Good Hydrophobicity Research Articles

Durably antifouling blends of fluorinated multiblock copolymers and polypropylene with micro-nano structures

Fluoropolymers are widely used as hydrophobic coatings on plastics, which have low stability and durability. Therefore, it has been a challenge to strengthen the bond force between plastics and fluoropolymers, to improve their chain entanglement, and to make the hydrophobicity of those materials more stable and durable. In this paper, fluorinated multiblock copolymers (PNANPF6-PCOE) with good hydrophobicity, processability and thermal stability were prepared by macromolecular cross metathesis (MCM) method. Notably, micro-nano structures were formed by simply controlling the reaction time of MCM due to the disparity of rigidity and flexibility and polarity in PCOE and PNANPF6 blocks. The micro-nano structures were also preserved in the blends of PNANPF6-PCOE/polypropylene (PP). The tensile mechanical properties and hydrophobicity of PNANPF6-PCOE/PP blends are affected by the length of PCOE and PNANPF6 blocks in multiblock copolymer. With the high temperature in melt-blending process, fluorinated segment groups could easily move and aggregate to the surface, and alkyl groups also would entangle and compatibly blend with polypropylene, which resulted in good thermal properties, well mechanical performance and great hydrophobicity. Most importantly, the antifouling durability to coffee, cola and ethanol was greatly enhanced by melt-blending process compared with solution coating method. This can provide a new strategy for the preparation of fluorinated multiblock copolymers with micro-nano structures, and would demonstrate a new way to achieve durable hydrophobicity and antifouling properties in general materials.

Novel thermal conductivity and anti-corrosion coating with hydrophobic properties for heat exchanger applications

Industrial heat exchangers commonly encounter the issue of metal corrosion. Conventional anti-corrosion coatings typically exhibit poor heat conduction, leading to diminished heat exchange efficiency. This study presents a novel coating that combines high thermal conductivity with enduring anti-corrosion performance. The interfacial compatibility between the boron nitride (BN) / silicon carbide (SiC) and fluorosilicone resin (FSR) is effectively enhanced through fluorosilane modification. This improvement, in conjunction with the superior thermal conductivity of the BN/SiC composite filler and the multi-barrier effects of the two-dimensional BN material, results in the composite coating with a high thermal conductivity of 1.65 W/(m·K). After 60 days of immersion in 3.5 wt% NaCl solution, the coating maintains a low-frequency impedance exceeding 1011 Ω·cm2. Good hydrophobicity can promote the long-term anti-corrosion performance of the coating. Thanks to the inherent hydrophobicity of FSR and the reduced surface energy of the filler due to fluorosilane modification, the coating also exhibits hydrophobic characteristics, evidenced by a water contact angle of 109.69°. The development of this novel multifunctional coating holds significant implications for heat exchangers and other applications requiring a balance between thermal conductivity and anti-corrosion performance.

Multi-functional and durable anti-corrosion coatings with hydrophobic, freeze time retardation and photothermal properties by means of a simple spraying method

In this study, a composite material consisting of perfluorinated quaternary silane-modified graphene oxide and modified CeO2 nanoparticles was prepared, and a hydrophobic, corrosion-resistant, self-cleaning and anti-icing composite coating was prepared by combining the composite material with polyphenylene sulfide (PPS) through high-temperature curing in a simple spraying method for the protection of iron sheets. The results show that the composite coating has excellent corrosion resistance, strong mechanical properties and certain photothermal properties. When the content of perfluorinated quaternary silane modified CeO2 nanoparticles with graphene oxide (P-GKC) was 10 wt%, the composite coating had a water contact angle of 145.6 ± 3° and a sliding angle of 5 ± 1°, with good hydrophobicity and low surface energy. Meanwhile, the hydrophobic modification of perfluoroquaternary silanes reduced the surface energy of the particles in the composite coatings and greatly improved the hydrophobicity. Surface temperature and laser irradiation tests of the composite coatings showed that the photothermal properties of the composite coatings were better than those of the single PPS and graphene oxide (GO) coatings, with good photothermal cycling stability.The Tafel curves and the EIS results showed that the PPS/10 wt% P-GKC composite coatings had the best corrosion resistance, with a corrosion current density of 5.01 × 10−9A cm−2. After 200 h of salt spray test in 3.5 % NaCl environment, the PPS/10 wt% P-GKC composite coating still has good substrate protection effect, which provides a practical basis for the research of composite coating anticorrosion.

