Search

The effect of incorporating different percentages of hydrophobic and hydrophilic nanosilica (HPB and HPL NS) particles and chain extender (CE) on the mechanical behavior of poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) blends was evaluated. The mechanical behavior of the samples was explained using different theoretical models. Microscopic studies showed that adding both types of NS particles and CE led to more uneven surfaces for blends. Also, no obvious aggregations were observed in both blend nanocomposites, and both kinds of NS particles were mainly present in the PBAT phase. Except for the blend containing 1 phr HPB NS particles, which revealed a continuous morphology, all the PLA/PBAT blends containing both types of NS particles indicated a droplet‐matrix morphology. The more the NS content, the more uniform the PBAT distribution. Adding CE in the blends improved Young's modulus, yield strength, and elongation‐at‐break to a particular loading of CE (2 phr), while these properties were diminished after introducing more CE. Also, the most improvements in the yield strength (45%) and Young's modulus (35%) were seen for the PLA/PBAT (75/25 w/w) containing 2 phr CE and 5 phr HPL NS particles. Besides, a good agreement was observed for experimental values and theoretical models for all samples. [ABSTRACT FROM AUTHOR]

In this research, by using different rheometric methods, the temperatures of phase transition for upper critical solution temperature phase diagram of polyethylene (PE) and poly(ethylene‐co‐vinyl acetate) (EVA) blends and filled systems with organically‐modified nanoclay (ONC) were measured. Since the PE/EVA‐based mixtures are widely applied in the film and foam industries, the evaluation of the phase behavior of these mixtures is of great importance. Microscopic observations show that ONC nanoparticles have a compatibilization role on the biphasic microstructure of PE/EVA. ONC nanoparticles have a remarkable impact on the viscoelastic properties of the EVA phase, leading to a reduction in the asymmetry of the viscoelastic properties of the two polymeric phases. The findings of this work focused on the isochronal dynamic temperature sweep tests on the well‐mixed and phase‐separated nanofiller‐filled systems with different cooling/heating rates indicated that these series of experiments did not have the necessary efficiency to determine the phase separation boundary and spinodal temperatures in thermodynamically equilibrium conditions. By using Han plot and dynamic temperature sweep tests at the minimum possible heating rate, 0.25 K/min, it was proved that by adding nanoparticles to PE/EVA blends, the area of well‐mixed region of the phase diagram did not show a significant increment. The pinning effects of nanoparticles on the polymeric chains and correspondingly, the reduction of molecular dynamics mainly affect the phase separation phenomenon. [ABSTRACT FROM AUTHOR]

As a packaging materials candidate, based on a polylactic acid/ polybutylene adipate terephthalate (PLA/PBAT) blends (90/10 and 75/25 wt/wt) containing 1, 3, and 5 phr hydrophilic (HPL) and hydrophobic (HPB) nanosilica (NS) particles in the presence of a multifunctional epoxide compatibilizer were prepared by melt mixing, in a twin-screw extruder. Scanning electron microscopic studies confirmed a matrixdroplet morphology with finer dispersed domains at higher NS content. Energy dispersive spectroscopy mapping also indicated uniform dispersion of NS in blends, with some agglomerates at higher content of nanoparticles. Moreover, transmission electron microscope was applied to study the impact of nanofillers' localization on the systems' morphology. It was observed that NS particles localized at the PLA-PBAT interface. In addition, thermogravimetric analysis (TGA) was used to investigate thermal stability and thermal degradation kinetics. Data indicates that hydrophobic NS improved thermal stability. The activation energy of degradation was calculated using several techniques of data modeling, including Friedman, Flynn-Ozawa-Wall, and Kissinger-Akahira-Sunose models. Among blend nanocomposites, 75/25 blend containing 5 phr HPB NS had the maximum degradation activation energy, suggesting that this sample had the most resistance to heat degradation. The intensity of the TGA/FTIR peaks of the evolved products was found to be correlated with the activation energy. The Criado's technique was also used to investigate the changes in the thermal degradation mechanism. [ABSTRACT FROM AUTHOR]

To expand the range of applications and overcome mechanical limitations of Polypropylene (PP), a commonly used industrial polymer, toughness modification is required. In this study, PP was toughened with ethylene octene copolymer (EOC) and nanoclay platelets and the blends and nanocomposites of PP/EOC were prepared by means of a melt mixing process, and the effect of different grades of EOC, the addition of nanoclay platelets, and the effect of compatibilizer on properties of the final system were investigated. Scanning and transition electron microscopy, X-ray diffraction, rheology, differential scanning calorimetry, and dynamic-mechanical analysis were conducted to correlate the structure to the resulting properties. The results indicate that different grades of EOC with different molecular weights and viscosity can have a tremendous impact on droplet size and final properties of the blend sample. From a morphological point of view, the addition of EOC grade with higher viscosity (ƞi) in PP/EOC blends results in droplet matrix structure with larger EOC droplets. To decrease the droplet size, and hence improvement in final properties, nanoclay and compatibilizer were introduced to the blend. According to the results, selective localization of nanoclay and proper dispersion degree of nanoclay in the PP/EOC blend with higher viscosity grade of EOC containing nanoclay up to 3 wt.% lead to amelioration of the final properties of the system including complex viscosity, storage modulus, damping, and crystallinity. Moreover, the addition of the compatibilizer to the nanocomposite samples with 5 wt.% nanoclay can compensate for the deteriorated properties which occurred as a result of nanoclay aggregation in this system. This indicates that the addition of the nanoclay and compatibilizer plays an important role in toughening, morphology, and determining the final properties of the system as well. [ABSTRACT FROM AUTHOR]

