Search Results (41)

This study focused on examining the reinforcement of milkweed fibers in polylactic acid (PLA) bio-composites used for dashboards in car interiors. Milkweed fiber is a natural fiber with a hollow structure that provides tremendous thermal insulation and noise resistance properties. Firstly, the milkweed fibers were blended with PLA fibers in a weight ratio of 75:25 using an air-laying process. Then, several layers of nonwoven material were compressed in a hydraulic press to obtain bio-composites. Finally, three bio-composites were obtained with different numbers of layers. The density, microstructure, thermal conductivity, sound transmission loss (STL), mechanical properties, dynamic mechanical analysis (DMA), and contact angles of the bio-composites were evaluated. The microstructure analysis revealed that some milkweed fibers collapsed due to the high-pressure molding process, which does not affect the bio-composite properties. The bio-composite with a higher number of nonwoven layers presented a poor interface between PLA and milkweed fibers, thus making it less homogeneous. This bio-composite showed a decrease of 5% in thermal conductivity values and a 19% increase in STL values. In addition, it exhibited a 160% increase in specific flexural strength and a 335% increase in specific flexural modulus compared to samples with a lower number of nonwoven layers. Therefore, it offers the best mechanical-property-to-density ratio, with values that conform to the specifications required for automotive dashboards. Full article

Background/Objectives: The endosomal escape of lipid nanoparticles (LNPs) is crucial for efficient mRNA-based therapeutics. Here, we present a cationic polymeric micelle (cPM) as a safe and potent co-delivery system with enhanced endosomal escape capabilities. Methods: We synthesized a cationic and ampholytic di-block copolymer, poly (poly (ethylene glycol)_4-5 methacrylate_a-co-hexyl methacrylate_b)_X-b-poly(butyl methacrylate_c-co-dimethylaminoethyl methacrylate_d-co-propyl acrylate_e)_Y (p(PEG_4-5MA_a-co-HMA_b)_X-b-p(BMA_c-co-DMAEMA_d-co-PAA_e)_Y), via reversible addition–fragmentation chain transfer polymerization. The cPMs were then formulated using the synthesized polymer by the dispersion–diffusion method and characterized by dynamic light scattering (DLS) and cryo-transmission electron microscopy (CryoTEM). The membrane-destabilization activity of the cPMs was evaluated by a hemolysis assay. We performed an in vivo functional assay of firefly luciferase (Fluc) mRNA using two of the most commonly studied LNPs, SM102 LNP and Dlin-MC3-DMA LNPs. Results: With a particle size of 61.31 ± 0.68 nm and a zeta potential of 37.76 ± 2.18 mV, the cPMs exhibited a 2–3 times higher firefly luciferase signal at the injection site compared to the control groups without cPMs following intramuscular injection in mice, indicating the high potential of cPMs to enhance the endosomal escape efficiency of mRNA-LNPs. Conclusions: The developed cPM, with enhanced endosomal escape capabilities, presents a promising strategy to improve the expression efficiency of delivered mRNAs. This approach offers a novel alternative strategy with no modifications to the inherent properties of mRNA-LNPs, preventing any unforeseeable changes in formulation characteristics. Consequently, this polymer-based nanomaterial holds immense potential for clinical applications in mRNA-based vaccines. Full article

Civil engineering structures need to be protected from earthquakes, representing a new area of research that is growing continuously and very rapidly. Design engineers are always searching for lightweight, stronger, and stiffer materials to be applied as vibration-damping materials. Stability in dynamics necessitates an active, robust, and convenient mechanism that can absorb the kinetic energy of vibration to prevent the structural system from resonance. Recently, many researchers have successfully used nanomaterials to develop energy-absorbing materials that are lightweight and cost-effective. Traditional damping treatments are based on combinations of viscoelastic, elastomeric, magnetic, and piezoelectric materials. In this paper, a review of various damping techniques for composites made of cement modified by various nanomaterials like Nano Al2O₃ (Aluminum Dioxide), Nano SiO₂ (Silicon Dioxide), Nano TiO₂ (Titanium Dioxide), Graphene, and CNTs (Carbon Nanotubes) is presented. The designs of various nano-composite dampers are presented to strengthen the information progress in this field. The current study’s goal is to discover how nanoparticles impact the cement-based material’s damping properties. The study examined several nanomaterials in cement composites at differing concentrations. With the help of the Dynamic Mechanical Analysis (DMA) method and the Logarithmic Decrement approach, the damping properties of these composites were examined. Scanning Electron Microscopy (SEM) was used to examine the effects of nanomaterials on the microstructure and pore size distribution of the composite. Increasing the quantity of nanoparticles in cement paste may improve its capacity to lessen vibration. The experiments also showed that certain nanomaterials may improve load transmission inside the cement matrix and connect neighboring hydration products, helping to reduce energy loss during the loading process. These nanoparticles will eventually replace the large machinery employed to dampen vibrations in buildings due to their small weight, increased mechanical strength, and effective damping properties. Full article

