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Highlights • Crack initiation and propagation under cyclic constant displacement loading, • CT specimens of two polymeric materials: ABS and PMMA. • Self-designed and constructed machine for constant displacement loading on CT specimens. • Fracture parameters obtained, such as K I , G, and ρ, under this modality of loading. • Description of principal trends on the fracture surfaces of CT specimens. Abstract Cyclic constant displacement tests on CT (compact tension) specimens, according to the ASTM E647-00 standard, have been carried out in order to investigate the crack initiation and propagation for two polymeric materials: the ABS (Acrylonitrile Butadiene Styrene) and PMMA (Polymethyl methacrylate). Experimental cyclic tests have been performed on a self-designed and constructed machine working under constant displacement at frequency of 0.25 Hz and with maximum displacement of 390 μm. The displacement control is implemented using the Arduino software, a personal computer together with an inductive proximity sensor, which allows determining the displacement with ±4 μm of precision. The stress intensity factor in mode I (K I), is obtained for different crack lengths "a", different amplitudes of displacement, for the two polymeric materials. In addition, the energy release rate G for plane stress and plane strain are obtained by using the stress intensity factors in mode I, previously calculated. Finally, the fracture surfaces are analyzed by scanning electron microscope in order to examine the general trends for crack initiation and propagation under the loading conditions being described. [ABSTRACT FROM AUTHOR]

Abstract Multi-sample X-ray micro-computed tomography (micro-CT) is used for the statistical analysis of the internal geometry of randomly oriented strands (ROS) composite – ultra-thin chopped carbon fiber tape reinforced thermoplastics (UT-CTT) with different tape lengths. The accuracy of the micro-CT measurements and their quantification for the local fiber orientation is assessed and the statistical significance of the observed trends in the fiber orientation is confirmed. The effect of tape length on structure morphology and orientation concentration is investigated. Increasing the tape length decreases the number of internal structure irregularities (scattered fiber clusters and out-of-plane fiber disturbance for instance) present in UT-CTT. [ABSTRACT FROM AUTHOR]

Abstract Embedded piezoelectric lead zirconate titanate (PZT) transducers in carbon fibre reinforced plastic (CFRP) composites are typically electrically insulated by interlaying materials such as polyimide Kapton films between the PZT and the laminate ply. However, the presence of polymeric films may cause debonding at the layer interface, thus reducing the structural performance. This paper proposes an alternative insulation technique in which PZTs are covered by a thin patch of woven E-glass fibre fabric for enhanced adhesion with the surrounding epoxy matrix. An analysis of variance on experimental test results showed that the compressive, flexural and interlaminar shear strengths of plain CFRP specimens were equal to the means of the smart CFRP composite (0.41 < p -value < 0.58), but significantly higher than those of Kapton specimens (0.0001< p -value < 0.05). Moreover, a post-test fractographic analysis indicated that damage opening in Kapton specimens was significantly larger (p -value = 0.03) than that in plain specimens. Brooming failure compression was also the same for the smart CFRP composite and plain samples, whereas Kapton specimens failed by through-thickness shear. Finally, nonlinear ultrasonic experiments were conducted on CFRP laminates with artificial in-plane delamination using glass fibre insulated PZTs. Remarkably, the effect of second harmonic generation was found to be nearly two times higher than conventionally surface-bonded PZTs. [ABSTRACT FROM AUTHOR]

Abstract The mechanical properties of polypropylene (PP) with 40% ash content were calibrated as a function of strain rate in the ranges 500 to 1000 s−1 and temperature from −35 to 85 °C using a special Split Hopkinson tension bar. In this system, an infra-red spot heater and a liquid nitrogen freezer were used to control the test temperature. The experimental results show that the tensile stress-strain response of polypropylene strongly depends on the applied strain rate and test temperature. [ABSTRACT FROM AUTHOR]

This study investigated the strength and microstructural characteristics of modified sulfur polymer composites employing several industrial wastes (such as sulfur and rubber) and binary cement (blend of fly ash and Portland cement) as primary components. Modified sulfur played a role of a binder in the sulfur composites. Portland cement was blended together with fly ash in the binary cement that was used as a micro-filler, as well as a potential crack-healing agent, in the sulfur composites. Rubber powder from waste scrap tires was used as a substitute of fine aggregate. A total of 24 different mixtures were tested by varying the mix proportions of sulfur, binary cement, and rubber powder. The test results revealed that the highest compressive strength of the sulfur composites for a given rubber powder ratio was acquired from the use of 40% binary cement ratio. A broad series of microstructural analyses, including SEM, XRD, and FT-IR spectroscopy, confirmed the beneficial effect of the binary cement (up to 40%) on the strength of the sulfur composites, and supported its potential role in crack healing. [ABSTRACT FROM AUTHOR]

