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Optimizing the maintenance cycles of rubber-lined components is of great importance. Especially for the industry sectors operating under demanding conditions, challenges in the lifetime evaluation of rubber linings may cause apparent premature failures. Thus, understanding the effect of environmental factors on the performance and durability of rubber linings, as well as on the weakest links of the structure in certain environments, is essential. The performances of bromobutyl rubber and rubber–steel interfaces after exposure to different environments, namely, high temperature (95 °C), moisture (95% relative humidity and immersion), and sulfuric acid (solution with 75 g/L of acid) were investigated. The weakest link of the rubber–metal structure and, consequently, the location of the fracture were mostly within the adhesive layer or at the primer–metal interface. However, the most degraded component of the adhesive system depends on the aging environments.

Despite substantial progress being made relating to 2D-nanofiller-based composite nanolaminates, the fabrication of composite nanolaminates with enhanced ductility and toughness is still challenging. In this study, layered structure graphene oxide (GO)/gelatin powder (GP) composites nanolaminates with enhanced ductility and toughness have been achieved by a simple vacuum filtration of aqueous dispersion of GO/GP composite solution containing 5 wt% of GO. The composite film containing 5 wt% GO shows outstanding improvement of 200% in the stress at break value, with simultaneous enhancement of 52% of the strain at break value compared to GP film. A significant improvement in toughness from 2.2 MJ m-3 to 9.5 MJ m-3 is observed in the composite film containing 5 wt% GO. These significant enhancements of the mechanical properties of the composite film are obtained via the formation of an intercalated nanolaminate structure, H-bonding interactions, and the tailoring of the crystal structure of GP in the composite film, as proved via field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, and wide-angle X-ray diffraction studies. The growing of fibroblast cells on the composite films signifies that they are not cytotoxic. These GO/GP composites with significant mechanical properties and biocompatibility are very promising for various biomedical applications. This journal is publishedVersion

This review article highlights and summarizes the recent developments in the field of surface modification methods for aramid fibers. Special focus is on methods that create a multifunctional fiber surface by incorporating nanostructures and enabling mechanical interlocking. To give a complete picture of adhesion promotion with aramids, the specific questions related to the challenges in aramid-matrix bonding are also shortly presented. The main discussion of the surface modification approaches is divided into sections according to how material is added to the fiber surface; (1) coating, (2) grafting and (3) growing. To provide a comprehensive view of the most recent developments in the field, other methods with similar outcomes, are also shortly reviewed. To conclude, future trends and insights are discussed.

Natural rubber (NR) is a versatile material possessing outstanding mechanical properties, which can be used in multiple applications including the rapidly developing dielectric elastomer generators (DEGs). One of the drawbacks of the existing DEGs is their low efficiency, which can be improved by lowering the dielectric and mechanical losses originating from the material. Therefore, the present research was focusing on assessing the ways to minimize the dielectric and mechanical losses of NR films rather than developing a DEG. In this article, the effect of natural proteins and the rubber stabilizers on energy dissipation of NR films was evaluated. Moreover, the effect of sample posttreatment (with water and acetone), curing and time after cure was discussed. As a result, deproteinized NR stabilized by ammonium caseinate outperformed unmodified NR due to reduced dielectric losses, mechanical hysteresis and stress relaxation. Moreover, the posttreatment methods were found to moderately reduce the material-relates losses. publishedVersion

Layered structure graphene oxide (GO)/methylcellulose (MC) composite films with excellent mechanical and gas barrier properties were achieved for the first time by a simple solvent evaporation assisted assembly of GO/MC composite solutions. 1, 3 and 5 wt% of GO composites with respect to MC were fabricated and denoted as GO1, GO3 and GO5, respectively. The interactions of the hydrophobic associated domains of MC (formed during solvent evaporation) with the π cloud of GO (hydrophobic interaction) and the oxygen-containing groups of MC with the oxygen-containing functional groups of GO (H-bonding interaction) govern the formation of self-assembled thick MC coated layered structure GO/MC composites. The obtained composite films were highly flexible and characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), wide angle X-ray scattering (WAXS), Simultaneous Thermal Analysis (STA), and mechanical and oxygen gas permeation studies. The FESEM analysis shows the formation of a layered structure as well as good dispersion of thick MC coated GO sheets in the MC matrix. WAXS studies also illustrate that the GO sheets remain in a highly exfoliated state in the MC matrix. The FTIR results indicate the presence of interfacial interaction between the GO and MC molecules. The GO/MC composite films exhibit a significant enhancement of mechanical properties compared to pure MC films. The stress at break and Young's modulus of GO5 were determined to be 104 ± 3 MPa and 3.8 ± 0.2, respectively. In addition to the mechanical properties, the oxygen gas barrier properties of the composites were also enhanced significantly. The GO1 film shows a 98% decrease of oxygen permeation with respect to pure MC films.