Chondroitin sulfate (ChS), chitosan (Chi), and fish gelatin (FG), which are byproducts of a fish-treatment small enterprise, were incorporated with glycerol (Gly) to obtain dense hydrogel membranes with reduced brittleness, candidates for dressing in wound healing applications. The mechanical properties of all samples were studied via Dynamic Mechanical Analysis (DMA) and tensile tests while their internal structure was characterized using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and X-ray Diffraction (XRD) instruments. Their surface morphology was analyzed by ThermoGravimetric Analysis (TGA) method, while their water permeability was estimated via Water Vapor Transmission Rate (WVTR) measurements. Wettability and degradation rate measurements were also carried out. Characterization results indicated that secondary interactions between the natural polymers and the plasticizer create the hydrogel membranes. The samples were amorphous due to the high concentration of plasticizer and the amorphous nature of the natural polymers. The integration of ChS led to decreased decomposition temperature in comparison with the glycerol-free sample, and all the materials had dense structures. Finally, the in vitro endothelial cell attachment studies indicate that the hydrogel membranes successfully support the attachment and survival of primary on the hydrogel membranes and could be appropriate for external application in wound healing applications as dressings. Full article

Ionic polymer membranes have not yet gained widespread practical application in areas such as water purification and energy harvesting due to their high cost and tendency to swell. The present study involved the fabrication of reinforced textile structures composed of polytetrafluoroethylene (PTFE)-reinforced Nafion membranes coated with non-precious metals, copper and silver, as a surface electrode by applying a chemical decomposition technique. Several mechanical, contact angle measurement and dielectric tests were conducted on membranes to evaluate their mechanical, wettability and conductivity properties. From scanning electron microscopy, it is clear that the formation of surface electrodes with uniform dispersion of metal particles. Scratch test reveals the adhesive strength between the coated metal particles and membrane. The silver-activated copper-coated membrane has a high contact angle of 121°. Thus, the fabricated membranes can have good antibacterial and adsorption properties for water treatment. The copper-coated membrane has a high Young’s modulus of 779 ± 80 MPa and a tensile strength of 29.1 ± 8 MPa, whereas the elongation at break is more for silver-activated copper-coated samples recorded as 158 ± 4%. The viscoelastic behavior of the membranes was analyzed through dynamic mechanical analysis (DMA). A sharp rise in the storage modulus (E′) value of 4.8 × 10¹⁰ Pa at ~80 °C at a frequency of 1 Hz on metal surface electrodes signifies an improvement in the strength of the material in comparison to the initial pure membrane. The successful enhancement of conductivity on the membrane surface via chemical deposition on the silver-activated membrane is 1 × 10⁻⁴ (S/cm) and holds great potential for facilitating voltage transmission through the tribolayer in the nanogenerators. Full article

