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A novel magnet-induced aligning magnetorheological elastomer (MIMRE) based on ultra-soft polymeric matrix was prepared through an innovative synthetic approach, enables the magnetic particles to mobile and align in elastomer matrix under magnetic field at room temperature. The effect of polymeric matrix modulus on the formation of MIMRE was investigated in detail. It was found that the MIMRE showed excellent magnetorheological (MR) effect, and the absolute and relative MR effect was of 3.61 MPa and 17,286%, respectively. The relative MR effect of magnetorheological elastomer was almost 100 times higher than that of elastomers reported in previous literature. In addition, the application of MIMRE in actuators and self-healing materials was evaluated. The present MIMRE thus opens up a new avenue for the improvement of MR effect of magnetorheological elastomer, while avoiding the use of conventional plasticizer (e.g. silicon oil). [ABSTRACT FROM AUTHOR]

By means of goal-directed flow designing and morphology controlling, this paper opened up an efficient method of continuously mass-producing biaxially reinforced polystyrene (PS)/polybutene-1(PB-1) tubes for medical application. The experimental results showed that the PS microfibers were in-situ formed by imposing a specific convergent flow onto the off-die PS/PB-1 blend melt, exhibiting excellent dispersion, high aspect ratio and good interfacial contact. As a result, the ultimate axial strength (UAS) of the microfibrillar PS/PB-1 tubes was enhanced from 29.9 MPa of conventional neat PB-1 tubes to 41.3 MPa. Moreover, by introducing the rotating mandrel or die to modify the flow to helical convergent flow, the formed PS microfiber deviated from axial direction to further improve hoop damage strength (HDS) performances. Particularly, via counter-helical convergent flow extrusion controlled by the counter-rotating mandrel and die system, the opposite-handed helical configuration of PS microfibers was brought out to eliminate the inter-fiber relative slip. As a result, the PS/PB-1 composite tubes exhibited remarkably reinforced mechanical performances in both UAS (40.3PMa) and HDS (34.9 MPa) tests, improved by 34.8% and 48.5% compared to Conv-E neat PB-1. These results suggest that such bi-axially reinforced microfibrillar tubes could be of benefit to ensure the structural integrity of artificial medical tubing systems. [ABSTRACT FROM AUTHOR]

Polypropylene and natural rubber blends with multiwalled carbon nanotube (PP/NR + MWCNT nanocomposites) were prepared by melt mixing. The melt rheological behaviour of neat PP and PP/NR blends filled with different loadings (1, 3, 5, 7 wt%) of MWCNT was studied. The effect of PP/NR blends (with compositions, 80/20, 50/50, 20/80 by wt) on the rheological percolation threshold was investigated. It was found that blending PP with NR (80/20 and 50/50 composition) reduced the rheological percolation threshold from 5 wt% to 3 wt% MWCNT. The melt rheological behaviour of the MWCNT filled PP/NR blends was correlated with the morphology observations from high resolution transmission electron microscopic (HRTEM) images. In predicting the thermodynamically favoured location of MWCNT in PP/NR blend, the specific interaction of phospholipids in NR phase with MWCNTs was considered quantitatively. The MWCNTs were selectively localised in the NR phase. The percolation mechanism in MWCNT filled PP/NR blends was discussed and for each blend composition, the percolation mechanism was found to be different. [ABSTRACT FROM AUTHOR]

In situ micro and nano fibrillar reinforced blends with olefin block copolymer as matrix and polypropylene (PP) as dispersed fibrils were successfully prepared by a simple extrusion-stretching process. Four parameters, that are screw rotating speed, post stretch ratio, die dimension, and PP content, are explored to study how they affect PP fiber morphology and the mechanical performance of the composites. At high stretch ratio, refined PP fibrils are obtained at three different screw rotating speeds and the diameters of the fibrils decrease as the speed increases; at low stretch ratio, only short fibrils with elongated ellipsoids are found in the composites whatever the screw rotating speeds are. When other processing parameters are kept constant, the blends prepared with smaller die exhibit a more impeccable fibrils structure. As the PP contents vary from 5 wt% to 20 wt%, all the composites nearly have same PP morphologies and the diameters of PP fibrils seem to be independent of PP content. Particularly, even refined nano-sized PP fibrils are formed under high screw rotating speed and post stretch ratio with smaller die. Rheological and mechanical analysis show that once the continuously PP fibrils network are established, the property of OBC could be well improved. This structure is proved to be superior to PP component of spheres, elongated ellipsoids and short fibrils. [ABSTRACT FROM AUTHOR]

The effect of the lateral dimensions of the graphene reinforcement on the physical properties of poly(methyl methacrylate) (PMMA) nanocomposites was studied. Electrochemically-exfoliated, few-layer graphene with average diameters of 5 μm (5-FLG) and 20 μm (20-FLG) were incorporated into a PMMA matrix at loadings from 0.5 to 20 wt.% by melt mixing using a twin screw compounder. The smaller graphene flakes were found to have only a slight effect on the rheological properties of the PMMA, whereas the larger flakes significantly increased the viscosity and dynamic moduli of the PMMA melt. Mechanical testing showed that the 5 μm flakes behaved in a similar way to short fibers and reinforced the PMMA matrix poorly compared to the 20 μm flakes, in line with previous predictions on the critical length of graphene. Significantly, these larger flakes gave a linear increase in the modulus with loading even at high loadings, without any of the detrimental aggregation effects seen in most other graphene systems. [ABSTRACT FROM AUTHOR]

In this study, the cure kinetics, rheological and electrical behaviors of the MWCNTs/epoxy nanocomposites produced using a three-roll mill are studied. After defining the domain of linear response, the influence of temperature and MWCNTs on the shear viscosity has been investigated. The shear-thinning effect caused by adding CNTs to the epoxy matrix is more pronounced at increased temperature and MWCNT weight content. Furthermore, a mechanical manifestation of the percolation phenomenon may have been observed. At last the electrical conductivity was investigated to characterize the percolation behavior and determine the best CNT content/electrical properties ratio. [ABSTRACT FROM AUTHOR]