Screening, probiotic properties, and inhibition mechanism of a Lactobacillus antagonistic to Listeria monocytogenes

Listeria monocytogenes is one of the most lethal foodborne pathogens, and there is a lack of microorganisms that can strongly inhibit its growth. Safe lactic acid bacteria with probiotic and antibacterial properties are ideal sources of antagonistic bacteria. This study isolated a strain of Lactobacillus plantarum 4–10 that completely killed L. monocytogenes from northeastern Chinese sauerkraut. Probiotic characterization revealed broad-spectrum bacterial inhibition, antagonizing 16 Gram-positive, Gram-negative, and fungal species. After tolerance to simulated intestinal and gastric fluids, the survival rate was >45 %. L. plantarum 4–10 was sensitive to chloramphenicol, doxycycline, erythromycin, and tetracycline, and exhibited good hydrophobicity, auto-aggregation, and co-aggregation. It could disrupt the cell structure when co-cultured with L. monocytogenes and act as a lethal agent within 15 h. Through transcriptomic analysis and validation experiments, we found that L. plantarum 4–10 could inhibit the expression of L. monocytogenes membrane transport-related genes by producing bacteriocins, thus disrupting the cell membrane structure and inhibiting the growth, metabolic viability, and biofilm formation of L. monocytogenes in a short time. In conclusion, L. plantarum 4–10 has good probiotic properties and antibacterial effects and shows excellent research and application prospects as a natural bacteriostat.

Preparation and Performance of Silicone Rubber Composites Modified by Polyurethane.

Silicone rubber composites with good comprehensive properties modified with polyurethane were obtained through mixing and vulcanizing methods. Firstly, the polyurethane prepolymer with double bonds was prepared by polytetrahydrofuran glycol (PTMG, Mn = 1000), isophorone diisocyanate (IPDI), and 2-hydroxyethyl methacrylate (HEMA). The prepolymer was then added to the silicone rubber compounds to prepare silicone rubber composites, combining the excellent properties of polyurethane with the silicone rubber materials. The effects of polyurethane content on the mechanical properties, insulation, hydrophobicity, thermal stability, and flame retardancy of composites were studied in detail. The results showed that the silicone rubber composites not only have good hydrophobicity, thermal stability and flame retardant properties, but the addition of polyurethane significantly improves the tensile strength at room and low temperatures and the volume resistivity of the materials. The tensile strength increased by 32.5%, and the volume resistivity nearly doubled. The excellent electrical insulation, high hydrophobicity and good mechanical properties make the silicone rubber composites appropriate for use in the field of polymeric house arresters.

Self-healing and malleable waterborne polyurethane bearing aliphatic disulfide linkages with hydrophobic branching chains

Self-healing polymers have attracted extensively interests to improving durability of materials. A promising strategy to prepare self-healing materials is the incorporation of dynamic disulfide bonds into polymer backbones. In this study, a novel hydrophobic chain extender containing disulfide bond (CY-OA) has been successfully synthesized and used to elevate the practical application capability of the self-healing WPU. FT-IR and Raman spectra confirmed that the disulfide bonds were successfully incorporated into the polyurethane backbones. The synthetic self-healing waterborne polyurethanes (SHWPUs) all had the high-water contact angle above 108° and the low water absorption below 5%, exhibiting the good hydrophobicity and water resistance. Increasing addition of CY-OA simultaneously optimized the mechanical properties and self-healing efficiency of SHWPUs. The mechanical properties of repaired SHWPU-4 film had been almost recovered to its original values (tensile strength and elongation at break were 12.79 MPa and 1003%) at 120 °C for 1 h. Meanwhile, the feature of dynamic disulfide bonds produced a relatively low activation energy of 54.78 kJ/mol, resulting in a good self-healing efficiency of 93%. Therefore, this hydrophobic self-healing WPU contributed the scratch resistance, water resistance, reprocess ability and further got the feasibility of practical applications.

