Higher Compressive Modulus Research Articles

A novel colorless flexible polymer aerogel with stable amine linkage enabled superior formaldehyde removal and multifunctional application

Massive formaldehyde emissions have seriously endangered environment and human health, while predictably polymer aerogel is a promising candidate for formaldehyde (FA) removal, whereas low FA adsorption capacity, high volume shrinkage, and mechanical brittleness restrict its further development. Herein, based on “rigid-soft combination” polycondensation strategy, trifunctional 1,3,5-benzenetricarboxaldehyde (BTC) and polyetheramine Jeffamine T403 are selected as building blocks to construct a novel amine-linked polymer aerogel (rBTA) with hierarchical micro-nano porous structure via mild sol-gel method and freeze-drying process. Stable amine linkages in rBTA are formed by NaBH4 reduction of imine bonds, improving acid/alkali resistance and chemical stability greatly, and creating numerous active amine sites for reaction with FA. Formation of robust 3D covalent network facilitates to simultaneously achieve ultra-low-shrinkage (5.4%), high specific compressive modulus (5.32 kN·m·kg-1), remarkable mechanical durability/fatigue-resistance, flexibility, and machinability. Benefiting from synergistic physical-chemical adsorption effect, FA adsorption capacity and removal ratio of rBTA reach as high as 459.84 mg·g-1 and 97.87%, respectively. Colorless rBTA is further ground into powders for preparing polyoxymethylene (POM)/rBTA composite without affecting its color and formaldehyde emission amount at 60/230°C effectively decreases by 66.87%/79.55%. Furthermore, rBTA exhibits hydrophobicity, low thermal conductivity, and high solar reflectance, being successfully applied in emulsion separation, thermal insulation, and energy-efficient buildings fields.

Upcycling Industrial Biomass Wastes Into Aerogels Using Zinc Chloride Salt Hydrates

AbstractEnd‐of‐life paper products, including food packages and rejected fibers from the paper industry, are unrecyclable biomass wastes and thus generally landfilled or incinerated. One of the major obstacles to their recycling is the existence of impurities besides cellulose fiber in the biomass wastes. In this study, a fabrication method is investigated to upcycle biomass wastes directly into high‐performance aerogels without separation of impurities. Surprisingly, this study observes that residual impurities participate in cross‐linking reactions for the aerogel formation. In this study, zinc chloride salt hydrate is applied to convert biomass wastes to aerogel via a dissolution‐regeneration process. The fabricated aerogels exhibited high water absorption capacity (15 times its weight), as well as comparable mechanical strength and thermal insulation performance to the reported cellulose aerogels. In addition, the impurities (i.e., calcium‐based inorganic salt) assisted in the cross‐linking of the cellulose network for the aerogel formation. The scanning electron microscopy (SEM) image of the aerogel generated from the rejected fibers showed a honeycomb inner structure. The rejected fiber aerogels also demonstrated a high compressive modulus of 51 MPa and a low thermal conductivity of 0.029 W m−1 K−1. The results for water absorption and thermal insulation suggest excellent potential across various application domains.

Highly conductive, mechanically robust and multi-purpose carbon aerogel composites derived from waste bread enable high-performance symmetric supercapacitors

Sustainable biomass-based carbon aerogels have attracted extensive concerns in the area of energy storage and wearable sensory electronics. However, the pristine porosity and low weight of aerogels result in unsatisfactory mechanical and electrical properties, limiting their practical applications. Herein, activated porous carbon (APC), reduced graphene oxide (rGO) and carbon nanoparticles (CNP) are utilized as raw materials to develop a novel type of hierarchically waste bread-derived carbon aerogel via a stepwise activation/calcination strategy. The obtained bread-derived carbon aerogels, named APC-rGO/CNP, exhibits an outstanding electrical conductivity (∼3.23 S cm−1) and a high compressive modulus (∼124.60 MPa) by the synergistic bonding interactions. As a supercapacitor electrode, the APC-rGO/CNP composite manifests an excellent capacitance of 474.8 F g−1 (1.0 A g−1). Furthermore, an all-solid-state symmetric APC-rGO/CNP//APC-rGO/CNP supercapacitor with polyvinyl alcohol/potassium hydroxide (PVA/KOH) gel electrolyte realizes an energy density of 17.4 Wh kg−1 at 895 W kg−1. Notably, even under large compressive stress of 20 kPa, the supercapacitor still achieves a high energy density of 25.6 Wh kg−1 at a power density of 822.8 W kg−1, as well as an excellent capacitance retention of 93.8 % over 10,000 cycles. Finally, we demonstrate the potential of the APC-rGO/CNP composite as a responsive pressure sensor with an ultra-wide detecting span of 0–3 MPa and a moderate sensitivity of 0.22 kPa−1, which can detect keyboard pressing and fist clenching movements distinctively. Overall, the desirable mechanical performances and electrical conductivity of the APC-rGO/CNP composites facilitate the development of versatile nanomaterials to exploit state-of-the-art wearable electronics.

