Improvement of interfacial adhesion between wood and polypropylene in wood–polypropylene composites

N-vinylformamide-grafted polypropylene (VFPP) was successfully synthesized through a free radical grafting reaction. Both polymeric methylene diphenyl diisocyanate (PMDI) and VFPP were effective compatibilizers for increasing both the strength and stiffness of the resulting wood–PP (polypropylene) composites. Both the modulus of rupture (MOR) and the modulus of elasticity (MOE) of the resulting wood–PP composites were further increased when PMDI and VFPP were used together as an integrated compatibilizer system. This new PMDI-VFPP compatibilizer system was comparable to maleic-anhydride-grafted polypropylene in terms of enhancing the strength and stiffness of the wood–PP composites. Study of the fractured surfaces of the wood–PP composites with scanning electron microscopy revealed that this new PMDI-VFPP compatibilizer system greatly improved the interfacial adhesion between wood and PP. This PMDI-VFPP compatibilizer system also greatly reduced the water absorption of the resulting wood–PP composites. In this PMDI-VFPP compatibilizer system, PMDI is proposed to function as a wood-binding domain and VFPP to function as a PP-binding domain. PMDI reacted with the amide group in VFPP, thus forming covalent linkages between PMDI and VFPP.     

Influence of mineral species on oil–soil interfacial interaction in petroleum-contaminated soils

The mineral species in soils vary in a wide variety of places,thus resulting in the petroleumcontaminated soil(PCS) with complex characters.Thus,the research on the effect of mineral species on oil-soil interactions in PCS takes on a critical significance.In this study,the desorption and adsorption behaviors of aromatic hydrocarbons(Ar) on two minerals surfaces were examined.Meanwhile,the interfacial forces between minerals and Ar were studied and the sources of these forces were analyzed.Moreov...     

Improving interfacial compatibility by a micro–nano synergetic structure for high-performance epoxy composites

A multiscale functional filler of micro–nano synergetic structure was successfully prepared via in-situ growth of silica (SiO₂) on biomimetic dopamine modified carbon fiber (CF) surface. The CF-SiO₂ hybrid as a reinforcement possessed lubricating and reinforcing effect to enhance tribological performance, thermal stability and thermomechanical property of epoxy (EP) composites. The micro–nano synergetic structure was of great importance for ameliorating the compatibility and interfacial adhesion between CF and EP matrix, which was conductive to transferring stress from matrix to fiber and alleviating stress concentration. It was concluded that the friction coefficient and wear rate of EP/CF-SiO₂ were 0.382 and 1.12 × 10⁻⁵ mm³/N·m, that is, a decline of 58% and 2.5 times, respectively, compared to EP/CF. The CF-SiO₂ hybrid exhibited excellent friction-reducing and anti-wear performance.     

An experimental investigation on the interfacial waves in air-water two-phase flow within horizontal pipelines

By using two-parallel conductance probes,the instantaneous film thickness of gas-liquidtwo-phase flow within a horizontal plexiglass pipe of 50mm inner diameter was experimentallymeasured.The pipe was 6680mm long.Several wave patterns were distinguished through statisticalanalysis of signals of film thicknesses.Wave pattern maps were obtained and compared with resultsof former studies.The characteristics of the interfacial waves,such as time-averaged film thickness,wave height,wave propagation speed,wavelength and wave frequency,were systematically investigated.The effect of the exit structure of the test section on interfacial waves was experimentally examined.     