In this study, we examine the effect of multi-wall carbon nanotubes (MWCNT) morphology on electrical and mechanical properties of MWCNT-filled polyurethane (PU) nanocomposites. The main objective of this study is to understand the role of aspect ratio and length of MWCNTs in determining the performance of nanocomposites. Highly aligned MWCNTs were prepared by aerosol-assisted chemical vapour deposition method and compared to commercially available MWCNTs in PU matrix for ease of dispersibility and performance. We observed opposing influence of the MWCNT on electrical and mechanical behaviour of the nanocomposites. The electrical properties were proportional to length of the MWCNTs whereas the mechanical properties were dependent on the aspect ratio of the MWCNTs. Moreover, thicker nanotubes (approximately 40 nm) with a higher aspect ratio (approximately 225) are less prone to shortening and impart better tensile and storage modulus along with improved electrical and therefore are more suitable for the MWCNT nanocomposites.

The modification of epoxy resin by 3-aminopropyltriethoxysilane (APTES) to improve the tensile properties of warp knitted viscose fabric composites is reported in this study. The study evaluates the efficiency of modification methods adopted to modify the epoxy resin and the influence of the resin modification on various properties of the cured castings. The influence of matrix resin modification on the tensile properties of viscose fabric composite is compared to those prepared from chemically modified fibre. The efficiency of the modification was determined through titration method to determine the epoxide content of epoxy resin, viscosity measurement and FTIR. The effect of APTES modification on various properties of cured castings is studied through differential scanning calorimeter, contact angle measurement and tensile testing. The addition of APTES into the epoxy resin decreased the epoxide content in the resin as evident from the titration method. The tensile strength of cured castings decreased after the resin modification. The tensile strength and elongation at break of the viscose fabric composites prepared from modified resin, increased up to 14 and 41%, respectively. The improved adhesion of APTES-modified epoxy resin to the viscose fibre is confirmed from SEM analysis of tensile fracture surface. acceptedVersion

In a recent paper Hernandez et al. claimed to have explored a self-healing behavior of (covalently crosslinked) natural rubber by mechanical and broadband dielectric spectroscopic studies 1. The authors demonstrated a dielectric relaxation study to understand the heterogeneous network structures at the healed interface that was established during the healing process of a rather weakly sulphur crosslinked rubber sample. We have no doubts that the study itself gives interesting insights, however we are convinced (and will argue in more detail below) that interpretations toward a ‘self-healing’ nature of natural rubber should be handled with care and is even wrong in this case. Several critical issues like the tackiness of natural rubber, sample fabrication for dielectric experiments etc. will be discussed in this comment.

Dielectric elastomers are materials often utilized for the fabrication of electroactive actuators. Acrylic rubber (ACM) is very widely used in dielectric elastomer actuators (DEAs). However, its overall good performance is limited by the high operating electric field required. In the present work, we compare the effect of different types of conventionally used carbon black (CB) as well as other carbon-based fillers on the dielectric and actuation properties of ACM in order to show that performance of DEAs can be improved by the development of ACM composites. Indeed, addition of CB, carbon nanotubes (CNTs), and synthetic graphite leads to an increase in the relative dielectric permittivity of elastomeric material. Moreover, incorporation of nanodiamonds results in reduction of dielectric losses. Finally, actuation stress is remarkably improved by CNTs and different grades of CB. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

