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Hybrid hydroxyapatite/polymer composites were prepared by the infiltration of nylon into porous hydroxyapatite. Porous hydroxyapatite (HAp) bodies were prepared from a whisker-like powder with high aspect ratio by pressureless-sintering at various temperatures. Pore characteristics, such as the fraction of open porosity and the pore size distribution, were designed and evaluated by mercury porosimeter. Through the in situ polymerization of ε-caprolactam, infiltrated into the porous HAp body, a polymeric secondary phase network interpenetrated with the HAp phase was obtained. The obtained hybrid HAp/nylon composites were evaluated with respect to their fracture behavior, i.e., fracture energy, and in vitro bioactivity in simulated body fluid (SBF) in the present paper. These HAp/nylon hybrid composite have a KIC of 1.65 MPam1/2 and also a good bioactivity according to the results of SBF immersion tests. [ABSTRACT FROM AUTHOR]

Knitted fabrics and particularly weft knitted fabrics are used as composite material reinforcements due to their ability to be draped and to give three-dimensional shape by molding or by knitting. This paper presents the strong connection of all the scales of the knitted fabric (fiber, yarn and fabric) on the final knitted fabrics and its mechanical and physical properties. For this purpose, only one polymer material is used, made of two different fibers in terms of length and fineness. These fibers are used to make different yarns with two structures then three plain-weft-knitted-fabrics are considered in terms of the loop length. The fibers have not the same bending rigidity because fiber cross-section areas are different. This has an influence on the three-dimensional loop shape and on the roughness, thickness and real area of contact of fabrics. This phenomenon is the same with the two yarn structures. The results presented here bring into light that the loop length does not influence the fabric thickness. [ABSTRACT FROM AUTHOR]

Knitted fabrics are known for their excellent stretching and draping properties due to their curved fabric architecture. In recent years knitted fabrics have been used as reinforcement network for polymer sheet thermo-processing. This paper describes a method for evaluating the product height, product profile and strain distribution of a flat polymer matrix sheet, reinforced with knitted fabric, undergoing the sheet thermoforming process. The availability of a knitted fabric reinforced PMC to stretch is proposed to be equal to the least ratio of curved loop length to its projected length. The product profile is then obtained from the availability of the material to stretch and the tool geometry involved. Finally a mapping scheme is proposed to evaluate the severity of deformation in terms of strain distribution. A reasonably good agreement is observed between the model and experimental results. An understanding of the severity of deformation distribution would shed light on the location of highest degree of deformation as well as its magnitude and should therefore assist the product designer in dealing with the thermoforming process of this new material. [ABSTRACT FROM AUTHOR]

Pure polyaniline (PANI) has a high electrical conductivity and can be made soluble and thermoplastic, but it still lacks adequate mechanical properties for large-scale commercial use and therefore, it has been blended with other polymers such as poly(methyl methacrylate) (PMMA). In the work described in this paper, the scaled up synthesis of conductive polyaniline by an oxidative chemical method under controlled pH and temperature has been optimised. Re-doping of deprotonated insulating base with excess of the mono-functional organic acids such as p-toluenesulfonic (TSA) or dodecylbenzenesulfonic (DBSA) in aqueous media was successful. A wide range of techniques including TGA, GPC, EA, FTIR, XRD and SEM were employed for the characterisation of PANI powders and blends. Compositions of PANI-HCI, TSA or DBSA and thermoplastic matrix PMMA with or without a plasticiser were melt-processed by compression moulding for 3 min at 210°C to produce plaques. The effectiveness of four different phenolic plasticisers was compared and hydroquinone was found to produce the blends with the highest conductivities. A few preliminary injection-moulded plaques were made and their conductivities were compared with those of the compression-moulded samples. [ABSTRACT FROM AUTHOR]

The mechanical properties of bone are studied mostly for reasons related to skeletal pathology. However, bone is also very interesting from a material science perspective because it is a natural hierarchical composite material. The mechanical properties of bone depend on both the structural arrangement and the properties of the constituting materials, namely the organic polymer collagen and the inorganic salt apatite. While the mechanical properties of bone samples at the macroscopic scale are measured routinely, mechanical tests on micrometer-sized specimens are still at development stage. In this paper, protocols for measuring the elasticity of cancellous bone trabeculae are reviewed. The published values for the elastic modulus of trabeculae vary between 1 GPa and 15 GPa. Reasons for this broad range of values may be located in the intrinsic difficulties of preparing, handling, and testing inhomogeneous, anisotropic and asymmetric micro-samples. We discuss the major error sources in existing testing procedures and suggest potential strategies to enhance their performance. [ABSTRACT FROM AUTHOR]

Biological tissues are made from nano-composite materials and given the recent interest in manufacturing synthetic nano-composites an analysis of natural nano-composites seems a worthwhile exercise. There is also potential for extracting natural nano-fibres and using them as reinforcements in other materials. In this paper a hierarchical mechanical model is formulated to describe potato tuber tissue and the model is used to back calculate the properties of cell wall nano-fibres. The model contains two structural levels, the cell structure and the cell wall structure. Material properties are assigned at the level of cell wall microfibrils (nano-composite fibres). Force deflection data from the compression of cubes of potato tissue were fed into the model and the properties of the cell wall microfibrils predicted. The modulus was found to vary with strain, but had a maximum value of 130 GPa, which is close to predictions from theoretical chemistry for the stiffness of cellulose microfibrils. At 8% wall strain (the value at which failures were suspected to begin), the stress was predicted to be 7.5 GPa which is also close to theoretical chemistry predictions for the strength of cellulose microfibrils. The large strains and decreasing stiffness indicate the influence of polymers other than cellulose. [ABSTRACT FROM AUTHOR]

For many years, ceramics have been added to polymeric materials as reinforcements or extenders. Recently, thin ceramic coatings have been applied to polymers for biomedical applications, and in this paper ceramic coatings are applied to an aerospace polymer, bismaleimide (BMI). Unreinforced BMI specimens were coated with a thin, protective layer of a dense silicate ceramic material. Vickers indentation testing on the coated and uncoated BMI specimens indicated that the coatings adhere surprisingly well to the substrate, with cracking of the coating taking place only within a diamond-shaped region with diagonal dimensions equivalent to the Vickers indentation impression. [ABSTRACT FROM AUTHOR]

