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Paper is a widely used packaging material and is nowadays regaining importance, e.g., as bio-based and biodegradable material. Moreover, new technologies such as polymer-fiber composites, printed electronics and the deep drawing of paper are developing. The process stability and also the resulting quality of paper converting processes such as coating, metallization, printing, and the printing of electronics are highly affected by the hygroexpansion of paper. In order to reduce production instability and to choose and develop paper substrates with ideal characteristics, critical parameters need to be known. This paper offers an extensive overview of those parameters, starting at a molecular and microscopic level with the effect of the constituents and morphology of single fibers, before moving on to paper contents, chemical modifications and additives and finally concluding with paper production and fiber network modification. It was found that the major influences are single fiber sorption, inter-fiber contacts, microfibril angle, fiber morphology (length, width, curliness) and fiber orientation. This review gives new ideas and insights for technologists working in research, development and production optimization of paper-based products. [ABSTRACT FROM AUTHOR]

The article presents a list of papers related to materials science published in volumes 39, 40 and 41 of the periodical. The articles include "Adhesively-Bonded Joints and Repairs in Metallic Alloys, Polymers and Composite Materials," by A. Baldan, "Thermo-Mechanical Fatigue of Shape Memory Alloys," by E. Hornbogen and "Models in Thermoluminescence," by C. Furetta and G. Kitis.

The article presents a list of articles related to materials science published in volumes 39, 40, and 41. The articles include "Adhesively-bonded joints and repairs in metallic alloys, polymers and composite materials," "Observations of common microstructural issues associated with dynamic deformation phenomena: Twins, microbands, grain size effects, shear bands, and dynamic recrystal," and "Role of entropy of fusion in phase transformation and selfdiffusion."

The article presents a list of review articles published in the previous issues of the journal including "Adhesively-Bonded Joints and Repairs in Metallic Alloys, Polymers and Composite Materials," "Thermo-Mechanical Fatigue of Shape Memory Alloys," "Role of Entropy of Fusion in Phase Transformation and Self-Diffusion," "Models in Thermoluminescence," and "Electrical Applications of Carbon Materials."

The article presents a list of articles published in the "Journal of Materials Science," including "Adhesively-Bonded Joints and Repairs in Metallic Alloys, Polymers and Composite Materials," "Thermo-Mechanical Fatigue of Shape Memory Alloys," "Role of Entropy of Fusion in Phase Transformation and Self-Diffusion," "Synthetic Routes, Properties and Future Applications of Polymer-Layered Silicate Nanocomposites," and "Models in Thermoluminescence."

The article presents several review papers published in the Volumes 39 and 40 of the "Journal of Materials Science" including "Adhesively-Bonded Joints and Repairs in Metallic Alloys, Polymers and Composite Materials," by A. Baldan, "Thermo-Mechanical Fatigue of Shape Memory Alloys," by E. Hornbogen, "Recent Developments in Polyurethane-based Conducting Composites," by J. Njuguna and K. Pielichowski, "A Review of Anode Materials Development in Solid Oxide Fuel Cells," by San Ping Jiang, Siew Hwa Chan, and "Advances in the Study on Wear of Metals by Polymers," by Si-Wei Zhang and Ren-Yang He.

Presents review papers in the volumes 39 and 40 of the February 15, 2005 issue of the "Journal of Materials Science". Adhesively-bonded joints and repairs in metallic alloys, polymers and composite materials; Thermo-mechanical fatigue of shape memory alloys; Electrical applications of carbon materials,

This paper presents the results obtained for the effects of the loading rate and of the testing temperature on the mechanical properties, particularly on the stiffness and on the ultimate tensile strength, of a geopolymer reinforced with glass or carbon fibres. HIGH-SILICA geopolymer powder from CLUZ- CYECH and two reinforcement fibres (glass fibres—type AR and carbon fibre - HTS 5631) were used. The displacement rate is varied from 0.02 until to 2 mm/s and the testing temperature is increased from the room temperature until the temperature of 300 °C. For the case of geopolymers reinforced with carbon fibres and glass fibres, the increase of the displacement rate from 0.002 to 2 mm/s led to an improvement on the ultimate flexure strength of about 33 and 31%, respectively. The same dependency was observed for the stiffness, with variations of loading rate of 39 and 53%, for carbon fibres and glass fibres, respectively. Increasing the room temperature until the temperature of 300 °C decreases significantly both the ultimate strength and the flexure stiffness for both reinforcements. However, a major drop on both the stiffness and the strength occurred up to 150 °C. [ABSTRACT FROM AUTHOR]

