Synergistic interactions of chemical additives on the strength development of silicate cement by a box‐behnken model optimization

The effect of water‐soluble polymers (polyvinyl alcohol (PVA), polyacrylamide (PAM)) and chemical additives (silicone defoamer (SD), polycarboxylate superplasticizer (PC)), on the development of the strength of mortar was investigated using the Box‐Behnken design (BBD). Quadratic equations were obtained for the correlation between dosages of chemicals and the strength of the mortar, and the order of the effectiveness of the chemicals was validated in Pareto charts with contour plots to illustrate the chemicals and their interactions on the strength enhancement of mortar. The results showed that the interaction effects of SD and PAM enhanced the strength of cement mortar for all curing times, and the rates of contribution were 16.5%, 20.1%, and 19.4%, respectively. On the basis of the performance analysis of the four additives, optimized formulations were highlighted via overlapped contour plots. Heat of hydration and scanning electron microscope (SEM) images were introduced to confirm the interaction between SD and PAM. The improvement of compressive strength attributes to the synergistic interactions between SD and PAM, including the physical interaction resulted from the doping of SD, which promoting the damage of air bubble, decreasing the porosity and increasing the compressive strength, and the chemical interaction resulted from the doping of PAM, which producing ionic compounds and forming dense structure. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41071.     

Experimental and numerical study of distortion in flat,L‐shaped,and U‐shaped carbon fiber–epoxy composite parts

In this study, flat composite panels were fabricated to find the effect of different manufacturing parameters, including stacking sequence, part thickness, and tooling material, on distortion of carbon fiber‐epoxy composite parts. L‐shaped and U‐shaped panels were also made to investigate the effect of stacking sequence on spring‐in angle and warpage of the curved panels. Results showed that distortion of the flat panels caused by asymmetry in the stacking sequence was an order of magnitude greater than distortion of the panels with an unbalanced stacking sequence; whereas in the curved panels, the panel with an asymmetric stacking sequence showed the least spring‐in angle, and the largest angle was observed in the symmetric panel. MSC Marc was used to predict distortion of the panels, and the simulation results were compared with the experimental results for several stacking sequences of the flat and the L‐shaped panels. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40439.     

TTT‐diagram for epoxy film adhesives using quasi‐isothermal scans with initial fast ramps

The characterization of film adhesives is challenging because they required freezer storage, contain an inseparable filler—thermoplastic knit or fiber‐reinforcement, and are heat activated systems with a pre‐cure and unknown chemistry. A testing protocol that eliminates these sources of error is proposed. This study presents a method to generate time–temperature‐transformation (TTT) diagrams of epoxy film adhesives via differential scanning calorimetry (DSC). Non‐isothermal and isothermal DSC scans are used to capture the reaction and the glass transition temperature. The use of an initial fast ramp—up to 500 K/min—in the isothermal scans is explored for the first time. This technique shows the potential to produce a quasi‐isothermal cycle, eliminating the loss of data in the initial stage of the reaction. The total heat released, the activation energy, and the fractional kinetic parameter, are estimated via model‐free methods. The Kamal–Sourour model and the formal kinetic model are fit to model the rate of cure. The simplest model that accurately captures the reaction, a parallel two‐step model, A , is outlined. The glass transition temperature is modeled via DiBenedetto's equation to include the diffusion‐controlled mechanism. The TTT‐diagrams of two commercial adhesives, DA 408 and DA 409, are shown with an analysis of processing optimization. The use of quasi‐isothermal scans with initial fast ramps combined with the correction for filler, moisture, and pre‐curing history can be applied to characterize fast curing thermosets, complex B‐stage resins, and thermosetting composites. The modeling results can also be used in numerical studies of residual stresses and dimensional stability in the manufacturing of thermosetting composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45791.     

