Boron nitride/epoxy resin nanocomposites: development,characterization and functionality

Journal of Thermal Analysis and Calorimetry - Polymer matrix composites with embedded ceramic nanoparticles receive not only enhanced scientific but also technological interest, due to their...     

Analysis of the acid and alkali resistance of superhydrophobic paper mulch

Agricultural paper mulch is an indispensable part of modern agriculture. It had the functions of heat preservation, moisture preservation, insect resistance, disease prevention, and weed growth inhibition. In order to extend the service life of the paper mulch, we use the solution immersion method to modify the surface of the paper mulch. A super-hydrophobic paper mulch is mainly prepared by using hydrophobic silica. The static contact angle of the super-hydrophobic paper mulch with water is 160.6°. The super-hydrophobic paper mulch samples were immersed in acid solution (pH?=?4.6 H₂SO₄) and alkaline solution (pH?=?8.5 NaOH). The main instruments are contact angle tester, tensile testing machine and high-speed camera. The hydrophobic properties, mechanical properties and rebound properties of the two kinds of paper mulches were compared. The results showed that the tensile strength and droplet bounce height of the superhydrophobic paper mulch decreased after being soaked in acid or alkaline solution for 48 h. The mass loss rate of paper mulch was more significant in acid solution, but its contact angle was still greater than 145°, and it had good bounce performance. After observing the microscopic morphology of its surface, it was found that silica had a micro-rough structure on the surface of the paper mulch. The method was simple and environmentally friendly, and can alleviate the problem of poor acid and alkali corrosion resistance of the paper mulch, and had extraordinary significance for environmental protection.

     

Investigation on surface properties of superhydrophobic nanocomposites based on polyvinyl chloride and correlation with cell adhesion behavior

The main aim was to study the roles of structural homogeneity and superhydrophobicity on the adhesion of SW colon cancer cells on the surface of polyvinyl chloride (PVC) nanocomposites. Concurrent use of a proper nonsolvent (ethanol) and silica nanoparticles resulted in superhydrophobic behavior and also different surface structures. The effect of added‐ethanol content on the surface properties of PVC nanocomposites was also studied. The synergetic combination of silica and ethanol has led to the formation of a porous surface layer resulting in a considerable boost in the hydrophobic behavior. The scanning electron microscopy, roughness, and X‐ray photoelectron spectroscopy (XPS) analysis results were all in total agreement indicating the substantial change in surface morphology, topography, and composition once the ethanol content was increased to 50 vol.%. The surface structure was notably changed by the addition of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles. It was found that the induced inhomogeneity as a result of POSS addition had an adverse effect on the surface properties. In conclusion, superhydrophobicity could be regarded as a prerequisite for achieving cell‐repellent behavior, but it cannot guarantee a cell repellent surface especially if the surface layer possesses structural inhomogeneity.     

Electrical and rheological percolation of PMMA/MWCNT nanocomposites as a function of CNT geometry and functionality

Composites of poly(methyl methacrylate) (PMMA) with multi-walled carbon nanotubes (MWCNT) of varying aspect ratio and carboxylic acid functionality were prepared using melt mixing. The extent of dispersion and distribution of the MWCNTs in the PMMA matrix was investigated using a combination of high-resolution transmission electron microscopy (HRTEM), wide-angle X-ray diffraction (XRD) and Raman spectroscopy. The electrical resistivity and oscillatory shear rheological properties of the composites were measured as a function of MWCNT geometry, functionality, and concentration. The fundamental ballistic conductance of the pristine free-standing MWCNTs was investigated using a mechanically controlled break-junction method. The electrical conductivity of PMMA was enhanced by up to 11 orders of magnitude for MWCNT concentrations below 0.5 wt.%. MWCNTs having higher aspect ratio, above 500, or functionalized with carboxylic acid groups readily formed rheological percolated networks with thresholds, determined from a power law relationship, of 1.52 and 2.06 wt.%, respectively. The onset of pseudo-solid-like behaviour and network formation is observed as G′, η∗, and tan δ⁻¹ are independent of frequency as MWCNT loading increased. Sufficiently long and/or functionalized tubes are required to physically bridge or provide interfacial interactions with PMMA to alter polymer chain dynamics. Carboxylic acid functionalization disrupts the crystalline order of MWCNTs due to a loss of π-conjugation and electron de-localisation of sp² C-C bonds resulting in non-ballistic electron transport in these tubes, irrespective of how highly dispersed they are in the PMMA matrix.     