The molecular relaxations in melt-extruded poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blends with less than 40 wt% PMMA were investigated using dynamic rheological measurement and broadband dielectric spectroscopy. According to dynamic rheology, the total chain entanglement density of the blend melts increased with adding PMMA, and the dissimilar chains were more likely to entangle with each other than similar ones. Furthermore, PMMA facilitated the relaxation process. The dielectric temperature spectra revealed strong structural heterogeneity in the semicrystalline blends whose α a and α c relaxations were accelerated by increasing PMMA content. The α a and α c relaxations were shown to follow the Vogel–Fulcher–Tamman and Arrhenius equations, which allows assigning their molecular origins clearly to amorphous PVDF interphase and the amorphous portions within the crystalline PVDF phase, respectively. However, there exist structural heterogeneities in amorphous PVDF/PMMA mixture phase associated to intermolecular entanglement between dissimilar chains, giving rise to one or two α m relaxations in the dielectric temperature spectra depending on the PMMA content. [ABSTRACT FROM AUTHOR]

Electrical and electromagnetic interference shielding properties of epoxy/multi-walled carbon nanotube (MWCNTs) composites are studied for low nanotube contents from 0.03 to 0.3 wt.% and different processing conditions. In situ chemical modification of carbon nanotube surfaces was achieved by ultrasonic irradiation of carbon nanotubes either in polyethylene polyamine or in liquid epoxy resin, resulting in amine-grafted or epoxy-grafted composites, respectively. Raman, TGA, and SEM analyses indicate a successful grafting of polymer chains to the nanotube surfaces. The amine-grafted MWCNT/epoxy composites show the presence of a thick polymer layer that has formed an extra phase on the carbon nanotube walls, which affects significantly the electrical conductivity and radio frequency response properties. Hence, the amine-grafted composites demonstrate a slightly higher percolation threshold ( p c = 0.08 wt.%) and, at the same time, a lower absolute values of dc-conductivity as compared to that of the epoxy-grafted composites, with p c = 0.05 wt.%. In the radio frequency range, almost 3 orders of magnitude rise of the values of ac-conductivity was observed for small contents of the amine-grafted MWCNTs in epoxy. The epoxy-grafted composites could be proposed for producing effective antistatic and electrostatic dissipation coatings. Around and above the percolation threshold, the amine-grafting is critical in the radio frequency range for producing coatings with large dielectric losses. The absolute values of microwave attenuation were found to be independent of the surface modification procedure, but strongly dependent on the concentration of MWCNTs and the thickness of the composite layer. [ABSTRACT FROM AUTHOR]

The cutting, lay-up and bagging of out-of-autoclave (OOA) prepregs for composite part fabrication can take from several days to weeks, depending on the desired part size. This period of ambient temperature “out-time” induces resin polymerization/cross-linking, and affects critical physicochemical phenomena such as minimum viscosity, gelation, and vitrification. Therefore, the capability to monitor out-time at ambient conditions and to understand its influence on key resin properties is valuable to minimize waste and increase efficiency. In this study, the dielectric properties of out-of-autoclave (OOA) carbon/epoxy prepreg aged from 0 to 7 weeks are investigated. The measured dielectric data is used to develop an in-situ out-time monitoring method at ambient condition. Furthermore, the effects of out-time and out-life on critical physicochemical parameters are identified. [ABSTRACT FROM AUTHOR]

The electrical conductivity behaviour of unsheared (static) and sheared poly(methyl methacrylate)/carbon black (CB) composite disc-shaped samples with various CB concentrations as a function of the radial position were investigated and analysed. It was found that the angular averaged electrical conductivity of the static samples is independent of the radius and CB concentration. In comparison to that, the angular averaged electrical conductivity of the samples with a shear history is decreasing as a function of the radius due to the linear increase of the deformation from the centre to the rim of the samples. It is shown, that this effect is less pronounced increasing the composite concentration. A simple model is proposed to explain this behaviour. The results obtained in this study are in a very good agreement with the investigations performed via coupled electrical and rheological measurements and provide a deeper insight into structural changes in conductive polymer composites induced by shear deformations. [ABSTRACT FROM AUTHOR]

The processing and final part quality of out-of-autoclave (OOA) prepreg composites are strongly influenced by the thermo-chemical and thermo-mechanical properties of the resin. These properties are primarily influenced by the out-time, or room temperature exposure time, of the resin prior to cure, and by the chosen cure cycle. However, both these factors can be difficult to control. Therefore, the capacity to track the resin cure state during processing is highly desirable. In this study, neat resin and prepreg samples are aged from 0 to 7weeks, and the resin cure kinetics and viscosity are measured using differential scanning calorimetry (DSC) and rheometry, respectively, and used to develop accurate predictive models. The dielectric properties of the resin are measured in situ, and correlations to resin cure kinetics and viscosity are developed. The study quantifies the effects of out-time on cure kinetics and viscosity, and shows that both properties can be predicted and monitored in situ with excellent accuracy. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the properties of hybrid composites made by epoxy reinforced with short glass fibers (GF) and exfoliated graphite nanoplatelets (GNP) were determined as a function of the GF loading. The addition of GNP, either within the matrix or at the GF surface (GFc), promoted the formation of a stronger GF–epoxy interface, as evaluated by the single-fiber microdebonding test, resulting in an increase of the interfacial shear strength by ∼60% exhibited by the hybrid epoxy composite reinforced with 5wt% GNP. Quasi-static tensile tests and impact tests were performed in order to explore how the combined effect of the nano- and micro- size reinforcements affected the macroscopic mechanical properties under low and high strain rates. The improved tensile modulus, ultimate tensile strength and impact resistance exhibited by the hybrid composites revealed that it is possible to introduce the nano-materials at the fiber/matrix interface and significantly improve the interfacial properties, leading to lighter and stronger composites. Furthermore, the storage modulus and the viscoelastic behavior of GF/epoxy composites were remarkably enhanced upon addition of GNP, indicating strong GNP–polymer interactions and immobilization of the polymer chains. In conclusion, the combined effect of nano-materials and micro-size reinforcements can be exploited to produce light-weight hybrid composites with enhanced mechanical properties. [Copyright &y& Elsevier]