Non‐isothermal crystallization of poly(ε‐caprolactone) (PCL) in semi‐crystalline/amorphous PCL/poly(styrene‐co‐acrylonitrile) (SAN) blends with lower‐critical solution temperature (LCST) phase behavior at temperatures higher than the beginning of PCL crystallization has been studied and quantitatively modeled using different kinetics models. Near‐ and off‐critical PCL/SAN blends were prepared by using two different PCL molecular weights. The kinetics model results verified that the samples containing PCL with higher molecular weight have lower crystallinity and faster crystallization behavior, while adding amorphous SAN chains to PCL retards the crystallization process. A lower crystallization activation energy was relatively required for higher molecular weight, PCL‐2, in off‐critical PCL/SAN blends. However, the easier crystallization with higher degree of crystallinity was attained in near‐critical P80S20 blend containing PCL with lower molecular weight, indicating a shift of the LCST phase diagram of the PCL/SAN blend to higher temperatures by increasing the PCL molecular weight. [ABSTRACT FROM AUTHOR]

One‐step extrusion foaming process of biodegradable poly(lactic acid) (PLA)‐based nanocomposites in the presence of chemical foaming agent and chain extender has great complexity to control. In this work, PLA‐based nanocomposites containing different carbonaceous nanoparticles with different geometric shapes were obtained through a co‐rotating twin‐screw extrusion process to get insight into the dominant phenomena, which control the structural and final properties of PLA foams. The reactive extrusion foaming of PLA melt was investigated in the presence of carbon black, carbon nanotubes (CNTs), graphene oxide (GO), and a chain extender additive as well as a chemical foaming agent. Nanoparticles affect the continuous extrusion foaming of PLA melt through several phenomena, including providing bubble heterogeneous nucleation sites, intensifying the chemical decomposition of the foaming agent, improving the PLA structural modification reaction, increasing PLA molecular weight and restricting the dissolved gas removal from the melt. By influencing the involved phenomena in process, the nanoparticles at low levels, especially CNT and GO, increased the void content and cell size of PLA foams. The incorporation of CNT and GO nanofillers at the 0.5 phr level increased the electrical conductivity of PLA foams sharply by 9 and 10 orders of magnitude, resulting in lightweight, biodegradable semi‐conductive foams. [ABSTRACT FROM AUTHOR]

Robust nanocomposite coatings based on polyvinylidene fluoride (PVDF) and molybdenum disulfide (MoS2) nanoplatelets were prepared by a spray coating method. To achieve various surface structures, the coatings were dried at room and oven temperatures (20 and 200°C). All the samples dried at room temperature exhibited a highly porous surface structure, attributed to the strong nonsolvent role of water vapor, which triggered the nonsolvent‐induced phase separation (VIPS). On the other hand, the oven‐dried coatings showed a dense structure with no pores, resulting from eliminating the VIPS process by enhancing the drying temperature. MoS2 nanoplatelets were localized at the surface layer and the adjacent beneath layers. The formation of α‐type PVDF crystals was intensified for the oven‐dried samples based on the surface morphology and X‐ray diffraction patterns. Roughness analysis demonstrated that MoS2 nanoplatelets interfere with the phase separation process leading to a lower porosity for the room‐dried coatings. The elimination of porosity by increasing the drying temperature caused the hydrophobicity of the coatings to be notably decreased. Polarization and electrochemical impedance spectroscopy results revealed that both polymeric and nanocomposite coatings improved the corrosion resistance of the aluminum substrates, and the oven‐dried pure PVDF coating exhibited the highest level of corrosion protection. [ABSTRACT FROM AUTHOR]

Polystyrene/polyolefin elastomer (PS/POE) (90/10 and 80/20 wt/wt) blends containing 1, 3, and 5 phr halloysite nanotubes (HNTs) in the presence and absence of a compatibilizer (polypropylene‐graft‐maleic anhydride) were prepared using the melt‐mixing technique. Scanning electron microscopic studies confirmed a matrix‐droplet morphology. Energy dispersive spectroscopy (EDS) mapping indicated that the blends containing 5 phr HNTs possessed aggregates, while no agglomeration was observed after incorporating 5 phr compatibilizer. Thermal stability and thermal degradation kinetics were investigated using thermogravimetry analysis (TGA). The results demonstrated that the PS/POE blend (90/10) containing 5 phr HNTs and compatibilizer (90/10/5/5) has the best thermal stability. Different methods such as Friedman, Flynn‐Ozawa‐Wall, and Kissinger‐Akahira‐Sunose were applied to calculate the degradation activation energy. The 90/10/5/5 nanocomposite exhibited the highest degradation activation energy, indicating that this sample is more difficult to degrade thermally than other samples. A correlation was obtained between the activation energy and the intensity of the TGA‐fourier‐transform infrared spectroscopy (TGA/FTIR) peaks of the evolved products. The Criado method was used to determine the changes in the thermal degradation mechanism of the samples. [ABSTRACT FROM AUTHOR]