Properties and interfacial bonding of regenerated cellulose films coated with polyurethane–chitosan IPN coating

Water-resistant films were prepared by coating a castor oil-based polyurethane–chitosan (PU–CH), in which grafted interpenetrating polymer networks (IPNs) were produced, on a regenerated cellulose (RC) film. The tensile strengths of the coated films cured at 90°C for 5 min reached 853 kg cm⁻² (dry state) and 503 kg cm⁻² (wet state) and were obviously higher than those of the films of uncoated and coated with PU coating. Moreover, the coated films have excellent water resistivity, low vapor permeability, and good size stability, and their optical transmittance is even better than that of the RC film in the range of 400–800 nm. The interfacial structure of the coated films was investigated by using spectroscopy infrared, ultraviolet spectroscopy, transmission electron microscopy, and electron probe microanalysis. It was shown that the strong interfacial bonding with chemical and hydrogen bonds between the RC film and the coating exists. The PU prepolymer in the IPN coating penetrated through the interface into the RC film and partly crosslinked with the cellulose, forming a semi-IPNs. The chitosan in the PU–CH coating plays an important role not only in accelerating the cure of the coating but also in improving the mechanical properties and biodegradability of the coated film. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1313–1319, 1998     

Protein–polymer interaction: Transfer loading at interfacial region of PES-based membrane and BSA

The adsorption of proteins onto polymeric surfaces is encountered in many natural and industrial processes and is a prerequisite to their efficient identification, separation, and purification by methods such as chromatography, and filtration. Nevertheless, the exact nature of the adsorption mechanisms and interfacial interactions is not easy to identify for a given protein–polymer system. Here, we aim to document the adsorption mechanism of a protein–polymer system by investigating the adsorption as well as desorption phenomenon of a protein [bovine serum albumin (BSA)] from the polymeric surface [polyethersulfone (PES)]. The analyses performed to document the adsorption mechanism of the BSA–PES system include scanning electron microscope (SEM), attenuated total reflection-Fourier transform infrared (FTIR), contact angle, zeta potential, surface charge density measurement, and Derjaguin–Landau–Verwey–Overbeek (DLVO). Here, SEM and FTIR identified the physical and chemical properties of pure PES and PES–BSA membranes. The low water contact angle of the PES–BSA membrane confirms its applicability for tissue engineering applications. Further, the zeta potential, surface charge density measurement, and DLVO analyses were performed to document the adsorption mechanism. The adsorption of BSA particles on the PES surface was carried out for pH values that ranged from 4 to 10 for contact times that ranged from 1 to 3 days. A monotonic increase in the zeta potential of the PES–BSA system indicated considerable adsorption of BSA particles on the PES surface. Further, BSA adsorption was very strong for pH values greater than 4.7 which confirms to strong electrostatic interactions between BSA and PES. The strong electrostatic interaction is also collaborated by low desorption rate, which was only ∼22% for pH 10 after 3 days of contact. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47931.     

Modeling of Rayleigh convection in gas–liquid interfacial mass transfer using lattice Boltzmann method

Interfacial Rayleigh convection can be generated by concentration gradient near the interface in mass transfer processes. In the present study, a 2D time-dependent lattice Boltzmann method (LBM) with a double distribution model was established for simulating the liquid-phase Rayleigh convection in the mass transfer process of CO₂ absorption into various solvents. Two random parameters P and C_D denoting respectively the possibility and the magnitude of concentration perturbation at interface were introduced to model the interfacial disturbance, which is known as one of the necessary conditions of onset of Rayleigh convection. The values of the parameters were identified (0.05 ≤ P < 0.3 and 0 < C_D ≤ 10⁻⁹ kg m⁻³) by comparing simulated critical onset times of the Rayleigh convection with the experimental result from Blair and Quinn (1969) and theoretical predictions proposed by Kim et al. (2006) and 0245 and 0250. The maximum penetration depths, maximum transient Rayleigh numbers, and critical times for the onset of Rayleigh convection were obtained by the proposed model. The simulations captured the detailed information of the onset and the temporal–spatial evolution of Rayleigh convection, and gave the concentration contours of typical plume convection patterns which were well consistent with literatures. Enhancement of mass transfer by the Rayleigh convection was also demonstrated by comparing the simulated instantaneous mass flux across the interface with that predicted by penetration theory.     