Abstract: The linear melt viscoelasticity of poly(butylene succinate) (PBS) nanocomposites containing different types of fumed silica nanoparticles (unmodified and modified fumed silica) was studied. Depending on the primary particle size and surface chemistry of fillers, distinct modes of polymer/filler interactions could be identified in the nanocomposites. The PBS nanocomposites containing silica nanoparticles with larger surface area appear to have higher density of temporary physical network structures leading to significantly increased modulus. Increasing the polymer–particle compatibility through introduction of a hydrophobic functionality on the surface of the particles resulted in strong immobilization of the PBS molecules. The presence of such improved polymer/filler interactions was confirmed by the secondary relaxation mode and rubber-like behavior, indicative of stronger adhesion between the modified SiO2 and the PBS matrix. The entangled polymer dynamic theory was used to discuss the influence of polymer/filler interactions on the relaxation behavior of PBS molecules. The relaxation hierarchy can be identified from the linear viscoelastic responses of PBS/modified fumed silica nanocomposites. Dynamic mechanical measurements showed that glass transition range was widened and the peak temperature was also shifted to higher temperature in the composites with enhanced PBS/silicainteractions. [Copyright &y& Elsevier]

Abstract: This study investigated the effect of wood cell wall composition on the rheological properties of wood particle/high density polyethylene (HDPE) blends. Four types of wood particle with different compositions were prepared: native wood flour (WF), hemicellulose-removed particle (HR), holocellulose (HC), and α-cellulose (αC). The particles were characterized in terms of functional groups, crystallinity, particle size, and morphology. Wood particle/HDPE composite formulations were melt-blended using a twin-screw extruder and the rheological properties of the blends were characterized using a Haake microcompounder, torque rheometer, capillary rheometer, and rotational rheometer. Results show that removal of lignin and/or hemicelluloses changed the crystallinity and microstructure of cell walls. These changes in cell wall composition and morphology altered the melt torque, shear stress, viscosity, and storage and loss moduli. Specifically, the melts viscosity decreased as αC/HDPE>HR/HDPE>WF/HDPE>HC/HDPE. This demonstrates that the composition of cell walls substantially affect the rheological behavior of wood particle/HDPE composites. [Copyright &y& Elsevier]

Abstract: Cation–π effect on physisorption of aromatic ionic salts to multi-walled carbon nanotube (MWCNT) was demonstrated by the excess adsorption over their pre-ionized aromatic compounds through thermogravimetric analysis. Their adsorption layer on the surface of MWCNT was confirmed by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Ionic salt-adsorbing MWCNT showed better dispersion in acetone than pristine and pre-ionized compound-adsorbing MWCNT. Incorporation of 1wt% ionic salt-adsorbing MWCNT is able to gel the epoxy resin at room temperature according to the rheological study. Based on our proposed model, 1wt% fully-dispersed MWCNTs are enough to form an interconnected network in epoxy resin resulting in gelation. After crosslinking with amine curing agent, the epoxy nanocomposites incorporating 1wt% ionic salt-adsorbing MWCNT displayed substantially higher glass and ß transition temperatures than that incorporating pristine MWCNT. [Copyright &y& Elsevier]

Abstract: Low density polyethylene/distillers grains (LDPE/DG) composites have been prepared by melt extrusion. The distillers grains fillers were characterized in terms of surface morphology and particle size distribution. The composite characteristics were investigated by melt flow index (MFI), mechanical tests (tensile properties and Izod impact strength), dynamic rheological measurements and thermal stability (TG). SEM analysis showed that NaOH-treated DG feature a huge potential as reinforcing agents of LDPE due to their rough surface morphology. The introduction of 40wt% DG in the LDPE matrix increased the tensile modulus by a factor 3 compared to the pure LDPE, which is ascribed to the higher modulus of the DG compared with LDPE. Whereas tensile strength and elongation at break of the composites decreased with the increasing of DG content. Dynamic rheological analysis showed that the storage modulus increased for all composites compared to LDPE, indicating that the addition of DG fillers to LDPE might be beneficial in applications to improve stiffness. The TG results showed that the thermal stability of LDPE/DG composites decreased slightly by adding DG as the percentage of mass loss at DG’s decomposition peak temperature increased monotonically from 4.51% to 15.13% for 10 to 40wt% addition of DG; however, their flame retardancy leveled up. The results showed that distillers grains, as renewable raw materials, hold great potential as fillers in thermoplastic composites. [Copyright &y& Elsevier]

Abstract: The influence of composite electrical properties on the plane-wave electromagnetic shielding effectiveness (EM SE) of carbon nanoparticle/polyethylene nanocomposites is reported in the VHF and UHF bands (30MHz–1.5GHz). Two highly graphitic carbon nanoparticles (heat-treated Pyrograf® III PR-19 carbon nanofibers and CheapTubes® multi-walled carbon nanotubes) were dispersed in a linear low density polyethylene (LLDPE) matrix to produce a nominally random in-plane particle orientation. For a concentration of 10vol% nanoparticles and a sample thickness of 2.5mm, EM SE values of 24dB and 22dB were obtained for MWNT HT and PR-19 HT nanocomposites, respectively. At a high concentration of 40vol%, EM SE values as high as 68dB and 55dB were obtained for the PR-19 HT and MWNT HT nanocomposites, respectively. Because such nanocomposites possess only moderate electrical conductivity, the composite permittivity was also used to predict the plane wave EM SE and its components. Based on the material properties of the nanocomposites, the predicted values of EM SE were found to be consistent with the experimental values. [Copyright &y& Elsevier]