Interpenetrated Multinetwork Hybrid Aerogels by Layered Montmorillonite and One-Dimensional Hydroxyapatite Fibers for Heat and Fire Insulation.

It is of practical significance to develop aerogels with effective thermal insulation characteristics together with fireproof properties as well as high mechanical strength. Here, an interpenetrated multinetwork hybrid aerogel realizing thermal insulation, flame retardancy, and high compression modulus is demonstrated. Specifically, one-dimensional hydroxyapatite nanowires (HAP) played dual roles as the aerogel support skeleton to entangle with layered montmorillonite (MMT) each other to form a three-dimensional interpenetrated multinetwork structure and to optimize the thermal conductivity by adjusting the pore space in current HAP/MMT/PVA hybrid aerogels. Therefore, the interpenetrated multinetwork hybrid aerogels exhibit superior thermal insulation performance in room temperature (0.033 W m-1 K-1, 298 K, air conditions) and largely enhanced ultrahigh compression modulus (80 MPa). Moreover, the obtained hybrid aerogels also exhibit excellent flame retardancy and self-extinguishing smoke suppression properties (peak heat release rate and total smoke production as low as 92.44 kW m-2 and 0.1 m2, respectively), which is the outstanding interpenetrated multinetwork hybrid aerogel that has achieved synergistic improvement in heat and fire insulation and mechanical performance. Therefore, the interpenetrated multinetwork hybrid aerogels are promising candidates for efficient heat insulation, fire prevention, and mechanically robust applications.

A lignocellulose nanofibril-poly(vinyl alcohol) hydrogel with controlled drug delivery for wound healing

Employing lignocellulosic nanofibers (LCNF) with natural, high specific mechanical performance and abundant functional groups to design a hydrogel as a drug-sustained release carrier, which conforms to the concept of green and sustainable development. Herein, we facilely extracted carboxylated lignocellulose nanofibrils (CLCNF) from bagasse via a deep eutectic solvent (DES) and mechanical defibrillation-based strategy. The CLCNF was crosslinked with poly(vinyl alcohol) (PVA) to obtain a nanocomposite hydrogel (PVA/CLCNF/B) whereupon the mechanical strength and drug release behavior were improved in the process. Consequently, the lignocellulose nanocomposite hydrogel presented a high compression modulus (3.92 MPa) and significant sustained-release effect with a release rate of 80.73 % after 336 h. The delivery behavior of the PVA/CLCNF/B composite hydrogel could be controlled by acidic pH conditions. The TH release kinetics of PVA/CLCNF/B hydrogel in different phosphate buffer saline (PBS) followed the Korsmeyer-Peppas model better, and the release of TH occurred through the Fickian diffusion mechanism. Importantly, in vivo experiments and histopathological studies showed that TH-loaded PVA/CLCNF/B hydrogel had a superior pro-healing rate. Overall, the incorporation of CLCNF into a hydrogel may have considerable potential as a drug delivery carrier for drug release and therapy. SynopsisAdding the CLCNF from bagasse into PVA dispersions obtained a hydrogel for pH-responsive drug delivery can accelerate wound healing.