The ability to provide effective and adaptable joints for pultruded fibre reinforced polymer (PFRP) is crucial for its widespread application in civil infrastructure. This experimental based study on 150 double lap joints specimens investigated the effects of threaded bolt and clamping pressure on the joint strength behaviour, failure mechanisms and joint efficiency of bolted joints in PFRP. Double lap joints in both longitudinal and transverse directions of the laminates and with different edge distance-to-bolt diameter (e/d b ) were prepared and tested in accordance with ASTM D5961 standards. The joint strength in the longitudinal laminates with plain bolt increased for e/d b ratio for up to 4 and with no appreciable strength gain after exceeding this ratio. On the other hand, about 30%–40% reduction in joint strength was observed in the longitudinal direction due to the bolt thread tearing through the laminates. This leads to a recommendation of 0.6 reduction factor in preliminary design of PFRP bolted connections with bolt thread present. Meanwhile, only a marginal difference of 7% was observed in transverse direction. Furthermore, the introduction of lateral clamping pressure had increased the joint strength by 60%–90% and this has lessened the thread casualty effect on the pultruded composite joints. [ABSTRACT FROM AUTHOR]

ABSTRACT: Carbonaceous nanoparticles (CNPs), including carbon black, carbon nanotubes, and graphene nanopiece, were selected as nanoadditives for investigating the rheological behavior dependence of their polymer‐based composites on morphological and interfacial structure. Polypropylene (PP) was adopted as matrix and a series of contents of CNPs were used for sample compounding. With identical concentration, the morphological structure of CNPs was emphasized as the dominant effect affecting the shear viscosity and the compressibility of PP/CNPs melts. The viscosity dependence on the CNPs contents and physical structure, such as particle size, aspect ratio, and specific area, was fully discussed in this work. The newly‐introduced inner voids, induced around the interface region between matrix and CNPs during physical mixing, were contributive to the rheological deviation, which was further reflected from the melt compressibility. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46416. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) composites has been widely used in the retrofitting of earthquake-damaged concrete structures. In literature, the studies on FRP-confined intact concrete columns have been well documented. However, research on FRP-confined damaged concrete columns is relatively rare. Aiming to solve this problem, the confinement performance of basalt FRP (BFRP) on pre-damaged concrete columns was investigated in the present study. In total, twenty-six concrete cylinders were constructed and tested under axial compression. The effects of pre-damage levels and number of BFRP wrapping layers on the compressive performance of the concrete cylinders were investigated. Eighteen plain concrete cylinders were preloaded at three different stress levels (i.e., up to f′ co , 0.9 f′ co and 0.8 f′ co on the descending branch of the axial compressive stress-strain curve of plain concrete, f′ co was compressive strength of plain concrete and was 37.7 MPa here) to represent the moderate, moderately-severe, and severe damage levels, respectively. The thin surface layer of the damaged plain concrete specimens was removed and the damaged concrete specimens were repaired using early strength cement mortar. Then, the cylinders were wrapped with BFRP sheets and retested under axial compression. The experimental results showed that compared with the plain concrete, the ultimate compression strength and axial strain capacities of the pre-damaged concrete were improved by 10–104% and 186–590% respectively after the BFRP confinement. The ultimate compressive strength and the initial elastic modulus of the BFRP-confined concrete tended to reduce with an increase in pre-damage level. Based on the test results, a modified strength expression and a strain expression were developed to predict the compressive behavior of the BFRP-confined concrete (undamaged). Based on the modified strength and strain expressions, a modified stress-strain expression was further proposed for BFRP-confined damaged concrete. This research concludes that BFRP is an effective external confining material for damaged concrete column members after earthquakes. [ABSTRACT FROM AUTHOR]

Natural fiber-reinforced polymeric composites are gaining significant attention in engineering applications. The present investigation is an attempt to assess the hybridization effects of different laminate stacking sequence involving jute/kenaf/E-Glass woven fabric through study of physical and mechanical properties of nine different resulting composites. The composite laminates were fabricated using vacuum bagging method. The assessment of mechanical properties and study of fractured surfaces indicate significant improvement in tensile and flexural properties of jute/kenaf fabrics reinforced epoxy composites. [ABSTRACT FROM AUTHOR]

Cellulose nanofibers (CNFs) and nanocrystals (CNCs) were prepared, and used to prepare thin CNF/CNC films. Rheological behavior of CNF/CNC suspensions and the other relevant properties of the films were characterized in comparison with a commercial porous polymer battery separator (PBS) film of similar thickness. The use of mixed CNFs and CNCs in the film-forming suspension led to significant variation of film morphology, and structural properties. With the addition of CNCs in hybrid nanocellulose material, the CNF/CNC suspension viscosity and zeta potential, film tensile strength, crystallinity index, and optical transparency were increased. With the increased CNF loading in the suspension, film porosity, thermal stability, and thermal expansion were enhanced. The CNF/CNC films exhibited better thermal stability, thermal expansion behavior, and optical properties than those of the commercial PBS film. The coefficient thermal expansion of the CNF/CNC and PBS films were 11.86–17.65 and 178.90 ppm/k, respectively. The CNF/CNC films had more uniform strength along all directions, whereas PBS film demonstrated anisotropic property. This work paves a new strategy to tailor the properties of nanocellulose based films. [ABSTRACT FROM AUTHOR]