In this research, glass fibre reinforced composite laminate samples were manufactured with filament winding technique using four different vinyl ester resin systems to study ageing. The manufactured laminate samples were conditioned in an environmental cabinet (70°C, 95 RH%), water immersion (95°C), and in sulphuric acid solution immersion under pressure (5% H2SO4, 95°C, 15bar). After 6 and 12months of conditioning, the samples were tensile tested and the results were compared with the initial values. Regardless of the matrix type, conditioning in the environmental cabinet resulted in the lowest weight gain and least decrease in tensile properties: the decrease in the tensile strength values was 10-25% after 12months' conditioning depending on the vinyl ester used. The water immersion was more detrimental to the samples than the 5% H2SO4 immersion causing the highest weight gain and the greatest decrease in tensile strength (up to 65%). However, when comparing the tensile performance, it was noted that the highest weight gain did not inevitably correlate with the strongest ageing effect. In water immersion, the ultimate strength deteriorates faster than the proof stress level leading to a decreasing damage tolerance of the vinyl-ester composite laminates. acceptedVersion

A two-step masterbatch mixing technique was studied for preparation of carbon nanotube-filled ethylene–propylene diene elastomer compounds, and compared to conventional one-step mixing process. In the two-step process, a masterbatch compound with carbon nanotube content of 50 parts per hundred was prepared by melt-mixing ethylene–propylene diene elastomer. This material was then compounded with pristine ethylene–propylene diene elastomer and composites with different carbon nanotube concentrations were compared. The aim of this study is to compare the efficiency of two different mixing processes on the dispersion of carbon nanotubes and to facilitate the handling of carbon nanotubes, as the masterbatch can be prepared in a controlled way and used for further dilution without the problems related to carbon nanotube processing. The compound properties were studied with emphasis on mechanical characterization and dynamic mechanical thermal analysis. Masterbatch mixing resulted in the similar mechanical properties of the composites compared to the direct mixing method. At the relatively low loadings of carbon nanotubes, the considerable improvements of the mechanical properties were observed. The aspect ratio of the carbon nanotubes determined by transmission electron microscope was found to be similar to the one calculated from the Guth equation. It showed a considerable reduction in aspect ratio independent of the used mixing method. acceptedVersion

Two austenitic stainless steel grades, 316L and 904L, and three duplex stainless steel grades, LDX 2101, 2205, and 2507, were erosion–corrosion tested as impeller blade materials for hydrometallurgical applications. Samples were attached to the pressure and suction sides of an impeller and were tested in 50 g/l H 2 SO 4 and 0.5 g/l Fe 2 (SO 4 ) 3 for 72 h at 80°C and 95 °C in a small-scale reactor using quartz sand slurry. The results showed that under lower erosion intensity the ranking of the grades was similar to that in pure erosion. Under higher erosion intensity the ranking of the grades changed completely: lean alloys LDX 2101 and 316L suffered from the highest mass losses followed by 2205, 2507, and 904L. To clarify this behavior, the ability of the grades to repassivate was investigated with scratch tests. It was found that the ranking could be explained by the repassivation rates. The only exception was that 2507 showed a similar repassivation rate to 904L but its erosion–corrosion mass loss under higher erosion intensity was larger. One contributing factor to this was found to be the selective dissolution of the austenite phase of all the tested duplex grades. The prerequisites for the galvanic coupling between the phases that was responsible for the selective dissolution are discussed.

This paper reports a failure analysis of a leaching reactor in a zinc plant that suffered from a catastrophic failure after less than two years of operation. During normal operation the bottom of the reactor fell out suddenly, releasing the contents, a high-temperature acidic solution, into the surroundings in an uncontrollable manner. The reactor was made of glass-fiber reinforced plastic. Microscopy, thermal analysis, mechanical testing and finite element analyses were employed to investigate the causes of the failure. There were several contributing factors but the root cause was poor adhesion between the bottom and the joint laminate, which was caused by insufficient grinding during the surface preparation stage of the joint.

A comparative study of the effects of various nanoparticles introduced into polyetherimide Ultem-1000 (Sabic)—such as carbon nanofibers, nanocones/discs, halloysite hydrosilicate nanotubes, and quasispherical zirconia particles doped with yttria―on the mechanical behavior of nanocomposites is performed. The introduction of nanoparticles into the polymer increases the Young’s moduli and yield stress of block materials relative to those of the unfilled polymeric material. These effects make themselves more pronounced with an increase in temperature, especially when сarbon nanocones/discs are used as a filler. The collected data are commensurable with the electron-microscopic study of the morphology of the material and its densitometry measurements, which make it possible to estimate the values of excess free volume in the studied composite materials, as well as with the previous data on the incorporation of analogous nanoparticles into polypyromellitimide films.