Lubricating adhesive hyaluronate patch promotes cartilage regeneration and functional restoration in osteoarthritis

Osteoarthritis (OA) is a common chronic degenerative joint disease characterized by gradual deterioration and pain. Viscosupplementation, involving hyaluronic acid (HA) injection into the affected joint, is a minimally invasive option to reduce pain by improving joint lubrication and potentially avoiding the need for replacement surgery. However, the low adhesion and rapid degradation of HA often lead to inadequate therapeutic effects. In this study, we present lubricating adhesive HA-based hydrogel patches designed to effectively treat OA. The HA patches, modified with pyrogallol, have high elastic and compressive moduli, delaying degradation when exposed to external stimuli. Furthermore, they securely adhere to cartilage tissue surfaces and efficiently lubricate damaged cartilage, leading to a reduced friction and wear. In addition to these benefits, our HA patches exhibit scavenging effect of reactive oxygen species and sustainably release an encapsulated anti-inflammatory drug (dexamethasone: Dex). These features further enhance their therapeutic potential for OA treatment. In a mouse OA model, the hydrogel patches loaded with Dex promote healing of damaged cartilage and restore its motor function. Overall, our bioinspired HA hydrogel patches present a promising treatment option for managing the debilitating joint disease by offering enhanced adhesion, lubrication for cartilage protection, antioxidant effect, and sustained drug release.

Mechanically Robust Lubricating Hydrogels Beyond the Natural Cartilage as Compliant Artificial Joint Coating.

Natural cartilage exhibits superior lubricity as well as an ultra-long service lifetime, which is related to its surface hydration, load-bearing, and deformation recovery feature. Until now, it is of great challenge to develop reliable cartilage lubricating materials or coatings with persistent robustness. Inspired by the unique biochemical structure and mechanics of natural cartilage, the study reports a novel cartilage-hydrogel composed of top composite lubrication layer and bottom mechanical load-bearing layer, by covalently manufacturing thick polyelectrolyte brush phase through sub-surface of tough hydrogel matrix with multi-level crystallization phase. Due to multiple network dissipation mechanisms of matrix, this hydrogel can achieve a high compression modulus of 11.8MPa, a reversible creep recovery (creep strain: ≈2%), along with excellent anti-swelling feature in physiological medium (v/v0 < 5%). Using low-viscosity PBS as lubricant, this hydrogel demonstrates persistent lubricity (average COF: ≈0.027) under a high contact pressure of 2.06MPa with encountering 100k reciprocating sliding cycles, negligible wear and a deformation recovery of collapse pit in testing area. The extraordinary lubrication performance of this hydrogel is comparable to but beyond the natural animal cartilage, and can be used as compliant coating for implantable articular material of UHMWPE to present, offering more robust lubricity than current commercial system.

Organic solvents-free and ambient-pressure drying melamine formaldehyde resin aerogels with homogeneous structures, outstanding mechanical strength and flame retardancy

Atmospheric drying method for fabricating aerogels is considered the most promising way for casting aerogels on a large scale. However, the organic solvent exchange, remaining environmental pollution risk, is a crucial step in mitigating the impact of surface tension during the atmospheric drying process, especially for wet gel formed through the alkoxy-derived sol-gel process, such as melamine-formaldehyde resin (MF) aerogel. Herein, a tough polymer-assisted in situ polymerization was proposed to fabricate MF resin aerogel with a combination of mechanical toughness and strength, enabling it to withstand the capillary force during water evaporation. The monolithic MF resin aerogel through the sol-gel method can be directly prepared without additional network strengthening or organic solvent exchange. The resulting MF resin aerogel exhibits a homogeneous as well as hierarchical structure with macropores and mesopores (~6 μm and ~5 nm), high compressive modulus of 31.8 MPa, self-extinguishing property, and high-temperature thermal insulation with 97 % heat decrease for butane flame combustion. This work presents a straightforward and environmentally friendly method for fabricating MF resin aerogels with nanostructures and excellent performance in open conditions, exhibiting various applications.