Since thermosetting resins have excellent resistance to chemicals, fiber reinforced plastics composed of such resins and reinforcement fibers are widely used as construction materials for equipment in chemical plants. Such equipment is usually used for several decades under severe corrosive conditions so that failure due to degradation may result. One of the degradation behaviors in thermosetting resins under chemical solutions is “corrosion-layer-forming” degradation. In this type of degradation, surface resins in contact with a solution corrode, and some of them remain as a corrosion layer on the pristine part. It is difficult to precisely measure the thickness of the pristine part of such degradation type materials by conventional pulse-echo ultrasonic testing, because the sound velocity depends on the degree of corrosion of the polymeric material. In addition, the ultrasonic reflection interface between the pristine part and the corrosion layer is obscure. Thus, we propose a pitch-catch method using a pair of normal and angle probes to measure four parameters: the thicknesses of the pristine part and the corrosion layer, and their respective sound velocities. The validity of the proposed method was confirmed by measuring a two-layer sample and a sample including corroded parts. The results demonstrate that the pitch-catch method can successfully measure the four parameters and evaluate the residual thickness of the pristine part in the corrosion-layer-forming sample. [ABSTRACT FROM AUTHOR]

The aim of this study was to verify the influence of the compression molding temperature on thermomechanical properties of the basalt-reinforced poly(lactic acid) (PLA) composites. The thermomechanical properties of the composites were determined in the course of dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), static tensile test and tensile impact strength test. The incorporation of basalt fiber into poly(lactic acid) matrix led to obtaining environmentally friendly composite materials with good mechanical properties. The composite production process carried out at different temperature set-ups (170°C, 180°C, 190°C and 200°C) led to the development of composite materials characterized with favorable mechanical properties and specific structure. The simultaneously realized thermal, thermo-mechanical and mechanical analyses allowed to describe the limitation processes resulting from the application of different compression molding temperatures. The best thermomechanical properties were recorded for the composites pressed at the highest temperature (200°C). [ABSTRACT FROM AUTHOR]

Copyright of Romanian Journal of Materials / Revista Romana de Materiale is the property of Foundation for Materials Science & Engineering Serban Solacolu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Romanian Journal of Materials / Revista Romana de Materiale is the property of Foundation for Materials Science & Engineering Serban Solacolu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRACT Aiming to manufacture biomaterials using renewable resources, we prepared, using a corotating and intermeshing twin-screw extruder, high-density green polyethylene composites reinforced with 20, 30, and 40 wt % of bleached cellulose fibers. Injection molded test samples are characterized for mechanical and thermal properties using thermogravimetry (TGA) and differential scanning calorimetry (DSC). These composites present improved mechanical properties relative to the pure matrix; the elastic modulus increases by 240% for the composite with 30 wt % of fiber. We characterize this composite, additionally formulated with lignin and a secondary antioxidant, by tensile and flexural mechanical properties, DSC, TGA, and oxidation induction time (OIT). Lignin has no effect on the mechanical properties; however, for the composite, the OIT increases from 24 to 77 min, clearly evidencing its effect as a stabilizer. Aging the composites for 1000 h, in a QUV chamber, confirms the stabilizing effect of lignin. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45219. [ABSTRACT FROM AUTHOR]

Observation of behaviour phenomena of ultrasonic waves in an object allows for quality assessment, identification and location of discontinuity. Physical nature of acoustic processes is based on propagation of mechanical waves constituting a disturbance of equilibrium of the state of material. The acoustic process identified by selected characteristics can be a source of information about state of material, its structure, and properties, which is particularly important for systems exhibiting anisotropy properties, and such are layered polymer composites. They are special materials because their properties depend greatly on the manufacturing technology. Therefore, while conducting acoustic tests which use the influence of elastic properties and homogeneity of material structure for propagation of sound waves the adopted method of measuring characteristics which identifies propagation of ultrasonic wave phenomenon is of particular importance. The aim of the work was quality evaluation of layered polymer composites made by winding and press moulding by the method of echo and C-scan, using head Phased Array. Composites have been tested by thermal and fatigue degradation. Quality evaluation has been made based on the transition time of the ultrasonic wave and the bending strength. [ABSTRACT FROM AUTHOR]

In this article, a continuum-based constitutive model is developed to predict the mechanical behavior of 5052 resin epoxy reinforced by multiwalled carbon nanotubes (MWCNTs) based on experimentally generated data. For this purpose, MWCNTs/epoxy specimens with various percentages of functionalized and nonfunctionalized MWCNTs are prepared. The SEM graphs indicate that functionalization leads to a better bound between epoxy and MWCNTs and a higher level of dispersion. The specimens are then tested under standard ASTM D638-02 a procedure and their true plastic stress–strain curves are extracted. Investigations on experimentally generated data reveal that a wt% dependent equation which is obtained using any two series of these data can be successfully implemented for others. The equation is then implemented into a finite element software using a developed user material subroutine in which is utilized based on a particular solution algorithm. In order to verify the accuracy of the model some tensile as well as load-unload-reload tension tests are performed according to standard conditions and acceptable agreement between the numerical and experimental results are observed. Results also indicate that the proposed empirical model can precisely predict the stress–strain behavior of 5052 resin epoxy containing arbitrary wt% of MWCNTs in the range 0–1 wt%. [ABSTRACT FROM AUTHOR]