Electroactive β phase content of poly(vinylidene fluoride‐hexafluoropropylene) (PHP) was enhanced by blending approach with polycarbonate (PC) combined with application of barium titanate–multi‐walled carbon nanotubes (BT–MWCNT) hybrid nanofillers to boost the dielectric performance of PHP. The samples were melt‐blended at 90/10 and 70/30 wt% (PHP/PC) in the presence of BT and/or MWCNT. Scanning electron microscopic (SEM) results indicated compatibilization of the structure by adding BT or MWCNT; however, the best refinement in morphology was obtained in (90/10)/1.5/1.5 (PHP/PC)/BT/MWCNT nanocomposite. Transmission electron microscopy (TEM) micrographs illustrated the selective localization of BT at PHP and MWCNT at PC while some of both nanofillers were found at the interphase. Fourier transform infrared spectroscopy and X‐ray diffraction analysis results depicted the increase in β/α ratio of the nanocomposites with a synergistic effect in (90/10)/1.5/1.5 nanocomposite, attributed to the combined utilization of BT and MWCNT and their selective localization in the PHP/PC immiscible blends. Differential scanning calorimetry analysis substantiated the nucleating effects of BT and MWCNT and consistency with SEM and TEM observations in nanofillers selective localization. The findings of this work suggest that simultaneous introduction of ceramic and conductive nanofillers with their selective localization in PHP/PC blends is efficacious in improving electroactive phase of composites at low filler content. [ABSTRACT FROM AUTHOR]

The current research focuses on suggesting a new potential application of polymeric materials for capacitor applications by focusing on polystyrene (PS)/ethylene‐α‐octene copolymer (EOC) blends. Polymeric materials have high dielectric strength (≈ 200 for PS), good processability, and flexibility. However, their low dielectric constants make them not suitable for capacitor applications. Therefore, suggesting a method for enhancing their dielectric constant accompanied by low tan δ proposes an excellent substitute for commonly used ceramic dielectrics. The current article investigates the control of the dielectric properties of PS/EOC blends by manipulating the graphene nanoplatelets (GNPs) surface polarity. Results confirm that the localization site of the GNPs is mainly controlled by their surface polarities; this matter leads to the change of the morphology from sea/island for the pure blend to co‐continuous for the blend containing the most polar GNPs resulting in the best dielectric properties. This manipulation of the morphology by low concentration of GNPs (1.5 wt%) and therefore, dielectric properties result in high dielectric constant ≈ 55.8 at 10 MHz and low tan δ = 0.007, accompanied by high flexibility, which is the main drawback of ceramic capacitors, makes it a fantastic option for capacitor applications. [ABSTRACT FROM AUTHOR]

In this study, the correlations between the mechanical performance and structural properties of injected‐molded polyethylene (PE)/ethylene‐vinyl acetate copolymer (EVA)/nanoclay (NC) nanocomposites are investigated by revisiting the interfacial phenomena and miscibility state of the component pairs. The effects of different parameters including the injection molding temperature, mixing sequence in melt‐compounding process, blend composition, and nanoclay loading are studied. A great complexity arises in the filling and cooling process of the injected‐molded parts owing to the phase behavior of the polyolefin blend, crystallization, and morphological changes. The injection molding temperature positively influences the elastic modulus, tensile strength and impact strength of PE/EVA/NC systems through the improvements in the PE/EVA partial miscibility, mutual solubility, and interfacial interactions of PE/clay and PE/EVA pairs. By applying a two‐step mixing process before the injection molding, more nanoclay stacks with smaller thicknesses and larger clay interlayer spacing are formed. The stronger pinning effect of nanoparticles in the second mixing sequence retards the phase separation phenomenon of PE/EVA blend during the cooling stage. As a result of improved mutual PE/EVA solubility, the elastic modulus and tensile strength decrease and the impact resistance increases in the PE‐rich systems. On the other hand, an opposite trend for these properties is found for the EVA‐rich systems. [ABSTRACT FROM AUTHOR]

This works systematically investigates the interfacial properties of the binary and the ternary blends based on polystyrene (PS), ethylene octene copolymer (EOC), and styrene–ethylene–butylene–styrene (SEBS) by analyzing the melt linear rheological behavior of the blends and neat components. Moreover, the relationship between rheology, phase morphology, and mechanical properties of PS/EOC ternary blends with various quantities of SEBS were studied. The surface shear modulus (β) and interfacial tension values obtained by Palierne model indicated that the EOC/SEBS blend has the best interfacial properties, while the lowest interaction was found for PS/EOC blend. Based on the Palierne model and Harkin's spreading coefficients a core–shell type morphology with EOC phase encapsulated by the SEBS shell dispersed in the PS matrix was determined for the ternary blends. Scanning electron microscopy results revealed that both fibrillar and droplet forms of dispersed phase could be developed during the blending of PS and EOC in presence of SEBS. The extent of fibrillar morphology and interfacial interactions in PS/EOC/SEBS ternary blends was dependent on the SEBS content. The improvement of the mechanical properties of PS/EOC blends in the presence of SEBS was evidenced by the tensile and impact resistance experiments. The tensile strength reinforcement was more pronounced for the ternary blends with more fibrillar dispersed phase. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48791. [ABSTRACT FROM AUTHOR]

