Resin Precursor Research Articles

Hierarchical Biobased Macroporous/Mesoporous Carbon: Fabrication, Characterization and Electrochemical/Ion Exchange Properties

With the goal of improving the mechanical properties of porous hierarchical carbon, cellulosic fiber fabric was incorporated into the resorcinol/formaldehyde (RF) precursor resins. The composites were carbonized in an inert atmosphere, and the carbonization process was monitored by TGA/MS. The mechanical properties, evaluated by nanoindentation, show an increase in the elastic modulus due to the reinforcing effect of the carbonized fiber fabric. It was found that the adsorption of the RF resin precursor onto the fabric stabilizes its porosity (micro and mesopores) during drying while incorporating macropores. The textural properties are evaluated by N2 adsorption isotherm, which shows a surface area (BET) of 558 m2g-1. The electrochemical properties of the porous carbon are evaluated by cyclic voltammetry (CV), chronocoulometry (CC), and electrochemical impedance spectroscopy (EIS). Specific capacitances (in 1 M H2SO4) of up to 182 Fg-1 (CV) and 160 Fg-1 (EIS) are measured. The potential-driven ion exchange was evaluated using Probe Bean Deflection techniques. It is observed that ions (protons) are expulsed upon oxidation in acid media by the oxidation of hydroquinone moieties present on the carbon surface. In neutral media, when the potential is varied from values negative to positive of the potential of zero charge, cation release, followed by anion insertion, is found.

Multi-thermo responsive double network composite hydrogel for 3D printing medical hydrogel mask

3D printing of multifunctional hydrogels offers great opportunities for developing innovative biomedical technologies as it can provide custom-designed shapes and structures conformal to arbitrary contours. There have been significant improvements of the 3D printing techniques, but the available printable hydrogel materials limit the progress. Here, we investigated the use of a poloxamer diacrylate (Pluronic P123) to augment the thermo-responsive network composed of poly(N-isopropylacrylamide) and develop a multi-thermoresponsive hydrogel for photopolymerization 3D printing. The hydrogel precursor resin was synthesised to be printable with high-fidelity of fine structures and once cured can form a robust thermo-responsive hydrogel. By utilizing N-isopropyl acrylamide monomer and a Pluronic P123 diacrylate crosslinker as 2 separate thermo-responsive components it was found that the final hydrogel displayed 2 distinct lower critical solution temperature (LCST) switches. This enables the loading of hydrophilic drugs at fridge temperature and improving the strength of the hydrogel at room temperature while still maintaining a drug release at body temperature. The thermo-responsive material properties of this multifunctional hydrogel material system were investigated, showing a significant promise as a medical hydrogel mask. Furthermore, it is demonstrated that it can be printed in sizes large enough to fit and adhere to a human face at 1:1 scale with high dimensional accuracy, as well as its ability to load with hydrophilic drugs.

Plant-derived p-hydroxyphenylacrylic acid-derived epoxy resins exhibit excellent flame retardancy, hydrophobicity, degradability, and low dielectric loss after curing with bio-based fluorinated Schiff bases

Epoxy resins are designed to achieve high flame retardancy, hydrophobicity, and dielectric properties. However, the search for sustainable bio-based epoxy resin precursors that do not require additional flame retardants is still underway. Herein, we report a p-hydroxycinnamic acid-derived epoxy resin monomer (HCA-EP) obtained via a simple one-step reaction. HCA-EP can be combined with 4,4′-((2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-dial)bis(azanylylidene))bis(methanylylidene))bis(2,6-dimethoxyphenol) (SA-BTB) and cured to prepare epoxy resins(HCA-EP/SA-BTB). In comparison to HCA-EP cured with a common petroleum-based curing agent(HCA-EP/MeHHPA), such as methylhexahydrophthalic anhydride (MeHHPA), HCA-EP/SA-BTB exhibited a significantly high glass transition temperature (170 °C), excellent hydrophobic properties, and lower dielectric loss. In addition, HCA-EP/SA-BTB passed the V-0 flame rating of the UL-94 test and exhibited an ultimate oxygen index of 43.3%. Notably, it demonstrated a coke yield of 42.3% under N2 conditions, whereas that of HCA-EP/MeHHPA was 18%. Moreover, its flame-retardant index was found to be 19.8, indicating its excellent flame-retardant properties. Further, it could be degraded under acidic conditions. These findings indicate that the proposed method can be used to develop high-performance bio-based thermoset materials.