Polymer matrix composites have recently gained attraction due to their light weight, low cost, and easy availability, but they are also known for their higher burning rate and low thermal stability. Polypropylene (PP) is one of the most used thermoplastic polymers, its thermal stability and flammability have been modified in this study by incorporation of oyster shell powder (OSP) into PP as a filler. Besides flammability and thermal properties, OSP incorporation has some effects on dielectric and mechanical properties of PP. Effect of concentration of OSP (0-50 wt%) on the properties of OSP/PP composites was studied. The burning rate was observed to decrease while thermal stability was increased as a result of OSP addition into PP. Similarly, relative permittivity (dielectric constant) of OSP/PP composites was found higher than that of pure PP. Flame retardancy, thermal stability, and dielectric properties are functions of OSP concentration. Optical tests including fluorescence spectroscopy and FT-IR were conducted to study any possible interactions between OSP and PP. A slight decrease in the tensile strength was observed. FESEM images revealed that the decrease in tensile strength is a result of interfacial flaws between filler particles and matrix. Tensile modulus was found to increase which is an evidence of stiffness, this is also correlated to the improvement in thermal stability. POLYM. COMPOS., 38:236-243, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The aim of this article is to investigate the influence of filler content and temperature on the rheological, mechanical, and thermal properties of wood flour polypropylene composites (WPCs). Testing WPCs at high temperatures and percentages of filler is extremely challenging because of reduced linear viscoelastic region, high viscosity, and degradation. In this work, a complete characterization of WPCs with different filler percentages (0-70 wt%) has been made. Rheological tests are performed at 170°C for the WPCs and in the 170-200°C range for neat polypropylene. A single master curve is obtained using two shift factors that can be described by a modified Eilers model and a Williams-Landel-Ferry equation. This master curve, fitted with a Carreau-Yasuda model, can be very useful for predicting the viscosity of WPCs at temperatures that are typically used during processing and for any percentage of filler. POLYM. COMPOS., 37:3460-3473, 2016. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Physical foundations for a technique of revealing cracks in laminated metal and nonmetal constructions by a low-frequency acoustic method are considered. In this technique, elastic vibrations in a product with one-sided access are excited and recorded by a double-crystal transducer when the product surface is scanned with simultaneous rotation of the transducer about its longitudinal axis. The technique allows one to improve the reliability and productivity of testing of multilayered constructions. [ABSTRACT FROM AUTHOR]

This paper investigates the repair of polymer matrix composites and validates the repair by static testing. Scarf repair is carried out on the laminates and cured under vacuum. It is observed that 80% of tensile strength is recovered due to this process. Therefore, this investigation highlights the significance of atmospheric pressure plasma treatment on repair of graphite epoxy laminate. It is observed that the surface energy of graphite epoxy laminate has improved significantly due to atmospheric pressure plasma treatment. Atmospheric pressure plasma treatment results in noteworthy increase in oxygen functionalities as detected by X-ray photoelectron spectroscopy, as well as surface roughness as detected by atomic force microscopy. The improvement in adhesion properties is correlated with lap shear strength of adhesive bonded joints and mode of failure has been analyzed by scanning electron microscopy. The plasma-treated laminates, when used for repair, provided an additional 12% in the tensile strength and thereby retaining a strength increase up to 92%. [ABSTRACT FROM AUTHOR]

Void characterization and porosity measurements of uncured and partially cured carbon/epoxy prepregs are challenging due to the soft nature of the matrix. If samples need to be cut from a larger laminate, the act of cutting and polishing can alter the void morphology. This paper presents a method to prepare samples for optical microscopy by infiltrating the pore space in the soft prepreg with a room-temperature curing low-viscosity resin to support the structure during cutting and polishing in preparation for optical microscopy. The methodology is validated by comparison with results obtained from porosity measurements using the ASTM D2734 standard density method. The paper also explores the use of thickness measurements to determine porosity. It is shown that thickness measurements can be used to estimate porosity for the no-bleed out-of-autoclave prepreg system used in the present study but that the accuracy is lower than using microscopy or density methods. [ABSTRACT FROM AUTHOR]

This work aims to investigate how compressive strength of a typical class C fly ash-based geopolymer would be changed with addition of mullite. In preparation of basic geopolymer, fly ash was collected from Mae Moh power plants, Lampang province, was alkaline activated and cured for a total period of 7 days. In making the composites, 20-60% of mullite powder was added to the basic geopolymer mixture and cured at the same condition. Porosity, density, and water absorption of the samples were determined by following ASTM C-642. The results showed that the compressive strength of the geopolymer mortar could be remarkably improved from 14 MPa to 71 MPa with mullite addition. The mechanical property variation of the composites was discussed along with their physical properties and microstructures. [ABSTRACT FROM AUTHOR]

