Hollow Glass Microspheres Research Articles

An enhanced fractal self-pumping dressing with continuous drainage for accelerated burn wound healing.

Massive exudates oversecreted from burn wounds always delay the healing process, accompanied by undesired adhesion, continuous inflammation, and high infection risk. Conventional dressings with limited draining ability cannot effectively remove the excessive exudates but constrain them in the wetted dressings immersing the wound bed. Herein, we fabricate an enhanced fractal self-pumping dressing by floating and accumulating hollow glass microspheres in the hydrogel precursor, that can continuously drain water at a non-declining high speed and effectively promote burn wound healing. Small hollow glass microspheres can split the fractal microchannels into smaller ones with higher fractal dimensions, resulting in higher absorption efficiency. In an in vivo burn wound model on the dorsum of murine, the enhanced fractal self-pumping dressing can significantly reduce the appearance of the wound area and alleviate tissue edema along the healing process. This study sheds light on designing high-efficiency and continuous-draining dressings for clinical applications.

PROPERTIES OF HOLLOW GLASS MICROSPHERES PRODUCED IN A PROPANE-AIR FLARE

Hollow glass microspheres from sodium borosilicate glass were obtained by high-temperature method, the composition of mass%: 10 Na2O; 8 CaO; 0,3 MgO; 0,2 Al2O3; 9 B2O3; 0,5 SO3; 72 SiO2. It is established that the maximum yield of microspheres up to 87% is observed when using a propane-air torch with the characteristics: the air/propane ratio is 1,3; the maximum temperature on the torch axis is 1900 °C; the opening angle is ~15°; the flow rate of the transporting gas is 0,2 g/s. The hollow glass microspheres obtained in this mode are characterized by a median diameter of 60 microns, an average wall thickness of 1,3 microns, a bulk density of 260 kg/m3 and a calculated strength of 50 MPa.

The Thermal Insulation Composites for Lithium-ion Batteries

In this paper, the high-efficiency thermal insulation composites were prepared and investigated, which are formed by the addition of hollow SiO2 microspheres, hollow glass microspheres, and hollow phenolic microspheres into addition-type liquid silicone rubber. The thermal conductivity of composites is as low as 0.054 W/(m·K), which is 70.65% lower than the matrix (the thermal conductivity of the matrix is 0.184 W/(m·K)), and the tensile strength is 1.003 Mpa, and the thermal decomposition temperature of the composites is 427 °C .

Durability and Thermal Behavior of Functional Paints Formulated with Recycled-Glass Hollow Microspheres of Different Size.

This study aims to assess the effect of hollow glass microspheres of different sizes derived from glass industry waste on the durability and thermal behavior of waterborne paint. The coatings were characterized by electron microscopy to investigate the distribution of the spheres and their influence on the layer morphology. The impact of the various glassy spheres on the mechanical feature of the coatings was assessed using the Buchholz hardness test and the Scrub abrasion test. The role of the spheres in altering the durability of the samples was analyzed by the salt spray exposure test and the electrochemical impedance spectroscopy measurements. Finally, a specific accelerated degradation test was carried out to explore the evolution of the thermal behavior of the composite coatings. Ultimately, this work revealed the pros and cons of using hollow glass spheres as a multifunctional paint filler, highlighting the size of the spheres as a key parameter. For example, spheres with adequate size (25-44 µm), totally embedded in the polymeric matrix, are able to reduce the thermal conductivity of the coating avoiding local heat accumulation phenomena.

Facile Synthesis of Hollow Glass Microsphere Filled PDMS Foam Composites with Exceptional Lightweight, Mechanical Flexibility, and Thermal Insulating Property.