The dynamic response experiment has been a difficult point of the metal/polymer interfacial bonding performance testing, in which the metal surface state and the loading condition are key independent variables that should be comprehensively investigated. This work investigates the effect of loading velocity and Al surface porosity on Al/PMMA interfacial dynamic shear bonding performance. Firstly, simulation is applied to predict dynamic response variation trends. Simulation results show that the maximum force (MF) has minor changes with initial bullet velocity (IBV), while the de-bonding displacement (DD) and interface failure work (IFW) decrease obviously with IBV. All three indicators increase smoothly with the area ratio of PMMA interlocks. In experiment, the result plots of the indicators are all discrete, but as a whole, the MF plots could not be distinguished by the variation of IBV, while the plots of DD and NW decrease with IBV, which are consistent with simulation. The dynamic response indicators obtained by simulation and experiment show similar variation trends with their respective independent variables at certain ranges (surface porosity: − 15–20%/dm2, area ratio: 0–0.33) and could be contrasted to evaluate the indicator value differences at full range. By further analysis within MF and DD indicators, the stability of the dynamic interfacial stiffness is discovered at their respective loading velocities, which is similar static loading in past work. The strengthening and weakening mechanisms of Al/PMMA interface are also inferred. This experiment–simulation combined work exhibits a systematic method to predict the dynamic response with the variation of the independent investigating variables at certain ranges, to evaluate the degree of deviation of the experimental plots from simulative ones and to help determine the porosity range where higher dynamic response would be obtained, which would be also applied to other metal/polymer layered system. [ABSTRACT FROM AUTHOR]

Experiments conducted at all combinations of the levels of two or more factors are called factorial experiments. Factorial experiments have been shown to be more efficient in exploring the effects of external factors on a response variable than non-factorial arrangements of factor levels. This paper presents a methodology for the analysis of test results obtained at all combinations of the levels of two two-level factors. The response variable is assumed to follow the two parameter Weibull distribution with a shape parameter that, although unknown, does not vary with the factor levels. The scale parameter on the other hand may vary in various ways with the levels of the factors. These assumptions well reflect the behavior of the fracture strength of glassy polymers as it is influenced by factors such as water sorption and silanation of filler. The purpose of the analysis is (1) to compute interval estimates of the common shape parameter and (2) to assess whether either factor singly or in combination with the other affects the Weibull scale parameter. The procedure is illustrated with an example using simulated data for which only one of the factors had a real effect. A further example is given using shear strength measurements made in a 22 factorial experiment conducted on a glassy polymer material used in dental restorations. [ABSTRACT FROM AUTHOR]

In order to obtain the high heat-resistant fibre, Si-Zr-C-O fibre has been developed. Si-Zr-C-O fibre was produced by the use of polyzirconocarbosilane as the precursor polymer. In this paper, the difference in heat-resistance between Si-Ti-C-O and Si-Zr-C-O fibres was clarified. Si-Zr-C-O fibre showed excellent heat resistance (up to 1773 K) compared with Si-Ti-C-O fibre (up to 1573 K). Generally speaking, decomposition reaction of this type of fibre proceeds accompained by the release of CO gas which was formed by the reaction between excess carbon and oxygen included in the fibre. In the case of Si-Zr-C-O fibre, Zr can strongly capture the oxygen atoms, so that the aforementioned decomposition hardly proceeds up to 1873 K (ZrO2 + 3C = ZrC + 2CO; ΔG < 0 at over 1906 K). [ABSTRACT FROM AUTHOR]

The shear-lag parameter, β, employed in various problems of shear-lag analysis of composites is an unknown parameter which, in certain cases, is impossible to define. In this paper, a new methodology is proposed for the definition and subsequent experimental measurement of β for various single-fibre model composites. It is argued that, if β is defined as a fitting parameter for the solution of the shear-lag differential equation, then it can effectively serve as a stress-transfer efficiency index. The dependence of β upon the conditions prevailing at the fibre–matrix interface will be demonstrated by measuring β as a function of the fibre sizing in a carbon–epoxy composite system. © 1998 Chapman & Hall [ABSTRACT FROM AUTHOR]

In-situ crystallization of Cs-bearing zeolites (especially pollucite) is an efficient way to enhance Cs immobilization in geopolymers. This study investigated the amounts of in-situ pollucite crystallized at different curing times (up to 7 days) in the fly ash geopolymer (FA-GP) systems containing 20 wt.% cesium dosage and cured at 90 °C. Pollucite content was then associated with the degree of Cs immobilization (expressed through the leachability index LX) and other FA-GP properties, not previously reported. Investigation of the kinetics of in-situ pollucite crystallization was conducted at three temperatures (56, 73, and 90 °C) for varying curing times of up to 14 days, with an aim to determine the activation energy of the pollucite crystallization using JMAK model and Arrhenius equation. The results suggested a linear correlation of in-situ pollucite content with the Cs immobilization. Significantly high leachability index (LX) value ≥ 12 was achieved within 6 h of curing at 90 °C, implying effective Cs immobilization. Relatively low activation energy (Ea) of ~ 25 kJ/mol, not reported hitherto, for in-situ pollucite crystallization was found in our system, suggesting feasible crystallization of pollucite via one-step synthesis process, at relatively low temperatures. [ABSTRACT FROM AUTHOR]

Herein, adenine-tailored polyimide is proposed as precursor to fabricate nitrogen-doped 3D carbon superstructure assembled by two-dimensional (2D) carbon nanosheets using ultrasonic atomization-assisted-ice template (UAIT) strategy. The structural evolution of adenine polyimide-derived carbon nanosheets (APCN) is strongly affected by pyrolysis temperature. The lithium-ion batteries assembled by APCN-600 electrode exhibits an impressive reversible capacity of 1046 mAh g−1 at 0.05 A g−1 and superior rate capability of 437 mAh g−1 at 5 A g−1. This work demonstrates the prospects of combining polymer precursor strategy and UAIT method to access high reversible specific capacity carbon-based anode for practical application. Two-dimensional (2D) carbon nanostructure with large specific surface areas and high conductivity can not only shorten the transport length for Li+ but also offer proper electrode–electrolyte interfaces for the ion transport reaction, leading to rate performance improvement and high cycle performance. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have received considerable investigation as oxygen reduction reaction (ORR) catalysts. Despite their excellent catalytic activity, many questions regarding the relationship between their structure and performance remain to be answered. In addition, these catalysts are facing slow reaction process, low raw material utilization, environmental pollution and other potential problems. Herein, inspired by the concept of MOFs, we create a remarkably homogeneous hierarchical N-doped carbon nanoflower (NCNF-m, m represents levodopa content) by a simple, fast and green pyrolysis-induced strategy using amino acid-zinc chelate and levodopa (L-dopa) as carbon and nitrogen sources. L-dopa is oxidatively polymerized and participates in the coupling process of amino acid-zinc chelates to form polymers, and the nanoflower structure is achieved under the induction of high-temperature gasification and dezincification. The structure and morphology of NCNF-m are significantly influenced by the L-dopa content. The as-prepared NCNF-1 has a hierarchical porous structure, more optimized N configurations, high specific surface area (921.88 m2 g−1) and mesopore volume fraction (55.67%), exhibiting excellent electrochemical activity and cycling stability. It is also comparable to commercially available Pt/C catalysts when designed as a cathode catalyst for Zn–air batteries, suggesting its potential for useful applications. This MOF-mimicking catalyst with abundant reactive centers will provide valuable advice for the creation and fabrication of metal-free catalysts for diverse electrocatalytic processes involving energy production. One-step pyrolysis of polymers of amino acid-zinc chelates and levodopa endows NCNF-1 with the most complete nanoflower structure, the most mesoporous structure and the best N configuration, thus leading to much improved ORR performance. [ABSTRACT FROM AUTHOR]