It is shown that when large products with a complex structure with a high integral attenuation of ultrasound are tested, it is expedient to use different electronic signal-processing methods (storage, normalization, and synchronous detection) that allow one to increase the thickness-measurement accuracy of vermicular cast iron products with complex structures and poor surfaces; when large polymer composite products with a high integral attenuation of ultrasonic signals are tested these methods allow one to not only increase the signal-to-noise ratio but the measurement accuracy of the bottom signal. It is possible to fully apply different electronic signal-processing methods if a multifunctional software-hardware measuring system that we designed is used, which is capable of selecting the optimum set of signal-processing methods for each new product. [ABSTRACT FROM AUTHOR]

It has been established that mathematical modeling and computer prediction of the deformation properties of synthetic filaments can be successfully used to study the corresponding properties of polymeric marine cables. This finding confirms the universal nature of these methods. Polymeric cables are more resistant to aggressive media (seawater) than steel cables. In addition, some polymeric cables do not sink in water, which is important for towing operations and hauling freight by water. [ABSTRACT FROM AUTHOR]

This study describes an experimental investigation of the degradation of the tensile properties of basalt fibers and epoxy-based composites in various corrosive environments, including alkaline, acid, salt and water solutions, and clarifies the corresponding degradation mechanisms. Carbon and glass fibers and their composites are adopted as references. Accelerated experiments were conducted at temperatures of 25℃ and 55℃ and the variation in tensile properties was studied by means of tension testing, mass loss weighing, scanning electron microscope imaging and energy spectrum analysis. The experimental results show that basalt fibers posses relatively strong resistance to water and salt corrosion, moderate resistance to acid corrosion and severe degradation in an alkaline solution. The tensile properties of basalt FRP composites are much better than those of basalt fibers. The degradation mechanism of basalt fibers involves damage by etching in salt, water and alkaline solutions and by change in the chemical composites in an acid solution. The fracture properties of basalt FRP composites are controlled by the failure of corroded interfaces between the fibers and the resin, making the interface the critical factor, rather than the fiber itself. [ABSTRACT FROM PUBLISHER]

The paper presents a comparison of the test results for the fiber volume fraction, static bending and Charpy impact strength of glass fiber reinforced polymer laminates reinforced by 0/90 fabric and chopped strand mat, produced by the hand lay-up and the vacuum-assisted resin infusion (VARI) method. The laminates were produced under equivalent conditions, with polyester matrix and lay-up areal mass 2100 g/m2. In the comparison of the obtained measurement results, similar mechanical performance was stated in the case of the hand lay-up and the VARI production. However, significantly smaller scatter of results and better uniformity of the reinforcement in the matrix with smaller amount of local structure defects was observed for the samples obtained by VARI method. The laminates obtained by VARI method show a much more advantageous coefficient of variation than that of the hand lay-up method, especially in the case of the mat reinforcement. [ABSTRACT FROM AUTHOR]

Semiconductor encapsulation is crucial to electronic packaging because it provides protection against mechanical stress, electrical breakdown, chemical erosions, $\alpha $ radiations, and so on. Conventional encapsulants are only applicable below 150 °C. However, with increasing demand for high-density and high-temperature packaging, encapsulants that are functional at or above 250 °C are required. In this paper, five types of encapsulants, including conformal coatings, underfills, molding compounds, potting compounds, and glob tops, are surveyed. First, recommended properties and selection criteria of each type of encapsulant are listed. Second, standard test methods for several crucial properties, including glass-transition temperature ( T_{g}) , coefficient of thermal expansion (CTE), dielectric strength, and so on are reviewed. Afterward, commercial products with high-operation temperature are surveyed. However, the results of the survey reveal a lack of high-temperature encapsulants. Therefore, this paper reviews recent progress in achieving encapsulants with both high-temperature capability and satisfactory properties. Material compositions other than epoxy, such as polyimide (PI), bismaleimide (BMI), and cyanate ester (CE), are potential encapsulants for high-temperature (250 °C) operation, although their CTE needs to be tailored to limit internal stress. Fillers are reported to be efficient in reducing the CTE. In addition, fillers may also have a beneficial impact on the thermal stability of silicone-based encapsulants, whose high-temperature capability is limited by their thermal instability. [ABSTRACT FROM PUBLISHER]

The rapid increase in the use of polymer composite materials recently has led to the investigation of their behavior under thermal loads. During thermal loading, for example a fire incident, the polymer materials start to degrade. The degradation rate is heating-rate dependent. In this work, medium heating rates were applied to a neat resin and two (2) resin batches doped with fire-retardant nanomaterials. The thermal decomposition behavior of these systems was investigated using multistage kinetics modeling, the kinetic triplets for each system were extracted using the van Krevelen methodology and finally the thermogravimetry tests were reconstructed. This is the first part of the work dealing with the fire response of polymer composites. It is a material characterization process and the outcome is used in Part B, where a progressive degradation material model is developed and implemented in a Finite Element code. [ABSTRACT FROM AUTHOR]