The feature of low-density and thermal insulation properties of polydimethylsiloxane (PDMS) foam is one of the important challenges of the silicone industry seeking to make these products more competitive compared to traditional polymer foams. Herein, we report a green, simple, and low-cost strategy for synthesizing ultra-low-density porous silicone composite materials via Si-H cross-linking and foaming chemistry, and the sialylation-modified hollow glass microspheres (m-HM) were used to promote the HM/PDMS compatibility. Typically, the presence of 7.5 wt% m-HM decreases the density of pure foam from 135 mg/cm-3 to 104 mg/cm-3 without affecting the foaming reaction between Si-H and Si-OH and produces a stable porous structure. The optimized m-HM-modified PDMS foam composites showed excellent mechanical flexibility (unchanged maximum stress values at a strain of 70% after 100 compressive cycles) and good thermal insulation (from 150.0 °C to 52.1 °C for the sample with ~20 mm thickness). Our results suggest that the use of hollow microparticles is an effective strategy for fabricating lightweight, mechanically flexible, and thermal insulation PDMS foam composite materials for many potential applications.

Characteristics of hollow glass microspheres and design of light polymer composite materials of different composition and dispersed structure

Currently, to obtain light polymer composite materials with high strength characteristics, hollow microspheres of various nature (glass, quartz, polymer, etc.) are used as fillers. Hollow glass microspheres of different grades (manufactured by JSC «SIO Stekloplastik») were studied by various methods, the disperse structure was described using the generalized parameters model, the light dispersion-filled polymer composite materials (DFPCM) were classified according to the structural principle, generalized and reduced parameters were calculated, and the structure, compositions of light CMs on polymer matrices of various nature were designed.

Study of the Compressive Properties of Heavy Calcium Carbonate-Reinforced Epoxy Composite Spheres (HC-R-EMS) Composite Lightweight Concrete.

Lightweight concrete is one of the effective means to solve the problems of structural component weight, energy efficiency, and fire safety in modern civil engineering. Heavy calcium carbonate-reinforced epoxy composite spheres (HC-R-EMS) were prepared by the ball milling method, and HC-R-EMS, cement, and hollow glass microspheres (HGMS) were mixed into the mold by the molding method to prepare composite lightweight concrete. The relationship between the HC-R-EMS volumetric fraction, the initial inner diameter of the HC-R-EMS, the number of layers of HC-R-EMS, the HGMS volume ratio, the basalt fiber length and content, and the multi-phase composite lightweight concrete density and compressive strength was studied. The experimental results show that the density of the lightweight concrete ranges between 0.953-1.679 g/cm3 and the compressive strength ranges between 1.59-17.26 MPa, where the volume fraction of HC-R-EMS is 90%, the initial internal diameter is 8-9 mm, and the number of layers of HC-R-EMS is three. The lightweight concrete can meet the requirements of high strength (12.67 MPa) and low density (0.953 g/cm3). In addition, the addition of basalt fiber (BF) can effectively improve the compressive strength of the material without changing the density of the material. From a micro-level perspective, HC-R-EMS is closely combined with the cement matrix, which is conducive to increasing the compressive strength of concrete. Basalt fibers connect the matrix into a network, improving the maximum limit force of the concrete.

Development of the epoxy resin phase change proppant based on the Pickering emulsification technology

Since the conventional solid proppant has many defects, such as poor migration and its rigid structures easy to plug cracks, liquid proppant has become a key development direction. A phase change proppant is developed based on the emulsified thermosetting resin system and evaluated in this paper. On the basis of the bisphenol A type epoxy resin, the phase change proppant system adopts the adduct of diethylene triamine and butyl glycidyl ether as epoxy resin curing agent and the SiO2 particles (1% of the resin mass) as the emulsifier, and then adds the hollow glass microspheres (1.25% of the resin mass) and the absolute ethyl alcohol (25% of the resin mass) as the thinner to reduce resin density and dilute resin. Proppant particles with major sizes of 4.5mm, 3mm, 2-2.5mm, 2mm, 1mm and 0.5mm are obtained through process optimization. After evaluation, the obtained proppants are of low density and high compressive strength, and their migration capability and flow conductivity are qualified for the exploitation of unconventional reservoirs with high closure pressures.