In the present paper, the following topics are reviewed in detail: (a) the available adhesives, as well as their recent advances, (b) thermodynamic factors affecting the surface pretreatments including adhesion theories, wettability, surface energy, (c) bonding mechanisms in the adhesive joints, (d) surface pretreatment methods for the adhesively bonded joints, and as well as their recent advances, and (e) combined effects of surface pretreatments and environmental conditions on the joint durability and performance. Surface pretreatment is, perhaps, the most important process step governing the quality of an adhesively bonded joint. An adhesive is defined as a polymeric substance with viscoelastic behavior, capable of holding adherends together by surface attachment to produce a joint with a high shear strength. Adhesive bonding is the most suitable method of joining both for metallic and non-metallic structures where strength, stiffness and fatigue life must be maximized at a minimum weight. Polymeric adhesives may be used to join a large variety of materials combinations including metal-metal, metal-plastic, metal-composite, composite-composite, plastic-plastic, metal-ceramic systems. Wetting and adhesion are also studied in some detail in the present paper since the successful surface pretreatments of the adherends for the short- and long-term durability and performance of the adhesive joints mostly depend on these factors. Wetting of the adherends by the adhesive is critical to the formation of secondary bonds in the adsorption theory. It has been theoretically verified that for complete wetting (i.e., for a contact angle θ equal to zero), the surface energy of the adhesive must be lower than the surface energy of the adherend. Therefore, the primary objective of a surface pretreatment is to increase the surface energy of the adherend as much as possible. The influence of surface pretreatment and aging conditions on the short- and long-term strength of adhesive bonds should be taken into account for durability design. Some form of substrate pretreatment is always necessary to achieve a satisfactory level of long-term bond strength. In order to improve the performance of adhesive bonds, the adherends surfaces (i.e., metallic or non-metallic) are generally pretretead using the (a) physical, (b) mechanical, (c) chemical, (d) photochemical, (e) thermal, or (e) plasma method. Almost all pretreatment methods do bring some degree of change in surface roughness but mechanical surface pretreatment such as grit-blasting is usually considered as one of the most effective methods to control the desired level of surface roughness and joint strength. Moreover, the overall effect of mechanical surface treatment is not limited to the removal of contamination or to an increase in surface area. This also relates to changes in the surface chemistry of adherends and to inherent drawbacks of surface roughness, such as void formations and reduced wetting. Suitable surface pretreatment increases the bond strength by altering the substrate surface in a number of ways including (a) increasing surface tension by producing a surface free from contaminants (i.e., surface contamination may cause insufficient wetting by the adhesive in the liquid state for the creating of a durable bond) or removal of the weak cohesion layer or of the pollution present at the surface, (b) increasing surface roughness on changing surface chemistry and producing of a macro/microscopically rough surface, (c) production of a fresh stable oxide layer, and (d) introducing suitable chemical composition of the oxide, and (e) introduction of new or an increased number of chemical functions. All these parameters can contribute to an improvement of the wettability and/or of the adhesive properties of the surface. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of magnetic field-assisted filler alignment technology on the morphology and the thermal conductivity of magnetite-filled epoxy composites. A magnetic field was applied during the solidification of the composite in order to change the position of the filler and its distribution in the polymer matrix. It is shown that the applied procedure leads to the filler being oriented along the direction of the magnetic field, and as a result, the thermal conductivity is improved by up to 120 % compared to a composite with randomly oriented filler obtained without the assistance of a magnetic field. This positive effect is caused by the appearance of conductive paths at a much lower content of the filler when the composite solidification is assisted by a magnetic field, relative to an equivalent isotropic sample. These morphological changes were confirmed by microscopic and X-ray microtomography imaging. The temperature dependences of thermal conductivity were also investigated over a broad temperature range for a magnetite-filled epoxy composite sample and compared to the bulk magnetite reference, showing that thermal behaviour of the magnetite-filled composite is stable, which is a promising result when considering the future application of the technology. [ABSTRACT FROM AUTHOR]

The present paper investigates the effect of adding silica nanoparticles to an anhydride-cured epoxy polymer in bulk and when used as the matrix of carbon- and glass-fibre reinforced composites. The formation of ‘hybrid’ epoxy polymers, containing both silica nanoparticles and carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber microparticles, is also discussed. The structure/property relationships are considered, with an emphasis on the toughness and the toughening mechanisms. The fracture energy of the bulk epoxy polymer was increased from 77 to 212 J/m2 by the presence of 20 wt% of silica nanoparticles. The observed toughening mechanisms that were operative were (a) plastic shear-yield bands, and (b) debonding of the matrix from the silica nanoparticles, followed by plastic void-growth of the epoxy. The largest increases in toughness observed were for the ‘hybrid’ materials. Here a maximum fracture energy of 965 J/m2 was measured for a ‘hybrid’ epoxy polymer containing 9 wt% and 15 wt% of the rubber microparticles and silica nanoparticles, respectively. Most noteworthy was the observation that these increases in the toughness of the bulk polymers were found to be transferred to the fibre composites. Indeed, the interlaminar fracture energies for the fibre-composite materials were increased even further by a fibre-bridging toughening mechanism. The present work also extends an existing model to predict the toughening effect of the nanoparticles in a thermoset polymer. There was excellent agreement between the predictions and the experimental data for the epoxy containing the silica nanoparticles, and for epoxy polymers containing micrometre-sized glass particles. The latter, relatively large, glass particles were investigated to establish whether a ‘nano-effect’, with respect to increasing the toughness of the epoxy bulk polymers, did indeed exist. [ABSTRACT FROM AUTHOR]