Structurally controllable hollow carbon spheres for gaseous benzene adsorption

Hollow carbon spheres (HCSs) with controllable morphology, stable physicochemical properties, high surface area, and large pore volume achieved without any acidic or alkaline activators, are likely to be an attractive adsorption material. Nevertheless, reports on applying HCSs for adsorption separation are relatively limited, especially for volatile organic compounds (VOCs). Herein, a series of HCSs were successfully synthesized by a simple one-pot, surfactant-free method and varying ethanol/water volume ratios, compositions of silicon alkoxides (tetrapropyl orthosilicate/tetraethyl orthosilicate, TPOS/TEOS), lag time for adding resorcinol-formaldehyde (RF) resin precursors, and system temperatures. The differences between these HCSs in terms of average particle size, internal cavity diameter, shell thickness, specific surface area, and porosity were well elucidated. HCS-11 synthesized at 10 °C had the most desirable specific surface area (2531.29 m2 g−1) and total pore volume (3.527 cm3 g−1) in this study, which was superior to many HCSs in the literature, and therefore was selected for subsequent benzene adsorption/desorption tests. As expected, HCS-11 exhibited a static benzene adsorption capacity of up to 21.363 mmol g−1 at 293 K. In addition, the effects of different initial concentrations, gas flow rates, and ambient temperatures on dynamic benzene adsorption by HCS-11 were systematically investigated. The high adsorption capacity of HCS-11 remained stable after six consecutive adsorption-desorption cycles, indicating its good thermal regeneration capability. The excellent porosity, high cyclic adsorption capacity, and rapid desorption kinetics of HCS-11 made it promising for VOC abatement.

N-doped composites prepared from ferro-based acrylate resin precursors for electromagnetic wave absorption

There are numerous challenges in the low-cost batch fabrication of high-performance absorbers. A low-cost preparation process for metal-containing acrylic resin ( 3SM-yAN , y=6, 9 and 12) employs a one-step free radical polymerization of iron (III) chloride, sodium methacrylate, and acrylonitrile. Fe-3SM-yAN was prepared using carbonization. The carbonization of metal-containing acrylic resin was performed at 800 °C in an argon atmosphere for two hours. The broadest effective absorption bandwidth (EAB) of Fe-3SM-9AN absorbing material yielded 8.07 GHz at 2 mm with a minimum reflection loss of -36.70 dB (11.41 GHz), and the EAB could cover 14.8 GHz (3.2~18 GHz) with a tunable absorber thickness from 1.0 to 5.0 mm. The synergistic effect of impedance matching and strong electromagnetic attenuation was found to yield excellent microwave absorption of Fe-3SM-yAN （y=6, 9 and 12）. The magnetic porous shell-like Fe-3SM-yAN is potentially highly suitable for batch production of lightweight and efficient microwave-absorbing materials.

New Metal-Plastic Hybrid Additive Manufacturing for Precise Fabrication of Arbitrary Metal Patterns on External and Even Internal Surfaces of 3D Plastic Structures.

Constructing precise metal patterns on complex three-dimensional (3D) plastic parts allows the fabrication of functional devices for advanced applications. However, it is currently expensive and requires complex processes. This study demonstrates a process for the fabrication of 3D metal-plastic composite structures with arbitrarily complex shapes. A light-cured resin is modified to prepare the active precursor allowing subsequent electroless plating (ELP). A multimaterial digital light processing 3D printer was newly developed to fabricate the parts containing regions made of either standard resin or active precursor nested within each other. Selective 3D ELP processing of such parts provided various metal-plastic composite parts having complicated hollow structures with specific topological relationships with the resolution of 40 μm. Using this technique, 3D devices that cannot be manufactured by traditional methods are possible, and metal patterns can be produced inside plastic parts as a means of further miniaturizing electronics. The proposed method can also generate metal coatings exhibiting improved adhesion of metal to substrate. Finally, several sensors composed of different functional materials and specific metal patterns were designed and fabricated. The present results demonstrate the viability of the proposed method and suggest potential applications in the fields of 3D electronics, wearable devices, and sensors.