One‐step immersion method for fabricating superhydrophobic aluminum alloy with excellent corrosion resistance

This work develops a facile one‐step immersion method for preparing the superhydrophobic aluminum alloy, i.e. the aluminum alloy is treated with stearic acid (STA)–ethanol–H₂O solution at 60 °C for 35 h. Results show that the aluminum alloy achieves flower‐like structure with both a great deal of pillars and pores, while the long hydrophobic alkyl chains are chemically grafted onto the hierarchical surface. Meanwhile, the water contact angle at the aluminum alloy surface gradually enhances with the decrease of the ethanol–H₂O volume ratio, and the water contact angle and rolling angle of 156.2° and 5°, respectively, are obtained when the ethanol–H₂O volume ratio is 1:3. Moreover, results show that the higher water contact angle at the aluminum alloy, the better corrosion resistance of the aluminum alloy. Consequently, the aluminum alloy with the superhydrophobic property has the best corrosion resistance, durability, and stability in corrosive environments. Copyright © 2016 John Wiley & Sons, Ltd.     

Creation of coating surfaces possessing superhydrophobic and superoleophobic characteristics with fluoroalkyl end-capped vinyltrimethoxysilane oligomeric nanocomposites having biphenylene segments

Fluoroalkyl end-capped vinyltrimethoxysilane oligomeric nanocomposites having biphenylene units [R(F)-(VM-SiO(2))(n)-R(F)/Ar-SiO(2)] were prepared by the sol-gel reaction of the corresponding oligomer [R(F)-(VM)(n)-R(F)] with 4,4'-bis(triethoxysilyl)-1,1'-biphenyl [Ar-Si(OEt)(3)] under alkaline conditions. R(F)-(VM-SiO(2))(n)-R(F)/Ar-SiO(2) nanocomposites were applied to the surface modification of PMMA to exhibit not only a good oleophobicity imparted by fluorine but also a fluorescent emission ability on the surface. Methanol sol solutions of R(F)-(VM-SiO(2))(n)-R(F)/Ar-SiO(2) nanocomposites were effective for the surface modification of glass through the dipping technique to exhibit good oleophobicity with superhydrophobicity on the modified glass surface. On the other hand, 1,2-dichloroethane sol solutions enabled R(F)-(VM-SiO(2))(n)-R(F)/Ar-SiO(2) nanocomposites to exhibit both superhydrophobic and superoleophobic characteristics on the modified surface through dipping the glass in these sol solutions.     

Formation of superhydrophobic cerium oxide surfaces on aluminum substrate and its corrosion resistance properties

Superhydrophobic cerium oxide film was introduced to aluminum substrate by an in‐situ growth process and surface modification. Different molar ratios between Ce(NO₃)₃ · 6H₂O and C₆H₁₂N₄ were involved in this research. The morphologies, chemical compositions and wetting properties of the films were analyzed by scanning electron microscopy (SEM), energy dispersive X‐ray detector, Fourier transfer infrared spectrometer and water contact angle (WCA) measurement, respectively. A great WCA of 158.8^o with a low angle hysteresis of about 3^o was obtained. Combination of uniform hierarchical micro‐nanostructure as revealed by SEM together with the hydrophobic alkyl groups from stearic acid was found to be responsible for the superior superhydrophobic property. The corrosion resistance performance of the superhydrophobic surface was evaluated by immersing in sodium chloride aqueous solution, the WCA kept as high as 152.1^o after immersion for 21 days, indicating our superhydrophobic surfaces had high chemical stability and durability in corrosive medium. Copyright © 2013 John Wiley & Sons, Ltd.     

PVC-laponite nanocomposites: Enhanced resistance to UV radiation

Laponite, a clay mineral, was treated by intercalation of two different phthalocyanine amide polymers based on aliphatic amine (MF-PcAl) as well as an aromatic one (MF-PcAr). The intercalation of the amide polymers was followed by X-ray diffraction (XRD). The different forms of laponite even in its untreated form were incorporated into poly(vinyl chloride) (PVC) formulations via melt blending method to produce PVC-laponite nanocomposites of exfoliated type which was confirmed by XRD. The stabilization mode of the incorporated laponites against UV radiation is discussed based on scanning electron microscopy (SEM), XRD, UV-vis absorption and transmission spectra, electron paramagnetic resonance (EPR), differential scanning calorimetry (DSC) and mechanical properties. Improved resistance to the UV degradative effect was explained on the light of the ability of the clay to scatter the light and to trap any growing radicals as well in addition to the sacrificing role of phthalocyanines by absorbing the incident light on the expense of the PVC and transmitting the rest of the light in another non-harmful form such as heat.     