The polymer composites filled with nanoparticles have good friction and wear properties and widely used in many fields. The performances of nanocomposites are influenced extensively by the nanoparticles morphology, size, volume fraction and dispersion. Nanometer ZrO2 particles have good properties, lower prices and shows good foreground in resist-materials of polymer composites. In this paper, the nanometer ZrO2 particles are treated by silane coupling agent of N-(2-aminoethyl)-γ-aminopropylmethyl dimethoxy silane. The effect of nanometer ZrO2 content and silane coupling agent on the friction and wear properties of BMI copmposites filled with nanometer ZrO2 are investigated. The composites filled with untreated ZrO2 and treated ZrO2 are prepared by the same way of mechanical high shear dispersion process and casting method. The sliding wear performance of the nanocomposites is studied on an M-200 friction and wear tester. The experimental results indicate that the frictional coefficient and the wear rate of the composites can be reduced by filled with nanometer ZrO2. The composites containing treated nanometer ZrO2 have the better tribological performance than that containing untreated nanometer ZrO2. The results are explained from the SEM morphologies of the worn surface of matrix resin and the composites containing nanometer ZrO2 and the TEM photographs of the nanometer ZrO2 dispersion in the matrix. [ABSTRACT FROM AUTHOR]

In this paper, we report a new method to prepare the polymer/inorganic nanoparticle composites using electron irradiation-induced polymerization. The mixture of nanoparticles and MMA solution were co-irradiated by 1.6 MeV electron beam to a dose of 10, 20 and 30 kGy at a dose-rate of 60 kGy/h in air at room temperature. The products after irradiation were extracted using a soxhlet extractor with boiling xylene and investigated by X-ray diffraction (XRD), Fourier transmission infrared (FTIR), X-ray photoelectron spectroscopy (XPS), optical absorption spectra (OAP) and photoluminescence (PL). The FTIR and XPS results show that there exist some unextractable PMMA in the nanocomposites after extraction, indicating a strong interaction between the PMMA and nanoparticles. PL results show that new luminescence peaks appear at 415 and 420 nm for the nanocomposites of anatase and γ-Al2O3. [ABSTRACT FROM AUTHOR]

The factors affecting the mechanical and environmental durability (or stability), and performance of the adhesively bonded joints in various adherends including metallic alloys, polymers and composite materials are studied in detail. The primary function of a joint is to transfer load from one structural member to another. In most bonded joints the load transfer takes place through interfacial shear. At present the use of adhesive bonded joints are largely applied to secondary non-critical structures. Whereas the use of adhesive bonding in primary structural applications has been somewhat limited because of the difficulty in defining and predicting joint strength, and designing the joint geometry to optimize strength and reliability. The determination of adhesive joint strength is complicated primarily by the nature of the polymeric material itself. Since these problems are mainly mechanical in nature, stress analysis is required to understand how the force loads are distributed along the adherends and adhesive layer. Most structural engineers consider the durability or stability of a joint to be fatigue related. This is only partly true for adhesive bonds as most durability issues are driven by environmental resistance rather than fatigue loads. The environmental resistance of an adhesive bond is determined by the chemical bonds formed during cure of the adhesive and the resistance of the chemical bonds to environmental degradation. Environmental resistance is fundamental to the durability of a bonded joint or repair. Most in-service failures are caused by environmental degradation of the interface between the bonding surface and the adhesive. Although the use of adhesive bonding is increasing rapidly, there are still important issues which need to be addressed in joint analysis, design, durability, and performance considerations. Therefore, the study of joints usually involves consideration of (a) joint geometries, (b) materials (i.e., adhesives and adherends), (c) loading conditions (i.e., static and dynamic loadings), (d) failure modes (i.e., cohesive, adhesive or mixed failure modes), and (e) temperature and moisture or environmental effects (humidity, solvents, corrosion, temperature extremes, thermal cyling etc.). Therefore, in the present paper the adhesive joints are critically assessed in terms of these factors which affect the durability and performance of them. There are two basic mathematical approaches for the analysis of adhesively bonded joints: (a) closed-form or analytical model and (b) numerical solutions (i.e., finite element analysis, FEA). In the closed-form approach, a set of differential equations and boundary conditions is formulated. The solutions of these equations are analytical expressions which give values of stresses at any point of joint. The analytical approach for the solution of complex stress distributions in the joints has been progressively refined until recent times. In the second approach, solutions of differential equations are obtained by numerical methods or the continuum is represented by a discrete model at the outset. The solution of these equations gives displacements at the determined points from which strains and stresses can be obtained for any point within the model. Among the numerical methods, finite element analysis (FEA) has been extensively used with success. The two- and three-dimensional finite element analyses approaches have been extensively applied by many workers to analyse the adhesive joints considering the linear and geometric nonlinearities. [ABSTRACT FROM AUTHOR]