Polymer materials, not described in the literature so far, were obtained in the process of UV polymerization between methacrylic monomer obtained on the basis of natural, terpene alcohol: citronellyl methacrylate and benzyl methacrylate with different composition. The structures of the novel, environmentally friendly copolymers were confirmed by the FTIR and 13C CPMAS/NMR spectra. The copolymers containing more than 50% mass of citronellyl methacrylate were characterized by a high conversion of the double bonds determined on the basis of the FTIR and NMR spectra (95–96% and 92–94%, respectively). The novel materials were highly resistant to polar and non-polar solvents and the chemical stability. The glass transition temperature was from 15.8 to 19.9 °C which confirms that the obtained materials are elastomers at room temperature. Their thermal stability depended on their composition. It was from 185 to 205 °C (inert conditions) and from 149 to 214 °C (oxidizing conditions). TG/FTIR/QMS studies confirmed that their decomposition took place mainly as a depolymerization process combined with a subsequent breaking of the bonds in the resulting monomer/s at higher temperatures, which led to the formation of the gases with lower molecular masses. The main decomposition products emitted in an inert atmosphere were benzyl methacrylate, citronellyl methacrylate, 2-methylpropenal, citronellal and higher molecular mass compounds formed as a result of radical reactions between intermediate volatile products. In turn, under oxidizing conditions, as volatiles, benzyl methacrylate, citronellyl methacrylate, 2-methylpropenal, citronellal and small amounts of inorganic gases (CO, CO2, H2O) as a result of depolymerization and some combustion processes of the residues were indicated. [ABSTRACT FROM AUTHOR]

Hexafluorides associated with polymers are a growing alternative to chromium-VI metal treatments. The polymers in these conversions enhance both the adhesion of the coating and the corrosion protection. The underlying mechanisms involve chemical bonding and surface interactions, the latter being readily accessible by measuring surface energy. We here investigate the link between surface energy, paint adhesion and corrosion resistance of painted aluminium panels. We evaluate zirconium hexafluorides conversion coatings with and without co-polymers made of acrylic acid and phosphonate or phosphate groups using an automated measurement of oil/solvent/metal contact angles. First, experimental results highlight that increased aluminium surface energies correlate with improved paint adhesion while limited corrosion seems related to low polar surface energies. Given this critical role of surface energy in these performances, the balance between adhesion and corrosion can be optimized by targeting specific values of contact angles of water and di-iodomethane. Second, the addition of polymer to hexafluoride treatments increases the polar surface energy and gives higher performances in corrosion and paint adhesion. Besides, a kinetic study reveals that the addition of polymer in zirconium conversions slows down the surface ageing over several days and allows a delayed paint application. Finally, as highlighted by the addition of phosphate or phosphonate functions in polyacrylic-acid polymers, the balance between adhesion and corrosion is improved by decreasing the polymer hydrophilicity to avoid corrosion while maintaining a sufficient functional density in its structure to develop covalent bonds with paint. This insight from contact angles and screening possibilities may contribute to speeding-up the development of new polymer chemistries in conversion technologies. [ABSTRACT FROM AUTHOR]

Metal–organic polymer CuBTC and composite with CuBTC and activated carbon (CuBTC/C) were prepared by hydrothermal method (BTC3− is a linker 1,3,5-benzenetricarboxylate ion, hydrolysis temperature 130 °C, ethanol + H2O in equal proportion as a solvent) and detailed characterized by a set of methods (X-ray diffraction—XRD, X-ray absorption spectroscopy—XAS, differential scanning calorimetry—DSC, scanning electron microscopy—SEM, low-temperature sorption capacity of samples to nitrogen—BET, X-ray photoelectron spectroscopy—XPS, FTIR-spectroscopy). According to XRD and XAS data, it was found that the composition of main phase CuBTC is [Cu3BTC2(H2O)3] × (nH2O + mC2H5OH) in both samples. The catalytic properties of CuBTC and CuBTC/C samples in the reaction of ethanol dehydrogenation were studied for the first time and the selectivity to acetaldehyde (AcH) was 100% in both cases. It was shown that on the CuBTC/C catalysis, the AcH yield is two times higher than on the CuBTC sample in the reaction of ethanol (Lewis base) dehydrogenation to acetaldehyde. This fact can be explained by the higher content of main phase CuBTC in composite CuBTC/C (~ 97.5 wt%) and the Cu2+ ions (Lewis acid sites) in bulk, the higher water and Cu2+ ions content on the particle surface in CuBTC/C (DSC, FTIR, XPS), the larger pore radii in CuBTC framework of the composite CuBTC/C (according to crystallochemical calculations) and the larger hydrogenation degree of CuBTC/C (XRD, DSC, FTIR) and the smaller specific surface area of CuBTC/C (SBET = 44.4 m2/g for CuBTC/C sample and SBET = 551.3 m2/g for CuBTC). It was found that in the reaction of propane conversion to ethylene C2H4 and methane CH4, the conversion degree on the samples CuBTC and CuBTC/C was the same from 100 °C up to 340 °C, which is caused by the absence of the Bronsted acid sites on the samples with CuBTC. [ABSTRACT FROM AUTHOR]

Form-stable composite phase change materials (C-PCMs) prepared by microencapsulation method and porous matrix adsorption method need for compression molding after preparation. In addition, as the molding intensity is relatively low and the mechanical property is poor, preparation of form-stable C-PCMs with good mechanical property and self-healing property by one-step preparation technology need to be studied. Herein, a novel form-stable SEBS/Paraffin C-PCMs with self-healing, elastic and deformable properties was prepared by one-step forming plate vulcanization method. Paraffins (RT52 and OP10E) were selected as the PCMs, and SEBS was choosed as the supporting material for physical cross-linking with paraffins. Most important of all, the physical cross-linking and self-healing mechanism were revealed by the XRD and FT-IR spectra and others, moreover, the influence factors of the self-healing efficiency were investigated. The SEBS/Paraffin C-PCMs with 85 wt% paraffin is optimal and the latent heat is up to 188.1 J·g−1, its good thermal stability showed by TG and the thermocycling test, the mechanical property test demonstrated its good elastic property with elongation up to 1160% even after the self-healing process. Moreover, its thermal release performance was explored by application to hot compress bag. The duration of temperature above 37 °C (65–37 °C) could last as long as 1620 s, which was enough to satisfy the need for the hot compress curative effect. In a word, the novel SEBS/Paraffin C-PCMs with self-healing property, deformable and good elastic property, good thermal stability and heat storage performance, indicating that it could be applied in many application fields, especially flexible wearable application. [ABSTRACT FROM AUTHOR]