In this paper, the influence of the silicon (Si) content on microstructure and impact property of submerged arc weld metals (WMs) for weathering bridge steel was clarified. Actual submerged arc welding (SAW) was carried out to produce WMs with 0.18 wt.%, 0.36 wt.%, 0.51 wt.%, and 0.60 wt.% of Si. The low temperature impact property of weld metal was detected, and the weld microstructures were characterized by optical microscopy (OM), scanning and transmission electron microscope (SEM and TEM), and electron backscatter diffraction (EBSD). The results indicate that WMs consist of polygon ferrite (PF), acicular ferrite (AF), granular bainitic ferrite (GBF), and martensite/austenite (M/A) constituents in each Si content. With increasing Si, the proportion of PF increased, while AF and GBF coarsened, the area fraction, f_M/A, and the mean size, d_M/A, of M/A constituents increased, the number of inclusions decreased, but the size increased. Further, the fraction of high-angle grain boundaries (HAGBs) with the misorientation tolerance angles (MTAs) greater than 15° reduced, while the mean equivalent diameter, MED_MTA≥15°, of ferrite grains with HAGBs increased. Accordingly, the impact toughness of WM was degraded from 108.1 J to 39.4 J with the increase in Si. The increase in M/A constituents and inclusions size reduced the critical fracture stress, thereby formation of larger microcracks and cleavage planes occurred. The reduced HAGBs exhibited a low hindering effect on crack propagation, and, consequently, the impact toughness decreased with increasing Si content. Full article

A strategy for optimizing the rolling resistance, wet skid and cut resistance of reinforced rubber simultaneously using a supramolecular filler is demonstrated. A β-alanine trimer-grafted Styrene Butadiene Rubber (A₃-SBR) pristine polymer was designed and mechanically mixed with commercially available styrene butadiene rubber to help the dispersion of a β-alanine trimer (A₃) supramolecular filler in the rubber matrix. To increase the miscibility of A₃-SBR with other rubber components during mechanical mixing, the pristine polymer was saturated with ethanol before mixing. The mixture was vulcanized using a conventional rubber processing method. The morphology of the assembles of the A₃ supramolecular filler in the rubber matrix was studied by Differential Scanning Calorimetry (DSC) and Transmission Electron Microscopy (TEM). The Differential Scanning Calorimetry study showed that the melting temperature of β-sheet crystals in the vulcanizates was around 179 °C and was broad. The melting temperature was similar to that of the pristine polymer, and the broad melting peak likely suggests that the size of the crystals is not uniform. The Transmission Electron Microscopy study revealed that after mixing the pristine polymer with SBR, some β-sheet crystals were rod-like with several tens of nanometers and some β-sheet crystals were particulate with low aspect ratios. Tensile testing with pre-cut specimens showed that the vulcanizate containing A₃-SBR was more cut-resistant than the one that did not contain A₃-SBR, especially at a large cut size. The rolling resistance and wet skid were predicted by dynamic mechanical analysis (DMA). DMA tests showed that the vulcanizates containing A₃-SBR were significantly less hysteretic at 60 °C and more hysteretic at 0 °C based on loss factor. Overall, the “magic triangle” was expanded by optimizing the rolling resistance, wet-skid, and cut resistance simultaneously using a β-alanine trimer supramolecular filler. The Payne effect also became less severe after introducing the β-alanine trimer supramolecular filler into the system. Full article

The epidemiology of yam viruses remains largely unexplored. We present a large-scale epidemiological study of yam viruses in Guadeloupe based on the analysis of 1124 leaf samples collected from yams and weeds. We addressed the prevalence of cucumber mosaic virus (CMV), Cordyline virus 1 (CoV1), Dioscorea mosaic associated virus (DMaV), yam asymptomatic virus 1 (YaV1), yam mosaic virus (YMV), yam mild mosaic virus (YMMV), badnaviruses, macluraviruses and potexviruses, and the key epidemiological drivers of these viruses. We provide evidence that several weeds are reservoirs of YMMV and that YMMV isolates infecting weeds cluster together with those infecting yams, pointing to the role of weeds in the epidemiology of YMMV. We report the occurrence of yam chlorotic necrosis virus (YCNV) in Guadeloupe, the introduction of YMMV isolates through the importation of yam tubers, and the absence of vertical transmission of YaV1. We identified specific effects on some cropping practices, such as weed management and the use of chemical pesticides, on the occurrence of a few viruses, but no crop-related factor had a strong or general effect on the overall epidemiology of the targeted viruses. Overall, our work provides insights into the epidemiology of yam viruses that will help design more efficient control strategies. Full article