Impact of oleuropein on LCD-based stereolithography-assisted fabrication of 3D printed PEGDMA hydrogels

Nowadays, personalized nutrition/medicine has become one of the hot topics to modify target agent dosage and allow personalized treatment by changing geometries of printed gels. Light-induced 3D printing technologies enable fabrication of solid forms by mixing photocurable monomer with drug/active agents. However, the use of synthetic polymers and toxic photoinitiators (PIs) makes a concern for SLA printing. In this study, it was firstly aimed to use natural PI, riboflavin in precursor resin. Then, poly (ethylene glycol) dimethacrylate (PEGDMA) based hydrogels embedded with oleuropein (OLE) were printed through UV-induced polymerization at varying shapes (radiator, hexagonal, square, ring, and round). Olive leaf extract including OLE as main antioxidant source is a valuable waste product for sustainability and additive/nutraceutical use in the food and pharmaceutical industry. This work investigated fabricated 3D gels in terms of their printability, physical properties, physicochemical features, and drug-release profiles. More importantly, encapsulated OLE within 3D printed gel was examined to see the effect of light-induced printing on its antioxidant acitivity. 3D OLE added gels showed very high printability ratios which were close to 1 whereas control gel without OLE was not printed successfully. Moreover, the results confirmed the existence of antioxidant activity (up to 87%) of 3D gels even after UV-induced printing. Based on surface area/volume (SA/V) ratio, radiator and square gels gave the highest release as they had high SA/V proportions. Structural changes in the compounds after UV curing process was also confirmed by FT-IR spectrum. The drug release profiles followed the Peppas model having n value in the range of 0.44–0.54, demonstrating that the release was mostly affected by diffusion. This study shows potential contribution to pharmaceutical and food industries in terms of designing personalized OLE dosages using the Stereolithography (SLA) printing with controlled release by manipulating geometry alone.

Additive manufacturing low shrinkage Si-based composite ceramics with SiCO microsphere/polyvinyl silicon acetylene slurry

In this paper, SiCO microsphere/polyvinyl silicon acetylene slurry was prepared for the first time with low viscosity and good rheological behavior. The dispersion of microspheres in the precursor resin and the UV-light curing performance of the slurry were investigated. After pyrolysis at 1000 °C, the properties of the three-dimensional (3D) printed samples were characterized. The introduction of SiCO microspheres reduced the specimen shrinkage of the pure precursor photosensitive resin used for additive manufacturing and improved their mechanical properties. When the addition of SiCO powder increased from 0 wt% to 10 wt%, the linear shrinkage decreased from 33 % to 26 %, and the flexural strength increased from 43.9 MPa to 79.8 MPa. This study realizes the preparation of Si-based composite materials through low-cost LCD additive manufacturing technology. It confirms the great potential of low-cost light-curing additive manufacturing to fabricate complex functional composite ceramic materials.

Manganese-Catalyzed Dehydrogenative Synthesis of Urea Derivatives and Polyureas

Urea derivatives have significant applications in the synthesis of resin precursors, dyes, agrochemicals, and pharmaceutical drugs. Furthermore, polyureas are useful plastics with applications in coating, adhesive, and biomedical industries. However, the conventional methods for the synthesis of urea derivatives and polyureas involve toxic reagents such as (di)isocyanates, phosgene, CO, and azides. We present here the synthesis of (poly)ureas using much less toxic reagents─(di)amines and methanol─via a catalytic dehydrogenative coupling process. The reaction is catalyzed by a pincer complex of an earth-abundant metal, manganese, and liberates H2 gas, valuable by itself, as the only byproduct, making the overall process highly atom-economic. A broad variety of symmetrical and unsymmetrical urea derivatives and polyureas have been synthesized in moderate to quantitative yields using this catalytic protocol. Mechanistic insights have also been provided using experiments and DFT computation, suggesting that the reaction proceeds via an isocyanate intermediate.