This paper focuses on polymer nanocomposites and their syntheses, properties and future applications, several of these application will be successful in the near future. This new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation, may be prepared via various synthetic routes comprising exfoliation adsorption, in-situ intercalative polymerization and melt intercalation. The whole range of polymer matrices covered, i.e., thermoplastics, thermosets and elastomers. Small addition—typically less than 6 wt%—of these nanoscale inorganic fillers promote concurrently several properties of the polymer materials, including tensile characteristics, heat distortion temperature, scratch resistance, gas permeability resistance, and flame retardancy. [ABSTRACT FROM AUTHOR]

Ethylene propylene diene rubber (EPDM) is a well-known versatile polymer, which is frequently used in the production of rubber goods based on conventional and specialty polymers. The present paper investigates the role of recycled natural rubber prophylactic waste compared to virgin natural rubber in the development of novel ethylene propylene diene rubber composites. The processing characteristics have been evaluated using a Monsanto rheometer at three different temperatures 150, 160 and 170°C. The cure curves of EPDM compounds have been found to be the resultant of slow curing or marching cure curve of EPDM and that of fast curing ‘S’ shaped cure curve of natural rubber. The curing properties such as optimum cure time, scorch time and induction time have been found to be decreasing with the loading of prophylactic filler. For most of the cases, the values obtained for compositions with virgin natural rubber (ISNR-5) have been found to be lower than that with prophylactic filler. The cure activating nature of the prophylactic waste in EPDM is higher at higher temperatures. The unaged tensile strength has been increased with the loading of prophylactic filler up to 30 phr. The aged tensile strength and unaged/aged elongation at break have been found to be a maximum at 20 phr prophylactic filler loading. The tear strength has been found to be a maximum at 40 phr. Better performance has been noted in the case of virgin natural rubber filled samples for unaged/aged tensile strength, elongation break and tear strength except at 40 phr loading. The diffusion process in EPDM vulcanizates is found to be anomalous. Crosslink density values determined using Mooney-Rivlin equation agree with the tensile strength values for most of the cases. An increase in the crosslink density has been noted with the thermal aging of the samples. [ABSTRACT FROM AUTHOR]

In this paper, the all-optical switching polymer composites based on poly(methyl methacrylate) (PMMA) and azobenzene dyes were prepared. The optical switching effects of the composites were measured by using 514 nm pump beam and 632.8 nm probe beam. The composites' photoinduced reversible and repeatable change in the transmittance of the probe beam is attributed to the photoisomerization of the azobenzene dyes. The influencing factors of the optical switching properties, such as the modulation frequency, pump beam intensity and temperature, were studied experimentally. The effects of pump beam power and temperature on the optical switching response were also studied experimentally. [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]

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]

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]

Further utilization of polymer matrix composites (PMCs) in the aerospace industry is threatened by the development of laser weapons, resulting from weak oxidation resistance, low operation temperature and poor anti-laser ablation performance of the PMCs. Preparing an adhesive inorganic coating on the surface of components is an effective method to improve the laser irradiation resistance. Anti-laser ablation coatings composed of ZrO as pigment and sodium silicate as binder with different curing agents (including SiO and NaSiF) are fabricated on the PMCs substrate with brush painting. Influence of the different curing agents on anti-laser ablation of the coatings at the laser wavelength of 1064 nm is investigated. The rear surface temperature of substrate with coatings, containing SiO and NaSiF, decreases from 240 to 60 and 70 °C, respectively, when testing at 1000 W for 5 s. After irradiation test at 1000 W for 10 s, the coating with SiO as curing agent shows slight molten state on the surface, while the coating with NaSiF is broke down, because coating containing SiO possesses more compact microstructure and fewer cracks than that with NaSiF. [ABSTRACT FROM AUTHOR]

In this article, the authors present their point of view on whether an analogy can be drawn between nano and classical microcomposites. Their opinion corresponds with a 25-year-old opinion article by Calvert and is based on their own extensive studies and a large body of studies in the scientific literature. They propose that polymer nanocomposites are in fact quasi-homogeneous molecular blends, which ought to be regarded as molecular composites or self-reinforced polymers. Hence, the micromechanical models of classical composites may not generally apply to nanocomposites, where-instead-the interactions on a molecular scale between the nanoparticles and the polymer matrix control the properties. A few examples, including of nucleation and confinement by nanoparticles, are discussed. [ABSTRACT FROM AUTHOR]