Lightweight, mechanically robust and scalable cellulose-based foam enabled by organic-inorganic network and air drying

Lightweight and high-strength cellulose-based foams have gained increasing momentum due to their combination of sustainability and high performance. However, complex modification to cellulose fibers can sacrifice the environmental friendliness and further limit productional scalability. Here, we engineer lightweight yet strong cellulose-based foams made from mechanically treated microfibrillated cellulose (MFC), reinforced by organic-inorganic network, and scaled by surfactant foaming combined with air drying. Consisting of strong coordination and extensive secondary interaction within the organic-inorganic network, the resulting cellulose composite foams achieve both a high compressive modulus of 451.3 kPa and a yield strength of 25.1 kPa at a low density of 32.9 mg cm−3, which exceed other MFC-based foams based on surfactant foaming. In addition, the incorporation of the organic-inorganic network has no negative effect on the scalability, recyclability, or biodegradability of cellulose composites foam, making closed-loop material recycling possible. The life-cycle assessment reveals that replacing petroleum-based foams with our cellulose composite foams result in substantial reductions in carbon emissions. The structural design and manufacturing of our cellulose-based foam can stimulate market interest for cellulose foam and the development of the bioeconomy.

Thin-Film Composite Membrane Compaction: Exploring the Interplay among Support Compressive Modulus, Structural Characteristics, and Overall Transport Efficiency.

Water scarcity has driven the demand for water production from unconventional sources and the reuse of industrial wastewater. Pressure-driven membranes, notably thin-film composite (TFC) membranes, stand as energy-efficient alternatives to the water scarcity challenge and various wastewater treatments. While pressure drives solvent movement, it concurrently triggers membrane compaction and flux deterioration. This necessitates a profound comprehension of the intricate interplay among compressive modulus, structural properties, and transport efficacy amid the compaction process. In this study, we present an all-encompassing compaction model for TFC membranes, applying authentic structural and mechanical variables, achieved by coupling viscoelasticity with Monte Carlo flux calculations based on the resistance-in-series model. Through validation against experimental data for multiple commercial membranes, we evaluated the influence of diverse physical parameters. We find that support polymers with a higher compressive modulus (lower compliance), supports with higher densities of "finger-like" pores, and "sponge-like" pores with optimum void fractions will be preferred to mitigate compaction. More importantly, we uncover a trade-off correlation between steady-state permeability and the modulus for identical support polymers displaying varying porosities. This model holds the potential as a valuable guide in shaping the design and optimization for further TFC applications and extending its utility to biological scaffolds and hydrogels with thin-film coatings in tissue engineering.

Novel MoS2/montmorillonite hybrid aerogel encapsulated PEG as composite phase change materials with superior solar-thermal energy harvesting and storage

Phase change materials (PCMs) offer significant advantages in energy conversion and storage by facilitating the storage and release of thermal energy during phase transition processes. However, challenges such as leakage during PCM phase transitions and poor light absorption properties have constrained their application in the field of photothermal energy storage. In this study, Montmorillonite (Mt) and molybdenum disulfide (MoS2) has been used to design and synthesize hybrid aerogels (MoS2/Mt) boasting high mechanical strength and excellent photothermal conversion performance. These aerogels are then used to encapsulate polyethylene glycol (PEG) to prepare composite PCMs with outstanding solar-thermal conversion and storage performances. The results show that the synthesized MoS2/Mt-PEG composite PCMs exhibit high enthalpies of melting and solidification of 169.16 J/g and 170.78 J/g, respectively, while the aerogel supporting material has a high compressive modulus of 1.96 MPa. Moreover, the composite material displayed excellent thermal stability and leakage resistance after undergoing 30 melting-cooling cycles. Furthermore, the incorporation of MoS2 imparted outstanding light absorption properties to the MoS2/Mt-PEG composite, resulting in a high light absorption and photothermal conversion-storage efficiency of 93.4 % and 96.47 %, respectively. Synthesized composite PCMs also demonstrate outstanding performance in solar-thermal-electricity conversion, achieving a voltage output of 458 mV under illumination conditions and maintaining a sustainable voltage output even after removing the light source. Thus, the composite PCMs prepared in this work can meet the requirements of high enthalpy, effective leakage prevention, efficient solar-thermal conversion and solar-thermal-electricity conversion performance, thereby presenting potential applications in practical solar energy collection, conversion, and storage.