The influence of various interface forces on membrane fouling during reverse-osmosis (RO) filtration of organic solutions is investigated. Some monoaromatic compounds are used as model foulants. Isothermal data demonstrate that the adsorption of aromatic compounds on the membrane surface fits the Freundlich model better than the Langmuir model. Kinetics data are better correlated with the pseudo-second-order model than the pseudo-first-order one. The affinity of monoaromatic compounds to the RO membrane is evaluated. Statistical analysis of results indicates that the initial fouling rate is dominated by the electrostatic attraction and the hydrophobic force while irreversible fouling is mainly controlled by the formation of a hydrogen bond between the membrane surface and organic compounds. [ABSTRACT FROM AUTHOR]

The amorphous ferroalloy particle was filled into the polymeric matrix. The filler concentration has much effect on the absorption properties of the composites and changes the matching frequency. Bruggeman-Hanai formula was also applied in analysis of the permittivity or the permeability. The reflection loss was calculated from the complex permittivity and complex permeability of the composites. The results indicate that the filler ratio and the thickness had important effect on the absorption properties of the composites, showing that the amorphous ferroalloy particle is one of the suitable candidates to achieve high microwave absorption in GHz range. [ABSTRACT FROM AUTHOR]

The extracellular polymeric substance (EPS) extracted from waste-activated sludge after short-time aerobic digestion was investigated to be used as a novel biosorbent for Cd removal from water. The sorption kinetics was well fit for the pseudo-second-order model, and the maximum sorption capacity of the EPS (430.3 mg Cd/g EPS) was markedly higher than those of the reported biosorbents. Both Langmuir model and Freundlich model commendably described the sorption isotherm. The Gibbs free energy analysis of the adsorption showed that the sorption process was feasible and spontaneous. According to the results of multiple analytical techniques, the adsorption process took place via both physical and chemical sorption, but the electrostatic interaction between sorption sites with the functional groups and Cd was the major mechanism. [ABSTRACT FROM AUTHOR]

The overall objective of the investigation presented in this paper was to study the effect of dispersion of core-shell polymer (CSP) particles within the ply interfaces on damage evolution of glass/epoxy laminates under impact loading. These laminates were fabricated with the CSP particle dispersion controlled to 14 % of the total weight of the used prepreg. A series of impact experiments were done with instrumental drop tower device at all probable impact energies within a practical low velocity impact range. The damage phenomena occurring in the internal microstructure of the laminates were analysed with the help of scanning electron microscope and correlated to the structural response of the laminate. The predominant damage modes were dependent on the magnitude of the applied impact energy. The CSP particle incorporation does not change the sequence of the fracture events but it delays and mitigates the damage creation. The deformation of the CSP particles and the tearing of their outer shells absorb most of the impact energy thereby preventing initiation of matrix cracks at lower impact energies and delaying fibre damage at higher energies. The crushed particles along with their nano-size rubber cores impede crack propagation requiring the cracks to follow torturous paths consequently dissipating additional amount of energy. These particles also promote elastic energy absorption of the laminates minimizing their tendency to fracture easily under impact. The ultimate load bearing capability of the modified laminate showed 60 % improvement and the deflection characteristics indicated lower proneness to impact. [ABSTRACT FROM AUTHOR]

The Poisson's ratio describes an extent of transverse deformation of a material when an axial strain is applied. A change of the Poisson's ratio from positive to negative can equip a material with a set of specific properties. In this paper, a study of a composite material with a tunable Poisson's ratio is presented. Samples of such a composite were first fabricated with two different polymers based on a composite structure proposed in our previous work using a multi-material additive-manufacturing system. Using both experimental and numerical methods, deformation mechanisms and mechanical properties of this composite material were analyzed. The obtained results demonstrate that its Poisson's ratio can be reduced by increasing the difference in stiffness of constituent materials and turned from positive to negative when this difference is sufficiently high. Additionally, the study also validates a possible method to fabricate composites with designed structures and multi-constituent materials using additive-manufacturing techniques. [ABSTRACT FROM AUTHOR]

In this study, the roles of polymer matrices and filler additives in controlling the positive temperature coefficient (PTC)/negative temperature coefficient (NTC) behavior of DC resistivity at high temperature for semicrystalline ethylene vinyl acetate copolymer, amorphous acrylonitrile butadiene copolymer, and their blend composites filled with different carbon fillers like Conductex carbon black, Printex carbon black, and short carbon fiber have been investigated. It is seen that the PTC/NTC behavior of resistivity depends on the characteristics of both polymer matrices and filler additives. The anomaly in the results are due to polymer crystallinity, shape and size of fillers, and their thermal expansion coefficient, that play major role in controlling the PTC/NTC of resistivity at high temperature for the composites. Finally, reproducibility of composite resistivity has been evaluated with their some proposed practical applications. These composites can be used as both PTC and NTC thermistors. [ABSTRACT FROM AUTHOR]