Sintering behaviors of highly sinterable Al-doped Li7La3Zr2O12 powder prepared by polymerized-complex method

We prepared highly sinterable Al-doped Li7La3Zr2O12 (LLZ) via a polymerized-complex chemical route and investigated the sintering behavior. Controlling the exothermic reaction during the calcination process of the polymerized resin precursors was important to suppress the grain growth and agglomeration of particles. Using the LLZ particles with a particle diameter of ∼0.7 μm, highly dense LLZ ceramics with 97% relative density were obtained by sintering at 1180 °C. A dilatometric study revealed that shrinkage occurred predominantly in the temperature range 1000–1050 °C. The isothermal shrinkage suggested that the major densification was controlled by grain-boundary diffusion. Substantial grain growth observed at temperatures greater than 1050 °C implies the influence of a liquid phase of Li2O–Al2O3, for which the melting point was 1055 °C (±10 °C).

Self-support semi-hollow carbon nanosphere supported palladium catalyst for biomass upgrading

Catalytic removal of oxygen from biomass by hydrodeoxygenation (HDO) as a promising process has been pursued for efficient utilization of biomass resources. Here we report a self-support semi-hollow carbon nanospheres (SHCN) supported palladium (Pd) catalyst for vanillin HDO under mild conditions. The shell-void-core structure of carbon nanospheres originates from the modulation of growth kinetics of resorcinol/formaldehyde resin precursors by a given volume of acetone. Notably, 0.5%Pd/SHCN-60 (acetone of 60 mL) catalyst exhibits >99.9% of vanillin conversion and creosol selectivity under 25 °C and 0.1 MPa of H2. The good catalytic results can derive from the self-support hollow carbon support and active metallic Pd. Raman results show that 0.5%Pd/SHCN-60 possesses the most abundant defect carbon (AD1/AG = 2.02), which leads to the small particle size (mean size of 2.9 nm) and well dispersion (29.5%) of Pd. Higher H2-desorption temperature (∼440 °C) of 0.5%Pd/SHCN-60 by H2-TPD demonstrates the strong interaction of Pd-defect carbon. The strong interaction favors the hydrogen storage and activation of substrates under low pressure of H2 and reaction temperature, which improves the hydrogenation and hydrogenolysis. Additionally, the contribution of unique core structure to support the shell to enhance mechanical stability leads to intact morphology of catalyst and stable catalytic performance after reused six times. This investigation can provide a design idea of carbon-based catalysts for mild HDO.

Strong interfacial modified aramid fabric reinforced degradable thermosetting composites: reinforcing and tribological effects

In this work, dense molybdenum disulfide (MoS2) nanosheets were grown onto polydopamine (PDA) functionalized aramid fabric (AF) surface via a simple hydrothermal method to improve the wettability between AF surface and polyhexahydrotriazine (PHT) resin, thus resulting in stronger AF/resin interfacial bonding. The PDA-assisted surface modification on AF generated a high active interface allowing the nucleation and subsequent growth of MoS2. Moreover, this nanosheet-coated reinforcement fiber enabled the viscous liquid of resin precursor to spread over and form intimate contact with its surface, which eventually promoted the formation of strong interfacial bonding between AF-MoS2 and cured resin matrix. In addition, the enhanced interfacial bonding between the reinforcement and matrix generated stable mechanical interlock within the resulting AF-MoS2/PHT composites, and thus, contributed better thermal stability, higher tensile strength, and tribological properties. Compared with AF/PHT composites, the tensile strength and elongation at break of the AF-MoS2/PHT composites increased by 32.5% and 50%, and the average friction coefficient and wear rate of AF-MoS2/PHT composites decreased by 43.9% and 86.3%, respectively. Furthermore, the composites realized the non-destructive recovery of expensive AF at 25 °C. Overall, our study demonstrates a dependable strategy to construct the recyclable AF-MoS2/PHT composites, which exhibit valuable applications in tribology.