A carbon fiber powder doped corrosion layer is used as an inner layer in large composite tanks to improve their chemical and wear resistance. In joints fabricated on site, this layer is embedded into the structure. This study evaluates the lap shear strength of specimens, simulating a laminated joint in between the corrosion layer and the inner joint laminate. Lap-shear tests were carried out for as-fabricated and aged laminates at room temperature and at elevated temperature. Ageing was carried out for half a year in a 95 °C pressurized sulfuric acid solution. The tests showed that, after ageing, the room temperature shear strength remained unaltered but high-temperature shear strength was lowered. When the temperature increased, the failure location shifted from the interface between the doped layer and the joint laminate to the doped layer. Thermal analysis and microscopy were employed to clarify the reasons for the observed behavior.

There is an increasing need for inexpensive packaging structures for demanding industrial electronics applications. This paper studies the usability of a polymer-based sensor package at very high temperatures. Resistance-based temperature sensors were attached with polymer-based electrically conductive adhesives (ECAs) onto flexible polyimide (PI) printed circuit boards (PCB). The materials used in the structure were not specifically designed for high temperature use. However, they were all commercial materials, easily available and typically reliable under normal use conditions of consumer electronics. The samples were aged at 240°C and electrically monitored during the test. Electrically, the sensor samples were observed to fail after 100 h of aging. However, material characterisation revealed that the materials started to degrade much earlier. The adhesive layer in the PI PCB and the ECA materials started to degrade after just 30 h of aging at 240°C, and mechanically the materials were observed to become brittle, making them prone to cracking and delamination. The results showed that such a polymer package is usable at 240°C for relatively short exposure times, but under longer exposure times the mechanical reliability of the package deteriorates and this needs to be taken into account.

Several electronic applications must withstand elevated temperatures during their lifetime. Materials and packages for use in high temperatures have been designed, but they are often very expensive, have limited compatibility with materials, structures, and processing techniques, and are less readily available than traditional materials. Thus, there is an increasing interest in using low-cost polymer materials in high temperature applications. This paper studies the performance and reliability of sensor structures attached with anisotropically conductive adhesive film (ACF) on two different organic printed circuit board (PCB) materials: FR-4 and Rogers. The test samples were aged at 200 °C and 240 °C and monitored electrically during the test. Material characterization techniques were also used to analyze the behavior of the materials. Rogers PCB was observed to be more stable at high temperatures in spite of degradation observed, especially during the first 120 h of aging. The electrical reliability was very good with Rogers. At 200 °C, the failures occurred after 2000 h of testing, and even at 240 °C the interconnections were functional for 400 h. The study indicates that, even though these ACFs were not designed for use in high temperatures, with stable PCB material they are promising interconnection materials at elevated temperatures, especially at 200 °C. However, the fragility of the structure due to material degradation may cause reliability problems in long-term high temperature exposure.

Experimental determination of elastic constants of anisotropic composite laminates in all orthogonal directions is generally a complex process. In this paper a simple direct technique to determine a broad set of elastic moduli is presented based on compression testing of a prism sample. Digital image correlation is used to measure the full-field deformations that allow the determination of Young's moduli and all six Poisson's ratios for the three orthogonal directions based on a single sample. Finite element model is used in evaluation of the effect of friction on the measured properties. In addition to quantitative characterization of the material properties, local strain mapping is used in qualitative evaluation of the sample structures. acceptedVersion

In this work, we report about the mechanical relaxation characteristics of an intrinsically self-healable imidazole modified commercial rubber. This kind of self-healing rubber was prepared by melt mixing of 1-butyl imidazole with bromo-butyl rubber (bromine modified isoprene-isobutylene copolymer, BIIR). By this melt mixing process, the reactive allylic bromine of bromo-butyl rubber was converted into imidazole bromide salt. The resulting development of an ionic character to the polymer backbone leads to an ionic association of the groups which ultimately results to the formation of a network structure of the rubber chains. The modified BIIR thus behaves like a robust crosslinked rubber and shows unusual self-healing properties. The non-covalent reversible network has been studied in detail with respect to stress relaxation experiments, scanning electron microscopic and X-ray scattering. publishedVersion