Abstract: This paper reports the compressive behavior of warp-knitted spacer fabrics (WKSF) impregnated with shear thickening fluid (STF) when subjected to quasi-static compression and low-velocity impact loadings. Silica/Polyethylene glycol suspension was prepared as the STF. From the rheological properties of the STF, it was observed that the STF experience shear thickening transition at a specific shear rate. The compressive behavior of the STF impregnated WKSF has a significant strain rate effect under compressions. The STF impregnated WKSF also shows higher energy absorption and a lower peak load than those of the WKSF under the same impact loadings. It was concluded that the STF-impregnated WKSF can be used as damping material for personal protection. [Copyright &y& Elsevier]

Abstract: Monodispersed titanium oxide nanospheres were synthesized via the controlled hydrolysis method in this study firstly. Then the rapid mixing method was used to in situ oxidation polymerize aniline, which can modify the surface of titanium oxide nanospheres to form a core/shell nanostructure. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and rotational viscometer were used to investigate its structure, morphology and properties. The different type and dosage of surfactants, different acids, crystal forms of titanium oxide and different dosages of aniline were studied to analysis the impact on the TiO2/PANI nanocomposites. The suitable type and dosage of surfactants, the ratio of aniline to titania were the key to synthesize the nanocomposite, which can include nanoring, nanofiber or nanoparticles core/shell composite depending the synthesis condition. The titania/polyaniline composite showed typical electrorheological (ER) behavior, which demonstrated its potential applications as an ER smart material. [Copyright &y& Elsevier]

Abstract: Rheological and electrical properties of polymer composites containing conductive fillers are influenced not only by the total content of the filler but also by the shape and dimensions of filler particles markedly. However, separate treatment of these two effects is often not feasible in composites prepared by melt mixing as the filler concentration affects the flow behaviour of the melt and, thus, has an effect on the final particles geometry. In this work, composites with polymethylmethacrylate matrix and short carbon fibres with defined lengths independent on the fibre concentration were prepared and their rheology and the electrical conductivity were investigated. A pronounced influence of the fibre length on the rheological and electrical properties of the composites was confirmed. Increasing the length of the fibres the rheological quantities were affected more significantly and simultaneously the percolation threshold was shifted to lower fibre volume fractions. [Copyright &y& Elsevier]

Abstract: The dispersibility of unfunctionalized multi-walled carbon nanotubes in a polymer matrix is studied focusing on the role of the morphology and structure of the primary aggregates. The particles, synthesized by fluidized bed catalytic chemical vapor deposition and purified through a scalable one-pot method, are dispersed in polystyrene by melt mixing. The filler percolation threshold, assessed through rheological analyses and dielectric spectroscopy, is one order of magnitude lower than that of commercially available nanotubes with similar features. This is ascribed to the hierarchical structure of the primary aggregates, which facilitates both the infiltration of the polymer in the earlier stages of mixing and the pulling out of the nanotubes required for their individualization. The high dispersibility is not achieved to the detriment of the nanotube integrity, and the nanocomposites exhibit enhanced thermal stability and dynamic mechanical properties at low amounts of filler. [Copyright &y& Elsevier]

Abstract: The encapsulation of laponite in poly(styrene-co-butyl acrylate) nanoparticles to obtain hybrid latexes with ultra-high clay contents is described. In-situ intercalative ad-miniemulsion polymerisation was used to prepare these hybrid latexes facilitating encapsulation up to 50wt% of laponite clay. The encapsulation of clay platelets resulted in latexes with crumpled particle morphology. Besides the polymerisation method, the encapsulation of clay was facilitated by careful choice modifier and use of non-dried modified clay. TEM and SAXS showed that the clay platelets were exfoliated and homogeneously distributed within the transparent polymer/clay nanocomposites films. The use of reactive clay modifier enhanced the clay exfoliation and polymer–clay interactions resulting in material showing significant storage modulus improved of up to 5000%. The high clay content incorporated was above the percolation threshold and the materials exhibited solid-like viscoelastic behaviour. [Copyright &y& Elsevier]

Abstract: This study demonstrates how the specific mechanical energy (SME) can be used to describe the influence of extrusion parameters such as screw rotation speed, feed rate and barrel temperature on clay dispersion in organoclay (OMMT) based polypropylene nanocomposites. These materials were prepared by a melt mixing masterbatch process via twin screw extrusion with a wide range of processing conditions. Maleated polypropylene (PP-g-MA) was used as a compatibilizer to allow clay exfoliation. Characterization of the morphological evolution along the extrusion profile revealed that microscale dispersion primarily happens in the melting zone, whereas continuous exfoliation is observed all along the kneading zones, up to the die exit. The results indicate that exfoliation in the kneading zones is mainly issued from clay tactoids and small aggregates with characteristic size inferior to 10μm, emphasizing the crucial role of primary microscale dispersion on the final structure and properties of the nanocomposites. Relevant quantitative prediction of the multiscale dispersion state along the extrusion profile was obtained using the melt state SME as unique parameter. [Copyright &y& Elsevier]

Abstract: Novel rheological features and conductivity results of irradiated PP/MWCNT nanocomposites are presented. Elongational flow measurements reveal a strain hardening behaviour which is compatible with the creation of long chain branched macromolecules provoked by irradiation. However, oscillatory shear flow results suggest that irradiation does not affect interactions of MWCNTs with PP chains. The addition of carbon nanotubes brings about conductivities of the order of 10−2 S/cm, but its scavenger effect reduces the number of radicals generated by irradiation, lessening the strain hardening effect. The employed mixing method provides a dispersion of MWCNTs in a PP matrix, which followed by an ad hoc irradiation, allows obtaining an electrical conductive polypropylene with a strain hardening behaviour. The obtained results open novel routes to conductive nanocomposites apt to be processed using methods discarded for linear PPs, such extrusion-blowing and others. [Copyright &y& Elsevier]