Flexural behavior of PP/Mica composites interfacial modified by a p‐phenylen‐bis‐maleamic acid grafted atactic polypropylene modifier obtained from industrial wastes

The study of the flexural behavior of the polypropylene/mica system with modified interface by the presence of an interfacial agent obtained from an industrial polymerization by‐product is one of the purposes of present work. The interfacial agent used was a p‐phenylen‐bis‐maleamic grafted atactic polypropylene, aPP‐pPBMA, obtained in authors’ laboratories. Jointly to the study of the effect of the interfacial modification in the composite system, this paper has tried to underline a mathematical model to make predictions of the ultimate properties of the composite. So, a statistical two independent variables Box‐Wilson experimental design have been used to model the behavior of the composite system. The two independent variables considered were the amount of mica particles and of interfacial agent. The fact that the flexural test consist in a combination of compressive and tensile stresses emerges from the analysis of both the data and the statistic parameters of the model. Additionally, a lower sensitivity to changes in the amount of the interfacial agent is found if compared to the obtained for tensile properties. Furthermore, an excellent correlation emerges between the flexural modulus forecasts and those obtained under tensile conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42437.     

Self‐assembled ultra‐thin films fabricated from diazoresin and phenol–formaldehyde resin via H‐bonding interaction

A photosensitive ultra‐thin film has been fabricated from diazoresin (DR) and various phenol‐formaldehyde resins (PR) through a self‐assembly technique (SA). The driving force is confirmed to be a hydrogen‐bonding (H‐bonding) interaction between the diazonium groups of DR and the phenolic hydroxy groups of PR. Under exposure of UV‐light or immersion in an alkaline solution, the hydrogen‐bonds between layers will be converted to covalent bonds. As a result, the stability of the film towards polar solvents improves dramatically. Copyright © 2004 Society of Chemical Industry     

Understanding the role of internal microstructure in capsule‐based healing of polymeric composites

The efficacy of microcapsules possessing varied internal microstructure toward introducing extrinsic self‐healing functionality in epoxy has been compared. Unsaturated polyester was encapsulated in microcapsules by adopting different methodologies. Microcapsules formed using dispersion polymerization exhibited “reservoir” microstructure while solvent evaporation led to the formation of “monolithic” microcapsules. Theoretical model was developed to predict the amount of healant released in the event of microcapsule rupture, which clearly highlighted the benefits associated with reservoir type microcapsules, especially at lower core contents. At larger core contents (≥50% vol/vol), all the micro‐droplets within the monolithic structure coalesced to form a healant reservoir. Self‐healing composites were prepared by introducing both types of microcapsules in an epoxy matrix and the healing efficiency was quantified. In line with the theoretical predictions, reservoir type microcapsules led to much higher healing efficiencies in comparison to monolithic microcapsules. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45471.     

1H‐ and 13C‐NMR spectroscopic study of chemical equilibria in the system acetaldehyde + water

Acetaldehyde is an important intermediate in the chemical industry and often used in mixtures with water. These mixtures are reactive multicomponent systems, as acetaldehyde forms oligomers with water. Quantitative studies of the resulting speciation are scarce in the literature and limited to the formation of the smallest oligomer, ethane‐1,1‐diol. Therefore, in the present work, a comprehensive study of chemical equilibria in mixtures of acetaldehyde and water was carried out by quantitative ¹H‐ and ¹³C‐NMR spectroscopy. The study covers temperatures between 275 and 338 K and overall acetaldehyde mole fractions between about 0.05 and 0.95 mol/mol. The peak assignment is given for both the ¹H‐ and ¹³C‐NMR spectra. From the speciation data, obtained from the peak area fractions, numbers for the chemical equilibrium constants of the oligomer formation are obtained and a correlation is presented. © 2014 American Institute of Chemical Engineers AIChE J, 61: 177–187, 2015     

Direct‐current conductivity at a cryogenically low temperature for polymer/carbon composites: Applicability of different theoretical models

In this study, we focused on the behavior of the direct‐current (dc) conductivity/resistivity in a cryogenically low temperature region (10–300 K) for ethylene vinyl acetate copolymer, acrylonitrile butadiene copolymer, and their 50/50 blend composites filled with different conductive carbons. The composites were prepared through a melt‐mixing technique. Different behaviors of the dc resistivity/relative resistivity for the composites were observed; these behaviors depended on the nature of the polymers, the filler types, and the filler concentration when plotted with respect to the temperature. The results of dc conductivity were fitted with some existing theoretical models, including Arrhenius, Kivelson, and Mott's variable range hopping, to check their applicability for these composite systems. We observed that none of the models was applicable within the entire range of measurement temperatures but were confined within limited temperature ranges. The reason behind the nonapplicability of the models is discussed with consideration of their drawbacks and limitations. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43541.     