This paper investigates the effects of thermal degradation on polyetheretherketone (PEEK) fibres. PEEK samples were aged at a constant temperature of 250 °C for 1-128 days and characterized with mechanical tests, FTIR (Fourier Transform Infrared Spectroscopy), DSC (Differential Scanning Calorimetry), rheology, TGA (Thermogravimetric Analysis), SEM (Scanning Electron Microscopy), and UV-Vis diffuse reflectance spectroscopy. The short-term thermal annealing had a positive effect on the mechanical properties, due to the formation and growth of secondary crystals. Crosslinking in the material was verified by rheological inspections. The crosslinking increased the mechanical strength and modulus but reduced the elongation at break of the fibres. FTIR tests showed that carbonyl and hydroxyl groups were slowly formed on the surface of the fibres while ring opening reactions took place. The thermal ageing reduced the thermal stability of PEEK. The decreased stability was observed in the decomposition onset temperature after 8 d and in the melting point and the glass transition temperature after 32 d. The first signs of degradation, crosslinking, embrittlement, and reduced thermal stability, were visible roughly after 8 d of ageing, whereas the deterioration in general usability occurred after 64 d. submittedVersion

This work includes an investigation of six different surface treatments for joining composites by overlamination. The durability of the pre-treated glass fibre-unsaturated polyester composite joints is investigated accounting for a 200-day water immersion at 64±1 °C. Degradation due to accelerated aging, by water and elevated temperature, is analysed using Fourier transform infrared spectroscopy (FTIR), water absorption measurement, tensile testing and a systematic sequence of four different fracture test methods. Based on the fracture tests, the mechanical abrading treatment outperformed all other treatments yet suffered an adverse effect due to the combined moisture and elevated temperature. We observed irreversible chemical degradation in the bulk composite in terms of permanent 2.3% weight loss. The softening and plasticization of the polyester matrix seemed to have played a fundamental role in the rupture of adhesion at the peel ply and tear ply pre-treated overlamination interfaces. However, the adhesion loss was partly reversible and it was concluded to signify the domination of mechanical interlocking at peel ply and tear ply modified interfaces.

Two austenitic stainless steel grades, 316L and 904L, and three duplex stainless steel grades, LDX 2101, 2205, and 2507, were erosion tested as impeller blade materials for hydrometallurgical applications. Samples were attached to the pressure and suction sides of an impeller and were tested for 72 h at 80 °C and 95 °C in a small-scale reactor using quartz sand slurry. Based on the mass losses measured, the steel grades could be ranked into two distinct categories; LDX 2101 and 2507 comprising the category with the better erosion resistance. The categories were the same for the pressure and suction side tests even though the erosion mechanism differed. In most cases, erosion was more severe in the suction side samples, which has practical implications for wear protection design. In the pressure side samples, the variation in the erosion mass loss with different experimental parameters was in line with earlier reported findings. In contrast, in the suction side samples, under some experimental conditions, increasing tip speed and increasing particle size were found to reduce erosion mass loss. This emphasizes the fact that the erosivity of particles for the impeller suction side cannot be deduced solely based on particle size. The reasons for the observed behavior are discussed.

This study reports the preparation of advanced carbon fiber composites with a nanocomposite matrix prepared by dispersing multiwall carbon nanotubes (CNTs) in a powder type epoxy oligomer with two different processing techniques (1) master batch dilution technique and (2) direct mixing (with the help of twin-screw extruder in both cases). The master batch technique shows a better efficiency for the dispersion of the CNTs aggregates. The rheological results demonstrate that the incorporation of the CNTs into the epoxy oligomer leads, as expected, to a marked increase in the viscosity and of the presence of a yield stress point that also depends on the processing technique adopted. Carbon fiber (CFRP) and glass fiber (GFRP) composite materials were produced by electrostatic spraying of the epoxy matrix formulations on the carbon and glass fabric, respectively, followed by calendering and mold pressing. The mechanical properties of the obtained epoxy/CNT-matrix composite materials, such as interlaminar fracture toughness, flexural strength, shear storage and loss moduli are discussed in terms of the processing techniques and fabric material. The incorporation of 1 wt% CNTs in the epoxy matrix results in a relevant increase of the fracture toughness, flexural strength and modulus of both CFRP and GFRP. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