Boronate affinity materials (BAMs) are gaining increasing attentions in the fields of separation, sensing, imaging, diagnostic, and drug delivery. However, poor selectivity caused by non-specific adsorption is still a shortcoming of the present BAMs, particularly organic BAMs. In this work, by investigating the effects of polymerization solvents and crosslinker types on binding selectivity of the PBA-functionalized polymers, we found that the phenylboronic acid (PBA)-functionalized polymers using N,N'-methylbisacrylamide (MBAA) as the crosslinker synthesized in DMSO by one-pot polymerization approach displayed ultrahigh selectivity to the cis-diol containing molecules. The physical features of all the polymers were characterized in detail. The PBA-MBAA particles synthesized in DMSO showed a high binding affinity with dissociation constants of 2.0 × 10–4 M and 9.8 × 10–5 M to adenosine and catechol, respectively, and a relatively high binding capacity (46 ± 1 μmol/g for adenosine and 166 ± 12 μmol/g for catechol). Binding kinetics measurement demonstrated that such PBA-MBAA particles required a long time (30 min) to reach the adsorption equilibrium due to their microporous structure. The recovery rates for the extraction of nucleosides by this polymer were high (63 ~ 88%, n = 3). In general, selection of MBAA as the crosslinker and DMSO as the polymerization solvent is opt to obtain highly selective BAMs, such protocol can be employed not only for producing BAMs for separation, but also making fluorescent BAM nanoparticles for sensing and imaging. [ABSTRACT FROM AUTHOR]

We review the literature describing the use of interleaves to increase interlaminar fracture toughness in fibre-reinforced polymer composites and hence to improve damage tolerance. From an analysis of data provided in the literature from the use of microfibre and nanofibre interleaves, we show that the performance of these widely researched systems is clearly differentiated when plotted against the mean coverage of the interleaf. Using a simple analysis, we suggest that this can be attributed to the influence of their porous architectures on the infusion of resin. We show also that the superior toughening performance of microfibre interleaves is only weakly influenced by the choice of fibre. We find also that the inclusion of carbon nanotubes within interleaves to deliver multifunctional composites can be optimised by using a hybrid system with microfibres. [ABSTRACT FROM AUTHOR]

Star-shaped glycopolymers due to the attractive combination of the physicochemical, morphological, self-assembly properties along with biological activity have gained increased attention as innovative agents in novel cancer therapies. Unfortunately, the production of these highly desirable biomaterials remains a challenge in modern macromolecular chemistry. The main reason for that is the low polymerizability of ionic glycomonomers originated from their steric congestion and the occurrence of ionic interactions that generally negatively influence the polymerization progress and hinder controllable reaction pathway. In this work, the new ionic sugar monomer was (co)polymerized for the first time via Activator Generated by Electron Transfer Atom Transfer Radical Polymerization (AGET ATRP) using a three-arm resveratrol-based core to obtain star-like (co)polymers. The obtained products were examined in terms of their physicochemical properties and morphology. Aside from the synthesis of these new glycopolymers, also a thorough description of their thermal properties, ability to self-assembly, the formation of stable superstructures was studied in detail. It was found that examined (co)polymers did not show any heterogeneities and phase separation, while their variation of glass transition temperature (Tg) was strictly related to the change in the number of glycomonomer. Also, the stability and shapes of formed superstructures strictly depend on their composition and topology. Finally, we have shown that synthesized carbohydrate-based polymers revealed high antiproliferative activity against several cancer cell lines (i.e., breast, colon, glioma, and lung cancer). The cytotoxic activity was particularly observed for star-shaped polymers that were systematically enhanced with the growing concentration of amine moieties and molecular weight. The results presented herein suggest that synthesized star-shaped glyco(co)polymers are promising as drug or gene carriers in anticancer therapies or anti-tumor agents, depending on their cytotoxicity. [ABSTRACT FROM AUTHOR]

Advanced electronic devices are supposed to highly integrated, such as wearable electronics, bioelectronics, and light-emitting diodes. The circuits are required to be fabricated compactly to the structure. This study proposed an approach to achieve close fabrication of circuit and structure. We used digital light processing additive manufacturing to rapidly form substrate structure, which is composed of ultraviolet-curable resin and Cu2(OH)PO4 particle. The substrate structure was then processed by laser activation and electroless plating metallization. As a result, the selective circuit can be fabricated on the surface of substrate structure. A series of characterizations were conducted using SEM, XPS, CLSM, and so on to investigate the morphology and analyze the surface chemistry of composite. After 5 min electroless copper plating, the resistivity of copper circuit on composite were 7.5 × 10−8 Ω·m. The obtained copper layer has good adhesion property (highest 5B level after adhesion test). This work provides an approach for complex structures of circuit and structure integrated devices, which has a potential application in advanced electronic devices. [ABSTRACT FROM AUTHOR]

Cold spray deposition, which can be framed in the wider family of additive manufacturing, is a manufacturing technique that is able to produce coatings on diverse types of substrates through the deposition of feedstock powder. As a low-temperature process, cold spray represents a potential solution for the metallization of temperature-sensitive materials, i.e. polymers and polymer matrix composites. The study of the cold spray technology for the metallization of polymers is still in its early stage, and the deposition mechanisms of metals on polymer-based materials are not thoroughly understood yet. On these premises, a review on this topic is needed to systematically depict the actual state of the art and to provide a reliable and well-organized overview discussing all the theories arisen in these years. In summary, this review aims: i) to collect all the available literature and enucleate the most discussed and interesting points (the most prevailing theories regarding the bonding mechanisms, the influence of the different process parameters and the main characteristics of cold-sprayed coating), providing a reliable and well-organized state of the art; ii) to define the open questions and to delineate the directions of future work. [ABSTRACT FROM AUTHOR]

Light-weight, cellular β-SiAlON/SiC ceramics were produced via dip-coating of an Al/Si-powder containing preceramic polymer slurry into corrugated cardboard. The coated cardboard preforms were pyrolyzed in Ar-atmosphere at 1200°C, where the cellulose fibres decomposed into carbon. Simultaneously the Al/Si melt infiltrated into the porous carbon and formed β-SiC. Subsequent nitridation at temperatures between 1200–1530°C resulted in the formation of a β-SiC-containing $$\beta{-}{\rm Si}_{6-z}{\rm AI}_z{\rm O}_z{\rm N}_{8-z}$$ composite. Different pre-oxidation treatment resulted in a variation of the oxygen content in the solid solution phase ( z = 0.6–1.2). [ABSTRACT FROM AUTHOR]