Preparation and application of sulfadiazine surface molecularly imprinted polymers with temperature‐responsive properties

Novel, temperature‐responsive molecularly imprinted polymers (TMIPs) based on potassium hexatitanate whiskers for selectively adsorbing sulfadiazine (SDZ) from aqueous media were prepared with methacrylic acid (MAA) and 4‐vinylpyridine (4‐VP) as cofunctional monomers and N‐isopropyl acrylamide (NIPAM) as a temperature‐responsive monomer. The template–monomer interactions were studied by molecular simulation. In particular, the effects of different kinds of crosslinkers on the selective recognition ability of the TMIPs in water media were investigated. The temperature–responsive adsorption performance and phase behavior of the molecularly imprinted polymers were studied by batch‐mode binding experiments, swelling experiments, and contact angle testing. The results demonstrate that the combination of MAA, 4‐VP, and NIPAM was a favorable temperature‐responsive imprinted system for SDZ in water, and the cocrosslinking agent of ethylene glycol dimethacrylate (EGDMA) and N,N′‐methylene bisacrylamide (MBA) was more suitable compared with either pure EGDMA or MBA. The adsorption kinetics and adsorption isotherms were analyzed by the fitting of different adsorption models. Also, the effect of the temperature on the recovery was investigated by the determination of the spiked SDZ in real‐water samples with solid‐phase extraction and high‐performance liquid chromatography. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41769.     

Preparation and electroanalytical characterization of polyaniline: Polyacrylonitrile composite films

Electrically conducting composite films of polyaniline:polyacyrlonitrile (PANI:PAN) prepared with varying composition ratios of aniline mixed with a fixed amount PAN. The films of optimum thicknesses (0.10 mm) were obtained using an electrically operated automatic pressure machine. The films polymerized by oxidative polymerization using 0.1M potassium persulphate (K₂S₂O₈), undoped in 1M aqueous ammonia (NH₄OH) and doped in 1M hydrochloric acid (HCl). The conductivity of composite films was studied by keeping it in 1M HCl for different time period using 4-in-line probe DC electrical conductivity measuring instrument and the temperature dependence of DC electrical conductivity was studied using isothermal technique. The PANI:PAN composite film is used as a working electrode in an electrochemical cell. Chemically doped composite film is used as cathode (working electrode), aluminum metal foil as anode (counter electrode) and platinum foil as reference electrode. The electrolyte is of 0.05M aluminum chloride (AlCl₃) in dimethyl sulfoxide (DMSO). The voltage of the working electrode is stabilized with respect to the reference electrode and current applied between the working and counter electrode through a 9-V battery. The change in voltage versus time is plotted as the discharge curve and reversing the cell processes results in the doping of the composite films. The diffusion coefficient of the dopant ion (Cl⁻) present in the fully doped films were estimated by the galvanostatic pulse technique and found to bedifferent in different samples in the range of 10⁻¹⁶ to 10⁻¹² cm² s⁻¹. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Annealing‐promoted unidirectional migration of organic‐modified nanoparticles embedded two‐dimensionally in polymer thin films

The spatial structures of oleic acid‐modified CeO₂ nanoparticles in polystyrene (PS) thin films spin‐coated on silicon substrates were observed by transmission electron microscopy, when the films underwent thermal annealing above the glass‐transition temperature of PS. Before annealing, the nanoparticles have segregated to the surface of the films, and formed two‐dimensional spatial structures in the PS films. Then, the nanoparticles migrated away from the film surface to the substrate/film interface during thermal annealing, maintaining the two‐dimensional spatial structures. In addition, we demonstrated that such unidirectional migration of nanoparticles across the PS film occurs regardless of the characteristics of the substrate surface, the concentration of nanoparticles, and the thickness of the films. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42760.     