PLLA/(MWCNTs-ZnO)@PDA composite with NIR-light induced shape memory effect, antibacterial properties and 3D printability

PLLA based shape-memory polymer composites with multifunctions have attracted growing attention in biomedical applications. Generally, a single nanofiller has the problem of insufficient functionalization and easy aggregation. Therefore, we design and fabricate polydopamine (PDA) surface modified MWCNTs-ZnO hybrid nanostructure ((MWCNTs-ZnO)@PDA). The dispersion of (MWCNTs-ZnO)@PDA in PLLA is improved in comparison with the pristine MWCNTs or ZnO. The results indicate that the (MWCNTs-ZnO)@PDA nanosystem shows a synergistic effect on the mechanical properties and photothermal properties of the composites. Comparative analysis with neat PLLA demonstrates a remarkable 17% increase in tensile strength and a 19% increase in elongation at break for PLLA/(MWCNTs-ZnO)@PDA composite. Additionally, the composites exhibit excellent NIR light-induced shape memory effects with a shape recovery ratio reaching 100%. Moreover, PLLA/(MWCNTs-ZnO)@PDA composites show favorable antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Furthermore, the polymer composites display good 3D printability, and the 3D-printed porous scaffold possesses high compressive strength and modulus. Also, the PLLA/(MCNTs-ZnO)@PDA scaffold can be compressed into a compact size and recover its original shape under NIR light irradiation. This work provides an approach to prepare novel shape-memory polymer composites with multifunctions including high strength, light-induced shape-recovery, antibacterial properties and printability.

Comparative study of the effect of cross‐linking degree on chitosan hydrogels synthesized with low and medium molecular weight chitosan

AbstractChitosan (CS) is often used in hydrogels due to its natural origin, sustainability, non‐toxicity, and biodegradability. However, the physicochemical properties of CS hydrogels generated via physical cross‐linking are relatively poor. CS hydrogels were prepared by cross‐linking with glutaraldehyde (GA) at different ratios ranging from 1% to 10% (w/w), using two different molecular weight CS. The swelling degree of hydrogels was investigated at pH 2.0, 5.6, and 7.4. The structure, morphology, and thermal characteristics of hydrogels were examined using Fourier transform infrared, scanning electron microscopy, differential scanning calorimetry, and thermogravimetric analysis, respectively. Compression tests were conducted using Zwick/Roell universal testing equipment following ASTM D695. In vitro degradation studies were performed in enzyme and enzyme‐free mediums at pH 7.4. The study demonstrated that low molecular weight CS (L‐CS) hydrogels have a lower sol content and higher swelling values than medium molecular weight CS (M‐CS) hydrogels. Both L‐CS and M‐CS hydrogels cross‐linked with 1% GA showed maximum swelling degrees at pH 2.0. Thermal analysis concluded that M‐CS hydrogels have higher thermal stability than L‐CS hydrogels. It was also found that the M‐CS hydrogels have higher compressive moduli. The degradation experiments in both enzyme and enzyme‐free media showed that L‐CS hydrogels have higher degradation rates.Highlights Chemically cross‐linked hydrogels synthesized using low and medium molecular weight chitosan. The mechanical and physical properties of medium and low molecular weight chitosan hydrogels were compared. Degradation experiments were performed in both enzyme and enzyme‐free media. Swelling values decreased noticeably with the increasing molecular weight. Low molecular weight chitosan improved the biodegradability of hydrogels.

Highly oriented BN-based TIMs with high through-plane thermal conductivity and low compression modulus.

In the pursuit of effective thermal management for electronic devices, it is crucial to develop insulation thermal interface materials (TIMs) that exhibit exceptional through-plane thermal conductivity, low thermal resistance, and minimal compression modulus. Boron nitride (BN), given its outstanding thermal conduction and insulation properties, has garnered significant attention as a potential material for this purpose. However, previously reported BN-based composites have consistently demonstrated through-plane thermal conductivity below 10 W m-1 K-1 and high compression modulus, whilst also presenting challenges in terms of mass production. In this study, low molecular weight polydimethylsiloxane (PDMS) and large-size BN were utilized as the foundational materials. Utilizing a rolling-curing integrated apparatus, we successfully accomplished the continuous preparation of large-sized, high-adhesion BN films. Subsequent implementation of stacking, cold pressing, and vertical cutting techniques enabled the attainment of a remarkable BN-based TIM, characterized by an unprecedented through-plane thermal conductivity of up to 12.11 W m-1 K-1, remarkably low compression modulus (55 kPa), and total effective thermal resistance (0.16 °C in2 W-1, 50 Psi). During the TIMs performance evaluation, our TIMs demonstrated superior heat dissipation capabilities compared with commercial TIMs. At a heating power density of 40 W cm-2, the steady-state temperature of the ceramic heating element was found to be 7 °C lower than that of the commercial TIMs. This pioneering feat not only contributes valuable technical insights for the development of high-performance insulating TIMs but also establishes a solid foundation for widespread implementation in thermal management applications across a range of electronic devices.

