Jianbing Hu

Enhanced Dielectric and Mechanical Properties of Ternary Composites via Plasticizer-Induced Dense Interfaces

High overall performance, including high dielectric constant, low loss, high breakdown strength, fine flexibility, and strong tensile properties, is difficult to achieve simultaneously in polymer nanocomposites. In our prior work, we modified the surfaces of alpha-SiC nanoparticles and chemically cross-linked the polymeric matrix to simultaneously promote the dielectric and mechanical properties of composites. In this work, a novel strategy of high-temperature plastification towards a polymeric matrix has been proposed to fabricate ternary nanocomposites with balanced dielectric and mechanical characteristics by the solution cast method in order to reduce costs and simplify steps during large-scale preparation. Poly(vinylidene fluoride-chlorotrifluoroethylene) with inner double bonds as matrix, unfunctionalized alpha-SiC nanoparticles (NPs) as filler, and dibutyl phthalate (DBP) as plasticizer were employed. By introducing DBP and high-temperature treatment, the dispersion of NPs and the degree of compactness of the interface regions were both improved due to the reduced cohesion of the fluoropolymer, resulting in an increase in the dielectric constant (by 30%) and breakdown strength (by 57%) as well as the lowering of loss (by 30%) and conductivity (by 16%) in nanocomposites. Moreover, high-temperature plastification contributed to the promotion of flexible and tensile properties. This work might open the door to large-scale fabrication of nanocomposite dielectrics with high overall properties through the cooperation of the plasticizer and high temperature.

Significantly Elevated Dielectric and Energy Storage Traits in Boron Nitride Filled Polymer Nano-composites with Topological Structure

Interface induced polarization has a prominent influence on dielectric properties of 0–3 type polymer based composites containing Si-based semi-conductors. The disadvantages of composites were higher dielectric loss, lower breakdown strength and energy storage density, although higher permittivity was achieved. In this work, dielectric, conductive, breakdown and energy storage properties of four nano-composites have been researched. Based on the cooperation of fluoropolymer/alpha-SiC layer and fluoropolymer/hexagonal-BN layer, it was confirmed constructing the heterogeneous layer-by-layer composite structure rather than homogeneous mono-layer structure could significantly reduce dielectric loss, promote breakdown strength and increase energy storage density. The former worked for a larger dielectric response and the latter layer acted as a robust barrier of charge carrier transfer. The best nano-composite could possess a permittivity of 43@100xa0Hz (~u20093.3 times of polymer), loss of 0.07@100xa0Hz (~u200937% of polymer), discharged energy density of 2.23xa0J/cm3@249xa0kV/cm (~u200910 times of polymer) and discharged energy efficiency of 54%@249xa0kV/cm (~u20095 times of polymer). This work might enlighten a facile route to achieve the promising high energy storage composite dielectrics by constructing the layer-by-layer topological structure.Graphical Abstract

Superhydrophobic nanocomposite coatings with photoinitiated three-dimensional networks based on reactive graphene nanosheet-induced self-wrinkling patterned surfaces

HYPOTHESISnBionic superhydrophobicity including high contact angle, low sliding angle and nonstick property, combined with both strong pH and ultraviolet (UV) resistance, is difficult to simultaneously achieve for large-scale preparation of superhydrophobic surfaces by blending polymer with a nonreactive inorganic nanofiller.nnnEXPERIMENTSnA series of high pH and UV-irradiation-resistant superhydrophobic nanocomposite films were prepared through UV-light-assisted chemical cross-linking among ternary components under nitrogen protection. Ethoxylated bisphenol A diacrylate, 2-(perfluorooctyl) ethyl acrylate, reactive thiol-coupled graphene nanosheets and photoinitiator were evenly mixed, followed by UV-irradiation curing.nnnFINDINGSnAbundant 3D networks could be formed. A robust self-wrinkling surface morphology was formed due to a UV-curing-induced inner tension in the composites, 2D morphology-induced flexibility for graphene nanosheets and fluorine-bearing component-induced phase separation at the wetted surfaces. High roughness and use of the fluorine element endows the surfaces with superhydrophobicity and oleophobicity. A favorable nonstick performance was obtained. Superhydrophobicity could be maintained despite changing the film-forming substrate, pH of soaking solutions from 1 to 12, or use of a prolonged UV-irradiation time reaching 120u202fh. Therefore, both superhydrophobicity/oleophobicity and strong pH/UV resistance are finely balanced. This work might open up the way for large-scale fabrication of promising superhydrophobic surfaces.

Enhancing High-Frequency Dielectric Properties of Beta-SiC Filled Nanocomposites from Synergy between Percolation and Polarization

Promising comprehensive properties, including high permittivity, low dielectric loss, high breakdown strength, low electrical conductivity, and high thermal conductivity, are very hard to simultaneously obtain in high-frequency applicable polymer nanocomposite dielectrics. Instead of traditional electric percolation, in this work, a novel route based on a synergy between electric percolation and induced polarization has been raised to prepare 0–3 type nanocomposites with an enhanced high permittivity (high-k) property and low loss at high frequency. This work aimed at optimizing that synergy to achieve the favorable properties mentioned above in composite dielectrics used at high frequencies such as 1 MHz and 1 GHz. Conductive beta-SiC nanoparticles with a particle size of ~30 nm were employed as filler and both insulating poly(vinyl alcohol) and polyvinyl chloride were employed as polymer matrices to construct two composite systems. Utilizing polyvinyl chloride rather than poly(vinyl alcohol) realizes higher comprehensive electrical properties in composites, ascribed to optimization of that synergy. The optimization was achieved based on a combination of mild induced polarization and polarization-assisted electric percolation. Therefore, this work might open the way for large-scale production of high-frequency applicable composite dielectrics with competitive comprehensive electrical properties.