Abstract: The performance of epoxy resins used for carbon fibre reinforced plastics can be significantly improved by the incorporation of nanoparticles. It is well known that the effect of material altering depends on many factors as filler material, particle distribution, particle size and shape. This paper investigates the hypothesis that particle surface modifications lead to a further improvement of the mechanical properties. Results of nanocomposites filled with four different surface modified boehmite particles are presented. The material was tested with different filler contents and analysed for chemical bonding, viscosity, thermal properties and bending performance. Surprising results show a strong influence of the surface modification on the viscosity, but no significant changes in the other material characteristics. The change of filler content in contrast has an influence on all tested performances of the nanocomposites. The results show a contrary effect of network interruption due to sterical hindrance by the particles and reinforcement due to the stiff ceramic fillers. For different filler contents these two effects have a varying influence on the material characteristics. From these results a model for the mechanism of the particle reinforcement in thermosets is concluded, which helps to understand the effectiveness of nanoparticles as reinforcement of epoxy resins. [Copyright &y& Elsevier]

Abstract: A methodology was devised to evaluate the newly-developed carbon nanotube reinforced polymer composites by means of mechanical performance and manufacturing cost. Glass fibre reinforced-epoxy composite plates were produced having different parameters: (a) three manufacturing processes, (b) geometrical dimensions, (c) carbon nanotubes concentration in the epoxy resin and finally (d) modified resin infusion temperature. Tensile coupons were machined out of the manufactured plates and their quasi-static mechanical properties were evaluated. Three cost models were developed to assess plates and tensile coupons manufacturing cost for each different case. Optimal values were evaluated for major manufacturing parameters, driving force being the mechanical properties of interest (quality) as well as their low manufacturing cost. It is demonstrated that the added cost to manufacture such nano-reinforced composites is attributed to increase strength on the expense of ductility; the main benefit of the carbon nanotube-based polymer composites seems to be their ability to be monitored. Almost 20% added cost is paid to attain this new function of piezo-resistivity for the RTM process, while this amount further increases for the non-automated processes such as the Hand Lay-up. [Copyright &y& Elsevier]

Abstract: Polylactide-layered silicate nanocomposites with and without a chain extender were prepared by melt mixing using a twin-screw extruder. An organo-modified clay, Cloisite® 30B, and a chain extender Joncryl®-ADR 4368F were employed in this study. The effect of the chain extender and processing conditions on the properties of the PLA-clay nanocomposites were investigated for different strategies of mixing. The resulting nanocomposites were characterized by X-ray diffraction (XRD), while their morphology was observed by SEM and TEM. The incorporation of the chain extender could enhance the degree of clay dispersion provided that it is judiciously added to the nanocomposite. The corresponding results revealed that the Joncryl-based nanocomposites, where nanoclay platelets were well-dispersed, exhibited a significantly reduced permeability as compared to others. The mechanical properties of the neat PLA, the PLA and Joncryl-based nanocomposites were also examined. The increased molecular weight in Joncryl-based nanocomposites caused a significant increase in the modulus, drawability and toughness of the samples. [Copyright &y& Elsevier]

Abstract: A study of the requirements necessary to fabricate novel MWCNT buckypaper/benzoxazine nanocomposites, based on rheological results, is presented. Best conditions to infiltrate the resin, without any diluents, in the buckypaper are selected from viscosity data obtained under time–temperature cycles. Infiltration results are analyzed using SEM microphotographs. The nanocomposite is obtained after an adequate curing process of the benzoxazine impregnated buckypaper. The mechanical and electrical properties of the nanocomposite are investigated. The obtained electrical conductivity values are several orders of magnitude larger than the values reported for conventional CNT/polymer nanocomposites. [Copyright &y& Elsevier]

Abstract: Hierarchically reinforced structures are widespread in nature but less common among man-made materials. In this paper, we show that polyurethane-based thermoplastic polymers can be hierarchically reinforced with laponite nanoplatelets and alumina microplatelets to reach strength and elastic modulus that are, respectively, 7- and 29-fold higher than that of the pure polymer matrix (91.7MPa and 6.97GPa, respectively). We find that the selective reinforcement of the polyurethane hard domains with laponite nanoplatelets is key to keep the polymer matrix sufficiently ductile for the incorporation of high concentrations of alumina microplatelets. Effective reinforcement of the polymer with microplatelets of different surface chemistries was only possible after annealing the composite at 130°C to promote strong bonding at the oxide/polymer interface. Large-area composite films and bulk parts exhibiting good alignment of alumina microplatelets were obtained through conventional tape-casting. The concept of hierarchical reinforcement demonstrated here can be explored to obtain composite materials covering a wide range of mechanical properties using only a few reinforcing building blocks within the same polymer matrix. [Copyright &y& Elsevier]

Abstract: Carbon nanofiber (CNF)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared via melt-compounding, solvent casting and in situ polymerization. Mechanical properties, rheological behavior and electrical resistivity were investigated in specimens with varying CNF loadings. The three processing techniques were compared. Improved properties were obtained in the solvent processed and in situ polymerized composites. The rheological and electrical percolation of these nanocomposites appeared in the same concentration set (between 1 and 5wt%). No changes were found in melt-compounding, even by the addition of 10wt% of CNFs. Electrical resistivity of the samples prepared by solvent casting was measured before and after pressing in the hot plate press. It is remarkable that in the non-pressed samples the CNFs formed an efficient 3-D conductive network, yielding composites with percolation thresholds even six orders of magnitude lower than after pressing, where this 3-D network was destroyed. [Copyright &y& Elsevier]