Ionomeric polymer transducers are electromechanical actuators fabricated from ion-exchange membranes that have been surface plated with conductive metal. In this paper we discuss a series of experiments that characterize the electromechanical actuation response of three families of ionomers: Nafion (a product of DuPont), BPSH (sulfonated poly(arylene ether sulfone)) and PATS (poly(arylene thioether sulfone)). The first polymer is commercially-available while the second and third polymers are synthesized by the direct polymerization of sulfonated monomers in our lab. The mechanical properties and actuation response of Nafion-117, BPSH, and PATS of varying ionic content are studied in the Lithium cation form. The strain response of the materials varies from 50 μ strain/V to 750 μ strain/V at 1Hz. A linear correlation was found between the strain response and the capacitance of the material. This correlation was independent of the polymer composition and the plating parameters. All of the ionomers analyzed in this work exhibited a strain-to-charge response between 9 $$\frac{\rm \mu strain}{\frac{C}{\rm m^2}}$$ and 15 $$\frac{\rm \mu strain}{\frac{C}{\rm m^2}}$$. Due to the fact that the low-frequency capacitance of an ionomer is strongly related to charge accumulation at the blocking electrodes, this correlation suggests a strong relationship between surface charge accumulation and mechanical deformation in ionomeric actuators. [ABSTRACT FROM AUTHOR]

This paper concentrates on a theoretical examination of the influence of roughness on the adhesive properties along metal-polymer interfaces. An algorithm has been designed to generate a self-affine surface roughness. It has been used to examine influence of the Hurst exponent on the interface strength during a pull-off test of metal-polymer laminates. The generated surfaces are implemented in a cohesive zone model representing the interface between a coated steel and polyethylene terephthalate (PET). From the model it can be concluded that a small increase in surface area is linear with the interface strength. This relation does not hold when the increase in surface area becomes larger than 150%. The deviation from the linear relationship increases with smaller Young’s moduli. This is caused by the reduced elastic energy storage in the polymer when local surface characteristics become more important. [ABSTRACT FROM AUTHOR]

Polymeric precursors to zirconium and hafnium diboride are described. Initial studies concentrated on carbothermal/borothermal reduction of metal alkoxides; however, improved results were obtained from oxide free-precursors prepared from the metal borohydride and borazine. The metal borides are obtained in good chemical and ceramic yield upon pyrolysis, and the polymeric precursors obtained through the reaction of borazine with the metal borohydride exhibit viscosities amenable to use as preceramic binders in powder processing. [ABSTRACT FROM AUTHOR]

A piezoelectric ceramic-polymer composite has been developed for use as a novel thick film strain sensor for vibration monitoring of structures. The material is in the form of a paint that can be applied to a wide range of substrates using conventional spraying equipment. The sensor properties depend on the morphology of the composite and on the electrodes that are used to couple it to the charge amplifier. Electrodes of various kinds have been tested. Interaction between the electrode and the piezoelectric paint sometimes occurs (for example, the organic vehicle for spray-coated electrodes may interact with the paint binder). The morphologies of the piezoelectric paint and of the electrode materials have been studied using light optical microscopy and scanning electron microscopy to investigate the effect of different compositions and of different processing conditions (e.g., paint mixing schedule). Preliminary work is reported on the characteristics of the piezoelectric particles and on the effect of heat treatment applied to anneal out defects produced by milling. X-ray analysis and particle size analysis have been used to characterize the changes that take place on heat treatment. X-ray diffractometry has also been used to follow the effect of poling on the paint sensors. At the present state of development sensors made using the paint have a dynamic range of at least 40-4000 microstrain and a bandwidth of at least 1 Hz-2 kHz, and piezoelectric coefficient d31 of approximately 20 pC/N. The sensors are resistant to outdoor exposure and a successful field trial has been conducted. [ABSTRACT FROM AUTHOR]

Carbon nanofillers such as carbon nanotube (CNTs), graphene and graphene–carbon nanotube (GCNT) hybrid play a significant role in a broad range of applications due to their outstanding properties. The outstanding properties of graphene and CNTs have not been entirely realized in polymer nanocomposites because of the serious concern of the agglomeration of CNTs and restacking of graphene at the times of the processing which resulted in the deterioration of properties of the final composites. To avoid these problems, graphene (2D) and carbon nanotube (1D) are used for the fabrication of three-dimensional (3D) hybrid nanofiller. GCNT hybrid is excellent nanofiller in which 3D interconnected hierarchical structures and their physico-chemical features enhance the properties significantly. The impressive 3D network structure of GCNTs hybrid-reinforced composites has to gain a significant improvement in the properties. GCNTs nanofiller has opened new paths of research for the production of next-generation advanced materials. This review article mainly summarizes the advancement in the GCNTs hybrid-reinforced polymer nanocomposites in terms of their synthesis, properties and applications. This review article is presented in four main sections. In the first section, the various synthesis techniques of CNTs, graphene and GCNTs are discussed. In the second section, GCNTs-reinforced hybrid composites prepared by three methods such as solution mixing, in situ polymerization and twin-screw extrusion techniques are discussed. In the third section, various properties like mechanical, electrical, thermal, rheological, dielectric properties of GCNTs-reinforced polymer nanocomposites are focused. In the last section, the focus is on the industrial applications of GCNTs-reinforced polymer nanocomposites as lightweight and high strength materials. Current challenges associated with GCNTs hybrid and future pathways for progress in GCNTs-reinforced polymer matrix composites are discussed. [ABSTRACT FROM AUTHOR]

We report on the transverse compression testing of fine,highly anisotropic polymer fibers. Single KEVLAR 29 fibers were laid on a flat, stiff platen, and compressed by a second, stiff, parallel platen. Test output was a force-deflection curve, from which the effective transverse modulus, apparent strain at yield and the work required to compress the fibers were determined. The effects of specimen aspect ratio was examined experimentally and by finite element simulation for loaded fiber lengths of 1/4 to 7 fiber diameters, and a method proposed to deduce the plane strain response from short aspect ratio tests. [ABSTRACT FROM AUTHOR]

We rely on polymer foams to build things from tissue engineer scaffold to airplanes. Still, traditional polymer foaming methods usually involve chemical agents or high-pressure gases, which can cause environmental and safety concerns. Therefore, we developed a novel microwave foaming method that uses only microwave irradiation as the driving force of foaming and water as the blowing agent. Using the microwave foaming method, we managed to generate polymer foams based on polyvinyl alcohol (PVA) within minutes. We also conducted experiments to study the influence of processing parameters on cell structures, such as the influence of microwave power and the initial water content, which shows that this method is controllable and has the potential to replace traditional foaming methods in future industrial application scenarios. [ABSTRACT FROM AUTHOR]