Lightweight ultra-high-performance concrete (UHPC) with expanded glass aggregate: Development, characterization, and life-cycle assessment

Ultra-high-performance concrete (UHPC) has high mechanical strengths and durability, but its density and carbon footprint are usually high. This paper developed a lightweight UHPC with low cost, low carbon footprint, low energy consumption, low thermal conductivity, and high ductility, by using three types of lightweight ingredients: hollow glass microsphere (460 kg/m3), expanded glass aggregate (800 kg/m3), and polyethylene fibers (970 kg/m3). Underlying mechanisms were investigated through thermogravimetry, X-ray diffraction, and mercury intrusion porosimetry analyses. Results showed that the hollow glass microsphere reduced the thermal conductivity of concrete; the expanded glass aggregate mitigated shrinkage while enhancing compressive strengths and flexural properties of concrete through internal curing; and the polyethylene fibers promoted multiple cracks, increasing ductility and toughness of concrete. With 20 % hollow glass microsphere, 1.5 % polyethylene fiber, and 25 % expanded glass, UHPC mixtures were developed to achieve high compressive strength (>127 MPa) and high flexural strength (>21 MPa), while reducing the density by 20 % and carbon footprint by 16 % as well as embodied energy by 27 %.

Treatment of antibiotic-containing wastewater with self-suspended algae-bacteria symbiotic particles: Removal performance and reciprocal mechanism

Emerging contaminants such as antibiotics in wastewater have posed a challenge on conventional biological treatment processes. Algae-bacteria symbiotic mode could improve the performance of biological treatment processes. Self-suspended algae-bacteria symbiotic particles (ABSPs) were prepared with Chlorella vulgaris and Bacillus subtilis using the sol-gel method and hollow glass microspheres in this study. The removal effect of nitrogen and phosphorus as well as the feedback mechanism of ABSPs under tetracycline stress were investigated through three-cycles wastewater treatment experiments. The antioxidant enzyme activity and phycosphere extracellular polymeric substance (EPS) content were identified as well. The results indicated that the removal rates of NH4+-N, TP, COD, and tetracycline in the ABSPs group finally reached 96.18%, 95.44%, 81.36%, and 74.20%, respectively, which were higher than the single algae group apparently. The phycosphere EPS content increased by 20.41% and algae cell structure maintained integrity in ABSPs group as compared with that in single algae group. This study demonstrates that the self-suspended ABSPs can improve contaminants removal performance and alleviate the antioxidant stress response of algae through algal-bacterial reciprocity mechanism.

Processing of Low-Density HGM-Filled Epoxy–Syntactic Foam Composites with High Specific Properties for Marine Applications

A solution casting approach is used to create hollow glass microsphere (HGM)-filled epoxy-syntactic foam composites (e-SFCs) by varying the concentrations of HGM in epoxy according to different particle sizes. Density analysis is used to investigate the impact of concentration and particle size regularity on the microstructure of e-SFCs. It was observed that e-SFCs filled with an HGM of uniform particle sizes exhibit a reduction in density with increasing HGM concentration, whereas e-SFCs filled with heterogeneous sizes of HGM exhibit closeness in density values regardless of HGM concentration. The variation in e-SFC density can be related to HGM packing efficiency within e-SFCs in terms of concentration and particle size regularity. The particle size with lowest true density of 0.5529 g/cm3, experimental density of 0.949 g/cm3 and tensile strength of 55.74 MPa resulted in e-SFCs with highest specific properties of 100.81 (MPa·g/cm3), with a 35.1% increase from the lowest value of 74.64 (MPa·g/cm3) at a true density of 0.7286 g/cm3, experimental density of 0.928 g/cm3 and tensile strength of 54.38 MPa. The e-SFCs' theoretical density values were obtained. The variance in theoretical and experimental density values provides a thorough grasp of packing efficiency and inter-particle features.