A thermoplastic polyurethane-based composite aerogel with low shrinkage and high specific surface area enhanced by activated carbon for highly efficient oil/water separation

Aerogels are attractive candidates in the field of oily wastewater treatment. Nevertheless, some disadvantages like sharp shrinkage, massive expense of drying process, and weak mechanical properties pose an obstacle to their wide practical applications. Herein, an activated carbon (AC) enhanced thermoplastic polyurethane (TPU-AC) composite aerogel was successfully prepared by simple thermally induced phase separation (TIPS) method followed by ambient pressure drying. The average drying shrinkage rate of TPU-AC was controlled to < 10% due to the AC-enhanced skeleton. With an optimal addition of AC, the resultant composite aerogel exhibited low density, reasonable porosity, and significantly improved specific surface area (105.86 m2/g). Good hydrophobicity endowed TPU-AC with superior oil/water selectivity. Therefore, an adequate oil adsorption capacity of up to 38.64 g/g was gained by TPU-AC with a fast adsorption rate. Thanks to the marvelous mechanical flexibility of TPU-AC, especially, the absorption and recovery of oil can be realized by facile adsorption-extrusion method as well as pump-assisted oil/water separation device with satisfactory separation efficiency and excellent recyclability. Along with the admirable cost effectiveness, the current study is expected to pave a facile way for aerogel preparation, providing a scalable and effective strategy for oily wastewater treatment.

Probiotic and functional potential of lactic acid bacteria isolated from pulque and evaluation of their safety for food applications.

Pulque is a traditional Mexican non-distilled alcoholic beverage to which several beneficial functions are attributed, mainly associated with gastrointestinal health, which can be explained by the presence of probiotic bacteria in its microbiota. Therefore, the objective of this work was to evaluate the safety, probiotic activity, and functional characteristics of seven strains of lactic acid bacteria (LAB) isolated from pulque using the probiotic strain Lactobacillus acidophilus NCFM as control. The LAB isolates were identified by 16S rRNA sequencing and MALDI Biotyper® MS as belonging to three different Lactobacillaceae genera and species: Lactiplantibacillus plantarum, Levilactobacillus brevis and Lacticaseibacillus paracasei. Most strains showed resistance to gastric juice, intestinal juice and lysozyme (10 mg/L). In addition, all strains exhibited bile salt hydrolase (BSH) activity and antibacterial activity against the pathogenic strain Listeria monocytogenes. Additionally, cell surface characteristics of LAB were evaluated, with most strains showing good hydrophobicity, auto-aggregation, and co-aggregation towards enteropathogenic Escherichia coli and L. monocytogenes. In terms of safety, most of the strains were sensitive to the tested antibiotics and only the Lact. paracasei UTMB4 strain amplified a gene related to antibiotic resistance (mecA). The strains Lact. plantarum RVG2 and Lact. plantarum UTMB1 presented γ-hemolytic activity, and the presence of the virulence-related gene agg was identified only in UTMB1 strain. Regarding functional characterization, the tested bacteria showed good β-galactosidase activity, antioxidant activity and cholesterol reduction Based on principal component analysis (PCA) and heat mapping, and considering the strain Lact. acidophilus NCFM as the probiotic reference, the strains Lacticaseibacillus paracasei UTMB4, Lactiplantibacillus plantarum RVG4 and Levilactobacillus brevis UTMB2 were selected as the most promising probiotic strains. The results of this study highlighted the probiotic, functional and safety traits of LAB strains isolated from pulque thus supporting the health benefits attributed to this ancestral beverage.

Antioxidant properties and molecular mechanisms of Lactiplantibacillus plantarum ZJ316: A potential probiotic resource

Oxidative stress is a hallmark of many cancers. Probiotics with antioxidant properties have been found to alleviate oxidative stress. Lactiplantibacillus plantarum ZJ316 (L. plantarum ZJ316) is an exceptional strain that shows excellent hydrogen peroxide (H2O2) tolerance, sensitivity to the seven antibiotics (ampicillin, gentamicin, kanamycin, erythromycin, glycine, tetracycline and chloramphenicol) recommended by the European Food Safety Authority (EFSA), and exhibits good cell hydrophobicity and Caco-2 adhesion ability, but its antioxidant mechanism is unclear. This study showed that L. plantarum ZJ316 can withstand 2.5mmol/L H2O2 and both its intact cells and fermentation supernatant exhibit strong free radical scavenging ability. Furthermore, cell homogenate and fermented supernatant (ZJ316 FS) of L. plantarum ZJ316 performed higher activity of antioxidant enzymes. In addition, the mRNA level of antioxidant genes in L. plantarum ZJ316 regulated cell redox homeostasis in an orderly manner, demonstrating the antioxidant mechanism of L. plantarum ZJ316 at the transcriptional level. In summary, L. plantarum ZJ316 has good adhesion and antioxidant properties, no hemolytic activity and no drug resistance transfer, indicating that L. plantarum ZJ316 holds the potential to be utilized as a redox modulator probiotic in functional foods.