Graphene nanoplatelets (GNPs) are an attractive additive for polymers to provide electrical conductivity to a composite. If the GNP surface and the polymer are incompatible, the interfaces are weak, resulting in a large drop in the flexural strength and toughness of the composite compared to the native polymer. In the present study, we show that adding core-shell rubbery (CSR) nanoparticles, that have a polyisobutadiene (PIB) core and a thin, polystyrene (PS) compatible shell, to a PS-GNP composite enhances the dispersion of the GNP and suppresses their restacking, increasing the electrical conductivity of the composite by several orders of magnitude. In addition, there is complete recovery of the flexural strength and a large increase in toughness compared to PS samples without fillers. The recovery of the mechanical properties is related to a uniform distribution of the CSR and good binding at the interfaces because of the compatibility of the filler surface with the PS matrix, as well as the rubbery nature of the PIB core. This strategy of using a second filler as both a toughening agent as well as a dispersion aid breaks a commonly encountered tradeoff between electrical and mechanical property enhancement by fillers. It can be deployed for applications where both a high electrical conductivity and excellent mechanical properties of polymer composites are desired. [ABSTRACT FROM AUTHOR]

The development of bio-based films from proteins for their utilization as packaging materials and composites has gained popularity due to the availability, renewable nature, and biodegradability of proteins. The most studied of these polymers is sourced from soy. However, other sources of proteins show great commercial potential when transformed into films. As such, zein from corn and keratin from low-value chicken feather can be plasticized into films which exhibit good mechanical properties. Films derived from pea proteins can resist UV light transmission due to the presence of disulfide bonds within the network and the presence of amino acids such as tyrosine, tryptophan, and phenylalanine. Proteins from rapeseed have not been extensively studied as feedstocks for bio-based films but show great potential since their amino acid composition is similar to soy proteins. This review aims at combining and condensing the body of research performed on the synthesis of zein-, keratin-, pea-, canola-, and rapeseed-based films. The structural diversity of these proteins highly influences their processing methods and the physical properties of the resulting films. The potential applications of these bio-based materials are also highlighted. [ABSTRACT FROM AUTHOR]

The electrical conductivity concentration and temperature dependences of polymer composite materials (CMs) with nanocarbon fillers [graphite nanoplatelets and multi-walled carbon nanotubes (MWCNTs)] were investigated. Epoxy resin modified with organosilicon compound was used as polymer matrix. The content of nanocarbon filler in varied from 1 to 10 wt%. To study of the synergetic properties the additional dispersed dielectric filler-boron nitride (BN) was added to given systems in content of 27 wt%. The electrical resistivity of CMs was investigated in the temperature range of 77-300 K. In the studied CMs the percolation transition at sufficient low filler content (0.01-0.022 vol. fr.) was observed. The values of critical index varied from 3.0 to 5.2. The electrical conductivity of investigated CMs was analyzed in the framework of proposed model that takes into consideration the morphology of filler particles. It was shown that the increase of electrical conductivity of GNP-polymer CM in the presence of BN is attributed to the decrease of contact resistance between filler particles, while for MWCNT-polymer CM is due to the increase of the number of conductive chains in this particular system. [ABSTRACT FROM AUTHOR]

Carbon fibers are widely used as a reinforcement in composite materials because of their high-specific strength and modulus. Current trends toward the development of carbon fibers have been driven in two directions; ultrahigh tensile strength fiber with a fairly high strain to failure (~2 %), and ultrahigh modulus fiber with high-thermal conductivity. Today, a number of ultrahigh strength polyacrylonitrile (PAN)-based (more than 6 GPa), and ultrahigh modulus pitch-based (more than 900 GPa) carbon fibers have been commercially available. In the present work, the tensile properties of polyimide-coated PAN-based (T1000GB, T300, and M60JB) and pitch-based (K13D and XN-05) carbon fibers have been investigated using a single-filament tensile test. The pyromellitic dianhydride/4-4′-oxydianiline polyimide coating was deposited on the carbon fiber surface using high-temperature vapor deposition polymerization (VDP). The Weibull statistical distributions of the tensile strength were characterized. The results clearly show that the VDP polyimide coating improves the tensile strength and the Weibull modulus of PAN- and pitch-based carbon fibers. [ABSTRACT FROM AUTHOR]

The present study intends to investigate the effect of temperature on cumulative fatigue damage ( D) of laminated fibre-reinforced polymer (FRP) composites. The effect of temperature on fatigue damage is formulated based on Ramkrishnan–Jayaraman and Varvani-Farahani–Shirazi residual stiffness fatigue damage models. The models are further developed to assess the fatigue damage of FRP composites at various temperatures ( T). This task is fulfilled by formulating the temperature dependency of Young’s modulus ( E) and ultimate tensile strength (σult) as the inputs of the models. Temperature-dependant parameters of Young’s modulus and ultimate tensile strength are found to be in good agreement with the experimentally obtained data when used for unidirectional, cross-ply and quasi-isotropic FRP laminates. The proposed fatigue damage model is evaluated using six sets of fatigue damage data. The proposed temperature-dependent model was also found promising to predict the fatigue damage of unidirectional (UD) and orthogonal woven FRP composites at different temperatures. [ABSTRACT FROM AUTHOR]