Shrinkage stress of thermal cured epoxy resin reduced by addition of functional hollow microspheres

The shrinkage stress of thermal cured epoxy resin developed during curing process can cause low film adhesion strength, low dimensional accuracy and even coating films warping which severely reduce service lifetime of the coating. Therefore, there is growing interest in developing effective means to reduce the shrinkage stress. In this paper, we report the use of hollow microspheres prepared from Pickering emulsion droplets in the thermal cured epoxy resin formulations and the shrinkage stress due to resin solidification is monitored in real time to reveal the effect of hollow microspheres upon shrinkage stress of the resin. Epoxy group functionalized silica nanoparticles from the Stöber method are used as Pickering emulsion stabilizer and the emulsion droplets are polymerized to obtain hollow microspheres with controllable mechanical properties and surface morphologies. Due to the reactivity of the hollow microspheres, they can be incorporated into the epoxy resin coatings and the shrinkage stress is thus reduced with the addition of hollow microspheres. It is revealed that the shrinkage stress is reduced from 195.79 kPa to 140. 40 kPa with the addition of 12 wt% hollow microspheres and polydisperse hollow microspheres are more effective in shrinkage stress reduction. As the modulus of the hollow microspheres is reduced and elasticity is increased, the shrinkage stress of the coating film is also reduced from 181. 37 kPa to 157.42 kPa which is not achieved by hollow glass microspheres. The hollow microspheres are well dispersed in the resin matrices which doesn't undermine the basic mechanical properties of the coating such as adhesion and surface hardness.

Double-sided functional infrared camouflage flexible composite fabric for thermal management

Irregular yttrium oxide nanopuncture-coated hollow glass microspheres (HGMs@Y2O3), as a lightweight, thermal insulating, and high IR reflectivity materials could be prepared by a simple hydrothermal and high-temperature calcination process. Here, a flexible composite fabric with sandwiched structure was designed to combine the good infrared camouflage performance with self-cleaning ability. Thereinto, aluminum foil (AF), HGMs@Y2O3, and polypropylene spunbond nonwoven fabric (PPF) were binded and applied for low emissivity layer, thermal insulating layer and self-cleaning layer, respectively. The flexible composite fabric can realize the infrared camouflage effect to effectively shield the heated object (62.8 °C). The radiation temperature detected by the infrared camera is only 32.4 °C, which had a reduction of 30.4 °C. Based on the functional fabrics (anti-fouling performance), excellent thermal insulation (K = 0.0908 W/m-K) and low infrared emissivity (Average emissivity (ε‾) of AF plane of composite <0.1; Average emissivity (ε‾) of PPF plane of composite <0.5), the composite material enables the choice of presenting antifouling or thermal camouflage properties in different environments. This work provides another insight into the fabrication of flexible infrared camouflage materials while facilitating the exploration of flexible infrared camouflage materials.

Water absorption in hollow glass microsphere composites under hydrostatic pressure: Mechanisms and influencing parameters

AbstractHollow glass microsphere composites, or syntactic foams, are widely used in marine environments due to their buoyancy. However, in service, loss of buoyancy occurs along time. This behavior is attributed to water absorption that leads to a mass increase of the material. This study investigates the water absorption of three types of syntactic foams under hydrostatic pressure with density ranging from 0.59 to 0.74 g. cm−3. Water absorption measurements are performed for a maximal duration of 3 years and under hydrostatic pressure up to 700 bars. Results show that water absorption is much higher than expected and attributed to the filling of microspheres that collapse over time. Based on results presented here, prediction of water absorption syntactic foams is proposed including the impact of applied hydrostatic pressure. This prediction allows estimating the buoyancy loss in hollow glass microsphere composite as a function of time, depth and sample size.