In the presence of multiwalled carbon nanotubes (MWCNT), polar nitrile-butadiene rubber (NBR) and nonpolar ethylene propylene diene rubber (EPDM) blends were prepared following a melt mixing method. For the preparation of MWCNT filled EPDM/NBR blends, two mixing methods were used: direct mixing and the masterbatch dilution method. Various physical, mechanical, and morphological properties are explored to elucidate the dispersion behavior of MWCNTs. It was concluded that the preparation method influences the dispersion of the nanotubes in different rubber phases and the properties of these blends are controlled by the degree of dispersion of the nanotubes in the two phases

Due to their good corrosion properties, fibre reinforced polymer composites are often used instead of metals for example in hydrometallurgical processes. However, the erosion performance of polymer composites is rather poor when compared to metals. This study focused on the effect of mineral fillers on the erosion performance of vinylester composites. The erosion rates were tested both in water and in acidic environments at high temperature. To improve the erosion performance of the filled composites in these environments, to increase the filler particle hardness was an effective method. Within similar filler materials, better adhesion to the matrix improved the erosion performance, regardless if it was achieved by adhesion promoters or better mechanical interlocking. The hardness of the matrix was found to be disadvantageous for filled composites, although for pure vinylesters higher hardness decreased erosion rate. At the high service temperature, softer matrix accommodated more deformations and better absorption of energy of the impacting erosive particles. Consequently, improved adherence of the filler particles into the matrix and slower erosion rate was observed. acceptedVersion

Several commercial surface treatments are used to increase the adhesion between aramid fibers and the matrix material in composite structures but each of these has some limitations. The aim of this study is to address some of these limitations by developing a surface treatment method for aramid fibers that would not affect mechanical properties of the fibers negatively, could be used with any matrix material and that could withstand handling of the fibers and ageing. The method used is microwave assisted surface treatment that uses microwave radiation together with dry reactive chemicals to create hierarchical structures to the fiber surface and so makes it possible to control the adhesion properties of the fibers. SEM and AFM imaging, fiber tensile tests and modified bundle pull-out test were used to investigate the outcome of the surface treatment and measure adhesion between aramid fiber bundles and rubber. SEM and AFM imaging revealed that nanoscale deposits are formed on to the fiber surface which enable mechanical interlocking between the fiber and the matrix material. Fiber tensile tests showed that the surface treatment does not influence the tensile properties of the fiber negatively. Results from the bundle pull-out tests confirmed that this kind of method can lead up to 259% improvement in adhesion when compared to untreated aramid fibers in the rubber matrix.

Conventional fillers used in rubber matrices include carbon black (CB), silica, and clay. However, the new demands on reinforced rubbers, especially the need to significantly enhance the overall performance while reducing the amount of filler, is currently expected to be met only through intelligent use of nano-sized fillers. Among carbon-based nanomaterials, such as fullerenes, carbon nanotubes (CNTs), graphene and nanodiamonds (NDs), nanodiamonds are a good candidate due to their nano-scale size, stable diamond core, highly reactive outer shell, biocompatibility, and potential for chemical functionalization. Here we review the state of the art and current research on nanodiamonds produced by laser ablation and detonation techniques with a special focus on their application in elastomers. The current understanding about structure and synthesis of nanodiamonds indicates some possible methods for their functionalization and dispersion in soft rubber matrix. We also discuss the effect of nanodiamonds on the various properties of elastomeric materials.

The overall mechanical performance of ionic elastomers, such as carboxylated nitrile rubber (XNBR), is largely governed by ionic clusters formed during the cross-linking of the elastomers with zinc oxide. These ionic aggregates promote microphase separation and show additional high-temperature relaxation behavior in dynamic mechanical analysis. In this study, the nature of these ionic aggregates is explored for the first time. We find that some zinc-containing compounds, such as zinc–aluminum-layered double hydroxide and zinc chloride, do not exhibit any extra high-temperature dynamic mechanical relaxation processes, although ionic cross-linking reactions with XNBR occur with all of these zinc compounds. Detailed analysis by Fourier-transform infrared spectroscopy and dynamic mechanical analysis revealed that this high-temperature relaxation behavior does not originate from ionic cross-linking but is associated with the formation of an additional zinc-enriched polymer phase that arises due to reactions be...

