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1. The Effect of Elastomer Content and Annealing on the Physical Properties of Upcycled Polyethylene Terephthalate-Maleated Styrene Ethylene Butylene Styrene Blends for Additive Manufacturing

   https://doi.org/10.3390/ma17246272  

   Bermudez, Diego; Moreno, Stephanie; Roberson, David A (December 2024, Materials)

   Santagata, Antonio (Ed.)

   In the work presented here, we explore the upcycling of polyethylene terephthalate (PET) that was derived from water bottles. The material was granulated and extruded into a filament compatible with fused filament fabrication (FFF) additive manufacturing platforms. Three iterations of PET combined with a thermoplastic elastomer, styrene ethylene butylene styrene with a maleic anhydride graft (SEBS-g-MA), were made with 5, 10, and 20% by mass elastomer content. The elastomer and specific mass percentages were chosen based on prior successes involving acrylonitrile butadiene styrene (ABS), in which the maleic anhydride graft enabled compatibility between different materials. The rheological properties of PET and the PET/SEBS blends were characterized by the melt flow index and dynamic mechanical analysis. The addition of SEBS-g-MA did not have a significant impact on mechanical properties, as determined by tensile and impact testing, where all test specimens were manufactured by FFF. Delamination of the tensile specimens convoluted the ability to discern differences in the mechanical properties, particularly % elongation. Annealing of the specimens enabled the observation of the effect of elastomer content on the mechanical properties, particularly in the case of impact testing, where the impact strength increased with the increase in SEBS content. However, annealing led to shrinkage of the specimens, detracting from the realized benefits of the thermal process. Scanning electron microscopy of spent tensile specimens revealed that, in the non-annealed condition, SEBS formed nodules that would detach from the PET matrix during the tensile test, indicating that a robust bond was not present. The addition of SEBS-g-MA did allow for shape memory property characterization, where deformation of tensile specimens occurred at room temperature. Specimens from the 20% by mass elastomer content sample group exhibited a shape fixation ratio on the order of 99% and a shape recovery ratio on the order of 80%. This work demonstrates a potential waste reduction strategy to tackle the problem of polymer waste by upcycling discarded plastic into a feedstock material for additive manufacturing with shape memory properties. 

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2. Enhancing the Strength of Acrylonitrile–Butadiene–Styrene with Gas-Phase-Synthesized Graphene for Injection-Molding Applications

   https://doi.org/10.1021/acsanm.3c06128  

   Dato, Albert; Griffin, Jonathan T.; Bhutani, Arpita; Flitz, Evan (February 2024, ACS Applied Nano Materials)

   Ling, Xing Y; Lee, T. Randall (Ed.)

   Increasing the strength-to-weight ratio of injection moldable polymers can benefit a broad range of applications, such as automobiles, aircraft, and consumer electronic devices. This paper demonstrates that incorporating miniscule quantities (0.1 wt %) of gas-phase-synthesized graphene into acrylonitrile–butadiene–styrene (ABS) can significantly increase the strength of injection-molded specimens by over 20%. The results transform our current understanding of the structure–property relationships of graphene-filled polymer-matrix nanocomposites because highly crumpled graphene sheets with nonfunctionalized surfaces and nanometer-scale lateral dimensions are shown to be more effective at strengthening ABS than flat graphene flakes with functionalized surfaces and micrometer-scale lateral dimensions. 

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3. Development and characterization of rigid polyester blends for 4D printing

   https://doi.org/10.26153/tsw/58052  

   Gonzalez, Jose; Martinez, Gamaliel H; Estrada, Benjamin; Delgado_Ramos, Katia L; Salazar, Jose F; Schuster, Brian E; Roberson, David A (January 2024, University of Texas at Austin)

   Incorporating thermoplastic materials with shape memory properties into the fused filament fabrication process enables what is commonly referred to as 4D printing. When the blends are composed of one or more materials with inherent shape memory properties, the tailoring of critical parameters such as shape recovery temperature can be realized. Previous work by our group demonstrated the creation of shape memory polymer blends where one component was elastomeric. The following work entails the development and characterization of rigid polyester blends that are biocompatible and biodegradable in addition to having shape memory properties. Dynamic mechanical analysis (DMA) was used to determine the critical deformation and recovery temperatures. The effect of print raster patterns on the DMA results was also evaluated. Micro- tensile testing was used to characterize the physical properties of the materials at elevated temperatures. Finally, scanning electron microanalysis was used to examine the fracture surfaces of spent tensile specimens. 