Polyethyleneimine/polydopamine-functionalized self-floating microspheres for caramel adsorption: Interactions and phenomenological mass transfer kinetics

A polyethyleneimine/polydopamine-functionalized self-floating microsphere (EHGM/PDA/PEI) bears an etched hollow glass microsphere as a support, polydopamine as an interfacial cross-linking “glue”, and polyethyleneimine as a functional monomer was fabricated and used as a decolorization sorbent for sugarcane juice. The advantages of EHGM/PDA/PEI for sugarcane juice decolorization were attributed to its richness of target polyethyleneimine monomers, well-connected and abundant three-dimensional network-like aperture structure, and nontoxicity. Moreover, EHGM/PDA/PEI has excellent self-floating performance to allow separation from the adsorption system after decolorization and may have a faster separation speed and lower energy consumption than conventional solid–liquid separation methods. Synthetic caramels were used as model colorants of sugarcane juice to assess EHGM/PDA/PEI performance. The adsorption capacity of EHGM/PDA/PEI for caramels was 18.36 mg/g with a removal efficiency of 91.80% in the adsorption equilibrium state. The interaction mechanisms revealed that the caramel adsorption on EHGM/PDA/PEI was mostly mediated by protonated amine groups, followed by electron sharing. Two layers of caramels adhered onto EHGM/PDA/PEI were mainly mediated by electrovalent bonds between carboxylate and protonated amine. On average, one caramel molecule can be shared by 3–4 protonated amine groups of EHGM/PDA/PEI, which suggests a parallel sorption orientation. Four phenomenological mass transfer models [external diffusion resistance (EXTDR), internal diffusion resistance (INTDR), EXTDR–INTDR mixed, and adsorption onto active sites (AOAS)] proposed new and unique insights into the dynamic properties of the adsorption process.

Research on the Sound Insulation Performance of Composite Rubber Reinforced with Hollow Glass Microsphere Based on Acoustic Finite Element Simulation.

The composite rubber reinforced with hollow glass microsphere (HGM) was a promising composite material for noise reduction, and its sound insulation mechanism was studied based on an acoustic finite element simulation to gain the appropriate parameter with certain constraint conditions. The built simulation model included the air domain, polymer domain and inorganic particles domain. The sound insulation mechanism of the composite material was investigated through distributions of the sound pressure and sound pressure level. The influences of the parameters on the sound transmission loss (STL) were researched one by one, such as the densities of the composite rubber and HGM, the acoustic velocities in the polymer and inorganic particle, the frequency of the incident wave, the thickness of the sound insulator, and the diameter, volume ratio and hollow ratio of the HGM. The weighted STL with the 1/3 octave band was treated as the evaluation criterion to compare the sound insulation property with the various parameters. For the limited thicknesses of 1 mm, 2 mm, 3 mm and 4 mm, the corresponding optimal weighted STL of the composite material reached 14.02 dB, 19.88 dB, 22.838 dB and 25.27 dB with the selected parameters, which exhibited an excellent sound insulation performance and could promote the practical applications of the proposed composite rubber reinforced with HGM.

Reusable self-floating carriers recover heavy metals from industrial wastewater through heterogeneous nucleation for resource reuse

Coagulation-flocculation in industrial wastewater treatment drives environmental pollution from landfilling heavy metal-laden sludge. Efficient separation of the sludge is crucial for cost-effective metal recovery. This study explored a new separation method of Cu2+, Ni2+, Zn2+ and Cr3+ via self-floating metal hydroxides assisted by hollow glass microsphere (HGM) carriers. The amount of OH− was stoichiometric to the positive charges of metal ions, mixed with 1 mg mL−1 HGM, causing metal hydroxides to attach to HGM surface via heterogeneous nucleation. The self-floating system removed 37.5% and 14.0% more metals than sedimentation at 50 and 200 mg L−1 metal concentrations. HGM additions increased the particle size of metal hydroxides by up to 12.5 times to that of HGM at 18.8 ± 1.1 µm, benefiting their solid-liquid separation. By pumping the wastewater downward in column reactor at velocities equal to or less than the self-floating sludge, 96.4% metals were removed in continuous flow. The recovery rates of HGM and metals reached 92.0 ± 2.2% and 92.7 ± 3.2%, and the concentration of the recovered metal reached 19,339 ± 394 mg L−1 for potential reutilization in industrial electroplating. This research investigated a new separation strategy based on solid self-flotation for sustainable treatment of metal-laden wastewater.