Abstract: The effect of ball milling on the structural characteristics and further on the dispersion and percolation behaviour of multiwalled carbon nanotubes (MWCNTs) in melt mixed composites using a maleic anhydride modified isotactic polypropylene as matrix was investigated. TEM and SEM revealed that ball milled nanotubes were considerably shorter and showed a compact primary agglomerate morphology compared to the as-synthesised MWCNTs. At macro scale ball milled MWCNTs were found to be better dispersed, whereas at sub-micron scale the states of dispersion of both nanotube materials were comparable. The differences in the composite morphologies as well as in the composites electrical and rheological percolation behaviour were assigned to the altered MWCNT structure due to ball milling treatment. The dispersibility of ball milled MWCNTs was restricted due to their more compact agglomerate morphology. Furthermore, the ability to form percolated network structures was restrained by their shorter length and, again, their compact primary agglomerates. An effective agglomerate interaction radius depending on the nanotube structural characteristics, length and agglomerate morphology, is suggested in order to explain the experimental findings. [Copyright &y& Elsevier]

Abstract: This paper investigates the effect of both the mixing technique and heating rate during cure on the dispersion of montmorillonite (MMT) clay in an epoxy resin. The combination of sonication and using a 10°C/min heating rate during cure was found to facilitate the dispersion of nanoclay in epoxy resin. These processing conditions provided a synergistic effect, making it possible for polymer chains to penetrate in-between clay galleries and detach platelets from their agglomerates. As the degree of dispersion was enhanced, the flexural modulus and strength properties were found to decrease by 15% and 40%, respectively. This is thought to be due to individual platelets fracturing in the nanocomposite. Complementary techniques including X-ray diffraction (XRD), small angle X-ray scattering (SAXS), scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDX), transmission electron microscopy (TEM) and optical microscopy were essential to fully characterise localised and spatial regions of the clay morphologies. [Copyright &y& Elsevier]

Abstract: To obtain an economical and applicable electrorheological (ER) material, a novel nanocomposite composed of polar inorganic compounds, NH4Al(OH)2CO3, AlO(OH) and (NH4)2SO4, has been synthesized using low-toxic and economical and facile starting materials by a simple chemical reaction process. The experimental result shows that this material has better ER performance. The static yield stress (τ y) of the suspension (50wt%) of the material in silicone oil reached 22.8kPa at a DC electric field of 4kV/mm, and the relative yield stress (τ r) (the ratio of the yield stresses with to without an electric field) is also higher (12.7–33.3 for different concentration suspensions). The composition, grain size, dielectric and surface properties of the material have been studied by the elemental analyses, X-ray diffraction (XRD), infrared spectroscopy (IR), transmission electron microscopy (TEM), dielectric spectroscopy and determinations of the surface area and surface energy of the material. The influences of the grain size, dielectric and surface properties on ER performance of the material have been discussed. [Copyright &y& Elsevier]

Abstract: We report the study of the effects of carbon nanofibers (CNFs) on the cure kinetics and on the chemorheology of unsaturated polyester resins (UP). Two main experimental techniques were utilized: differential scanning calorimetry and rheometry. Isothermal and dynamic tests were performed on the neat polyester resin and on two nanocomposite systems, with 0.5 and 1.0wt.% of CNFs. Furthermore, a TGA study of the selected systems at different isothermal temperatures was performed to evaluate the styrene consumption and related loss rate during the curing process. Subsequently, a phenomenological model (autocatalytic approach) was applied to the experimental data, both in isothermal and dynamic conditions. In the case of dynamic curing, the evidence of multiple peaks in the heat flow curves was studied through the deconvolution of the overall reaction thermogram in single reaction steps. An empirical rheological model coupled with the reaction kinetics was successfully applied to simulate the viscosity changes of the UP matrix. Experimental and modelling results demonstrate the presence of a delay effect of the CNFs on the cure of the UP resin matrix. [Copyright &y& Elsevier]

Abstract: Nanocomposites based on poly(styrene-co-hexylacrylate) copolymer and cellulose whiskers as the nanosize filler were prepared by in situ miniemulsion polymerization and their melt rheological behaviours were investigated under dynamic shear conditions. The effects of γ-methacryloxypropyl triethoxysilane (MPS) content along with the whisker loading were explored. In the absence of whiskers, a transition from a liquid- to a solid-like behaviour was observed when the polymer was synthesized in the presence of MPS. When cellulose nanofiller was added, the storage modulus G′ and the dynamic viscosities η of the nanocomposites increased monotonically with whisker content and the resulting materials displayed a solid-like behaviour. Above 2wt.%. loading, a percolated interconnected whisker–whisker network is built up, producing a jump in the storage modulus and strong shear-thinning behaviour of the viscosity. However, as the nanocomposites were prepared in the presence of 3% of MPS, no enhancement nor in the storage modulus nor in the viscosity was observed up to 5wt.%. of whisker loading. Such a phenomenon was ascribed to inhibition of build-up of the whisker network. The non-linear viscoelastic behaviour of the nanocomposites was also investigated and analysed in terms of the breakdown of different networks, namely the filler–filler and the polymer–filler networks. [Copyright &y& Elsevier]

Abstract: The present study provides original experimental data concerning the evolution of the microstructure of a bundle of fibres during its deformation. For that purpose, a model saturated fibre bundle was processed and was subjected to a compression loading by using a specially designed micro-compression rheometer which was mounted on a synchrotron X-ray microtomograph. Thus, 3D images of the evolving fibrous microstructure could be obtained. Results first show that the compression induced both the bundle consolidation and liquid phase migration. Secondly, (i) the position, the orientation, the displacement and the deformation of each fibre together with (ii) the position and the evolution of each fibre-fibre contact were followed during the compression. The in situ tracking of these microstructure descriptors allows the consolidation micro-mechanisms to be analysed and provides useful information for theoretical or numerical models used to predict fibre bundle deformation during processing of fibre bundle reinforced polymer composites. [Copyright &y& Elsevier]