This study evaluated some physical and mechanical properties of injection-moulded polypropylene (PP) composites reinforced with various mixtures of the wood flour (WF) and the olive mill sludge (OMS). Water resistance of the composites improved by the increasing OMS flour content. However, the flexural properties of the composites decreased with increasing OMS flour content. The addition of a coupling agent improved the compatibility between the lignocellulosic material and PP through esterification and thus reduced the water absorption and improved the stability and mechanical properties. The findings obtained in the study showed that the OMS was capable of serving as new reinforcing filler in the manufacturing of thermoplastic polymer composites. [ABSTRACT FROM AUTHOR]

Composites of pyroelectric ceramics and polymers are very important as their unique features and properties can be easily tailored for various specific applications. Lithium tantalatum oxide (LiTaO3, LT), the pyroelectric ceramic powder has been incorporated into a polyvinylidene fluoride–trifluoroethylene [P(VDF–TrFE) 70/30 mol%] copolymer matrix to form 0–3 composites. The composite films were prepared using ‘solvent casting’ (SC) method to disperse the ceramic powder homogeneously in the P(VDF–TrFE) copolymer matrix with various wt% of LT powder. In order to derive high pyroelectric performance, the samples were poled. Electric properties, such as the dielectric constant, dielectric loss, and pyroelectric coefficient, have been measured as a function of temperature and frequency. In addition, material figures-of-merit, very important factors for assessing many sensor applications have also been calculated. The results show that the fabricated lead free lithium tantalite: P(VDF–TrFE) composite materials have a good potential for pyroelectric infrared sensor applications. [ABSTRACT FROM AUTHOR]

Traditionally, most equipment that was used for containing corrosive solutions and fumes for the steel industry was fabricated from steel with a rubber-lined interior. An additional acid-resistant brick lining was used to protect the rubber lining and also to act as thermal insulation. This investigation focussed on a geopolymer material that would simultaneously solve the two issues, recurrent acid leakage from the brick-lined structure and minimal thermal stress during operation. The scope of this project was limited to identify the extent of weight loss in a strong HCl acidic environment for a standard geopolymeric composite at 90 °C. Accelerated tests on geopolymer samples were conducted over 110 days and the weight loss results were extrapolated over a time period of 300 days. Visual inspection showed that OPC had a reduced diameter after 40 days of acid exposure, and therefore, the overall acid penetration for OPC was significantly higher than GPC. The mechanism of weight loss or material degradation was not the key aim in this investigation, rather we aimed to obtain a new composition to withstand highly acidic condition (which are not encountered with ordinary Portland cement (OPC) concrete, e.g. in sewage conditions). The average weight loss of a theoretical slab of geopolymer sample in accelerated test conditions (90 °C and 22% HCl) is found to be 1.8 wt% in 60 days for single-face exposure and the average thickness loss predicted for a 40 mm thick slab is about 3.5% after 300 days of exposure in operating conditions of 18% HCl and 80 °C after reaching steady-state weight loss. This is significantly better compared to a standard concrete and brick slab or steel-lined rubber slab. This initial investigation indicated that with further scientific investigation and understanding of the material, the application could be broadened to further minimise acid corrosion over longer time periods (10 years). [ABSTRACT FROM AUTHOR]

In this study, we investigated the improvement in electrical conductivity of a polymer with the addition of dissolved lithium hexafluorophosphate (LiPF6) in an ether based solvent, butyl glycidyl ether (BGE). Thin film samples were fabricated by adding LiPF6 (up to 1 wt%) to poly (methyl-methacrylate) (PMMA). Film with 0.75% LiPF6 showed the highest improvement of electrical conductivity by three orders of magnitude. Both FTIR spectra and X-ray diffraction studies confirmed the formation of BGE–LiPF6 complex. Differential Scanning Calorimetry was used to characterize the PMMA/LiPF6 specimens further. Dielectric experiments revealed the existence of multiple composition dependent relaxation processes: β (high frequency) and β (low frequency) relaxation processes. The results suggest that electrical conductivity could be improved without influencing the domain polymer and the composite materials, including their processability. This work suggests that the conductivity of nanocomposites with various solid conductive fillers may be sufficiently enhanced in combination with this ion conduction approach involving a “liquid conductive filler.” Since BGE is compatible with epoxy molecules, further study is expected to lead to an effective solution to conductive epoxy composites in their wide field of applications including aircraft and multifunctional energy sources such as structural batteries. [ABSTRACT FROM AUTHOR]

Polymer composites of epoxy resin and Nb2O5 doped BaTiO3 were prepared in the form of film (thickness 30–300 μm) using a dipping technique. Samples containing various amounts of ceramic filler were examined by thermal analysis and SEM analysis. Dielectric measurements were performed from 20 Hz to 1 MHz and 20 °C to 120 °C. It was found that the final materials had high permittivities increasing with the filler concentration. Electrical relaxations were assigned to interfacial phenomena due to the particles and α-relaxation because of the resin. [ABSTRACT FROM AUTHOR]