Polystyrene (PS)/ethylene–octene copolymer (EOC) blends with 80/20 wt % composition containing different amounts (0, 1.0, 2.5, 5.0 and 7.5 wt %) of an organically modified nanoclay were prepared by one‐step melt‐mixing method. Also, the EOC‐rich blends with 80 wt % EOC content loaded with 0 and 5.0 wt % of the nanoclay were prepared under the similar processing conditions. Presence of both PS and EOC chains in between clay layers localized at the interface of the blends could be deduced by X‐ray diffraction analysis, which suggested formation possibility of PS‐EOC physical structures at the blend interface. Transmission electron microscopy results confirmed that clay nanoparticles were mainly localized at the interface of the blends and also partly in the PS and EOC components of the systems. The localization of the nanoclay was also described by the linear viscoelastic melt rheological studies. It is also revealed that nanoclay had stronger interactions with PS than EOC. This is reflected in the higher tensile properties in the PS‐rich system. The analysis of morphology of the developed systems by emulsification curve revealed that the optimum amount of nanoclay to modify PS‐rich blend is 2.5 wt %. At this clay loading, the blend exhibited the highest impact resistance. According to the overall results, suitability of nanoclay was confirmed for compatibilization of the PS/EOC blends. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48748. [ABSTRACT FROM AUTHOR]

In this study, under the same conditions, two different nanoparticles, namely, titanium dioxide (TiO2) and polyhedral oligomeric silsesquioxane (POSS) were added to the poly(lactic acid) (PLA) matrix via the solution casting technique. Morphological analysis showed that POSS had a better distribution within the PLA matrix. However, rheological analysis revealed the stronger influence of TiO2 on shear viscosity values, and a more notable viscosity upturn at moderate to high inclusions of TiO2 within the low shear rate zone. On the other hand, POSS was found to act as a lubricant even at a content of 3 wt% which was attributed to the very small dimensions of POSS. Such lubricating role, found from rheology, caused a boost in the crystallinity of PLA based on differential scanning calorimetry results. Moreover, it was found that TiO2 had an adverse effect on the crystallinity of PLA which was ascribed to the hindered motions of PLA chains upon addition of moderate to high inclusions of TiO2. The results of this study emphasize the crucial role of nanoparticle type and content on the properties of PLA. [ABSTRACT FROM AUTHOR]

Effects of trifluoropropyl-substituted polyhedral oligomeric Silsesquioxane (POSS), on the morphological, rheological and dynamic mechanical properties of a series of poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends were explored, thoroughly. Microscopic techniques including scanning electron microscope (SEM) and transmission electron microscope (TEM) utilized in conjunction with viscosity measurements to explain morphological dissimilarities between different samples. A remarkable morphological refinement was observed upon addition of POSS into the 50/50 PLA/TPU blend. This morphological change was detected by means of frequency sweep rheological experiments, where the shoulder-like plateau appears as a result of increase in the contribution from the interfacial component of elasticity in the enhancement of storage modulus. Based on the results of the dynamic time sweep small amplitude oscillatory shear (SAOS) experiments, a scaling relation was proposed to quantify the kinetics of phase separation and the associate time evolution of elasticity. It turned out that POSS particles can slow down the rate of morphological coarsening up to the 50%. Using dynamic mechanical thermal analysis (DMTA) and rheological experiments, the differences in the rate of undergoing dynamics in all the length scales, starting from segmental up to the chain level, were compared for various compositions and the discrepancies were fully described based on the dissimilarities in the entanglement densities, combinatorial effects of soft and hard segments of TPU, lubricating role of POSS particles, crystallinity, and morphological characteristics of samples. GRAPHICAL ABSTRACT [ABSTRACT FROM AUTHOR]

The main aim was to study the roles of structural homogeneity and superhydrophobicity on the adhesion of SW colon cancer cells on the surface of polyvinyl chloride (PVC) nanocomposites. Concurrent use of a proper nonsolvent (ethanol) and silica nanoparticles resulted in superhydrophobic behavior and also different surface structures. The effect of added‐ethanol content on the surface properties of PVC nanocomposites was also studied. The synergetic combination of silica and ethanol has led to the formation of a porous surface layer resulting in a considerable boost in the hydrophobic behavior. The scanning electron microscopy, roughness, and X‐ray photoelectron spectroscopy (XPS) analysis results were all in total agreement indicating the substantial change in surface morphology, topography, and composition once the ethanol content was increased to 50 vol.%. The surface structure was notably changed by the addition of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles. It was found that the induced inhomogeneity as a result of POSS addition had an adverse effect on the surface properties. In conclusion, superhydrophobicity could be regarded as a prerequisite for achieving cell‐repellent behavior, but it cannot guarantee a cell repellent surface especially if the surface layer possesses structural inhomogeneity. [ABSTRACT FROM AUTHOR]