Abstract: Both glutaraldehyde (GA) and 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) can crosslink the cell wall polymers and dimensionally stabilize wood particles and the treated wood particles are thus expected to enhance the properties of the resulting wood particle/polypropylene composites. Compared to the composites filled with untreated particles, treatments of wood particles with both GA and DMDHEU showed a great reduction in water uptake and dimensional swelling of the resulting composites up to 39% and 46%, respectively. Both the flexural and tensile moduli increased due to wood particles treatments with GA and DMDHEU. Treatments of wood particles improved the tensile strength but moderately weakened the flexural strength and Charpy impact strength of the composites. Dynamic mechanical analysis and microscopy suggested an improved interfacial compatibility between wood particles and matrix due to GA and DMDHEU treatments. Chemical treatment resulted in smaller particle sizes and altered microscopic fracture appearance after composite production as compared to untreated particles. Morphological changes were attributed to embrittlement of wood particles, which may negatively influence the mechanical properties of the resulting composites. [ABSTRACT FROM AUTHOR]

Abstract: A polymer material system has been developed to propose an injectable, UV and in situ curable hydrogel with properties similar to the native nucleus pulposus of intervertebral disc. Neat hydrogels based on Tween® 20 trimethacrylates (T3) and N-vinyl-2-pyrrolidone (NVP) and composite hydrogels of same composition reinforced by nano-fibrillated cellulose were synthesized with different T3 concentrations and their curing kinetics was investigated by photorheology using UV light. The T3 concentration has an influence on the time of curing and final shear stiffness of the material. NFC does not alter the time of curing but increases the final mechanical performance of the hydrogels for a same chemical composition. Hydrogel samples, neat and composite, were then tested in unconfined compression at different hydration stages and in confined compression and their elastic modulus was determined. The amount of fluid present in the network is mostly responsible for the mechanical properties and NFC fibres proved to be an efficient reinforcement. The elastic modulus ranged from 0.02 to 8MPa. Biocompatibility studies showed that cells are confluent at 90% and do not show any morphology change when in contact with the hydrogel. The present hydrogel can therefore be considered for NP replacement. [ABSTRACT FROM AUTHOR]

Abstract: The rheological analysis of epoxy pre-polymer/MWCNT dispersions indicates that a physical network is formed. This is destroyed with an imposed shear, giving a viscoplastic and shear thinning behavior. Such destruction is not reflected in dynamic viscoelastic experiments, due to the very rapid recovery of the MWCNT network in the pre-polymer matrix. This responds to the observed lower electrical than rheological percolation threshold. Electrical conductivity results fulfill electron hopping/tunnelling mechanism, which implies a tube–tube distance close to 5nm. However, rheological percolation requires nanotubes should touch each other, since no polymer chains are implied in the network. [Copyright &y& Elsevier]

Abstract: Abaca fibre reinforced PP composites were prepared using a high speed mixer followed by injection moulding with 30wt.% of fibre load. Prior to composite production, the fibres were modified by fungamix and natural enzyme. The effects of modification of the fibre were assessed on the basis of morphology and thermal resistance and as well as on mechanical, thermal and environmental stress corrosion resistance properties of the resulting composites. Coupling agent (MA-PP) was also used with unmodified abaca fibre to observe the coupling agent effect on resulting composites properties. The moisture absorption of the composites was found to be reduced 20–45% due to modification. Tensile strength found to be 5–45% and flexural strengths found to be 10–35% increased due to modification. Modified fibre composites found to better resistance in acid and base medium. [Copyright &y& Elsevier]

Abstract: The inherent multifunctional properties of carbon nanotubes provide an opportunity to create novel composites, but their dispersion into a polymer matrix is challenging due to nanotube dimensions, interparticle forces, and poor interaction with the polymer. In this study, we used melt mixing to disperse multiwalled carbon nanotubes (MWNTs) in a polyimide resin under various process conditions to understand the efficacy of the process and the energy required to achieve dispersion and distribution. Through controlled variation of process conditions, we achieved various degrees of nanotube dispersion and distribution. The different dispersion and distribution states were observed by microscopy and correlated with the magnitude of the changes seen in the glass transition temperature and viscosity when compared to the neat resin. The results of these studies will be used to assess the compatibility of nanocomposite resins with composite fabrication methods and predict appropriate processing conditions for producing multiscale composites. [Copyright &y& Elsevier]

Abstract: We report on the preparation of nanocomposites consisting of laser synthesized single-walled carbon nanotubes (C-SWNTs) reinforcing a polyurethane. Prior to their incorporation into the polymer matrix, the C-SWNTs were purified, and characterized by means of various techniques. The purification in nitric acid added carboxylic groups to the C-SWNTs. A procedure to properly disperse the nanomaterials in the polymer was developed involving high shear mixing using a three-roll mill and a non-covalent functionalization of the nanotubes by zinc protoporphyrin IX molecule. The incorporation of the C-SWNTs into the resin led to an increase of the viscosity and the apparition of a slight shear-thinning behavior. A further increase of the shear-thinning behavior using fumed silica particles enabled the direct-write fabrication of microbeams. Mechanical characterization revealed significant increase in both strength (by ∼64%) and modulus (by more than 15 times). These mechanical enhancements are believed to be a consequence of the successful covalent and the non-covalent functionalizations of the nanotubes. [Copyright &y& Elsevier]