Polymer-embedding of nano-sized indium tin oxide (SnO·In2O3, ITO) produces electrically conductive materials transparent to the visible light at filling factors higher than the percolation threshold. ITO powders are commercially available in an aggregated form and a disaggregation technique was required. Here, aggregated ITO nanoparticles were transformed to colloidal suspension by high-speed stirring. This finely dispersed ceramic suspension was stabilized by addition of poly(vinyl pyrrolidone) and the obtained colloidal system was cast on an optical-grade substrate (PET) to produce electrically conductive-transparent nanocomposite films. Preliminary mechanical and electrical characterization of these films showed good conductivity and interfacial properties. [ABSTRACT FROM AUTHOR]

The diglycidyl ether of bisphenol A (DGEBA) epoxy resin system filled with organo clay (OC) and unmodified clay (UC) were processed separately by two different curing agents. Triethylene tetramine (TETA) and Diaminodiphenyl methane (DDM) hardeners were used as curing agents. The nanocomposites were processed by shear mixing at different clay concentrations (1, 2, 3,5 and 10 wt%). The OC and UC were characterized by x-ray diffraction (XRD) technique. The morphology of the nanocomposites was obtained by XRD and Transmission Electron Microscopy (TEM). Bending and Impact tests conducted on these materials revealed that the organo clay filled epoxy resin showed good improvement in property over unmodified clay filled epoxy composites. The mass uptake of the nanocomposites was studied in the acid, base and water mediums. It is observed that the mass uptake in the acid medium is higher than in other mediums. The equilibrium mass uptake in all the mediums for nanocomposites was found to be lower compared to neat epoxy polymer system. [ABSTRACT FROM AUTHOR]

A novel route for production of auxetic fibres has been adapted from conventional melt extrusion techniques. These fibres were reproduced, characterised and tested, for the first time, to assess the potential of auxetic fibres as reinforcements in composite materials. Initial experimental work has included the embedding of single fibres in modified epoxy resin. Auxetic fibre specimens were then compared with conventional fibre specimens through a specially designed fibre pullout testing procedure. The auxetic specimens displayed superior anchoring properties. The average maximum force at de-bonding of the auxetic fibres (0.95 N) was observed to be over 100% higher than that for conventional ones (0.44 N) and the average energy required to fully extract the auxetic fibre from the modified resin was 8.3 mJ while the conventional fibre required only 2.5 mJ on average. The results indicate that composites employing auxetic fibres as the reinforcement phase will exhibit enhanced resistance to failure due to fibre pullout. [ABSTRACT FROM AUTHOR]

Reports on the time dependence of the percolation habit in response to organic vapor. Percolation behavior in polymer composites within a uniform framework; Approach to inspect the structure evolution of the composite materials in solid state; Model composite.

A piezoelectric composite has been prepared with highly aligned BaTiO3 whiskers as the active phase and polyvinylidene fluoride (PVDF) as the matrix. Its dielectric and electromechanical properties are characterized. It is found that the dielectric constant (ε), piezoelectric constant (d33) and remnant polarization (Pr) are considerably higher in the whisker composite than in the corresponding composite containing BaTiO3 powders as the active phase, while the loss factors follow the opposite trend. For the whisker composite, ε, d33 and Pr along the direction of the whisker orientation are much higher than the values normal to the whisker orientation. The reasons for the observed differences are discussed. [ABSTRACT FROM AUTHOR]

Discusses a coating of sintered hydroxyapatite particles on poly(2-(o-[1′-methylpropylideneamino] carboxyamino) ethyl methacrylate)-grafted silk fibroin fibers through covalent linkage. Nano-scaled hydroxyapatite/polymer composite; Biocompatibility for hard and soft tissue; Unique physicochemical properties.

Evaluates mechanical properties of two glass-fiber-reinforced polymers (GFRP), using transverse impact, double cantilever beam (DCB) and end-notched flexure tests. Results of the transverse impact and DCB tests showed a clear difference in delamination resistance between the two GFRP; Similarity of the delamination resistance in the shear mode; Effect of the toughness variation in different modes of loading.

Polyethylene/palygorskite nanocomposites with “macromolecular comb” structure were prepared via in situ polymerization. The TiCl4 catalyst was first loaded on the surface of the nanoscale whiskers of palygorskite. Subsequently the ethylene was introduced into the reaction system, and the polyethylene molecular chain was generated directly at the surface of the palygorskite whiskers. As a result, a polyethylene molecular chain with “macromolecular comb” structure was generated. The product thus obtained was blended with regular polyethylene to make a polymer blend, which was characterized by transmission electron microscope (TEM). Finely dispersed palygorskite whiskers in polyethylene matrix were found, which resulted in the improvement of mechanical strength of the polymer blends. Compared with regular polyethylene, the impact strength and tensile strength of the polymer blend were improved by 63.5% and 21.3% respectively at 25°C, when the palygorskite content of the nanocomposite was 20 wt%. [ABSTRACT FROM AUTHOR]