Improving the physical and chemical functionality of starch‐derived films with biopolymers

The physical and chemical properties of composite starch‐based films containing cellulosic fiber, chitosan, and gelatin were investigated. Films containing both cellulosic fibers and chitosan demonstrated tremendous enhancements in film strength and gas permeation. The water absorbency of composite films could be greatly reduced in film composites containing cellulosic fibers and gelatin, but the inclusion of chitosan into these films provided a higher hydrophilicity, increasing water absorbency. Film transparency was not noticeably affected in the composite films that were made. These films may have wide application in the food packaging, agricultural mulching, and the medical industries. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2542–2548, 2006     

Dielectric properties of thin films of Babassu‐based polymer and polyaniline blends

In the present work, we describe the preparation and subsequent characterization of polymeric blends consisting of a monoglyceride (MG) synthesized from the Babassu's oil and the already commonly employed polyaniline (PAni). By following changes in the complex impedance of capacitor‐like devices we observe that the presence of MG in the PAni/MG blends decreases electrical conductivity and that this decrease is a function of the content of MG in the blend, i.e., the blend with 30% of MG shows Z′ about seven times greater than the one with 10% of MG. Fourier transform infrared measurements prove the formation of MG and the presence of secondary amine groups (N? H bonds) in the blends, which allow for the chemical doping of PAni by protonation, further studies are necessary to access the viability of employing this new material as active layer in electronic organic devices. Atomic force microscopy images show the formation of agglomerates due to the presence of MG. In addition, the polymeric mixture acts only as a blend, providing a physical interaction between different components. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46198.     

Hybrid polyaniline–TiO2 nanocomposite Langmuir–Blodgett thin films: Self‐assembly and their characterization

Polyaniline (PANi)–titanium dioxide (TiO₂) nanocomposite materials were prepared by chemical polymerization of aniline doped with TiO₂ nanoparticles. Surface pressure–area (π‐A) isotherms of these nanocomposites show phase transformations in the monolayer during compression process. Multiple isotherms indicate that the monolayer of the nanocomposite material can retain its configuration during compression‐expansion cycles. Langmuir–Blodgett thin films of PANi–TiO₂ nanocomposite were deposited on the quartz and indium tin oxide coated conducting glass substrates. Fourier transfer infrared spectroscopy and UV–visible spectroscopy study indicates the presence of TiO₂ in PANi, whereas X‐ray Diffraction study confirmed the anatase phase of TiO₂ and particle size (～nm) of PANi–TiO₂. The morphology of Langmuir–Blodgett films of these nanocomposites was also characterized by atomic force microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41386.     

Phase‐dependent binary interaction parameters in industrial low‐density polyethylene separators

In the production process of low‐density polyethylene (LDPE), an important step is the flash separation of monomers and other small molecules from the polymer produced. The process is carried out adiabatically in two stages. To improve the performance of thermodynamic models, it is very important to analyze the use of model binary interaction parameters (BIP) dependent on the phase characteristics for each phase (phase‐dependent BIP). In this work the PC‐SAFT (perturbed‐chain statistical associating fluid theory) equation of state (EOS) is applied to the flash simulation of LDPE industrial separators using eight different resins. The main numerical aspects are examined with emphasis on the optimization strategy for the EOS BIP that explicitly characterizes each phase involved separately. The results demonstrate good predictive behavior. As a result of improved and more consistent modeling, a new strategy for optimized operation can be envisaged for the sequence of separators. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2106–2117, 2013     

Probing the viscoelastic moduli of thin,soft films with a quartz crystal resonator

Coating biomaterials with thin, soft films can alter properties, such as the biocompatibility of the materials, whereas it remains a great challenge to probe the properties of such films. In this article, we show a method that allows for the determination of the viscoelastic moduli of thin, soft films deposited on the surface of a quartz crystal through the measurement of resonance frequency shifts and the broadening of the acoustic resonance of the crystal as a resonator. The method is based on transcendental equations, which describe the mechanical response of the quartz resonator with the deposited films. It differs from the currently widely used ones, which use a thin film approximation numerically through the solution of transcendental equations to determine the viscoelasticity of the films. We estimated the glass‐transition temperature of a thin poly(vinyl butyral) film by measuring the change in the viscoelastic moduli of the film with increasing temperature, and the results agree well with the temperature obtained from other techniques. The method was not constrained to the range of the elastic moduli of the film, except where the acoustic film resonance occurred, and thus, could be applied to the study of a wide variety of thin, soft layers under different conditions. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44532.     