The optimization of poly(vinyl)-alcohol-alginate beads with a slow-release compound for the aerobic cometabolism of chlorinated aliphatic hydrocarbons.

Chlorinated aliphatic hydrocarbons (CAHs), such as cis-1,2-dichloroethylene (cDCE), are prevalent in groundwater at many locations throughout the United States. When immobilized in hydrogel beads with slow-release compounds, the bacteria strain Rhodococcus rhodochrous ATCC 21198 can be used for the in situ bioremediation of cDCE. These hydrogel beads must exhibit high mechanical strength and resist degradation to extend the lifetime of slow-release compounds and bioremediation. We engineered poly(vinyl)-alcohol - alginate (PVA-AG) beads to immobilize ATCC 21198 with the slow-release compound, tetrabutoxysilane (TBOS) that produces 1-butanol as a growth substrate, for high mechanical strength. We optimized three inputs (concentration of PVA, concentration of AG, and the crosslinking time) on two responses (compressive modulus and rate of oxygen utilization) for batch incubation experiments between 1 and 30 days using a design of experiments approach. The predictive models generated from design of experiments were then tested by measuring the compressive strength, oxygen utilization, and abiotic rates of hydrolysis for a predicted optimal bead formulation. The result of this study generated a hydrogel bead with immobilized R. rhodochrous ATCC 21198 and TBOS that exhibited a high compressive modulus on day 1 and day 30, which was accurately predicted by models. These hydrogel beads exhibited low metabolic activity based on oxygen rates on day 1 and day 30 but were not accurately predicted by the models. In addition, the ratio between oxygen utilization and abiotic rates of hydrolysis were observed to be roughly half of what was expected stoichiometrically. Lastly, we demonstrated the capability to use these beads as a bioremediation technology for cDCE as we found that, for all bead formulations, cDCE was significantly reduced after 30 days. Altogether, this work demonstrates the capability to capture and enhance the material properties of the complex hydrogel beads with predictive models yet signals the need for more robust methods to understand the metabolic activity that occurs in the hydrogel beads.

Strength and Chemical Characterization of Ultra High-Performance Geopolymer Concrete: A Coherent Evaluation

The objective of this review article is to analyze published data encompassing compressive strength, tensile strength, elastic modulus, and flexural strength, as well as the utilization of scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD) for Ultra High-Performance Geopolymer Concrete (UHP-GC), with the focus of establishing the current research trends regarding its mechanical, microstructural, and chemical characteristics. After a critical evaluation of the published data from the literature findings, it became evident that UHP-GC can attain a remarkably high level of engineering performance. In UHP-GC, the optimum percentage of silica fume as a slag partial replacement to achieve high compression, tensile, and elastic modulus were traced to be 25, 30, and 35%, respectively. The optimum ratio of sodium silicate to sodium hydroxide and sodium hydroxide molarity for UHP-GC were identified to be 3.5 and 16, respectively. All in all, the review provides a thorough understanding of the review gap and distinct functions of different raw materials in decreasing porosity and enhancing the formation of geopolymeric gels that not only bond but also strengthen UHP-GC. UHP-GC stands as an energy-saving material in concrete technology, poised to forge a path towards a sustainable future for the building sector. Doi: 10.28991/CEJ-2023-09-12-020 Full Text: PDF

Development of lightweight, high-strength, and highly porous ligno-nanocellulosic foam with excellent antioxidant and insulation properties