The nanofiller zirconium phosphate (ZrP) was mixed into poly(lactic acid) (PLA) to ameliorate its thermal stability. The elastomer ethylene-methyl acrylate-glycidyl methacrylate copolymer (E-MA-GMA) was introduced into the PLA/ZrP nanocomposite through melt-mixing to improve its toughness and obtain a super-tough PLA/ZrP/E-MA-GMA nanocomposite. The impact strength of the PLA/ZrP/E-MA-GMA nanocomposite, with a composition ratio of 72/3/25, was improved to 71.5 kJ/m², about 25 times greater than the impact strength of pure PLA. The dynamic mechanical analysis (DMA) confirmed that E-MA-GMA has excellent compatibility with the matrix of PLA. A typical core–shell structure that can cause massive shear-yielding deformation was characterized by transmission electron microscopy (TEM), which gave the nanocomposite excellent toughness. Full article

Resins are important for enhancing both the processability and performance of rubber. Their efficient utilization requires knowledge about their influence on the dynamic glass transition and their miscibility behavior in the specific rubber compound. The resins investigated, poly-(α-methylstyrene) (AMS) and indene-coumarone (IC), differ in molecular rigidity but have a similar aromaticity degree and glass transition temperature. Transmission electron microscopy (TEM) investigations show an accumulation of IC around the silanized silica in styrene–butadiene rubber (SBR) at high contents, while AMS does not show this effect. This higher affinity between IC and the silica surface leads to an increased compactness of the filler network, as determined by dynamic mechanical analysis (DMA). The influence of the resin content on the glass transition of the rubber compounds is evaluated in the sense of the Gordon–Taylor equation and suggests a rigid amorphous fraction for the accumulated IC. Broadband dielectric spectroscopy (BDS) and fast differential scanning calorimetry (FDSC) are applied for the characterization of the dielectric and thermal relaxations as well as for the corresponding vitrification kinetics. The cooling rate dependence of the vitrification process is combined with the thermal and dielectric relaxation time by one single Vogel–Fulcher–Tammann–Hesse equation, showing an increased fragility of the rubber containing AMS. Full article

In this study, silicate nanofillers; dicalcium silicate, magnesium silicate, tricalcium silicate, and wollastonite; were synthesized using four different methods and incorporated into the epoxy resin to improve its mechanical properties. Characterization of the newly synthesized nanofillers was performed using Fourier-transformation infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The purpose of this study was to analyze newly developed composite materials reinforced with silicate nanoparticles utilizing tensile testing and a full-field non-contact 3D Digital Image Correlation (DIC) method. Analysis of deformation and displacement fields gives precise material behavior during testing. Testing results allowed a more reliable assessment of the structural integrity of epoxy composite materials reinforced using different silicate nanofillers. It was concluded that the addition of 3% of dicalcium silicate, magnesium silicate, tricalcium silicate, and wollastonite lead to the increasement of tensile strength up to 31.5%, 29.0%, 27.5%, and 23.5% in comparison with neat epoxy, respectively. In order to offer more trustworthy information about the viscoelastic behavior of neat epoxy and composites, a dynamic mechanical analysis (DMA) was also performed and rheological measurements of uncured epoxy matrix and epoxy suspensions were obtained. Full article

Herein, an effective technique of curing reaction-induced phase separation (CRIPS) was used to construct a reduced graphene oxide (RGO) network in the immiscible diglycidyl ether of the bisphenol A/polyetherimide (DGEBA/PEI) polyblend system. The unique chemical reduction of RGO facilitated the reduction of oxygenated groups and simultaneously appended amino groups that stimulate the curing process. The selective interfacial localization of RGO was predicted numerically by the harmonic and geometric mean technique and further confirmed by field emission transmission electron microscopy (FETEM) analysis. Due to interfacial localization, the electrical conductivity was increased to 366 S/m with 3 wt.% RGO reinforcement. The thermomechanical properties of nanocomposites were determined by dynamic mechanical analysis (DMA). The storage modulus of 3 wt.% RGO-reinforced polyblend exhibited an improvement of ~15%, and glass transition temperature (T_g) was 10.1 °C higher over neat DGEBA. Furthermore, the total shielding effectiveness (SE_T) was increased to 25.8 dB in the X-band region, with only 3 wt.% RGO, which represents ~99.9% shielding efficiency. These phase separation-controlled nanocomposites with selective localization of electrically conductive nanofiller at a low concentration will extend the applicability of polyblends to multifunctional structural nanocomposite applications. Full article