In situ synthesis and interfacial bonding mechanism of SiC in MgO–SiC–C refractories

Adding SiC directly to MgO–C refractories possesses the disadvantages of low dispersion and interfacial bonding strength. Herein, the in situ synthesized SiC was introduced into the MgO–SiC–C refractories to maintain the original excellent performance of MgO–C refractories and reduce the carbon dissolution in molten steel. With the increase of Si and C content in raw materials, the morphology of SiC changed from whisker to network, whose growth mechanism was vapor–solid and vapor–liquid–solid. The network structure and uniform distribution of SiC improved the thermal shock resistance of MgO–SiC–C refractories. According to the analysis of molecular dynamics simulation by Materials Studio software, SiC strengthened the relationship between periclase and graphite to enhance the structure of the compound.     

Improving the interfacial properties of carbon fiber–epoxy resin composites with a graphene-modified sizing agent

We successfully prepared a graphene-modified carbon fiber (CF) sizing agent with good dispersity and stability by dispersing reduced graphene oxide (RGO) into an emulsion-type sizing agent. RGO was obtained by the reduction of graphene oxide (GO) with the help of gallic acid. The influence of the graphene-modified sizing agent on the interfacial properties of the CF–epoxy resin composites was investigated with microbond testing and the three-point bending method. The results show that optimized interfacial properties were achieved when the size of the modified graphene was less than 1 μm, the content of RGO was 20 ppm, and the pH value of the sizing agent was 10.5. The interfacial shear strength of the composites reached 92.3 MPa, which was 29.6% higher than that of the composites with unmodified CFs. Compared with commercial-CF-fabric-reinforced composites, the interlaminar shear strength of the composites treated with the RGO-modified sizing agent increased by 21.5%. Both the interfacial and interlaminar failure morphologies of the composites were examined with scanning electron microscopy (SEM). The results show that a large amount of residual resin adhered to the surfaces of the CFs treated with the RGO-modified sizing agent; this indicated good interfacial properties between the CFs and the resin matrix. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47122.     

Low interfacial tension liquid–liquid extraction with impinging-jets contacting method: Influencing parameters and relationship

Liquid–liquid extraction process with the recommended low interfacial tension chemical system of butanol–succinic acid–water was performed in a two impinging-jets contacting device (TIJCD), working continuously with opposed impinging jets. A range of extraction efficiency of 58–96% was achieved under different conditions. Overall volumetric mass transfer coefficient and specific power input criteria clearly indicate the great performance capability of TIJCD. An increase in nozzle diameter and/or jets force results an efficiency enhancement, while increase in inter-nozzle distance leads the efficiency diminish. The overall volumetric mass transfer coefficient was satisfactorily correlated in the form of ordinary and dimensionless correlations.     

Controlled growth of ZnO/Zn₁-xPbxSe core-shell nanowires and their interfacial electronic energy alignment

ZnO/Zn(1-x)Pb(x)Se core-shell nanowires (NWs) have been synthesized by a solution based surface ion transfer method at various temperatures. The energy dispersive spectroscopic (EDS) mapping of single NWs suggests that the Zn, Pb and Se atoms are uniformly distributed in their shell layers. The ternary Zn(1-x)Pb(x)Se layers with tunable bandgaps extend the band-edge of optical absorption from 450 nm to 700 nm contrasting with the binary ZnSe layers. The ultraviolet photoelectron spectroscopic (UPS) analysis reveals a transition from the type I to type II band alignment when the x fraction decreases from 0.66 to the value of 0.36 in the nanoshell layers. This quantitative investigation of electronic energy levels at ZnO and Zn(1-x)Pb(x)Se interfaces indicates that the proper type II band alignment is well suited for photovoltaic energy conversion. The photovoltaic cells comprising a ZnO/Zn(1-x)Pb(x)Se nano-heterojunction with the optimized Pb content are expected to be more efficient than the devices sensitized by binary ZnSe or PbSe.     