ABSTRACT: Prediction of viscoelastic behavior of polymers over a long‐term period is of vital importance for engineering applications. An attempt was made to uncover the interplay between the morphology and viscoelastic behavior of compatibilized polypropylene/ethylene vinyl acetate (EVA) copolymer blends in the presence of layered double hydroxide (LDH) nanoplatelets. The time–temperature superposition (TTS) principle and WLF equations were merged to obtain master curves of storage modulus at defined reference temperatures enabling prediction of storage modulus at high frequency ranges which are not experimentally measureable. Moreover, the creep compliance master curves were acquired for different reference temperatures to predict the creep compliance of nanocomposites over long period of times. It was found that the presence of LDH decreases the creep compliance at long period of times while it decreases the unrecoverable deformation of EVA domains. A simple mechanism was proposed to explain the creep and recovery behavior of samples blend at different temperatures. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46725. [ABSTRACT FROM AUTHOR]

ABSTRACT: Poly(ethylene oxide) (PEO)/poly(vinyl pyrrolidone) (PVP) blends containing different amounts of PVP (0, 10, 25, 50, and 100 wt %) prepared by a solution casting method were characterized in terms of microstructure, thermal, and mechanical properties along with their drug release behavior. Fourier‐transform infrared spectroscopy results confirmed formation of hydrogen bonds between PEO and PVP. Although scanning electron microscopy micrographs showed no phase separation in the blends, the elemental analysis data obtained by energy dispersive X‐ray technique revealed partial miscibility between the blend components. The miscibility of the blend and degree of crystallinity of PEO component of the blend were decreased with increasing PVP content of the blend. The nucleating role of PVP in crystallization of PEO was confirmed by differential scanning calorimetry analysis. A synergistic effect on mechanical properties was obtained as a result of blending PVP with PEO. The results of curcumin release studies from the films indicated that, the blends have lower diffusion coefficients and slower drug release rate as compared to the neat PEO. Theoretical analysis of the drug release data using Peppas's model revealed that the kinetic of drug release from all the films is governed by a non‐Fickian diffusion mechanism. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46403. [ABSTRACT FROM AUTHOR]

ABSTRACT: A series of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) loaded with various contents of layered double hydroxides (LDHs) nanoparticles were prepared via a melt mixing method. Detailed investigations on LDH dispersion state in the polymeric matrix conducted by TEM revealed intercalated/exfoliated, and agglomerated structures at low (1 wt %) and high (>3 wt %) loadings of LDH contents, respectively. Wide angle X‐ray scattering and DSC results showed that incorporation of LDH into PVDF‐HFP matrix reduced its overall crystallinity and helped to form polar crystallites, while the crystal size at 020 crystallographic directions was found to be most affected by presence and dispersion state of LDH in the matrix. TGA results showed LDH improved thermal stability of matrix however, unlike many other nanomaterials it significantly reduced the residual mass which highlights catalytic role of LDH in degradation of residual carbon char. Detailed analysis on creep and recovery data over wide range of selected temperatures revealed that the creep compliance of nanocomposites are basically controlled by crystallinity and presence of LDH at low and high temperatures, respectively. Based on obtained storage modulus and creep compliance master curves it was also found that the influence of LDH on decreasing the creep compliance and improving viscoelastic properties of PVDF‐HFP over long time period and over high frequency ranges becomes more pronounced. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46352. [ABSTRACT FROM AUTHOR]

In this study, morphological and rheological characteristics of bimodal polypropylene reactor blends synthesized by binary catalysts based on I: rac-Me2Si(2-Me-4-PhInd)2ZrCl2and II: (2-PhInd)2ZrCl2at different molar ratios were investigated. Gel permeation chromatography, scanning electron microscopy, and rheometry analysis were performed to evaluate the effect of molar ratio of catalyst II, responsible for the formation of elastomeric stereoblock polypropylene with low molecular weight, to catalyst I, responsible for production of high molecular weight isotactic (i) polypropylene, on the molecular weight, molecular weight distribution, morphological characteristics and rheological behavior of the synthesized products. The gel permeation chromatography results indicated that once a hybrid of the two catalysts is used, a broad and bimodal molecular weight distribution would be obtained, and the molar ratio of the catalysts governs the values of molecular weight and molecular weight distribution.13C NMR results suggest that the different polypropylene tacticity resulting from the two catalysts (stereoblock vs. isotactic) is hardly influenced using a binary system. The effect of molecular weight enhancement and molecular weight distribution broadening was confirmed through the linear rheological data (G′ at lower frequencies, crossover modulus and crossover frequency) due to the impeded molecular motions of chains with high molecular weights which play an important role in the elasticity of chains. The zero shear rate viscosity and relaxation time, determined by fitting the Carreau–Yasuda model, are in great conformity with the experimental data at low-frequency region. Likewise, the miscibility and increased level of heterogeneity of microstructure, which is a result of changing the molar ratios of catalysts II/I, are confirmed through the Cole–Cole and Han plots and were further corroborated through the obtained scanning electron microscopy results. [ABSTRACT FROM AUTHOR]

