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1. Rendering Polyurethane Hydrophilic for Efficient Cellulose Reinforcement in Melt‐Spun Nanocomposite Fibers

   https://doi.org/10.1002/admi.202201979  

   Redondo, Alexandre; Bast, Livia K.; Djeghdi, Kenza; Airoldi, Martino; Jang, Daseul; Korley, LaShanda T. J.; Steiner, Ullrich; Bruns, Nico; Gunkel, Ilja (February 2023, Advanced Materials Interfaces)

   Abstract Many commodity plastics, such as thermoplastic polyurethanes (PUs), require reinforcement for use as commercial products. Cellulose nanocrystals (CNCs) offer a “green” and scalable approach to polymer reinforcement as they are exceptionally stiff, recyclable, and abundant. Unfortunately, achieving efficient CNC reinforcement of PUs with industrial melt processing techniques is difficult, mostly due to the incompatibility of the hydrophobic PU with hydrophilic CNCs, limiting their dispersion. Here, a hydrophilic PU is synthesized to achieve strong reinforcement in melt‐processed nanocomposite fibers using filter paper‐sourced CNCs. The melt‐spun fibers, exhibiting smooth surfaces even at high CNC loading (up to 25 wt%) indicating good CNC dispersion, are bench‐marked against solvent‐cast films—solvent processing is not scalable but disperses CNCs well and produces strong CNC reinforcement. Mechanical analysis shows the CNC addition stiffens both nanocomposite films and fibers. The stress and strain at break, however, are not significantly affected in films, whereas adding CNCs to fibers increases the stress‐at‐break while reducing the strain‐at‐break. Compared to earlier studies employing a hydrophobic (and stiffer) PU, CNC addition to a hydrophilic PU substantially increases the fiber stiffness and strength. This work therefore suggests that rendering thermoplastics more hydrophilic might pave the way for “greener” polymer composite products using CNCs. 

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2. Jet Milling as an Alternative Processing Technique for Preparing Polysulfone Hard Nanocomposites

   https://doi.org/10.1155/2019/3501402  

   Llorente, Amaia; Serrano, Berna; Baselga, Juan; Gedler, Gabriel; Ozisik, Rahmi (February 2019, Advances in Materials Science and Engineering)

   This work describes how a solid-state blending method such as jet milling can be used to successfully prepare polysulfone (PSU)/ γ -alumina nanocomposites. For comparison purposes, conventional melt extrusion was used as well. Morphological analysis revealed how jet mill blending allows obtaining well-dispersed γ -alumina nanoparticles within a polysulfone matrix without any surface treatment, with an important decrease of particle size promoted by the breakup of agglomerates and aggregates due to the particle-particle impacts during processing, which was not observed in the extruded nanocomposites. DSC analysis demonstrated that jet-milling processing promoted T g enhancements with alumina addition, while TGA experiments confirmed the increment of thermal stability of the nanocomposites prepared by jet milling when compared with the composites prepared by extrusion. The tensile tests showed that ductility remains at a high value for milled nanocomposites, which agreed with the fracture surface images revealing large plastic deformation as a function of the alumina content. This comparative study indicates that the dispersion of nanoparticles in PSU was more homogeneous, with smaller nanoparticles when preparing nanocomposites using jet milling, showing a strong correlation with the enhanced final properties of the nanocomposites. 

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3. Molecular Mass Engineering for Filaments in Material Extrusion Additive Manufacture

   Yost, S.F.; Pester, C.W.; Vogt, B.D. (January 2023, Journal of polymer science)

   3D printing of thermoplastics through local melting and deposition via Material Extrusion Additive Manufacturing provides a simple route to the near net-shape manufacture of complex objects. However, the mechanical properties resulting from these 3D printed structures tend to be inferior when compared to traditionally manufactured thermoplastics. These unfavorable characteristics are generally attributed to the structure of the interface between printed roads. Here, we illustrate how the molecular mass distribution for a model thermoplastic, poly(methyl methacrylate) (PMMA), can be tuned to enhance the Young’s modulus of 3D printed plastics. Engineering the molecular mass distribution alters the entanglement density, which controls the strength of the PMMA in the solid state and the chain diffusion in the melt. Increasing the low molecular mass tail increases Young’s modulus and ultimate tensile strength of the printed parts. These changes in mechanical properties are comparable to more complex routes previously reported involving new chemistry or nanoparticles. Controlling the molecular mass distribution provides a simple route to improve the performance in 3D printing of thermoplastics that can be as effective as more complex approaches. 

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4. Locating the granitic composition water-saturated solidus

   Rufledt C, Thomas JB (December 2022, AGU Fall Meeting)