The fabrication and characterization of stretchable carbon nanotube and graphene nanocomposite electrodes on different rubber substrates is reported. Electrodes are fabricated at low temperatures using solution processable carbon nanomaterials. Rubber substrates are stretched while performing simultaneous electrical measurements for the electrodes. During 20% elongation of rubber substrates a 2- to 120-fold increase in the electrode resistance was observed, depending on the sample. The relative increase in the resistance with stretching was smaller in the case of graphene electrodes, whereas the resistance change during the elastomer relaxation was smaller in the case of carbon nanotube electrodes. Our results suggest that solution processed carbon nanomaterials on rubber substrates have potential for stretchable wiring and sensor applications. (C) 2014 Elsevier B.V. All rights reserved. submittedVersion

Hybrid structures are widely used since they enable unique combinations of properties for the final structure. Within polymer/metal hybrids, stainless steel instead of more regularly used mild steel or aluminium is a tempting choice but it is difficult to join adhesively. Thus improved solutions for the stainless steel joining with polymeric materials are needed. This study concentrates on the idea of utilisation of thin rubber layer as an adhesive between stainless steel and glass fibre reinforced epoxy composite (GFRP). Both mild steel and stainless steel with different surface finishes together with GFRP laminates were used as substrates for the ethylene propylene diene (EPDM) based rubber. The adhesion and microstructure of the interfaces were characterised. Transmission electron microscopical (TEM) studies indicated that a close contact between the components can be achieved and thus high quality interfaces are created by vulcanising the rubber to the steel or GFRP surface without pre-treatments. Stainless steel/rubber/GFRP hybrid structures where the strength of the steel/GFRP joint is defined by the cohesive strength of the rubber can be manufactured, as seen from the results of the peel tests. Since the fracture is located inside the rubber and not at the interface, the prediction of the structure's behaviour is also easier.

The objectives of this study were to investigate the effect of impact energy and rubber thickness on the impact properties of layered steel/rubber/composite hybrid structures. Both stainless steel and mild steel based hybrid structures were investigated. The degree of damage, the failure modes, and the absorbed energy were studied. It was found that rubber between steel and composite layers absorbs the impact energy and decreases the interfacial and internal damage in the studied hybrid structure and in its components. The amount of the absorbed energy did not change substantially when comparing structures with and without rubber. However, the area of permanent damage showed a decrease of nearly 50% with the use of rubber when comparing a structure without rubber to a structure with 1.5 mm rubber. In addition, it was observed that the area of the damage is linearly dependent on the impact energy. The main damage mechanisms found were delamination at the steel/rubber and composite/rubber interfaces and fibre/matrix debonding in the composite layer.

We present surface modification of thin-film-composite (TFC) polyamide (PA) reverse osmosis (RO) membrane by atomic layer deposition (ALD) process using trimethylaluminium (AlMe 3 ). The aim of the inorganic ALD coating is to improve the anti-fouling performance of TFC PA membranes. The ALD processing parameters were systematically studied because of the lack of previous investigations of the ALD coated RO membranes. Two different processing temperatures (70 °C and 100 °C) and three different ALD cycles (10, 50 and 100) were used to deposit the Al 2 O 3 ALD coatings on TFC PA membranes. The ALD process parameters affected on the hydrophilicity and the surface polarity as well as on the surface roughness of the coated membranes. The bacteria attachment test results indicated that the lowest number of Pseudomonas aeruginosa cells was adhered on the most hydrophilic and polar surface, among the ALD coated membranes. RO tests showed the effect of ALD coating on the water and salt permeability as well as on the salt rejection of the membranes.

The basic objective of this study is to investigate the mechanical properties of tyre tread compounds by gradual replacement of carbon black by multiwalled carbon nanotubes (MWCNTs) in a natural rubber–butadiene rubber-based system. A rapid change in the mechanical properties is noticed even at very low concentrations of nanotubes though the total concentration of the filler is kept constant at 25 phr (parts per hundred rubber). The correlation of the bound rubber content with MWCNT loading directly supports the conclusion that MWCNTs increase the occluded rubber fraction. Transmission electron microscopy reveals a good dispersion of the MWCNT up to a certain concentration. In the presence of MWCNT, a prominent negative shift of the glass transition temperature of the compound is found. Thermal degradation behavior, aging, and swelling experiments were also carried out to understand the resulting effect of the incorporation of MWCNT in the rubber matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3153–3160, 2013

The mechanical characteristics of block-shaped samples of a number of thermally stable thermoplastics for structural applications are investigated over a wide range of temperatures: from the room temperature (RT) up to 250°C. Together with several commercially available materials, namely, polyetheretherketone, polyphenylene sulfide, and a polyetherimide Ultem-1000; a number of polyimide thermoplastics designed at the Institute of Macromolecular Compounds RAS having both semicrystalline and amorphous structures were studied. The tribological behavior of these thermoplastics was investigated in the tribometers of different types using polymer–steel couples with the variation of both the temperature (from RT to 250°C) and the contact pressure. The experimental determination of the overheating values of the contact surface of the polymer sample was carried out during the friction process at different medium temperatures. The possibilities of obtaining a maximally broad temperature range for applications of th...