Preparation of polybenzoxazine/resorcinarene composites with low dielectric constants

AbstractA series of polybenzoxazine (PBZ)/resorcinarene composites with low dielectric constants were prepared by the thermal curing of a siloxane‐containing benzoxazine (P‐aptmds) with C‐methylcalix[4]resorcinarene (CMCR). CMCR with active hydroxyl groups could serve to lower the thermal curing temperature of P‐aptmds. The results of differential scanning calorimetry (DSC) showed that the peak exothermic temperature of P‐aptmds decreased from 262°C to 192°C. The introduction of CMCR increased the crosslinking density of the PBZ/CMCR composites and improved the thermal properties. Due to the incorporation of CMCR with macrocyclic structure, the dielectric constant and the dielectric loss of the PBZ/CMCR composite could be reduced to 2.63 and 0.0055 at 1 MHz, respectively. Moreover, the PBZ/CMCR composites possessed good hydrophobicity and low water absorption. This approach was expected to provide a facile design strategy of low dielectric composite materials.

Study on the Corrosion and High‐Temperature‐Resistant Coating for In Situ Crosslinking Reaction Catalyzed by a Special “Egg Inlaid Egg Tray” Structure

A new type of water corrosion‐resistant coating which is similar to the “egg inlaid egg tray” structure is successfully prepared. Modified chitosan (MCS) and graphene oxide (GO) are crosslinked with waterborne epoxy resin to form a unique 3D “tray” hybrid structure, and the crosslinking reaction is catalyzed by modified nano‐SiO2 (MSiO2) with an egg‐like morphology. The uniformly dispersed MSiO2 can provide crosslinking reaction sites and is firmly “fixed” in the composite coating, thus not only catalyzing the crosslinking reactions with good performance, but also improving the interaction between itself and the as‐formed GO‐MCS structure. Consequently, with the help of “fixed catalytic in situ crosslinking reactions” and synergistic effect between MSiO2 and GO‐MCS, the coating not only shows an improved corrosion resistance with a large impedance modulus at low frequency (|Z|0.01 Hz) of 1.8 × 106 Ω cm2, but also possesses good thermal stability and high hydrophobicity. The protective effect of the composite coating on the substrate is more comprehensive and multiple.

Successful Fabrication of Hydrophobic Surfaces of Microstructures Cooperating with Solid-Liquid Nanomaterials on the CuZnPb Alloy Substrate.

For protecting the exquisite structural patterns of such coins, developments of simple preparation methods were explored to achieve good hydrophobic capability and the wear-damage resistance of CuZnPb surfaces. A self-cleaning nanoliquid (SN) was combined with microstructured Ag-dispersed CuZnPb (MAC) to realize good hydrophobicity functions of the SNMAC. This was because the cooperative functions of silver and the SN enhanced the water reunion ability and increased solid-liquid-gas contact areas, leading to high contact angles of SNMAC. Their cooperations produced discrepant forces in their respective areas of the water drops and increased heterogeneous flowing, resulting in a high-angle hysteresis of SNMAC. Subsequently, the wear-damage resistance of the hydrophobic interface was measured in a ball-on-flat tribopair system, and the results showed that sliding injuries made a height distribution of the hydrophobic surface trend toward an equalization, allowing the cooperation of nano-silver, SN, and CuZnPb to form a new-style interface for achieving excellent hydrophobicity, thus producing the highest contact angles of the SNMAC among the as-prepared samples.

Superhydrophobic, photothermal, and UV-resistant coatings obtained by polydimethylsiloxane treating self-healing hydrophobic chitosan-tannic acid surface for oil/water separation

Surface hydrophobicity is generally created by lower surface energy materials. However, it is predictable. Simultaneously, it is rare to construct a self-healing surface hydrophobicity using hydrophilic materials, which is an emerging and significant aspect. Herein, we for the first time fabricated the unpredictable surface hydrophobicity on the cotton fabric surface by utilizing chitosan and tannic acid (labelled as Cot@PTA@PTA-CS), in which chitosan played the decisive role. Interestingly, the surface hydrophobicity of Cot@PTA@PTA-CS could be recovered under the heating treatment. Notably, using the hydrophilic materials realizes the unpredictable surface hydrophobicity with self-healing characteristics, which is an advanced work in contrast to the conventional predictable surface hydrophobicity created by fluorine-free hydrophobic or fluorinated materials. Then, Cot@PTA@PTA-CS was treated with polydimethylsiloxane to obtain surface superhydrophobicity, regarded as Cot@PTA@PTA-CS@PDMS. Cot@PTA@PTA-CS@PDMS and Cot@PTA@PTA-CS all exhibited good hydrophobicity after mechanical abrasion. Moreover, Cot@PTA@PTA-CS@PDMS exhibited good repellency to 95 °C water, diiodomethane, ethylene glycol, and dimethyl sulfoxide. So, the surface free energies of modified cotton fabrics were calculated. Besides, the modified cotton fabrics also possessed excellent UV resistance, anti-oxidation activity, photothermal effect, and self-cleaning. Finally, Cot@PTA@PTA-CS@PDMS was used for the high-efficient oil/water separation. Briefly, this work provides a novel and feasible strategy for creating unpredictable surface hydrophobicity with self-healing performance by chitosan and tannic acid, inspiring more scholars to fabricate hydrophobic surface by hydrophilic materials.