Thermal welding is commonly used in polymer composite pipeline, and the strength of the polymer welding joint remains a weak link. Short carbon fiber (SCF) is used to reinforce polymer welding joint, where a hybrid welding interface between SCF-reinforced polymer composite and polymer is introduced. The hybrid welding interface involves joining of dissimilar materials, and there is a lack of understanding about the strength of the composite–polymer welding interface. In this study, shear and peel tests were conducted to evaluate the strength of the hybrid welding interface. Strain distribution around welding interface during testing was measured by digital image correlation, and the failure surfaces were analyzed by microscope observation. The results showed that both shear and peel strength of the hybrid welding interface were improved due to the bridging effect of SCF on the hybrid welding interface. However, it was also found that the SCF near the welding interface tended to orientate parallel to the welding interface after welding, and the welding-induced orientation limited the strengthening effect of SCF. The hybrid welding interface had larger shear rigidity, which led to a more even strain distribution, and could bear larger shear load comparing to pure polymer welding interface. [ABSTRACT FROM AUTHOR]

The strategy of ternary blend is one of the most important approaches to enhance the power conversion efficiency (PCE) for polymer solar cells (PSCs). The present work prepared a new series of ternary PSCs, PBDB-T-2F:IT-4F:ITIC, based on the perspective of compatibility of non-fullerene molecule (ITIC) and its derivative (IT-4F) and studied the effect of the third component (ITIC) on the morphology and photoelectric conversion process of PBDB-T-2F:IT-4F solar cells. The results showed that surface roughness and phase scale of the PBDB-T-2F:IT-4F changed with the ITIC content, leading to variable morphology, optical, photophysical and electrical characteristics in ternary blend active layers. When the content of ITIC reached 20%, the ternary PSCs achieved the highest PCE (13.41%) among the PSCs. Morphology and optical spectroscopy studies showed that the enhanced performance of ternary device can be attributed to the morphology optimization of ternary active layer with the content of ITIC, and consequently the improved charge photogeneration processes. This work provided another way to achieve the high-performance ternary polymer solar cells via the combination of compatible non-fullerene molecules. [ABSTRACT FROM AUTHOR]

In the development of copper-based composite materials, the dilemma of improving the mechanical properties without affecting the electrical properties is an important issue that must be solved. Here, carbonized polymer dot (CPD), as a novel reinforcement, was employed to fabricate CPD/Cu (pure copper) composite via powder metallurgy technique for the first time. The microstructure analysis revealed that the CPD was uniformly dispersed in the copper matrix in the form of nanoclusters, and the nanoclusters of CPD are composed of a three-dimensional amorphous carbon (AC) network structure and inserted carbon dots (some of them have a typical graphene structure, while others not). More importantly, excellent interface combination between the CPD and copper matrix is observed due to the existing of plenty of chemical functional groups. Based on this special microstructure, our prepared CPD/Cu composite achieves excellent mechanical and electrical conductivity simultaneously. Compared to pure Cu, the ultra-tensile strength of 0.2CPD/Cu composite is increased by about 17.0%, while the elongation is only ~ 2% lower. The electrical conductivity of the composite is ~ 98% IACS, which is much higher than that of pure copper prepared under the same condition (only ~ 92% IACS). New insights into how to prepare advanced copper matrix composites with simultaneously improved overall performance will be found from our research. [ABSTRACT FROM AUTHOR]

This experiment aims to study the performance of multilayered transparent wood (MLTW) under the condition of partial delignification, including the effect of lamination structure between layers and delignification process on the properties of MLTW. New Zealand pine (Pinus radiata D.Don) and Basswood (Tilia) were selected. The acid method was used to remove part lignin for preparing wood templates with natural wood color and texture, and then the polymer impregnated wood templates. During the lamination process, three wood templates were laminated by parallel direction (MLTW∥) or perpendicular direction (MLTW⊥) to prepare for MLTW. Under macro- and microtest, it can be seen that the laminate structure has a certain impact on the mechanical properties and light transmittance of MLTW, and MLTW can effectively reduce the anisotropy of single-layer one with the same thickness. MLTW is suitable for home decoration and structure materials and has broad application prospects. [ABSTRACT FROM AUTHOR]

Highly thermally conductive but electrically insulating polymer composites play an increasingly important role in thermal management applications due to their features of easy processing and lightweight. Herein, a unique segregated network, which consists of graphene nanoplatelets (GNP) and boron nitride fibers (BNF), was constructed in polypropylene (PP)-based composites via two-screw extrusion. The thermal conductivity and electrical insulation characteristic of the composites could be well controlled by adjusting the content and size of GNP and BNF. When PP was filled with 9wt% GNP and 30wt% short BNF, the highest thermal conductivity of 1.32 W/(m·K) was achieved in this work, which is about six times higher than the value of neat PP, while remained a good electrical insulating (as low as 2.98 × 10−9 S/m). It proposed that the unique segregated network, where the BNF play as a bridge to connect the scattered GNP, could benefit for phonons transmission but effectively interrupt electron conduction. Our work provides a facile method to design and fabricate the highly thermally conductive but electrically insulating composites applied in thermal management materials. [ABSTRACT FROM AUTHOR]

In this study, high-performance flexible strain sensors based on carbon nanotube (CNT) and graphene nanoplatelet (GNP) filled thermoplastic polyurethane (TPU) composites were fabricated via Fused Filament Fabrication (FFF) 3D printing. The introduction of GNPs generated a more complete conductive network of the composites due to the improved nanofiller dispersion. Due to the synergy of CNTs and GNPs, the printed CNT/GNP(3:1)/TPU sensor shows higher sensitivity (GF = 136327.4 at 250% strain), larger detectable range (0–250% strain), and better stability (3000 cycles) compared with the CNT/TPU and GNP/TPU sensors with a nanofiller content of 2 wt%. Furthermore, the printed sensors can accurately detect strains at different frequencies (0.01–1 Hz). A modelling study based on tunneling theory was conducted to analysis the strain sensing mechanism, and the theoretical results agreed well with the experimental data. The capability of the sensors in monitoring physiological activities and speech recognition has also been demonstrated. [ABSTRACT FROM AUTHOR]

Examines the two-step positive temperature coefficient effect in immiscible polymer blends filled with carbon black. Conductive polymer composite materials; Use of high density polyethylene (HDPE) and polypropylene (PP) as the polymer matrix; Dependence of the log resistivity on HDPE content in the HDPE/PP blends.