   The accepted water-saturated solidus for granitic compositions (granitic water-saturated solidus, G-WSS) was largely determined >60 years ago. Significant experimental resources using modern approaches have been allocated to defining, refining, and parameterizing the solidus positions for other rock compositions, but limited work has been performed to accurately define G-WSS. Modern experimental and analytical techniques afford the opportunity to re-investigate the position of the G-WSS. Various thermobarometric applications to many granitic and rhyolitic composition rocks commonly return temperature estimates significantly lower than the widely accepted G-WSS determined largely by Tuttle and Bowen (1958). To evaluate the apparent discrepancies and help distinguish igneous from metamorphic processes recorded in granitic mineral assemblages, we performed experiments at temperatures ranging from 575 to 900°C and 0.5 to 10 kbar on 12 granitoid compositions composed of natural and synthetic starting materials. Most starting materials were melted in the presence of water at 10 kbar and 900°C in piston cylinders and quenched to room temperature in under one minute to produce water-saturated glasses for usage in subsequent crystallization experiments. The results of experiments on glass compositions were further validated in several runs using finely-ground crystalline starting materials. We ran crystallization experiments at P-T conditions spanning the accepted G-WSS. Decreasing experimental temperatures along each isobar caused systematic decreases in melt percentages until achieving complete crystallization at solidus conditions. A time-series of experiments at P-T conditions with ~20% melt did not reveal any kinetic effects on melt crystallization. All compositions investigated contained melt to temperatures ~75 to 100°C below the accepted G-WSS. Experimental results demonstrating that the G-WSS is significantly lower than unanimously accepted estimates will help us to better understand the storage conditions and evolution of silicic magmatic systems. Tuttle O, Bowen N (1958) Origin of Granite in the Light of Experimental Studies in the System NaAlSi3O8–KAlSi3O8–SiO2–H2O. Geological Society of America 

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5. Identifying the granitic composition water-saturated solidus

   Rufledt C, Thomas JB (September 2023, Xth Hutton Symposium)

   The granitic water-saturated solidus (G-WSS) is the lower temperature limit of magmatic mineral crystallization. The accepted water-saturated solidus for granitic compositions was largely determined >60 years ago1. More recent advances in experimental petrology, improved analytical techniques, and recent observations that granitic systems can remain active or spend a significant proportion of their lives at conditions below the traditional G-WSS2–5 necessitate a careful experimental investigation of the near-solidus regions of granitic systems. Natural and synthetic starting materials were melted at 10 kbar and 900°C with 48 wt% H2O to produce hydrous glasses for subsequent experiments at lower PT conditions used to locate the G-WSS. We performed crystallization experiments and melting experiments at temperatures ranging from 575 to 800°C and 1, 6, 8, and 10 kbar on 12 granitoid compositions. First, we ran a series of isothermal crystallization experiments along each isobar at progressively lower temperatures until runs completely crystallized to identify apparent solidus temperatures. Geochemical analyses of quenched glass compositions demonstrate that progressive crystallization drives all starting compositions towards silica-rich, water-saturated rhyolitic/granitic melts (e.g., ~7578 wt% SiO2). After identifying the apparent solidus temperatures at which the various compositions crystallized, we then ran series of reversal-type melting experiments. With the goal of producing rocks with hydrous equilibrium microstructures, we crystallized compositions at temperatures ~10°C below the apparent solidus identified in crystallization experiments, and then heated isobarically to conditions that produced ~20% melt during the crystallization experiments. Importantly, crystallization experiments and heating experiments at the same PT conditions produced similar proportions of melt, crystals, and vapor. A time-series of experiments 230 days at PT conditions previously identified to produce ~10% to 20% melt did not reveal any kinetic effects on melt crystallization. Experiments at 6 to 10 kbar crystallized/melted at temperatures close to the published G-WSS. However, at lower pressures where the published G-WSS is strongly curved in PT space, all compositions investigated contained melt to temperatures ~75 to 100°C below the accepted G-WSS. The similarity of crystallization temperatures for the higher-pressure experiments to previously published results, similar phase proportions in melting and crystallization experiments, and the lack of kinetic effects on crystallization collectively suggest that our lower pressure constraints on the G-WSS are accurate. The new experimental results demonstrating that the lower-pressure G-WSS is significantly lower than unanimously accepted estimates will help us to better understand the storage conditions, evolution, and potential for eruption in mid- to upper-crustal silicic magmatic systems. (1) Tuttle, O.; Bowen, N. Origin of Granite in the Light of Experimental Studies in the System NaAlSi3O8–KAlSi3O8–SiO2–H2O; Geological Society of America Memoirs; Geological Society of America, 1958; Vol. 74. https://doi.org/10.1130/MEM74. (2) Rubin, A. E.; Cooper, K. M.; Till, C. B.; Kent, A. J. R.; Costa, F.; Bose, M.; Gravley, D.; Deering, C.; Cole, J. Rapid Cooling and Cold Storage in a Silicic Magma Reservoir Recorded in Individual Crystals. Science 2017, 356 (6343), 1154–1156. https://doi.org/10.1126/science.aam8720. (3) Andersen, N. L.; Jicha, B. R.; Singer, B. S.; Hildreth, W. Incremental Heating of Bishop Tuff Sanidine Reveals Preeruptive Radiogenic Ar and Rapid Remobilization from Cold Storage. Proceedings of the National Academy of Sciences 2017, 114 (47), 12407–12412. https://doi.org/10.1073/pnas.1709581114. (4) Ackerson, M. R.; Mysen, B. O.; Tailby, N. D.; Watson, E. B. Low-Temperature Crystallization of Granites and the Implications for Crustal Magmatism. Nature 2018, 559 (7712), 94–97. https://doi.org/10.1038/s41586-018-0264-2. (5) Glazner, A. F.; Bartley, J. M.; Coleman, D. S.; Lindgren, K. Aplite Diking and Infiltration: A Differentiation Mechanism Restricted to Plutonic Rocks. Contributions to Mineralogy and Petrology 2020, 175 (4). https://doi.org/10.1007/s00410-020-01677-1. 

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