Study on preparation and properties of PVDF/CB composite films

Carbon black was often used as a UV stabilizer, due to its ability to absorb high-energy ultraviolet radiation. In this study, carbon black was added to PVDF resin, and PVDF film with carbon black (PVDF/CB composite film) was fabricated using a precision co-extrusion casting mechanism. The properties of the films were characterized by differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), field emission scanning electron microscope (FESEM), water contact angle (WCA), and universal material testing machine. Furthermore, the DSC results suggested that the melting temperature (Tm) of PVDF/CB composite film was 168.7°C. The TGA results showed that the initial decomposition temperature (Td) of PVDF/CB composite film was 358.9°C. The FESEM observation showed that the surface of the PVDF/CB composite film was smooth without obvious defects. The WCA results indicated that PVDF/CB composite film had good hydrophobicity. In addition, the UV transmittance results presented that PVDF/CB composite film had higher UV aging resistance than that PVDF film.

Hydrophobic Nano-Microcapsules Effectively Improve the Waterproof Performance of Coatings

Due to the special surface wettability, self-cleaning, drag reduction, anti-icing and other properties, superhydrophobic materials are widely used as coating or coating additive on the surface of building materials, ships, and even for liquid transportation, biomedicine, etc., which have become one of the research hotspots in the direction of coating in recent years. However, the hydrophobic surface itself has weak stability and poor durability, which affects its application value. Therefore, in this study, PS nano-microcapsule was prepared by the multiphase emulsion method, and their particle size was measured by SEM electron microscopy to be about 350–550 nm, with a relatively uniform distribution. The hydrophobicity of PS nano-microcapsule modified with trimethoxy (1H, 1H, 2H, 2H-trifluoroctyl) silane (PFOTMS) at different molar ratios was investigated. SEM results showed that the surface roughness of the modified PFOTMS-PS nano-microcapsule could be changed. The contact angle proved that the greater the content of PFOTMS, the better the hydrophobicity of the modified PFOTMS-PS nano-microcapsule. When the content reached 50%, the hydrophobic performance was the best. As a coating, PFOTMS-PS nano-microcapsule has no specific requirement for the properties of the substrate material. It should be noted that the hydrophobicity of the coating did not change significantly after 30 days at room temperature. The above results indicated that PFOTMS-PS nano-microcapsule had good hydrophobicity and stability, and is expected to be used in many fields such as waterproof textiles and architectural coatings in the future.

Investigation of the impact of annealing temperature on characteristics of porous SiOCH films

Porous SiOCH films with different porosity and low dielectric constant (k) were prepared by sol-gel and spin coating using methyltrimethoxy-silane (MTMS) and 1, 2-bis (trimethoxysilyl) ethane (BTMSE) as precursors and cetyltrimethylammonium chloride (CTAC) as porogen. The impact of different annealing temperatures on the chemical composition, hydrophobicity, pore arrangement, and dielectric constant of porous SiOCH films was investigated. The experimental results show that the SiOCH films with MTMS and BTMSE as precursors contain -C-C-bond and terminal methyl (Si-CH3). After annealing at 400 °C, the chemical composition of the films is stable. The water contact angle (WCA) is larger than 90°, and the films have good hydrophobicity.

Colourful phase change material-incorporated flexible film for efficient passive radiative cooling.