ABSTRACT In this study, the melt linear viscoelastic rheological properties of polyamide 6 (PA6)-acrylonitrile butadiene styrene terpolymer (ABS) immiscible blends were analyzed with the help of Coran and fractional Zener models (FZMs) to assess the microstructure of the blends. For this purpose, dynamic shear flow experiments and scanning electron microscopy investigations were performed. The nonzero value of the elastic modulus of the spring element ( G e) of the FZM for ABS-rich blends was explained by the formation of a networklike structure because of the agglomeration of the rubber phases of the ABS matrix, whereas for the PA6-rich blends with a high content of ABS, the interactions and/or interconnectivity of the ABS dispersed phase led to a nonzero value of Ge. The value of the fitting parameter of the Coran model ( f) was near to 0.5 for the 50/50 blend; this was fully in agreement with the formed cocontinuous morphology for this blend composition. On the other hand, the f value for the blends with a matrix-droplet-type morphology was near to zero for the PA6-rich blends; this indicated the lower continuity of the ABS dispersed phase as a harder phase compared to the PA6 soft matrix, whereas the f value was near to 1 for ABS-rich blends. This confirmed the formation of an interconnected networklike structure for this series of blends. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45423. [ABSTRACT FROM AUTHOR]

A novel binary homogeneous catalyst system based on (I): rac-Me2Si(2-Me-4-PhIn)2ZrCl2 and (II): (2-PhIn)2ZrCl2 catalysts at various molar ratios was utilized for the synthesis of polypropylene (PP) reactor blends with bimodal molecular weight distribution (MWD). The results of gel permeation chromatography analyses revealed that the catalyst (I) was responsible for the production of i-PP with high molecular weight (MW) while the individual use of catalyst (II) led to the production of an elastomeric PP with relatively low MW. However, application of the binary catalyst system led to high MW bimodal MWD products being highly dependent on the catalysts' molar ratios. Increasing the molar ratio of catalyst (II) to catalyst (I) resulted in a notable enhancement of the products' complex viscosity due to the increased MW, a higher level of chains' entanglements and formation of amorphous blocks along the polymer chains. All products exhibited a single relaxation that shifted towards longer times upon changing the catalysts' molar ratios. Scanning electron microscopy results revealed that the fracture surface of the blends, synthesized by the binary catalyst system, became more heterogeneous in comparison with the products obtained by the individual use of the catalyst (I). The observed heterogeneity was found to increase by increasing the amount of catalyst (II). Such morphological change was further corroborated by the dynamic rheological data, indicating a promising correlation between the linear rheological results and the morphological features of the synthesized PP reactor blends. [ABSTRACT FROM AUTHOR]

Reactive compatibilization of HDPE based ternary blends with intrinsic tendency to form core-shell microstructure was discussed in view of microstructure-property correlations. A series of binary and ternary blends containing HDPE, PA-6, EVOH, and maleated HDPE were prepared by melt processing and. The rheological, thermal, and mechanical characteristics of the resulting blends were then assessed in terms of transitions in the phase morphologies. The state of stress transfer and the degree of interfacial adhesion were also quantified by tracking changes in the particle size, particle size distribution, and crystallization behavior of the systems having different amounts of compatibilizer. [ABSTRACT FROM AUTHOR]

ABSTRACT Monodisperse poly(2-hydroxyethyl methacrylate), p-HEMA, microspheres in size ranging from 16 to 340 (μm) were synthesized by in situ emulsion photopolymerization of HEMA monomer with polyethylene glycol diacrylate (p-EGDA) by means of a three-dimensional microfluidic flow-focusing device. An aqueous solution of HEMA, p-EGDA as chain extender and UV-photoinitiator serving as dispersed phase formed microdroplets in a continuous oil phase mainly consisting of n-heptane. A downward coaxial orifices design in the device led to confinement of the reaction admixtures thread to central axis of the microchannels. This design strategy could solve the wetting problem of dispersed phase with the microchannels leading to a successful production of monodisperse microspheres with size variation of less than 4%. The effects of concentration of p-EGDA, surfactant, and flow rate ratios on microsphere size were examined. It was observed that increasing the concentration of p-EGDA slightly increases the size whereas increasing the flow rate ratios of continuous to dispersed phase effectively decreases the size of microspheres. The rapid continuous synthesis of p-HEMA based microspheres via the microfluidic route with reliable control over size, size distribution, and composition opens new doors for mass production of biocompatible and degradable polymeric microspheres for enormous biotechnological applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40925. [ABSTRACT FROM AUTHOR]

This article seeks to address morphological evolutions in polyolefinic ternary blends. To catch this target, different binary and ternary blends comprising HDPE, PP, and PA-6 constituents were prepared varying the type of polyolefinic matrix and composition in minority phase. Afterward, development of microstructure was monitored based upon theoretical and experimental analyses. In case of HDPE-based ternary blends, experimental microstructure observations agreed well with predictions, whereas SEM images provided from PP-based systems did not give strong evidence for encapsulation of PA-6 by HDPE minor domains. Analysis of stress-transfer across the matrix/shell/core provided a profound sense of morphological changes in these systems. [ABSTRACT FROM AUTHOR]