Development of ultramicropore-mesopore interconnected pore architectures for boosting carbon dioxide capture at low partial pressure

The physical adsorption of carbon dioxide (CO2) using porous solid adsorbent is greatly hindered by high temperature and low pressure, resulting in a decrease in capture performance in terms of capacity, selectivity, and kinetics. Here we report an effective synthesis of 3D hierarchical porous carbon with ultramicropore-mesopore interconnected pore architectures that are able to boost the CO2 adsorption at elevated temperature and low partial pressure. This unique pore structure is benefit from the uniform introduction of a combination of alkali metals (Li, Na, K) and other metals (Mg, Ca, Zn) in the resin precursor. Specifically, the employed dual metal in-situ activation method allows generation of extensive mesopores with pore size in the range of 3–5 and 7–9 nm without sacrificing distribution of ultramicropore. These properties result in an enhanced dynamic CO2 capacity from 1.36 to 1.54 mmol/g (40 °C and 0.15 bar), higher CO2/N2 selectivity from 73 to 85 as well as advanced mass transport kinetics. This work paves the way for the development of high-performance CO2 adsorbent at low partial pressure and provides a strategy to prepare interconnected pore architectures for a variety of potential adsorption application.

One-pot fabrication of crosslinked nanochains composed of resorcinol–formaldehyde resin hollow nanospheres with tunable shell thickness by using poly(acrylic acid) as template

One-dimensional nanostructures of hollow sphere nanochains have exhibited promising potentials owing to their unique geometry. However, it is still a challenge to achieve their facile and controllable fabrication. Herein, we successfully achieved the facile one-pot fabrication of resorcinol–formaldehyde (RF) resin hollow sphere nanochains for the first time by employing ammonium polyacrylate (APA) nanoaggregates as a core template. The APA core template can be easily removed by simply washing with water during centrifugation. The thickness size of RF resin shell can be easily tuned by adjusting the amounts of RF resin precursors. It is worth noting that the addition of more ethanol is in favor of the formation of RF hollow nanospheres with isolated hollow cavities. This strategy can be expanded to prepare 3-aminophenol-formaldehyde (APF) resin hollow nanochains, which can be employed as a carrier to load Au nanoparticles. This work should give some enlightenment for the controllable fabrication of resin hollow nanospheres/nanochains and the supported nanocomposites.

Characterization of carbon fiber-reinforced thermoplastic and thermosetting polyimide matrix composites manufactured by using various synthesized PI precursor resins

Currently, it is important to manufacture thermoplastic advanced composites with high mechanical and thermal properties because of their higher impact resistance than thermoset composites. In this study, carbon fiber (CF)-reinforced thermoplastic and thermosetting polyimide (PI) matrix composites were manufactured by vacuum bagging followed by compression molding . Before the manufacturing process, prepregs were also prepared with various PI precursor resins by using two-step impregnation. These precursors were synthesized as poly (amic acid) (PAA), polyester amine salts (PEAS) and poly (amic acid) ammonium salts (PAAS). The PAAS precursor resin was applied as a novel method for manufacturing CF-reinforced PI matrix advanced composites. The advanced thermoplastic composite obtained from the PAAS precursor (PAAS-T) exhibited superior mechanical properties and enhanced thermal properties (near the thermal properties of thermoset advanced composites) in comparison to the other advanced composites in this study and those in the literature. However, the NA-terminated PAAS precursor (thermosetting PI precursor) did not exhibit a similar effect in terms of mechanical properties. On the other hand, the thermosetting composites exhibited highly enhanced storage modulus values up to 400 °C and outstanding thermal stability at TGA . The thermosetting composite that was obtained from the NA-terminated PAA precursor resin exhibited high mechanical properties besides its thermal properties.

Sequential Assembly Tailored Interior of Porous Carbon Spheres for Boosted Water Decontamination through Peroxymonosulfate Activation

AbstractSelf‐assembly is an appealing strategy for preparing nanospheres with different interiors, which are essential for their applications. Although many assembly strategies have been proposed, controlling the assembly processes from kinetic aspects is a big challenge. Here, by employing the different reaction kinetics of the assembly precursors, a sequential assembly strategy is proposed to tailor the interior structure of porous carbon spheres. Through changing the feeding interval of resin and silica precursors from 0 to 60 min, their nucleation order can be controlled in the assembly process to prepare porous carbon spheres (≈450 nm in size) with tunable type (i.e., hollow or solid) and size (from less than 100 nm to around 230 nm) of interiors. The hollow spheres exhibit over three times the catalytic activity of the core–shell counterparts for activating peroxymonosulfate to remove organic water contaminants, and the activity can be further improved by decreasing the cavity size. These results show the great significance of the sequential assembly strategy for interior engineering of nanospheres. This work opens up a new approach for rational design and synthesis of interior‐structured nanospheres.