Polymer nanocomposite performance depends not only on the compatibility between nanoparticles and polymer matrix, but also the sequence in which the nanoparticle is incorporated into the polymer and the compounding device applied. In this study, we report the morphology, oxygen permeability, thermal and mechanical properties of the polypropylene nanocomposites change due to the use of a thermokinetic mixer when specific preparation steps are followed based on the dispersing agents used. Two organically modified clays and dispersing agents were applied: montmorillonite and hydrotalcite; hydrogenated hydrocarbon resin and poly (propylene-g-maleic anhydride) as compatibilizer with different maleic anhydride content. For the nanocomposites containing montmorillonite, poly (propylene-g-maleic anhydride), with low maleic anhydride content and the hydrocarbon resin prepared using the thermokinetic mixer, a more efficient clay dispersion was achieved. As a result, an increase in mechanical stiffness (57% in the Young modulus), higher thermal stability and a decrease in oxygen permeability (58%) were obtained. However, samples prepared with hydrotalcite achieved a better distribution and dispersion by preparing directly on a twin-screw extruder. Wherein, higher mechanical stiffness (36% in the Young modulus) with reduction in the oxygen permeability (52%) was reached when poly (propylene-g-maleic anhydride) with low maleic anhydride content and the hydrocarbon resin were present. These results point to that by using the dispersing agents in combined with a proper mixing system is possible to improve polyolefin nanocomposite properties, increasing the range of application in the packaging industry. [ABSTRACT FROM AUTHOR]

Polymerized high internal phase emulsion (polyHIPE) monoliths have attracted much attention because of their ease of preparation, precise control of porous structure and useful properties. For many applications, such as chromatographic separation media, reactivity or absorptivity, post-modification of surface functional groups is required to achieve the desired functionality. However, for fluoro-polymers, it has been a challenge to fabricate high-performance foams with uniform porous structures using HIPE due to the lack of suitable surfactants to stabilize the fluorinated emulsions. In our work, we proposed a bottom-up approach where the same surfactant that stabilized the water droplets within the oil phase was used to control the solid foam surface chemistry. We employed reversible addition–fragmentation chain transfer living radical polymerization to synthesize amphiphilic-fluorinated macrosurfactant (mPEG5K-PHFBMA) to stabilize water-in-oil (W/O) HIPE. Using hexafluorobutyl methacrylate as the oil-phase monomer and divinylbenzene as the cross-linking agent, we achieved a one-pot preparation of polyHIPEs based upon poly(ethylene glycol) (PEG) with biocompatible pore surfaces and potential use in tissue engineering. The effects of amphiphilic macromolecular surfactant concentration, PHFBMA block length and initiator oil/water solubility on the emulsion droplet size, pore morphology, porous surface performance and mechanical properties were studied. The PEG modification on porous surface in the polyHIPE was also confirmed by a contact angle test and water uptake experiment. It was found that short-chain fluorinated materials demonstrated very little bioaccumulation potential and consequently better environmental safety attributes. The addition of PEG gave good biocompatibility, and the properties of these porous materials may have great potential in cell tissue engineering applications. [ABSTRACT FROM AUTHOR]

This study examines perfluorocyclobutyl (PFCB) aromatic ether polymers and demonstrates, for the first time, their potential as corrosion-resistant coatings. PFCB polymers are a distinct class of semi-fluorinated polymers that are based on thermal cyclopolymerization of aromatic trifluorovinyl ethers. They combine the flexibility and thermal stability of aromatic ethers with strong fluorocarbon linkages. Electrochemical impedance spectroscopy and potentiodynamic scans reveal that PFCB coatings display protective barrier properties against corrosion attack nearly equal to that of polyvinylidene fluoride (PVDF) coatings. The PFCBs also show excellent adhesion to metal surfaces and nonstick properties comparable to that of PVDF. Combined with their high thermal resistance, PFCBs may lead to new corrosion-resistant coatings in marine, oil and gas, and other applications. [ABSTRACT FROM AUTHOR]

In this study, a novel surface modification approach for preparation of nanoscale titanium dioxide using aluminate coupling agent was developed. By optimizing the adding content of aluminate coupling agent and the reaction temperature, modified titanium dioxide (A-TiO2) particles with a minimum Z-average size of 32 nm and a narrow PDI of 0.214 were obtained. Further tests revealed that A-TiO2 was super-hydrophobic with water contact angle of 151.39°. Moreover, the dispersion behaviors and morphologies of TiO2 and A-TiO2 particles in different solvents were further investigated. The results indicated that A-TiO2 could be well dispersed in hot liquid caprolactam, making it suitable for preparing full-dull polyamide-6 polymers. [ABSTRACT FROM AUTHOR]

Design and synthesis of heteroatoms-doped porous carbon model materials with controllable nitrogen contents and similar pore structure are of great importance for fundamental understanding of the correlation between their intrinsic properties and applications. Herein, we report a synthetic strategy for synthesis of nitrogen-doped hollow carbon nanospheres with variable nitrogen contents, similar pore structure and morphology by pyrolysis of mixed polymer brushes formed through surface-initiated atom transfer radical polymerization of monomer mixtures of styrene and 4-vinylpyridine. With increasing 4-vinylpyridine fractions in the monomer mixture, nitrogen contents in the final carbon products increase up to about 5.5 wt%. As example applications, electrocatalytic performance for oxygen reduction reactions in both basic and acidic media and carbon dioxide adsorption properties of the thus-formed materials are investigated to evaluate the synthetic approach. The results reveal that the higher nitrogen contents doped in carbon do not guarantee the better performance for either electrocatalysis or carbon dioxide adsorption. It is the fraction of pyridinic nitrogen that dominates the electrocatalytic activity and carbon dioxide adsorption capacity. The findings demonstrate that mixed polymer brushes are promising precursors for the formation of heteroatoms-doped carbon materials, particularly as model materials for fundamental understanding their structure-properties correlations. [ABSTRACT FROM AUTHOR]

The development of efficient heterogeneous catalysts for reductive conversion of 4-nitrophenol (4-NP) is of vital significance for environmental remediation, dyestuff industry, pharmaceutical industry. We reported that Au@D201, a polymer gold nanocomposite of gold nanoparticles loaded on D201 resin, was prepared using macroporous styrenic ion exchange resin D201 as carrier, chloroauric acid as gold source and sodium borohydride as reducing agent. The average diameter of gold nanoparticles in Au@D201 composites is 5 nm, which has excellent catalytic properties for the reduction of 4-nitrophenol. The Au@D201 was characterized by ultraviolet-visible spectroscopy, X-ray diffraction, mercury injection instrument, transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). The results reveal that some of the gold nanoparticles were loaded on the surface of the resin, and most of the gold nanoparticles were in the resin pores. A strong chemical interaction, between the gold nanoparticles and the resin, is similar to the cross-linking action of the macromolecules. The gold nanoparticles provide a new cross-linking point for the resin, increasing the degree of cross-linking of the resin and causing some degree of resin ordering to occur. XPS shows that the electron density of the outer layer of the gold atom increases, indicating that there are some conjugated interactions between the resin and gold atoms. Conjugated interactions and the gold quantum size effect are the main reasons for improving the catalytic effect of the composite material. When the gold nano-loading amount is 0.1%, it still has an excellent catalytic effect on the reduction reaction of 4-nitrophenol. [ABSTRACT FROM AUTHOR]