Separation of liquid–liquid dispersion in a batch settler: CFD-PBM simulations incorporating interfacial coalescence

Several commercially important chemical processes involve liquid–liquid phase separation. In the present work, we have developed a multi-fluid Eulerian CFD model using OpenFOAM that incorporates binary and interfacial coalescence processes. We simulated separation of kerosene dispersed in water in a batch settler and validated the predictions using the measurements of time-evolution of coalescing and settling interfaces, local dispersed-phase volume fraction (α_O) and drop size distribution (DSD). Simulations are performed to understand the contributions of binary and interfacial coalescence processes to the phase separation process. While the time-evolution of coalescing and settling fronts can be predicted reasonably well using the two-fluid model with empirically-corrected drag models, local α_O and DSD could not be predicted. We have shown that the comprehensive multi-fluid Eulerian model, which incorporates binary and interfacial coalescence, predicts the time-evolution of the coalescing and settling fronts, local α_O and the DSD in an excellent agreement with the measurements.     

The gap between the measured and calculated liquid–liquid interfacial tensions derived from contact angles

We present our new findings about the causes of discrepancies between the measured and calculated liquid-liquid interfacial tensions derived from contact angles. The calculated ones are based on either the equation developed by Fowkes or that by van Oss, Chaudhury and Good (VCG), while the measured ones are based on the sessile drop, weight-volume by Jańzuk et al. and the axisymmetric drop shape analysis (ADSA) by Kwok and Neumann. Indeed, there are deviations between the calculated and measured results. For an immiscible liquid-liquid or liquid-solid interface, we prefer to employ Harkins spreading model, which requires the interfacial tension to be constant. However, for the initially immiscible liquid-liquid pairs, we propose an adsorption model, and our model requires the interfacial tension to be varying and the surface tensions of bulk liquids at a distance from the interface to remain unchanged. Thus, the difference between the initial and final interfacial spreading coefficients (S_i) equals the equilibrium interfacial film pressure (π_i)_e. According to our findings, the calculated interfacial tension represents the initial value (γ₁₂)_o, which differs from the equilibrium value (γ₁₂)_e obtained experimentally after some time delay. This expected gap at a reasonable time frame is chiefly caused by the equilibrium interfacial film pressure between the two liquids. The initial (or calculated) interfacial tension can be positive or negative, while the equilibrium (or measured) one can reach zero. In fact, the former is shown to have more predictive value than the latter. A negative initial interfacial tension is described to favor miscibility or spontaneous emulsification but it tends to revert to zero instantaneously. Thus, a miscible liquid mixture should have zero interfacial tension. In response to recent papers by Kwok et al., we show that the disagreements between the calculated and measured interfacial tensions are definitely not caused by the failure of the VCG approach. Correct interfacial tensions are calculated for liquid pairs containing formamide or dimethyl sulfoxide (DMSO) by using the dispersion components cited in Fowkes et al.'s later publication. With the corrected surface tension components, the equilibrium interfacial film pressures (π_i)_e's for at least 34 initially immiscible liquid pairs have been calculated. These values are generally lower than the corresponding spreading pressures π_e's obtained by others using the Harkins model. Recently, we established a relationship between these two film pressures with the Laplace equation and found a new criterion for miscibility to be (π_i)_e = π_e.     

Local bubble size distribution,gas–liquid interfacial areas and gas holdups in an up-flow ejector

Particle image velocimetry (PIV) was used to measure local bubble size distributions (BSD), gas–liquid interfacial areas and gas holdups in an up-flow ejector, based on the water–air system with different liquid and gas flow rates under the presence/absence of the swirl body. The results show that the bubble flow patterns are different whether to add the swirl body into the nozzle, especially at low gas flow rate because the bubbles formed “bubble chain” in the ejector with swirl. The mean bubble sizes D₃₂ of the two are both related to the pressure drop between import and export, gas ratio and liquid flow. The interfacial area and D₃₂ are both mainly dependent on the local gas holdups. The mean bubble sizes in the absence of swirl body are smaller than that in the presence of swirl under different operating conditions. The gas holdups and interfacial area are larger with swirl than those without swirl. With the increase of the gas fraction, the differences of D₃₂, a_t and e_G become smaller.     