This study reports an environmentally friendly ligno-nanocellulosic foam prepared by utilizing lignin (LGN), cellulose nanofiber (CNF), and citric acid (CA) as a green crosslinker through an easy, low-cost, and environmentally friendly process. The FTIR study and XPS analysis of the prepared LGN/CNF foams confirm the crosslinking between the components, which leads to lower shrinkage, lower density, and higher porosity than the neat CNF foam, achieving a remarkably low density of 19.59 mg/cm3 and high porosity of 98.84 % The morphology and microstructure of the foam show a uniform three-dimensional porous network built by strong cell walls. The crosslinked LGN/CNF foams indicate 182 % higher compressive modulus and 306 % higher compressive strength at 70 % strain than the neat CNF foam. Further, the addition of LGN and CA enhances the antioxidant activity of the foam. The prepared foam shows lower thermal conductivity and better sound absorption performance than the neat CNF foam, indicating a potential to be used as thermal insulation and sound-absorbing materials that can mitigate greenhouse gas emissions.

The flexural and compressive properties of sandwich composites with different 3D-printed core structures

In this study, different core structures are produced with polylactic acid (PLA) and carbon fiber reinforced PLA (CFR-PLA) filaments using a 3D printer with fused deposition modeling (FDM) technique. An alternative new core structure is proposed to the honeycomb and square core structures commonly used in the literature. Then, sandwich composites are produced by bonding carbon fiber-epoxy plates to the lower and upper surfaces of these core structures. The effect of carbon fiber reinforcement and core types on the mechanical properties of sandwich composites was investigated. The core structures produced with carbon fiber-reinforced PLA showed lower compressive strength but higher compressive modulus than those produced with pure PLA. Among the core structures, the designed structure showed the highest compressive strength with a value of 9.867 MPa, which is 32.18% and 54.36% higher than the honeycomb and square structure. While the flexural strength and flexural stiffness of the sandwich composites increased with carbon fiber reinforcement, the designed sandwich composite showed approximately 1.40 and 3.15 times the flexural strength of the honeycomb and square sandwich composites, respectively.

Multiscale Design for Robust, Thermal Insulating, and Flame Self-Extinguishing Cellulose Foam.

Cellulose foams are in high demand in an era of prioritizing environmental consciousness. Yet, transferring the exceptional mechanical properties of cellulose fibers into a cellulose network remains a significant challenge. To address this challenge, an innovative multiscale design is developed for producing cellulose foam with exceptional network integrity. Specifically, this design relies on a combination of physical cross-linking of the microfibrillated cellulose (MFC) networks by cellulose nanofibril (CNF) and aluminum ion (Al3+), as well as self-densification of the cellulose induced by ice-crystal templating, physical cross-linking, solvent exchange, and evaporation. The resultant cellulose foam demonstrates a low density of 40.7mg cm-3, a high porosity of 97.3%, and a robust network with high compressive modulus of 1211.5 ± 60.6kPa and energy absorption of 77.8 ± 1.9kJ m-3. The introduction of CNF network and Al3+ cross-linking into foam also confers excellent wet stability and flame self-extinguish ability. Furthermore, the foam can be easily biodegraded in natural environments , re-entering the ecosystem's carbon cycle. This strategy yields a cellulose foam with a robust network and outstanding environmental durability, opening new possibilities for the advancement of high-performance foam materials.

Preparation of robust and light‐weight anisotropic polyimide/graphene composite aerogels for strain sensors

AbstractThis study reports the fabrication of a serious of anisotropic composite aerogels comprising polyimide and graphene (PI/G) through a simple and eco‐friendly technique. Poly(amic acid) ammonium salt/graphene dispersion, which was produced through the mixture of poly(amic acid), graphene aqueous dispersion, triethylamine, and water, was utilized in the process of creating PI/G composite aerogels employing unidirectional freezing, freeze‐drying, and thermal imidization. The PI/G aerogels displayed anisotropic mechanical properties, thermal insulation, and electrical conductivity. The PI/G aerogels with an anisotropic microstructure demonstrated notable rigidity and a high compressive modulus (52.7 MPa) along the axial direction, while displaying favorable flexibility and a low modulus (18.2 MPa) along the radial direction. Furthermore, the PI/G aerogel exhibited anisotropic thermal conductivity (axial: 64 mW m−1 K−1; radical: 55 mW m−1 K−1). These properties enable the PI/G aerogel to have a wider range of potential applications, especially strain sensors. The research presented herein establishes a simple and eco‐friendly strategy for the production of anisotropic PI/G‐based composite aerogels.