Two types of nanoclays, montmorillonite nanoflakes and halloysite nanotubes, at various concentrations were tested as nanofillers in epoxy powder coatings applied on an aluminum foil and a steel panel. The produced coatings were separated from the aluminum foil, enabling determination of peel strength, and mechanical properties and water permeability were determined for the obtained free films. Coated steel panels were characterized in terms of microstructure and corrosion protection properties in 0.5 M NaCl solution. The results showed that nanoclays may be used to improve both mechanical and corrosion protection properties of the epoxy coating. Addition of flake-like montmorillonite nanoparticles introduced a homogeneous coating structure, with the nanoparticles being fully embedded in the epoxy matrix, and improved the moduli values and water barrier properties of the epoxy coating at all studied amounts, evidently due to a favorable aspect ratio and orientation of the nanoparticles. Dispersion of montmorillonite nanoparticles in the epoxy matrix and the resulting interfacial strength were the best at the lowest nanoparticle amounts, 0.5 and 1.0 wt.%, giving slightly improved tensile strength, ductility and corrosion protection properties. As far as electrochemical behavior is concerned, particularly dielectric constant of the epoxy coating was decreased by montmorillonite additions. Halloysite nanotube additions in the epoxy matrix yielded coatings where the nanotubes were relatively randomly oriented and which introduced occasionally even greater improvement in mechanical properties, particularly elongation at break, than montmorillonite additions, due to good dispersion. However, the barrier and corrosion protection properties were clearly compromised, probably as a result of less favorable aspect ratio and relatively random orientation of the nanotubes.

The effect of various fillers on the mechanical, barrier, and flammability properties of polypropylene (PP) was studied. PP was filled with 4 wt% of nano-sized calcium carbonate, titanium dioxide, organoclay, and multiwalled carbon nanotube (MWCNT). For comparison, micron-sized calcium carbonate was also studied. Two-step masterbatch dilution approach of the composites suggested no or only minor improvements in Young's modulus and tensile yield strength, whereas their ductility decreased compared to coupling agent-modified PP matrix. The water vapor transmission results of filled films showed increased permeability compared to their coupling agent-modified counterpart. Oxygen permeability, however, decreased for the composites. The MWCNT-filled matrix showed the highest barrier and fire performance, attributed mainly to its higher filler volume content, but also other reasons such as the effect of filler dispersion, composite's thermal stability, and polymer crystallinity were discussed.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers

Commingled composites of polylactide (PLA) and seed flax fibers were prepared by carding and needle pressing of PLA and flax fibers to nonwoven mats followed by compression molding. The nonwoven mats were treated using two different types of cellulolytic enzymes, namely cellobiohydrolases and endoglucanases. Both the enzymes changed the properties of the seed flax fibers surface. The resulting composites were studied using scanning electron microscopy, mechanical testing and thermal analysis. The effects of these modifications were minor on the thermal and mechanical properties measured. However, in the scanning electron micrographs, a difference in the fiber pull-out behavior of the untreated and treated fibers was observed. Treated seed flax fibers showed an improvement in adhesion with PLA.

This paper studies changes in the surface chemistry of carbon nanotubes (CNTs) while they are under ultra-sonication process in Jeffamine D-230 polyetheramine medium. Jeffamine is used as curing agent in the nanocomposite manufacturing process. In the nanocomposite technology, ultrasonication process is employed as a method for dispersion of CNTs in a suspension. This research tries to investigate the effect of ultrasonic dispersion with different time and energy on the surface chemistry of CNTs by Fourier transform infrared (FTIR) spectroscopy. The results show ultrasonication of CNTs in the Jeffamine medium leads to significant oxidation and hydration along with creation of new chemical bonds on the CNTs surface.