Mechanical and thermal insulation performance of hollow glass microsphere (HGMS)/fumed silica/polyester microcomposite coating

Numerous insulating materials such as coatings have been developed and are commercially available. Hollow glass microspheres (HGMS) as well as fumed silica, despite their intrinsic properties, have received less attention in formulation of coatings. Here, we hypothesized the utilization of the fillers to evaluate and compare their effects on the insulating efficiency, mechanical response and surface adhesion of a class of micro-composites functioning as thin coatings. Polyester-based composite coatings were prepared using 0–30 wt% of HGMS and 0–12 wt% of fumed silica. The results confirmed the positive influence of the HGMS and fumed silica on the insulating performance of the fabricated coatings exhibiting around 20 % improvement compared to the pure polyester. It was shown that elastic response, impact resistance and the coatings/substrate strength are sensitive to the presence of fillers and are governed by the fillers type and loading as well as the interfacial restricted region and morphology of the composites.

Investigation of mechanical characterization of hybrid sandwich composites with syntactic foam core for structural applications

In this work, mechanical performance on sandwich composites consisting of syntactic foam filled with hollow glass microsphere in an epoxy resin matrix as the core material and hybrid kenaf/glass fibers face-sheet based composites panel is studied. The main purpose of this work is to design a suitable lightweight composite panel material for structural application. Four different sequences of face-sheet reinforcement (e.g., kenaf-kenaf; glass-glass; glass-kenaf, and kenaf-glass) were adopted. In this study, the mechanical properties and failure modes are carefully investigated. The sandwich composites were characterized by compressive, tensile, and flexural properties. The results showed that compressive strength was highest at the “kenaf-glass” face-sheets, tensile strength was highest at “glass-glass” face-sheets, and flexural at “glass-glass” face-sheets with 52.1%, 67.6%, and 74.4% increase to “kenaf-kenaf” face-sheets, respectively. The tensile strength and modulus values with the specific strengths and modulus values showed that the mechanical properties of the sandwich composites can be influenced by hybridizing the face-sheet laminates of the composite. This shows that kenaf fiber has limited strength when used as reinforcement alone but gave an excellent performance when combined with glass fiber.

Effect of Hollow Glass Microsphere (HGM) on Impact and Flexural Properties of High-Density Syntactic Foam Based Epoxy Composites

Syntactic foam composite offers versatile application possibilities in marine, structural, aerospace industries due to their good tensile, flexural, and compressive strength, corrosive resistance, high specific strength and modulus, light weight nature. Their porous structure is by mixing hollow particles called microspheres as fillers into matrix materials such as polymer, metal or ceramic etc. In this study, a high-density hollow glass microsphere is used to fabricate syntactic foam by mixing it with epoxy resin. Five different compositions 5, 10, 15, 20 and 25 vol% of hollow glass microspheres were varied in fabricating the syntactic foam. Impact and flexural properties were investigated on the syntactic foam. All the compositions of the volume fraction variations of hollow glass microsphere content in the syntactic foam increased more than the neat epoxy. The highest impact resistance, flexural strength and flexural modulus is at 5 vol%, 113.12 kJ/m2, 86.7 MPa, and 80 GPa respectively with 25.2%, 38.29%, and 33.25% increase respectively more the neat epoxy while the specific impact and flexural strength is at 25 vol% with 53.78% and 57.77% increase respectively more than the neat epoxy.