A systematic study was done on morphological, electrical and rheological behavior of co-continuous or dispersed-type polycarbonate (PC)/acrylonitrile-styrene-butadiene (ABS) blends, containing different amounts of multiwalled carbon nanotubes (MWNT). The MWNTs gave substantial electrical conductivities to these nanocomposites at very low concentrations, owing to the effective melt processing method. Because of selective localization of MWNTs in the PC phase, along with double percolation phenomenon, the blend with co-continuous morphology showed a lower electrical and rheological percolation threshold, higher melt viscosity and elasticity, as compared to the system with dispersed morphology. The morphology of both the blend systems was refined as a result of MWNTs incorporation but the morphology type remained unchanged. A typical role of compatibilizer in refining blend morphology was observed in both the systems. The electrical conductivity of the system filled with MWNTs in presence of compatibilizer, was lower than the systems filled with MWNTs only, which was attributed to role of compatibilizer in directing a part of MWNTs from PC matrix toward ABS phase. With increasing compatibilizer/MWNTs ratio, the influence of compatibilizer on morphology refinement and conductivity reduction was intensified. By comparing TEM micrograph of PC/SAN/MWNTs with that of PC/ABS/MWNTs, it was revealed that small portion of MWNTs was also located on polybutadiene rubber fraction of ABS. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 739-748, 2013 [ABSTRACT FROM AUTHOR]

Polylactide (PLA)/linear low-density polyethylene (LLDPE), (PLA/LLDPE), blends and nanocomposites were prepared by melt mixing process with a view to fine tune the properties. Two different commercial-grade nanoclays, Cloisite® 30B (30B) and Cloisite® 15A (15A) were used. A terpolymer of ethylene, butylacrylate (BA) and glycidylmethacrylate (GMA) was used as a reactive compatibilizer. The influence of type of clay on the morphology and mechanical properties of two PLA-rich and LLDPE-rich blend systems was studied. Morphological analysis using X-ray diffraction, transmission electron microscopy, and scanning electron microscopy revealed that the organoclay layers were dispersed largely at the interface of PLA/LLDPE. Decreasing the PLA content changed the morphology from droplet-in matrix to coarse co-continuous. In comparison with 30B, due to less affinity of 15A towards compatibilizer and PLA phase, the reduction of the size of dispersed phase was less than that of the equivalent 30B composites. The mechanical results demonstrated that the composites containing both types of organoclay exhibited higher modulus but lower elongation and tensile strength as compared to the neat blends. The injection molded nanocomposites were shown to have the sequential fracture behavior during tensile test. The tensile testing results on the neat blends and nanocomposites showed significant increase in elongation at break and decrease in the modulus as compared with the neat PLA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 749-758, 2013 [ABSTRACT FROM AUTHOR]

Compatibilized and noncompatibilized nanocomposites based on polypropylene (PP)/ethylene-vinyl acetate copolymer (EVA) blends, having 75/25 (wt %/wt %) PP/EVA ratio, with different contents of organoclay (OMMT) and maleated polypropylene as compatibilizer were made through a melt-mixing process with a twin-screw microcompounder, and their properties were investigated. X-ray analysis revealed mainly intercalated/partially exfoliated structures for the blend-based nanocomposites. Through a thermodynamic theoretical approach and transmission electron microscopy investigation, it was shown that the OMMT nanoparticles were mainly placed at the EVA phase of the nanocomposites. Also, scanning electron microscopy analysis showed that OMMT acted like a compatibilizer and reduced the average size of the EVA dispersed phase by preventing coalescence. Dynamic mechanical analysis revealed that the addition of OMMT in the presence of the compatibilizer increased both the storage modulus and damping factor of the corresponding blends. The critical interparticle distance of the EVA domains for achieving supertoughening behavior was obtained at about 100 nm. The addition of OMMT led to a significant improvement in the thermal stability of the blends, especially in the presence of the compatibilizer. A correlation between the morphological, dynamic mechanical, and thermal properties was established to determine the best performing composition, in which desirable damping and stiffness and good thermal stability could be achieved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Highlights: [•] Different mixing methods were used to prepare epoxy/nano-glassflake (NGF) composite. [•] The combination of mechanical mixing and sonication process is an effective way. [•] The rheological results showed that adding NGF up to 1% can form microstructure. [•] The barrier properties of the epoxy/NGF coating systems were improved up to 0.5% NGF. [Copyright &y& Elsevier]

Abstract: This paper reports on the influence of morphology on gas permeability and selectivity of membranes made from polypropylene (PP)/ethylene vinyl acetate copolymer (EVA)/clay (OMMT) nanocomposites. The morphology was adjusted by variation in the EVA (25, 50wt%), OMMT (0 and 5wt%) and compatibilizer (PP-g-MAH) (0 and 5wt%) contents. Gas permeation properties of membranes with different morphologies, were studied for pure CO2, O2 and N2 gases. X-ray diffraction (XRD) patterns showed no changes in crystalline structure of samples. TEM analysis confirmed high tendency of OMMT flacks for locating in the EVA phase. SEM results revealed that an increase in OMMT loading decreases the EVA droplet size (D n ) in samples with droplet type morphology and increases continuity index of EVA (CCI) in the samples with co-continuous morphology. Changes in compatibilizer/OMMT ratio imposed a dual effect on the morphology of the system with respect to D n and CCI. A good correlation could be established between these morphological parameters with gas solubility parameters, gas permeability and CO2/N2 as well as CO2/O2 gas selectivity. Annealing was shown to change the morphology which in turn had a very strong influence on the membranes gas permeability behavior. [Copyright &y& Elsevier]