Films with anisotropic electric properties were created by a processing technique that produces an alignment of ,am sized iron particles in a polymer film. The magnetic aligning process was observed to create a formation of iron particle columns parallel to the aligning magnetic field. The degree of alignment can be quantified by measurements of the electrical impedance. [ABSTRACT FROM AUTHOR]

To identify the best reinforcement condition for development of tough glass polymer multi-layer composites (GPMLC) with high failure strain, two such model composite structures were developed. Soda-lime-silica glasses of two different thicknesses viz (A—1.01 mm and B—1.17 mm) were used as the matrix layers. The A-glass and B-glass based GPMLC samples were prepared by a novel, low pressure lamination technique applied to the alternating planar structure of the matrix and reinforcing phases. These GPMLC materials were fabricated with and without a thin sprayed layer of kerosene, between the glass layer and the reinforcing layer in the interface where; the interface was either epoxy (a thermosetting resin) or polyvinyl butyral (PVB, a thermoplastic resin). The GPMLC samples which exhibited stepped load—displacement behaviour in the most pronounced fashion, had the thermoplastic resin at the interface. Most of these GPMLC samples had a thin layer of kerosene intentionally introduced between the glass layer and the reinforcing polymer layer such that a weak interface is obtained. Fractographic evidence suggested that more of controlled delaminaton cracking occurs in such samples. Apart from the chemical nature of the reinforcing polymer phase, the interfacial layer thickness (hi) and the interfacial shear stress (τxy) were found out to have significant influence on the specific failure load and the failure stress of the current glass polymer multi-layer composites. [ABSTRACT FROM AUTHOR]

Rayleigh's method is used to find the electric potentials of a composite of poly-dispered spherical particles in a linear continuum in an external electric field. Based on the solutions of potentials, analytical formula for the effective electric conductivity is derived. Based on the formula, several factors, such as the number of spherical inclusions, the spatial distribution of the spheres, the contrast ratio σi/σh (where, σi and σh are the conductivities of the spherical inclusion and the host medium, respectively) and volume fraction of the inclusions, are discussed. Our results show that at high volume fraction, the effective conductivity is also affected by the spatial distribution of the inclusions. [ABSTRACT FROM AUTHOR]

An attempt has been made to review and analyze the developments made during last few decades in the field of high performance carbon fibers. The focus is primarily on high technology sector, which includes aerospace and nuclear engineering or other areas, where the large scale use of carbon fibers is driven by maximum performance and not by cost factors. We have identified and suggested some specific areas for future research in order to minimize the gap between theoretical and practically realized tensile strengths and other mechanical properties of carbon fibers. [ABSTRACT FROM AUTHOR]

A three-dimensional anisotropic contact algorithm has been developed to analyse the contact behaviour of metal–composite bodies. The elements of the influence matrix are obtained by coupled finite-element anisotropic models. Linear elastic and approximate elastic–plastic techniques can evaluate the contact parameters (the normal approach, the size of the contact area and the contact pressure distribution) following different failure criteria. The contact technique is applied to the problem of a steel ball indented into a polymer composite material having either normal or parallel unidirectional fibre orientation. Finally, the contact results are verified by experimental evaluations. The latter were obtained by the use of a static testing machine, a laser profilometer, an optical microscope and a scanning electron microscope, and they illustrate the real response of the composite structure subjected to ball indentation. Good agreement between both methods could be demonstrated. © 1998 Chapman & Hall [ABSTRACT FROM AUTHOR]

Carbon black/polymer composites can be used in a variety of industrial applications, where a high conductivity is an important physical parameter. The relationship between the positive temperature coefficient (PTC) effect and the room temperature volume resistivity has been investigated. These are two of the more important operating parameters. Resistivity-temperature measurements were performed on a radiation crosslinked high structure (H) carbon black mixed at different concentrations in HDPE. The results obtained for composites with a range of carbon black properties showed that there was a linear relationship between log (R2/R1) and log R1, where R2=maximum resistivity and R1=room temperature volume resistivity. The relationship can be taken as a reference line for the assessment of the relative effect that modifying the carbon black structure and changing the mixing variables on the relative magnitude of the PTC effect and the room temperature volume resistivity. The high structure (H) carbon black structural characteristics were modified by both gas phase (carbon dioxide at 900°C) and liquid phase (nitric acid) treatments. The former treatment procedure resulted in a decrease, while the latter an increase in the volume resistivities of the final composites. These results are discussed in terms of the effect of surface functionality and carbon structural characteristics. [ABSTRACT FROM AUTHOR]

Investigates the observed phenomenon that the resistivity of carbon particles/polymer composites would decrease with time under an invariant uniaxial pressure, similar to a "resistivity creep" behavior. Use of a room temperature vulcanized liquid silicone rubber as a polymer matrix in the experiment; Compression deformation of the samples.

Reports on an attempt to overcome stress-caused birefringence in polymers through modification of existing polymer systems to control or compensate for molecular orientation. Reduction of orientation-related birefringence; Suitability of polymers for waveguide applications; Achievement of index reproducibility.