Heteroatoms co-doped porous carbons from amino acid based polybenzoxazine for superior CO2 adsorption and electrochemical performances

A series of N, O, and S heteroatomic doped porous carbon were developed by fabricating bio-based benzoxazine resin precursors from cysteine and phenols. The bio-based benzoxazines were successfully prepared with their structure confirmed by NMR, FTIR, and Mass spectra. The ring-opening curing mechanism was explored by DSC and FTIR spectroscopy with a low onset temperature of 188 °C. The polybenzoxazine, poly(Ph-cysme), exhibited 5% weight loss temperature as high as 350 °C. The as-synthesized carbon materials after pyrolysis possessed rich heteroatom content (up to 17.89%) and high specific surface area (1810 m2 g−1), which led to a high CO2 adsorption capacity of 6.78 mmol/g at 800 mmHg, 273 K and excellent stability. Furthermore, the prepared carbon material exhibited a superior electrochemical performance as anode for supercapacitors with a specific capacitance of 310 and 221 F g−1 in 6 M KOH at a current density of 0.1 and 1 A g−1, respectively. This work provides a new strategy for the further development of carbon material precursors in the future.

Design of carbon–ceramic composite membranes with tunable molecular cut-offs from a carboxylic benzoxazine ligand chelated to silica–zirconia

This study presents a concept that focuses on the structure design of preceramic resin precursors by the sol–gel method for fabricating carbon–ceramic molecular sieving membranes.

Effect of Lattice Structure and Composite Precursor on Mechanical Properties of 3D-Printed Bone Scaffolds

This article presents an investigation on designing and fabricating scaffolds with different structures, desired porosity, composition, and surface area to volume ratio (SA:V) for orthopedic applications by using the computer-aided design (CAD) and the stereolithography (SLA) 3D printing technique. Different triply periodic minimal surfaces (TPMS) and functionally graded lattice structures (FGLS) were designed based on various cell geometries. Finite element analysis (FEA), tensile and compression tests were carried out, and the results are presented. Two different resin compositions were used to print the models and compare the effect of resin precursors on the mechanical properties of scaffolds. The first was a biodegradable resin made from soybean oil commercially available on the market (made by Anycubic Co.). The second was a mixture of biodegradable UV-cured resin with 5% W/W of hydroxyapatite (HA) and 5% W/W calcium pyrophosphate (CPP). Bio-Hydroxyapatite and Bio-Calcium Pyrophosphate were obtained from eggshells waste and characterized using XRD and FESEM. The obtained data show that adding resin precursors (HA/CPP) slightly decreases the mechanical strength of printed scaffolds; however, considering their extraordinary effect on bone regeneration, this small effect can be ignored, and HA/CPP can be used as an ideal agent in bioscaffolds.

Silica-Assisted Controlled Engineering of Nitrogen-Doped Carbon Cages with Bulges for High-Performance Supercapacitors.

The bulge structure of N-doped carbon cages is beneficial to improving the specific surface area and increasing the active sites of a chemical reaction. Therefore, this structure plays a role in increasing capacity in energy storage. However, the precise and most effective method of ensuring the bulge structures is still a challenge. Herein, a silica-assisted method is used to prepare N-doped carbon cages with bulges. The effective assembly of a nitrogen-rich resin and silica precursor is employed to construct the bulge structure on the surface. The reaction temperature of the assembly system and the amount of silica precursor are the key influences on the number and degree of bulges. In contrast to conventional carbon materials that have a smooth surface, the bulge structure allows for exposure and accessibility of the activity sites. Due to the N-doping features, a rich mesoporous structure and controllable bulges, the synergism of the high density, large ion-accessible surface area, and fast charge transfer, lead to high performance under the premise of high rate capability in supercapacitor. This silica-assisted strategy can also work on other preprepared corresponding templates that have a different architecture to prepare core-shell carbon tubes, carbon spheres, and carbon rods with a bulge structure.