Passive radiative cooling (PRC) involves the emission of thermal radiation into cold space and the reflection of solar radiation, which aims to cool and lower the temperature of objects. However, currently most radiative coolers have a white appearance which restricts their potential applications. We develop a coloured bilayer radiative cooling membrane using polyvinylidene fluoride/tetraethoxysilane (PVDF/TEOS) fibres, with incorporation of phase change materials (PCMs) and active dyes through a simple and large-area electrospinning process. In comparison to traditional emitters, PCM-incorporated colourful coolers provide energy storage capacity and colourful appearances. Our phase-transition-based colourful flexible film (PCFF) achieves a total solar reflectance of 0.81 and a mid-infrared (MIR) (8-13 μm) emissivity of 0.85 with superior mechanical strength and good hydrophobicity. We experimentally demonstrate that our PCFF can significantly reduce the temperature of objects exposed to direct sunlight, with a cooling effect of up to 9 ℃ compared to commercial fabrics of similar materials and colours. Our work provides a promising starting point for the design and manufacture of colourful and flexible thermal control films.

Carboxyl-based deep eutectic solvent modified magnetic graphene oxide as a novel adsorbent for fast enrichment and extraction of estrogens in milk prior to HPLC-UV analysis

In this study, a magnetic graphene oxide modified with green carboxyl-based deep eutectic solvent (MGO@DES) was synthesized for the first time and employed as a highly efficient adsorbent for the magnetic solid-phase extraction (MSPE) of three estrogens in milk samples. With large specific surface, good hydrophobicity and abundant adsorption sites, MGO@DES exhibited excellent extraction performance for estrogens. The adsorption kinetic experiment revealed that 5 mg of MGO@DES reached the equilibrium of estrogen adsorption within 3 min. MGO@DES based MSPE coupled with HPLC-UV method was developed and applied to the determination of three estrogens in milk samples. Good linearity (R2 > 0.9953) was obtained in the range of 1–200 ng mL−1 and the low limits of detection were 0.20–0.28 ng mL−1. The spiked recoveries were in the range of 90.3–105.7%, with RSDs less than 7.9%.

Probiotic properties and antimicrobial evaluation of silymarin-enriched Lactobacillus bacteria isolated from traditional curd

Nowadays, the increasing use of medicinal plants in the treatment and prevention of diseases has attracted the attention of researchers. The aim of this work was to investigate the probiotic properties and antibacterial and antifungal activity of silymarin-enriched Lactobacillus bacteria against several important pathogenic bacteria and also Aspergillus flavus as one of the harmful molds in the food and health industries. For this purpose, 52 g-positive and catalase-negative bacteria were isolated from 60 traditional curd samples from Ilam province. Five of the 52 bacterial strains had more than 90% viability in high bile salt and acidic conditions and were selected for further investigation. The five strains with positive results showed good hydrophobicity (≥ 50.30%), auto-aggregation (≥ 53.70%), coaggregation (≥ 28.20%), and high cholesterol removal ability (from 09.20 to 67.20%) and therefore can be considered potential probiotics. The tested strains displayed acceptable antibacterial and antifungal activity against all 12 pathogenic bacteria and A. flavus. Also, the results of the simultaneous antifungal activity of probiotic strains and silymarin showed that the combination of silymarin and probiotics has a significantly better (P < 0.05) antifungal effect than the control group or the probiotic groups alone. Interestingly, in addition to the Limosilactobacillus fermentum C3 strain, the Limosilactobacillus fermentum C18 and Lactiplantibacillus pentosus C20 strains also had significant inhibitory effects against A. flavus when used with silymarin extract in methanol. Meanwhile, silymarin extract in DMSO and PEG increased the antagonistic activity of all five potential probiotic strains.

Effects of mechanical grinding on the physicochemical properties of silica aerogels

Mechanical grinding is a facile method to get silica aerogels (SAs) with various particle sizes. However, the relationship between the grinding parameters and physicochemical properties is still unclear. In this study, we concentrated on the effects of grinding time and grinding speed on the physical and chemical properties of silica aerogels. The results reveal that the physicochemical properties of silica aerogels are more sensitive to the grinding speed rather than the grinding time. When the grinding speed is over 200 rpm, large particles of silica aerogels are crushed into smaller particles with obviously decreasing particle sizes and the silica skeletons of silica aerogels have collapsed. The reduction of particle sizes and the collapse of skeleton lead to an increase in both the tap density and thermal conductivity. Therein, the thermal conductivity is positively proportional to the density. Furthermore, the grinded silica aerogels powders still possess the contact angles over 135°, indicating the good hydrophobicity. All these demonstrate that the mechanical grinding has evident effects on the microstructure, density, thermal conductivity and particle sizes, which further impact the performance of silica aerogels during the practical applications. Given the expanding applications of SAs across various industries, the study serves as a valuable reference for optimizing the mechanical post-treatment of SAs, facilitating the achievement of desired particle sizes. Ultimately, this research holds great potential in diversifying the application fields of SAs in their powdered form.