Abstract: In this study, morphological properties of polypropylene (PP)/ethylene vinyl acetate copolymer (EVA) (75/25 wt/wt) blend-based nanocomposites containing various amounts of organically modified montmorillonite (OMMT) were primarily investigated. The incorporation of compatibilizer into nanocomposites decreased EVA droplet size in PP matrix while increasing compatibilizer/OMMT ratio showed a dual behavior with respect to the variations of OMMT interlayer spacing. By a rough estimation it was found that at EVA droplet size of Dn  = 0.43 μm, the highest OMMT interlayer spacing would be acheived. Increasing Dn had a negative effect on the OMMT interlayer spacing. Activation energy of thermal/thermo-oxidative degradation based on Flynn model was obtained. Isothermal degradation test was also performed and desired temperature range for predicting degradation behavior was obtained by means of a free prediction model. An attempt was made to establish a correlation between morphological and thermal/thermo-oxidative parameters and also charred residue morphology. A mechanism for degradation process was proposed according to the changes of chemical bonds during the degradation process probed by FTIR analysis. [Copyright &y& Elsevier]

Herein, polyaniline (PANI) with tuning morphology was in-situ synthesized within bacterial cellulose (BC)/silver nanoparticles hydrogels (AgNPs) that were prepared by green hydrothermal reduction method in different molarity of 0.01 and 0.25 of HCl solution along with the presence of polyethylene glycol (PEG). The synthesis of PANI in the presence of PEG in 0.01 M HCl led to the formation of rose-like morphology within nanocomposite aerogels with a size of 1.5–5.2 μm. All aerogels had the porosity and shrinkage of higher than 80% and lower than 10%, respectively. Rheology results showed a higher value of storage modulus (G′) than that of loss modulus (G″) for all samples over the whole frequency regime. It confirmed by the loss factor (tan δ) value of less than 1 for all hydrogel samples. The synthesis of PANI within BC/Ag in 0.25 M of HCl solution resulted in a substantial rise of G′ to nearly 1.5 × 104 Pa that was one order of magnitude higher than that of other hydrogels. However, the synthesis condition of PANI did not influence the antibacterial activity. In spite of unfavorable cell attachment onto nanocomposite aerogels, the cell proliferation increased steadily over the whole period of incubation. Unlabelled Image • PEG and pH had significant impact on the synthesis of PANI with distinct morphology. • The coexistence of PANI and AgNPs within BC increased the storage modulus. • The addition of silver nanoparticle (AgNPs) into BC improved antibacterial activity. • Different morphology of PANI had no influence on the antibacterial activity. • Cell proliferation in ternary nanocomposite aerogels of BC/PANI/Ag rose dramatically. [ABSTRACT FROM AUTHOR]

In this study, polystyrene (PS) based nanocomposite surfaces with extreme wettabilities were prepared by solution casting technique using an improved phase separation process. The individual incorporation of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles made the PS-based films superhydrophilic. However, once a hybrid of POSS and titanium dioxide (TiO 2 ) nanoparticles was employed, according to scanning electron microscopy results, POSS fernlike structure acted as a support for deposition of TiO 2 layer leading to the creation of a unique hierarchical morphology which caused a transition from superhydrophilic to superhydrophobic. X-ray photoelectron spectroscopy results proved that all the three components including POSS, TiO 2 and PS are present at the surface layer of the hybrid-based nanocomposite. The idea of using a hybrid of nanoparticles was further corroborated by the improved mechanical resistance of superhydrophobicity. In conclusion, incorporation of a hybrid of nanoparticles alongside a proper non-solvent might lead to unique morphologies which could result in superhydrophobicity. [ABSTRACT FROM AUTHOR]

In this work, the effects of amorphous poly(styrene- co -acrylonitrile) (SAN) chains and hydrophilic and hydrophobic nanosilica at different loadings on the non-isothermal crystallization kinetics of PCL phase have been evaluated using different theoretical models including Avrami, modified Avrami, Ozawa and Mo equations. Using microscopic observations, the interrelations among the changes in the kinetics parameters and the morphology and phase behavior of PCL/SAN and PCL/SAN/nanosilica mixtures have been thoroughly investigated. Microscopic observations on the nanocomposites showed differences in the nanofiller dispersion and distribution state as well as preferential migration and localization state. These differences lead to contradictory trends in the effects of hydrophilic and hydrophobic nanosilica on the crystallization kinetics of pure PCL and PCL/SAN blends. The nanoparticle migration during non-isothermal DSC tests in PCL/SAN blends, the formation of nanoparticle agglomerates at higher loadings, the restrictions imposed on the molecular movements in the crystallization growth stage and slower phase separation and dissolution of PCL/SAN/silica mixtures result in the cooling rate dependence of the kinetics parameters. • The non-isothermal crystallization kinetics of PCL/SAN/nanosilica mixtures was studied. • LCST over UCST phase diagram of PCL/SAN blends added further complexities to the study. • The interrelationship among kinetics, phase miscibility and morphology was investigated. • Phase separation and dissolution along with silica migration influence the crystallization. • The kinetics is controlled by cooling rate from melt, SAN presence and nanosilica type. [ABSTRACT FROM AUTHOR]