Influence of maleation of polypropylene on the interfacial properties between polypropylene and ethylene–vinyl alcohol copolymer

In order to improve the miscibility between the components of a blend, it is possible to modify the chemical structure by functionalizing one or more of the components. This results in better adhesion at the interface between the components and, consequently, in better mechanical properties. In this work, the influence of maleation of polypropylene on the interface between polypropylene and ethylene–vinyl alcohol copolymer was studied using the measurement of interfacial tension, surface analysis with electron spectroscopy for chemical analysis (ESCA), and morphological observation, using scanning electron microscopy (SEM). The interfacial tension between a 0.1-wt % maleated polypropylene and ethylene–vinyl alcohol copolymer was shown to be 25% lower than the interfacial tension between nonmaleated polypropylene and ethylene–vinyl alcohol copolymer. This resulted in better adhesion between maleated polypropylene and ethylene–vinyl alcohol copolymer. The surface analysis indicates that this decrease of interfacial tension is due to migration of the maleic groups of the maleated polypropylene to the interface between the 2 polymers and that, probably, a chemical interaction occurs at the interface between maleated polypropylene and ethylene–vinyl alcohol copolymer. It is also shown in this work that additives, such as SiO₂, found in commercial polymers, can influence the interfacial tension between 2 polymers. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 75–87, 1998     

Entransy dissipation analysis of interfacial convection enhancing gas–liquid mass transfer process based on field synergy principle

An exploration of the gas CO2 absorbed into liquid ethanol accompanied with Rayleigh convection is performed by analyzing the mass entransy dissipation; this new statistical quantity is introduced to describe the irreversibility of mass transfer potential capacity. Based on the general advection–diffusion differential equation for an unsteady mass transfer process, the variation of the included angle between the velocity vector and concentration gradient fields is investigated to reveal the underlying mechanism of interfacial convection enhancing mass transfer. Results show some identical characteristics with the qualitative analyses of the synergy effects generated by the concentration and velocity fields after interfacial convection occurring for a boundary condition of fixed surface concentration. And the equivalent mass resistance for convective mass transfer process presents the similar variation with the reciprocal of instantaneous mass transfer coefficient. Accordingly, it is reasonable to be seen that mass transfer dissipation rate could be provided to assess the convection strength and explain fundamentally how Rayleigh convection improves mass transfer performance through establishing a close relationship between the mass transfer capacity and field synergy principle from the view of mass transfer theory.     

Study on interfacial interaction energy of Cu–SAM–epoxy systems in a hot and humid environment

Due to poor adhesion, the interfacial delamination is one of the typical failure modes in electronic packages. In this paper, two kinds of self-assembly monolayers (SAMs), SAMA and SAME, are added to Cu–epoxy interface and the effects of temperature, moisture, and cross-link conversion on the modified interfaces are investigated with molecular dynamics (MD) simulation. The results show that the interfacial interaction energy of the systems with SAMA increases with the increasing temperature, decreasing moisture content, and cross-link conversion. However, the interfacial interaction energy of the systems with SAME decreases with the increasing temperature and moisture content, while it is reluctant to the cross-link conversion. In addition, the simulation reveals that the covalent bonds between SAMA and epoxy enhance the interfacial adhesion of Cu–epoxy. However, the nonbond interactions of SAME and epoxy resin weaken the interfacial adhesion. This paper provides a new method for research and valuation the effects of SAM or other adhesive on interfacial adhesion. MD simulation is an efficient tool in predicting the performances of materials.