Abstract: We report the synthesis and characterization of nanocomposite thin films consisting of single-walled carbon nanotubes with different functionalization schemes dispersed in an epoxy matrix. The thermal, rheological, and mechanical properties of nanocomposite thin films were experimentally characterized to establish a relationship between processing and performance. The results from the rheological analysis confirmed that the nanotube type and functionalization strongly affect the resin viscosity during cure. A correlation between the rheological behaviour and the measured elastic properties was established. Nanotubes produced by plasma and functionalized with carboxyl group had the lowest influence on viscosity and led to the highest improvement in elastic properties. The measured increase in elastic modulus was consistent with predictions based on Mori–Tanaka micromechanics. [Copyright &y& Elsevier]

Abstract: In self-healing polymers and composites, the activity of the embedded chemical catalyst within the thermosetting matrix is critical to healing efficiency. Rheological behavior of ring-opening metathesis polymerization (ROMP)-based healing agents, triggered by 1st or 2nd generation Grubbs catalyst suspended in various thermosetting resins, was investigated using an oscillatory parallel plate rheometer. Gel times for various healing agents were determined from the crossover of storage and loss moduli vs. time curves to indicate the activity of the ROMP reaction. Gelation of healing agents initiated by 1st generation Grubbs catalyst occurred faster than those triggered by 2nd generation catalyst. It is suggested that the dissolution rate of the catalyst by the healing agent is an important factor in determining the overall ROMP reaction rate in situ. Optical and scanning electron microscopic observations showed that the finer, rod-like solid particles of the 1st generation catalyst were distributed more homogeneously throughout the cured matrix. The effects of different healing agents and thermosetting matrix systems on the ROMP reaction are discussed in detail. [Copyright &y& Elsevier]

Abstract: Polypropylene (PP)/multi-wall carbon nanotubes (MWNTs) nanocomposites were prepared by diluting a PP/MWNT masterbatch by melt compounding with a twin screw extruder and prepared nanocomposites were characterized for their rheological, mechanical and morphological properties in terms of MWNT loading. The rheological results showed that the materials experience a fluid–solid transition at the composition of 2wt.%, beyond which a continuous MWNT network forms throughout the matrix and in turn promotes the reinforcement. The tensile modulus and yield stress of the nanocomposites are substantially increased relative to the neat polypropylene. Nanotube reinforcement thus enhanced the yield stress, while reducing the ductility. The same behavior is observed in flexural tests. Charpy impact resistance of the notched samples increases slightly by the addition of MWNT, while impact resistance for the un-notched samples decreases with the addition of MWNTs. Finally, optimum in mechanical properties was observed at 2wt.% MWNTs, which is near the rheological percolation threshold. From transmission electron microscopic (TEM) and scanning electron microscopy (SEM) images, it was observed that nanotubes are distributed reasonably uniformly indicating a good dispersion of nanotubes in the PP matrix. These results reveal that, preparation of nanocomposites from masterbatch dilution is an excellent method to obtain well-dispersed CNTs, while limiting the handling difficulties in plastics processing industrial workshops. [Copyright &y& Elsevier]

Abstract: Since a carbon fiber reinforced plastic (CFRP) structure is complicated in the adoption of integral molding, local molding faults such as under curing and dry spots are liable to occur. To solve this problem, the distribution of the degree of curing for the entire composite structure must be measured. In the present study, we propose a patch-type flexible matrix sensor based on permittivity measurements. Multiple electrodes and wirings are readily fabricated simultaneously using a photolithographic process. Moreover, the sensor has only m + n wirings for m × n sensors, and is thereby suitable for multipoint cure monitoring. We also constructed a method for estimating the degree of curing considering the effect of frequency dependence of the permittivity of resin and viscosity variation due to temperature change. Experiments of multipoint cure monitoring are carried out using a CFRP plate and an actual aircraft structure. As a result, we confirmed the effectiveness of this method by comparing with results using a conventional differential scanning calorimeter. [Copyright &y& Elsevier]

Abstract: Multiwall carbon nanotubes (MWNT) were incorporated in melt-mixed co-continuous blends of polyamide 6 (PA6) and acrylonitrile–butadiene–styrene (ABS) using a conical twin-screw microcompounder. The state of dispersion of MWNT in the blends was assessed through AC electrical conductivity measurements and melt-rheological investigations. The electrical and rheological percolation threshold in PA6/ABS blends was ∼3–4 and ∼1–2wt% MWNT, respectively. A unique reactive modifier (sodium salt of 6-amino hexanoic acid, Na–AHA) was employed to facilitate ‘network-like’ structure of MWNT and to confine them in a specific phase. This was achieved by establishing specific interactions with the delocalized ‘π-electron’ clouds of MWNT and melt-interfacial reaction during melt-mixing. The electrical percolation threshold was significantly reduced in the blends (∼0.25wt%) in the presence of Na–AHA modified MWNT and even coincided with the rheological percolation threshold. Significant refinement in the co-continuous structure was also observed in the presence of Na–AHA modified MWNT. [Copyright &y& Elsevier]

Abstract: Electromagnetic interference shielding composite materials were developed from the conductive blends of nanostructured polyaniline (PANI) and polyaniline-clay nanocomposite (PANICN) with ethylene vinyl acetate (EVA) as host matrix. Electrically conducting nanostructured PANI and PANICNs were prepared using amphiphilic dopants, 3-pentadecyl phenol 4-sulphonic acid (3-PDPSA) derived from cashew nut shell liquid, a low cost renewable resource based product and dodecyl benzene sulfonic acid (DBSA). Effects of type and quantity of conductive fillers on the electrical conductivity, mechanical properties, thermal stability, morphology and electromagnetic shielding efficiency were investigated. The presence of exfoliated nanoclay and interaction between the conductive filler–host matrix in conductive films containing PANICNs manifested from the measurement on rheological property. Films with conductive filler (∼15% loading) showed a shielding effectiveness of ∼40–80dB at 8GHz which makes these conducting composites potential candidate for the encapsulation as EMI shielding materials for electronic devices. [Copyright &y& Elsevier]