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4. Effect of Process Parameters on Mechanical Properties of the 3D Printed Silk-PLA Specimens Fabricated via Fused Deposition Modeling

   https://doi.org/10.1115/IMECE2024-144616  

   Islam, Razaul; Shahriar, Saquib; Jiang, Lai; Peng, Xiaobo; Park, Jaejong (November 2024, American Society of Mechanical Engineers)

   Abstract Fused deposition modeling (FMD) is considered one of the most common additive manufacturing methods for creating prototypes and small functional parts. Many researchers have studied Polylactic acid (PLA), Polycarbonate (PC), and Acrylonitrile butadiene styrene (ABS) as a material for fused deposition modeling printing. Among them, Polylactic Acid (PLA) is considered one of the most popular thermoplastic materials due to its low cost and biodegradable properties. In this study, silk PLA material was used. In Fused deposition modeling (FMD), the selection of printing parameters plays a pivotal role in determining the overall quality and integrity of the 3D-printed products. These parameters significantly influence the quality and strength of 3-D printed products. This study investigates the mechanical properties of silk-PLA printed specimens under different printing conditions, such as layer thickness, nozzle temperature, and print speed. All the tensile specimens were tested using ASTM D638 to characterize Young’s modulus and ultimate tensile strength. The thickness of the layers of tensile specimens was set to 0.1 mm, 0.15 mm, and 0.2 mm. The temperatures of the nozzle used during printing varied from 200°C, 210°C, and 220°C, whereas print speeds of 100 mm/s, 120 mm/s, and 140 mm/s were considered. The other printing parameters were kept consistent for all specimens. The result indicates tensile strength generally increases with increasing temperature of the nozzle, up to 220°C; however, a decline was observed in the average Young’s modulus value when the thickness of the layer increased from 0.10 mm to 0.20 mm. According to the results of the ANOVA analysis, the interaction between layer thickness, nozzle temperature, and printing speed significantly affects the tensile strength and Young’s modulus of Silk-PLA. This study reveals that nozzle temperature is the most critical parameter regarding the ultimate tensile strength and Young’s modulus, providing crucial insights for optimizing 3D printing parameters. 

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5. 3D printing using powder melt extrusion

   https://doi.org/10.1016/j.addma.2019.100811  

   Boyle, B. M. (August 2019, Additive manufacturing)

   Additive manufacturing promises to revolutionize manufacturing industries. However, 3D printing of novel build materials is currently limited by constraints inherent to printer designs. In this work, a bench-top powder melt extrusion (PME) 3D printer head was designed and fabricated to print parts directly from powder-based materials rather than filament. The final design of the PME printer head evolved from the Rich Rap Universal Pellet Extruder (RRUPE) design and was realized through an iterative approach. The PME printer was made possible by modifications to the funnel shape, pressure applied to the extrudate by the auger, and hot end structure. Through comparison of parts printed with the PME printer with those from a commercially available fused filament fabrication (FFF) 3D printer using common thermoplastics poly(lactide) (PLA), high impact poly(styrene) (HIPS), and acrylonitrile butadiene styrene (ABS) powders (< 1 mm in diameter), evaluation of the printer performance was performed. For each build material, the PME printed objects show comparable viscoelastic properties by dynamic mechanical analysis (DMA) to those of the FFF objects. However, due to a significant difference in printer resolution between PME (X–Y resolution of 0.8 mm and a Z-layer height calibrated to 0.1 mm) and FFF (X–Y resolution of 0.4 mm and a Z-layer height of 0.18 mm), as well as, an inherently more inconsistent feed of build material for PME than FFF, the resulting print quality, determined by a dimensional analysis and surface roughness comparisons, of the PME printed objects was lower than that of the FFF printed parts based on the print layer uniformity and structure. Further, due to the poorer print resolution and inherent inconsistent build material feed of the PME, the bulk tensile strength and Young’s moduli of the objects printed by PME were lower and more inconsistent (49.2 ± 10.7 MPa and 1620 ± 375 MPa, respectively) than those of FFF printed objects (57.7 ± 2.31 MPa and 2160 ± 179 MPa, respectively). Nevertheless, PME print methods promise an opportunity to provide a platform on which it is possible to rapidly prototype a myriad of thermoplastic materials for 3D printing. 

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