Optimal design of an imprinted preassembled system by quantum chemical calculations and preparation of a surface‐imprinted material for the selective removal of quinoline

In this study, we examined the rational preparation of molecularly imprinted polymers (MIPs) for the selective removal of quinoline from octane. Before the preparation, density functional theory, as one of the methods of quantum chemical calculation, was used for the simulation of a quinoline‐imprinted preassembly system. Methacrylic acid turned out to be the more suitable monomer for quinoline compared with acrylamide, and different template–monomer ratios, including 1:1, 1:2, and 1:3, were studied and are discussed. On the basis of the result of molecular simulation, quinoline‐imprinted polymers were prepared with a combination of surface imprinting and living polymerization. The prepared quinoline–MIPs were characterized and used as selective adsorbents for batch‐mode binding experiments. The fitting result of the adsorption data indicates that the adsorption kinetics and adsorption isotherms of the quinoline‐imprinted polymers fit well a pseudo‐second‐order kinetics model and the Freundlich model, respectively. A selective recognition ability was demonstrated by equilibrium binding analysis. This study will provide needful guidance and a theoretical basis for the preparation of imprinted materials in the field of industrial denitrification. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41730.     

Compatibilization of polyethylene/polyaniline blends with polyethylene‐graft‐maleic anhydride

The use of compatibilizers as interfacial agents in composites can offer a convenient way to improve the mechanical properties of immiscible polymer blends. The aim of this article is to illustrate the compatibilization effect of polyethylene‐graft‐maleic anhydride (PEgMA) in blends of low‐density polyethylene (LDPE) and n‐dodecylbenzene sulfonate doped polyaniline (PANIDBSA) prepared by extrusion. Films with different compositions of the coupling agent were evaluated with optical spectroscopy and thermomechanical, electrical, mechanical, and morphological techniques. The incorporation of PEgMA into the LDPE/PANIDBSA composites resulted in an improvement of their electrical conductivity and changes in the mechanical and morphological properties of the films. When 5 wt % of the coupling agent was added to a 30 wt % of the polyaniline‐containing film, the conductivity increased by more than three orders of magnitude, and the ductility also improved qualitatively. The morphology analysis also indicated that the addition of PEgMA produced a strengthening of the filler–matrix interfacial region. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Micromechanical modeling of roll‐to‐roll processing of oriented polyethylene terephthalate films

In this article, the thermo‐mechanical time‐dependent behavior of oriented polyethylene terephthalate (PET) films, which are used as a substrate material for flexible Organic Light‐Emitting Diode (OLED)s, is analyzed. These films are subjected to conditions that are representative for the industrial manufacturing process. Effects of creep and thermal shrinkage are experimentally observed simultaneously. The aim of the article is to demonstrate the ability of the micromechanically‐based model, which was previously used to separately describe both creep and thermal shrinkage of the polyethylene terephthalate film, to simulate experimentally observed anisotropic behavior of the film under complex loading conditions. This anisotropic behavior results from the microstructure, the internal stress state, and differences in constitutive behavior of the phases. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43384.     

Characterization of the draping behavior of jute woven fabrics for applications of natural‐fiber/epoxy composites

In this study, we investigated the draping behavior of jute woven fabric to study the feasibility of using natural fabrics in place of synthetic glass‐fiber fabrics. Draping behavior describes the in‐mold deformation of fabrics, which is vital for the end appearance and performance of polymer composites. The draping coefficient was determined with a common drapemeter for fabrics with densities of 228–765 g/m² and thread counts under different humidity and static dynamic conditions. The results were compared to glass‐fiber fabrics with close areal densities. Characterization of the jute fabrics was carried out to fill the knowledge gap about natural‐fiber fabrics and to ease their modeling. The tensile and bending stiffnesses and the shear coupling were also characterized for a plain woven jute fabric with a tensile machine, Shirley bending tester, and picture frame, respectively. As a case study, the draping and resin‐transfer molding of the jute fabric over a complex asymmetric form was performed to measure the geometrical conformance. The adoption of natural fibers as a substitute for synthetic fibers, where the strength requirements are satisfied, would thus require no special considerations for tool design or common practices. However, the use of natural fibers would lead to weight and cost reductions. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1453–1465, 2013