Robust wear and pH endurance achieved on snake-shaped silica hybrid nanowire self-woven superamphiphobic membranes with layer-stacked porous 3D networks

Bio-inspired superamphiphobicity, including high contact angles, low sliding angles and non-stick traits, in combination with high durability, such as strong wear resistance, pH endurance and mechanical properties, are difficult to simultaneously obtain in the large-scale fabrication of amphiphobic materials with the presently used blends of polymers and surface-modified hard inorganic nanoparticles. In the current work, a series of highly abrasion-resistant superamphiphobic membranes applicable in a wide pH range were fabricated by a facile vacuum filtration process from suspensions containing snake-shaped silica hybrid nanowires. Tetraethyl orthosilicate, trimethoxyoctadecylsilane and 2-perfluorooctylethyltrimethoxysilane monomers were hydrolyzed and condensed to yield silica nanowires through finely regulated anisotropic sol–gel growth in a water/oil emulsion. The snake-shaped morphology, aspect ratio and elemental distribution of the nanowires were tailored to endow them with strong self-assembly capacity due to capillary force action. As a result, a porous 3D network morphology and hierarchical structure were achieved across the entire membrane thickness based on the self-weaving behavior of the nanowires. Superamphiphobicity was acquired, including a maximum water contact angle (WCA) of ca. 162° and an oil contact angle (OCA) of ca. 155°. The water sliding angle (WSA) and oil sliding angle (OSA) were less than 5°. Desirable non-stick, anti-fouling, flexible and self-standing traits were obtained. Well-maintained superamphiphobicity was observed in a wide pH range (1 to 12). After 300 abrasion cycles, the superamphiphobicity was retained due to the porous 3D network morphology and hierarchical structure across the whole membrane thickness. Therefore, excellent superamphiphobicity and damage tolerance were finely balanced on the surfaces of these nanowire membranes. This work may enable large-scale preparation of promising superamphiphobic surfaces.

Study on affecting factors of curing rate in ultraviolet curing adhesives containing modified acrylic ester prepolymers

Ultraviolet (UV) curing adhesives have been extensively utilized in fields of health care and electronic components due to low energy consumption and solvent pollution. The most used system is modi...

Highly Retained Electric and Mechanical Traits in Micron-Sized Glass Fibers Filled Epoxy Composite Based on Heat-Oxygen Ageing

The epoxy based composite materials with a high ageing resistance property have attracted a wide attention in the field of high-electric-insulation electronic packaging. However, both of the highly retained electrical and mechanical performances are difficult to simultaneously achieve in composite materials once a longer heat-oxygen ageing at a high temperature is applied onto the materials. In order to realize the ageing-resistant high mechanical, electric breakdown and dielectric properties simultaneously in composite, in this work, an epoxy based composite filled with the high-insulation micron-sized glass fiber filler has been prepared, and its shock resistance strength, electric breakdown strength, dielectric constant, dielectric loss and conductivity after a severe heat-oxygen ageing have been investigated in detail, compared with that before the ageing. Although the ageing was operated at 150xa0°C for 25xa0days, the electric and mechanical properties of the composite were still finely retained, including 60% retention for shock resistance strength, 70% for breakdown strength, 80% for dielectric constant, dielectric loss below 0.1 and conductivity below 2u2009×u200910−9xa0Sxa0cm−1. The epoxy matrix and glass fiber filler were responsible for the small decline and high retention for the properties in composite, respectively. This work might open the way for the large-scale preparation of the promising epoxy based composites with the highly retained ageing-resistant electric and mechanical properties based on incorporating the high-insulation fiber fillers.

Study on gel weight fraction of ultraviolet-cured acrylic adhesives

Ultraviolet (UV)-cured adhesives have attracted plenty of attention in the fields of health care and electronic components thanks to low energy loss and environment pollution. UV-cured adhesives bearing epoxy acrylate prepolymers have been extensively utilized, ascribed to low cost and high stability. However, the gel content of UV-cured adhesives has hardly been investigated in detail. The gel content has been found to strongly affect the mechanical properties and serving life of adhesives. We have found the strong composition dependence of adhesive performances of UV-cured adhesives before. To clarify the influencing factors of gel content in UV-cured adhesives containing epoxy acrylate prepolymers, in this work, a family of UV-cured adhesives with epoxy acrylate constituents have been elaborately designed and further fabricated. The influences of prepolymer kind, UV photoinitiator kind, UV photoinitiator concentration, reactive diluent concentration, feed style during preparing prepolymers and film thickness on gel weight fraction of cured adhesive films were deeply researched. This work might open the door to the large-scale preparation of promising high-performance UV-cured adhesives with a higher gel weight fraction based on regulating the formula.Graphical Abstract