A conceptual model is presented of two MW-scale low enthalpy mine water geothermal heat pump schemes that are being developed in Tyneside, UK. The Abbotsford Road scheme (54.955° N 1.556° W) is operating (as of May 2021) at 20–30 L/s, abstracting groundwater (and heat) from an unmined Coal Measures Upper Aquifer System (UAS) and reinjecting to the deeper High Main Aquifer System (HMAS), associated with the High Main (E) coal workings and the overlying High Main Post sandstone. A similar scheme, 700 m away at Nest Road (54.959° N 1.564° W), abstracts at 40 L/s from the HMAS, recovers heat from the mine water and reinjects the thermally spent water to deeper workings associated with the Hutton (L), Harvey-Beaumont (N) (and possibly other) coal seams, termed the Deep Mined Aquifer System (DMAS). The three aquifer systems are vertically discontinuous and possess different hydraulic (storage, transmissivity and continuity) properties that would have been near-impossible to predict in advance of drilling. At the sites, 10 boreholes were drilled to obtain five usable production/reinjection boreholes. Development of mine water geothermal energy schemes thus carries a significant project risk, and also a potential ongoing maintenance burden related to iron hydroxide scaling. These do not preclude mine water geothermal as a useful low carbon heating and cooling technology, but the involvement of skilled hydrogeologists, hydrochemists, mining and groundwater engineers is a pre-requisite. Full article

Thermoresponsive poly((N,N-dimethyl acrylamide)-co-(N-isopropyl acrylamide)) (P(DMA-co-NIPAM)) copolymers were synthesized via reversible addition−fragmentation chain transfer (RAFT) polymerization. The monomer reactivity ratios were determined by the Kelen–Tüdős method to be r_NIPAM = 0.83 and r_DMA = 1.10. The thermoresponsive properties of these copo-lymers with varying molecular weights were characterized by visual turbidimetry and dynamic light scattering (DLS). The copolymers showed a lower critical solution temperature (LCST) in water with a dependence on the molar fraction of DMA in the copolymer. Chaotropic and kosmotropic salt anions of the Hofmeister series, known to affect the LCST of thermoresponsive polymers, were used as additives in the aqueous copolymer solutions and their influence on the LCST was demonstrated. Further on, in order to investigate the thermoresponsive behavior of P(DMA-co-NIPAM) in a confined state, P(DMA-co-NIPAM)-b-PS diblock copolymers were prepared via polymerization induced self-assembly (PISA) through surfactant-free RAFT mediated emulsion polymerization of styrene using P(DMA-co-NIPAM) as the macromolecular chain transfer agent (mCTA) of the polymerization. As confirmed by cryogenic transmission electron microscopy (cryoTEM), this approach yielded stabilized spherical micelles in aqueous dispersions where the PS block formed the hydrophobic core and the P(DMA-co-NIPAM) block formed the hydrophilic corona of the spherical micelle. The temperature-dependent behavior of the LCST-type diblock copolymers was further studied by examining the collapse of the P(DMA-co-NIPAM) minor block of the P(DMA-co-NIPAM)-b-PS diblock copolymers as a function of temperature in aqueous solution. The nanospheres were found to be thermosensitive by changing their hydrodynamic radii almost linearly as a function of temperature between 25 °C and 45 °C. The addition of kosmotropic salt anions, as a potentially useful tuning feature of micellar assemblies, was found to increase the hydrodynamic radius of the micelles and resulted in a faster collapse of the micelle corona upon heating. Full article

A shape memory polymer was prepared by melt mixing a semicrystalline maleated polyolefin elastomer (mPOE) with a small amount of polyaniline (PANI) (up to 15 wt.%) in an internal mixer. Transmission electron microscopy (TEM), FTIR analysis, DMA, DSC, melt rheological analysis, and a tensile test were performed to characterize the structure and properties of the mPOE/PANI blends. The results revealed that the blends form a physically crosslinked network via the grafting of PANI onto the mPOE chains, and the PANI dispersed at the nanometer scale in the POE matrix served as a photo-thermal agent and provided increased crosslinking points. These structural features enabled the blends to exhibit a shape memory effect upon near-infrared (NIR) light irradiation. With increasing PANI content, the shape recovery rate of the blend under NIR stimulation was improved and reached 96% at 15 wt.% of PANI. Full article