing on Material Extrusion (MEX). The performance of filaments made from pre-consumer recycled PLA (rPLA) and PETG, with varying weight percentages of hemp and jute short fibers, was evaluated through tensile testing. Comparisons were made between the original filaments (PLA, carbon fiber-reinforced PLA [CF–PLA], and PETG) and their recycled versions. Multi-material compositions—neat PLA and PETG, single-graded (PLA + CF–PLA, PETG + CF–PETG), and multi-gradient (PLA + CF–PLA + PLA, PETG + CF–PETG + PETG)—were analyzed for mechanical properties. Optical microscope images of multi-material specimens were captured before and after fracture to assess failure mechanisms. The results indicate that the original CF–PETG filaments achieved a tensile strength of 50.14 MPa, which is higher than rPLA, PLA, and CF–PLA by 2%, 70%, and 6.7%, respectively. The re-manufactured PLA filaments reinforced with 7 wt% hemp fibers exhibited a tensile strength of 38.8 MPa, representing a 29% increase compared to the original PLA filaments and a 26% improvement over recycled PLA. Additionally, incorporating 7% jute fiber into PETG resulted in a tensile strength of 62.38 MPa, reflecting a 12% improvement over the original PETG filaments and a 15% increase compared to the recycled PETG filaments. Among specimens produced by AM, CF–PLA and rPLA demonstrated the highest tensile and compressive strengths. However, multi-material composites showed reduced mechanical performance compared to neat PLA and PETG, highlighting the need for improved interlayer adhesion. This study emphasizes the importance of optimizing material combinations and fiber reinforcement to enhance the mechanical properties of composites produced through AM.

Three-dimensional analysis of force distribution on maxillary dentition while distalization of first and second molars simultaneously with clear aligners

Objective: To explore the force distribution on the maxillary dentition when the first and second molars distalized simultaneously with different step sizes using clear aligners in vitro in order to provide a theoretical basis for the rational design of molar distalization. Methods: Clear aligners were designed to simultaneously distalize the maxillary first and second molars bilaterally, with rectangular attachments placed on the buccal surfaces of the first and second premolars, as well as the second molars. Based on different step sizes, the aligners were divided into three groups: Group A (0.15 mm per step), Group B (0.20 mm per step), and Group C (0.25 mm per step). Ten aligners were fabricated for each group using 0.76 mm thick polyethylene terephthalate glycol (PET-G) sheets. A three-dimensional force measurement system was used to measure the forces exerted on each tooth by the aligners, the first and second molars served as the target teeth and the remaining teeth as anchorage teeth. The three-dimensional force data were compared among the three groups. Results: In the mesiodistal direction, the forces on the central and lateral incisors were relatively small among all three groups, with no statistically significant differences (P>0.05). However, significant differences were observed in the forces on the canines, first premolars, second premolars, first molars, and second molars (P<0.05). The distal forces on the second molars in Groups B and C were (6.13±1.45) N and (6.83±1.58) N, respectively, significantly higher than that in Group A [(3.51±1.01) N] (P<0.05). The distal force on the first molars in Group C [(6.62±0.89) N] was significantly higher than that in Groups A and B (P<0.05). The mesial reactive forces on the first and second premolars in Groups B and C were significantly higher than those in Group A (P<0.05). The mesial reactive force on the canines in Group C [(-2.98±1.33) N] was significantly higher than that in Group A [(-1.69±0.68) N] (P<0.05), while there were no significant differences between Groups B and C in the forces on the canines, first premolars, and second premolars (P>0.05). In the buccolingual direction, there were no statistically significant differences in the forces on the central and lateral incisors among three groups (P>0.05), but significant differences were observed in the forces on the canines, second premolars, and second molars (P<0.05). The buccolingual forces on the canines, second premolars, and second molars in Group B were (-0.56±0.54), (-2.07±0.95), (1.13±0.55) N, respectively, significantly higher than those in Group A (P<0.05), but there were no significant differences compared to Group C (P>0.05). Compared to the mesiodistal and buccolingual forces, the vertical forces on the target and anchorage teeth were relatively small in all three groups. Conclusions: When using 0.76 mm thick PET-G sheets to fabricate clear aligners for simultaneous molar distalization, a step size of 0.20 mm per step is recommended. To prevent buccal tipping of the molars during distalization, it is advisable to design lingual displacement for the molars and buccal displacement for the adjacent anchorage teeth to counteract the unfavorable forces, with attachments placed on the primary anchorage teeth.

Statistical Analysis of Large Format Additively Manufactured Polyethylene Terephthalate Glycol with 30% Carbon Fiber Tensile Data.

In large format additive manufacturing (LFAM), a keener understanding of the relationship between the manufacture method and material temperature dependency is needed for the production of large polymer parts. Statistical analyses supported by material properties and a meso-structural understanding of LFAM are applied to elucidate tensile data trends. The data from LFAM polyethylene terephthalate glycol with 30% carbon fiber (CF) (PETG CF30%) panels (diagonal, horizontal, and vertical in the x-y print plane) and injection-molded specimens tensile tested at six different testing temperatures (room temperature, 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C) were used for statistical analyses. A standard deviation, a coefficient of variation, and a two-way and one-way analyses of variance (ANOVA) were conducted. The manufacturing method (44.2%) and temperature (47.4%) have a strong effect on the ultimate tensile strength, in which temperature (82.6%) dominates Young's modulus. To explain the difference between the ultimate tensile strength of vertical, diagonal, and horizontal specimens at room temperature, a visual inspection of the specimen failure was conducted and the maximum stress at the crack tip was calculated analytically. The decreased strength in the diagonal specimens resulted from the reliance on interlaminar adhesion strength. Future work will consider the effect of the void space variation on tensile strength variance.