Polymer particles with sophisticated wrinkle patterns for addressing specific functional demands have found increasing applications in many fields. Here, we describe a novel strategy to prepare controllable wrinkled-surface polymer microspheres by soap-free emulsion polymerization method via using amphiphilic 1,1-diphenylethylene-capped hydrolyzed poly (glycidyl methacrylate) (D-PGMA) as emulsifier and initiator, which simplified the emulsion system to only three components, water, monomer and D-PGMA. It was found that both cross-linked polymer network and swelling were essential to wrinkle morphology formation of polymers by carefully monitoring the structural evolution during polymerization process. Furthermore, we investigated that wrinkle wavelength and amplitude could be controlled easily not only by varying mass ratios of D-PGMA and monomer, but also by introducing different types and dosages of solvents. Scanning electron microscopy, transmission electron microscopy, and atomic force microscopy were used to characterize wrinkle phenomenological features. Besides, by combining with mercury porosimetry, the possible internal groove structures were deduced. At last, X-ray photoelectron spectroscopy was applied to further explore the relationship between chemical components and wrinkle morphology. [ABSTRACT FROM AUTHOR]

A triphenylamine-functionalized A3B2-type covalent organic polymer (TPA-COP) was synthesized by the palladium-catalyzed Sonogashira polycondensation reaction from tris(4-ethynylphenyl)amine and 4-bromo-N-(4-bromo-2-methoxybenzylidene)-2-methoxyaniline. The obtained polymer possessing amorphous structure and good thermal stability exhibited strong yellow-green luminescence with an emission band at 498 nm. It is worth noting that the polymer also shows selective turn-on fluorescence response to Fe3+ ion over a variety of other competing metal ions such as Na+, K+, Ca2+, Mg2+, Ba2+, Mn2+, Cr3+, Cu2+, Ni2+, Zn2+, Co2+, Al3+. The fluorescent detection limit of TPA-COP sensor for Fe3+ in solution was 4.3 × 10−7 M. Furthermore, the proposed sensing mechanism should result from complexation between tridentate-coordinated Schiff base sites and Fe3+ ion, which was further investigated by fluorescence titration, 1H NMR and IR measures, together with fluorescence lifetime analysis. [ABSTRACT FROM AUTHOR]

Polymers with high dielectric constants are widely used in electronic devices and electric systems. However, polymers exhibit low dielectric constants, which greatly limit their applications. Currently, ferroelectric ceramic fillers and conductive filler are commonly filled into polymer matrix to achieve enhanced dielectric constants. Unfortunately, even though the loading fraction of ferroelectric ceramic fillers exceeds 50 vol%, the enhancement of dielectric constant is still limited. On the contrary, although ultrahigh dielectric constant could be realized in conductor/polymer composites containing small loading fractions of conductive fillers, the loss is usually very high owing to severe leakage conduction. To overcome the shortcomings of the above-mentioned two types of high dielectric composites, this work combined them together and designed a series of trilayer polymer composites consisting of one carbon nanotube/polyimide composite layer sandwiched by two BaTiO3/polyimide composite layers. Fortunately, the trilayer architecture could effectively overcome the drawbacks of carbon nanotube/polyimide and BaTiO3/polyimide single-layer composites, hence the balanced dielectric constant and loss. When the BT content of the outer layer is 50 wt% and the carbon nanotube content of the middle layer is 4 wt%, the trilayer film possesses a high dielectric constant of ~ 35 @10 kHz, which is about 700% over pristine PI matrix (ε′ ≈ 5 @10 kHz). Meanwhile, the loss tangent of the trilayer composite (tanδ ≈ 0.03 @10 kHz) is still comparative to pristine PI (tanδ ≈ 0.01 @10 kHz). [ABSTRACT FROM AUTHOR]

Plasma-based technology is an alternative to produce universal polymer coatings with the appropriate requirements of robustness and stability for antibacterial applications. Here, we proposed a sequential two-step alternative to synthesize antibacterial polymer coatings. A non-isothermal plasma reactor, operated at atmospheric pressure (Patm) and room temperature (Troom), was used to induce free radical polymerization of 4-vinyl pyridine (4VP) on high-density polyethylene (PE). In a subsequent step, the poly-4VP (P4VP) films were treated with a bromoethane/He gas stream to produce quaternized P4VP (P4VPQ) films. Chemical structure of polymer films was validated by infrared and UV-visible spectroscopy, and morphology was evaluated by optical and atomic force microscopy; scanning electron microscopy was used to determine films thickness, which was then used to estimate the surface charge density. The bactericidal capacity was determined with a standard test by using Escherichia coli. Both types of films had an estimated charge density in the order of 1016 positive charges per cm2; P4VP films removed about 95-99% of bacteria, whereas 4PVPQ films eliminated 100%. The methodology proposed for the synthesis of antibacterial polymer coatings is simpler, faster, and more environmentally friendly than other plasma-based methods; operation at Troom and Patm may also have a significant effect on the economics and the ease of implementation of the process at commercial scale. The suggested approach may facilitate the development of new universal coatings, and operating plasma conditions could be extrapolated for engineering antibacterial coatings in industrial areas where bacterial attachment is of concern. [ABSTRACT FROM AUTHOR]

With the development in the modern technologies such as telecommunication instruments and scientific electronic devices, large amount of the electromagnetic radiations are produced, which lead to harmful effect on the highly sensitive electronic devices as well as on the health of human beings. To minimize the effect of electromagnetic radiations produced by different technologies, more efficient shielding materials are required which must be cost-effective, lightweight and good corrosion resistive. In this review, we focused on the shielding materials based on composites of carbon nanotubes and graphene. The typical surface modification of carbon nanotubes and graphene to optimize their interactions with polymers matrix has also summarized. It was found that the composites based on these carbon fillers were more efficient for electromagnetic interference shielding due to their unique properties (i.e., superior electrical, mechanical and thermal) together with lightweight, easy processing. Hence, the carbon nanotubes and graphene-based composites are excellent shielding materials against the electromagnetic radiations. [ABSTRACT FROM AUTHOR]

The powder compaction modeling of advanced sintering techniques such as spark plasma sintering is a crucial step in the conception of complex shape objects and the understanding of the process. The complete identification of common powder compaction models requires lengthy experimental investigations based on creep and compaction tests. In order to circumvent this problem, a semi-theoretical approach can be employed whereby the mechanical behavior of the powder material is determined theoretically and the temperature-dependent equivalent creep behavior of the material is determined experimentally. Extending the use of this approach to polymers, metals and ceramics is discussed and compared to other independent methods. [ABSTRACT FROM AUTHOR]