A new versatile method to measure rates and determine activation energies for the Brønsted acid catalysed hydrolysis of cellulose and cellobiose (and other polymeric carbohydrates) in ionic liquids is demonstrated by following the C–O stretching band of the glycoside bond with in situ ATR-FTIR. An activation energy in excellent agreement with the literature was determined for cellulose hydrolysis, whereas a distinctly lower activation energy was determined for cellobiose hydrolysis. The methodology also allowed to independently determine activation energies for the formation of 5-hydroxymethylfurfural in the systems. [ABSTRACT FROM AUTHOR]

In order to further investigate shear-induced interfacial crystallization of polymer-based composites, an improved fiber-pulling device was designed and built. Its peculiar characteristic is that a force transducer is assembled to in situ monitor the variation of interfacial shear stress between the polymer matrix and pulling fiber. Thus, the relationship between interfacial shear stress and the subsequent crystalline morphology can be quantitatively established. In the preliminary study via this device, isotactic polypropylene (iPP)/glass fiber composite was adopted as a model system. The results indicate that interfacial crystallization kinetics is promoted by the presence of interfacial shear stress. Furthermore, there are two thresholds of interfacial shear stress for interfacial crystalline morphology. To be specific, one (0.017 MPa) is for the induction of iPP nucleation, above which α-form iPP crystals are obviously encouraged during the subsequent isothermal crystallization; the other is for the generation of β-form iPP crystals (0.042 MPa), above which β-form crystals are favored to be triggered in the transcrystalline region. [ABSTRACT FROM AUTHOR]

A carbon black (CB)/low-density polyethylene (LDPE)/ultrahigh-molecular-weight polyethylene (UHMWPE) composite with a segregated and double-percolated structure has been fabricated using the solution mixing and high-speed mechanical mixing method. Structural observations show that the conducting CB/LDPE layers were only dispersed at the interface of UHMWPE granules and formed a well-developed CB conductive network with a percolation threshold of 0.26 vol%. The low percolation threshold in CB/LDPE/UHMWPE composites can be explained by the segregated and double-percolated networks of CB within the polymer matrix. A noticeable double positive temperature coefficient of resistivity can be observed around the melting temperature of LDPE and UHMWPE followed by a negative temperature coefficient of resistivity. The microstructure evolution of CB/LDPE/UHMWPE composites can be observed and explained by in situ optical micrographs. [ABSTRACT FROM AUTHOR]

The tensile properties and fracture behavior of polyacrylonitrile (PAN)- and pitch-based hybrid carbon fiber/polyimide composites with several types of nanoparticles (25 nm C, 20-30 nm β-SiC, 130 nm β-SiC, 80 nm SiO, and 300 nm SiO) added to the matrix were investigated. The tensile stress-strain curves of PAN- and pitch-based hybrid carbon fiber/polyimide composites with 25 nm C, 20-30 nm β-SiC, and 80 nm SiO nanoparticles have complex shapes (jagged trace), whereas the tensile response of hybrid carbon fiber/polyimide composites with 130 nm β-SiC and 300 nm SiO nanoparticles indicates an instantaneous failure. The stress after the initial failure in hybrid carbon fiber/polyimide composites improves by adding 25 nm C, 20-30 nm β-SiC, and 80 nm SiO nanoparticles to the matrix and correlates with the fracture toughness of the polyimide matrix. [ABSTRACT FROM AUTHOR]

Isotactic polypropylene/polyamide/carbon black (PP/PA/CB) composites with microfibrillar morphology were designed and prepared using a multistage stretching extruder with an assembly of laminating-multiplying elements (LMEs). CB was selectively located in PA. With the increase of LME number from zero to seven, the conductive PA/CB phase was found to experience an elongating-breaking-elongating process. This morphological development resulted in the strong dependence of electrical resistivity on the LME number. When no LME was used, PP/PA/CB materials with 2.0, 3.0, or 4.0 wt% (1.0, 1.6, and 2.1 vol%) CB employed were insulators (resistivity: 10 Ω cm) due to their droplet morphology. With the introduction of LMEs, a conductive network was formed because of the microfibrillation of the conductive PA/CB phase; these materials became conductors (resistivity: 10-10 Ω cm). The percolation threshold can lower to 1.5 wt% (0.9 vol%). The low resisticity and percolation threshold cannot be obtained through the conventional method. [ABSTRACT FROM AUTHOR]