Recyclable grease-proof cellulose nanocomposites with enhanced water resistance for food serving applications

Cellulose - Recyclable cellulose nanofibril (CNF) and lignin-containing cellulose nanofibril (LCNF) coated wood flour composites were fabricated using a vacuum-filtration process for food serving...     

Wear resistance of electrolytic nickel-boron alloy deposited from a chloride electrolyte

Dependence of the wear resistance of an electrolytic nickel-boron alloy deposited from a chloride electrolyte on the alloy composition, thermal treatment temperature, and specific load on friction surfaces was studied.     

Completely superhydrophobic PDMS surfaces for microfluidics

This study presents a straightforward two-step fabrication process of durable, completely superhydrophobic microchannels in PDMS. First, a composite material of PDMS/PTFE particles is prepared and used to replicate a master microstructure. Superhydrophobic surfaces are formed by subsequent plasma treatment, in which the PDMS is isotropically etched and PTFE particles are excavated. We compare the advancing and receding contact angles of intrinsic PDMS samples and composite PTFE/PDMS samples (1 wt %, 8 wt %, and 15 wt % PTFE particle concentration) and demonstrate that both the horizontal and vertical surfaces are indeed superhydrophobic. The best superhydrophobicity is observed for samples with a PTFE particle concentration of 15 wt %, which have advancing and receding contact angles of 159° ± 4° and 158° ± 3°, respectively.     

Water droplet bouncing--a definition for superhydrophobic surfaces

The ability of water to bounce on a surface provides an indication of many of the surface's properties. The technique described in this article uses water bouncing to determine the hydrophobicity of a surface, with a relationship established between water contact angle and number of bounces, which is dependent on the surfaces microstructure.     

Epoxy-POSS/silicone rubber nanocomposites with excellent thermal stability and radiation resistance

Due to the rigid Si-O-Si backbone, silicone rubber (SR) have a widespread application in extreme environment such as high temperature and high-level radiation. However, the radiation stability of SR still does not meet the practical needs in special radiation environments. Herein we prepared epoxy POSS(ePOSS)/SR nanocomposites with excellent thermal stability and radiation resistance. As a physical crosslinking point in the SR, addition of small amount of ePOSS not only enhanced the mechanical properties of the matrix, but also improved its thermal stability greatly due to their good compatibility. ePOSS/SR had higher radiation stability in air than SR owing to the inhibition of radiation oxidation by ePOSS, and the yield of main gaseous radiolysis products (CH₄, H₂, CO and CO₂) of SR and ePOSS/SR nanocomposites was determined. By analyzing the changes of chemical structure, thermal properties and mechanical properties of the ePOSS/SR nanocomposite, combined with the characteristics of gas products after γ-irradiation, the radiation induced crosslinking and degradation mechanism of the nanocomposites was proposed comprehensively.     

Decoupling the effects of screw speed and particle surface functionality on the filler suspension state in PBS/fumed silica nanocomposites

This work assessed the relative effects of processing conditions and interfacial interactions on the structure and properties of PBS/fumed silica nanocomposites. Rheology and scattering were used to investigate the dispersion state of silica particles with different surface treatments in nanocomposites produced by ultra‐high speed twin‐screw extrusion. Structural parameters of the silica, such as fractal dimension and Fisher exponent, were estimated by low‐frequency rheology responses and lower q scattering data. This study demonstrates that both decreased bulk polymer properties and improved filler suspension caused by high shear compounding determine the final properties of these PBS based nanocomposites. While the molecular weight of bulk polymer matrix was significantly reduced, the extreme shear increased the probability of forming percolated clusters, leading to remarkable reinforcement (up to 4000%) as evidenced by the low‐frequency rheological response. Further, the improvement in dispersion was enhanced when the filler was functionalized with a compatibilizing surface treatment. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1820–1828