The properties of aqueous acetic-acid solutions of chitosan and copolyacrylmethacrylate Eudragit E, which contains tertiary amines, were studied. It was shown that monophasic solutions in a common solvent in a certain pH range that enabled the degree of protonation of the amines and the conditions for chemical cross-linking of chitosan to be controlled could be prepared by using amine-containing polymers with different types of amines. IR spectroscopy of films formed from solutions of combined chitosan and Eudragit E showed that the functional groups of the studied amine-containing polymers did not interact. The ability to change the degree of swelling and the solubility of the films by adding a bifunctional reagent that reacted only with primary amines was demonstrated. [ABSTRACT FROM AUTHOR]

A series of core-shell polymeric particles with poly( n-butyl acrylate- co-methacrylic acid- co-ethylene glycol dimethylacrylate) as core and poly(styrene- co-methyl methacrylate) as shell were prepared by seeded emulsion polymerization. The role of ethylene glycol dimethylacrylate (EGDMA) is to crosslink the core so as to avoid any probability of gel formation and to bind both the core and the shell phase together. The spherical morphology of the core-shell structure was achieved at 60:40 core to shell ratio. The core-shell morphology was confirmed by SEM and TEM analyses. GPC analysis of the particles reveals that the polymer shows a bimodal mode. The first peak has M = 382700 and M = 245200 with polydispersity index of 1.6, and the second peak has M = 21200 and M = 14800 with polydispersity index of 1.4. These core-shell latexes were applied as a pigment/binder in emulsion paint and the paint properties like gloss, rock hardness, washability, opacity, etc. were compared with the standard. The results show that these core-shell latexes can provide similar hiding power with 17% reduction of TiO in the paint formulation. [ABSTRACT FROM AUTHOR]

Scratching of polymeric coatings on hard substrates is studied experimentally and numerically from a mechanical point of view. In particular, the behavior of local and global mechanical properties, as well as the delamination behavior, at scratching due to pressure-sensitive effects is of interest. The numerical investigation is performed using the finite element method (FEM) where pressure sensitivity is modeled using the classical Drucker-Prager plasticity model (Drucker, Prager, Q. Appl. Math., 10 157-165 (1952)) while the adhesion of the coating to the substrate is modeled as a cohesive zone where relevant model parameters are determined experimentally using the double cantilever beam test with uneven bending moments (DCB-UBM). Good correlation between experimental and numerical results were achieved and the most important finding concerns the fact that the dependence of pressure sensitivity proved to be different for different mechanical quantities. [ABSTRACT FROM AUTHOR]

The article reports on the refractive index of fluorinated α-fluoroacrylates in telecommunication spectral point. Topics mentioned include the high transparency of fluorinated polymeric materials, the polymer waveguide arrays, and the analysis of monomers. Also mentioned are the optical waveguides manufacturing and the ultraviolet (UV) exposition of α-fluoroacrylate.

Anti-rodent polymer composites were prepared using non-toxic substances denatonium benzoate (DB) and capsicum oleroresin (CO) mixed with polyvinyl chloride (PVC) matrix. DB is mixed in zinc stearate (ZnSt) called DB/ZnSt, and CO, providing burning sensation, is impregnated in mesoporous silica named SiCO. There are three sets of sample: Blank, composites Set I and Set II. Set I consists of DB/ZnSt at concentration of 1.96 wt% and SiCO at concentration of 12.16 wt%, 14.47 wt%, 18.75 wt% and 23.53 wt%. Set II comprises SiCO at the same amount of Set I. The anti-rodent composites studied are anti-gnawing, surface morphology, thermo-mechanical and rheological properties. Anti-rodent testing is analyzed by one-way blocked analysis of variance (ANOVA) and compared with Tukey test with a 95% level of significance, presenting good anti-gnawing efficiency. The best rat-proof sample is II.4, consisting of SiCO 23.53 wt%, which presents percentage of weight loss from gnawing at 1.68% compared to weight loss of neat PVC at 59.74%. The addition of SiCO at concentration ranging from 12.16 to 23.53 wt% reduces tensile strength around 25–50%, elongation at break strength around 2–23%, shear storage modulus (G′) around 30%, shear loss modulus (G″) shear viscosity (η) and glass transition (Tg) around 43% compared to Blank. The increase in SiCO concentration slightly improves the thermal stability of PVC composites around 3%, but the addition of DB/ZnSt at 1.96 wt% slightly reduces those properties. [ABSTRACT FROM AUTHOR]

New partially fluorinated acrylic copolymers, synthesized specifically for the protection of cultural heritage stone materials, were applied on limestone, tested in the laboratory and evaluated in comparison with two well-known commercial products employed in this field. The tests were carried out according to Italian standard methodologies. The surface characteristics of the polymeric films were studied by scanning electron microscopy. The introduction of fluorine in the side-chain of the macromolecules resulted in better resistance to UV aging and higher water repellence, while the polar acrylic sections of the molecule facilitated good bonding to the stone. Two different copolymers containing the fluorinated monomer trifluoroethylmethacrylate proved to be quite effective on highly porous stone (calcarenite) and competitive on stone of low porosity (marble). The materials tested are very promising, in view of their ready accessibility through radical polymerization and their moderate crosslinking after UV aging. [ABSTRACT FROM AUTHOR]