Blend Nanocomposites Research Articles

Preparation of tough, high modulus, and creep-resistant PS/SIS/halloysite blend nanocomposites

In this work, polystyrene (PS)/poly(styrene-b-isoprene-b-styrene) (SIS)/organophilic halloysite nanotube (Org-HNT) blend nanocomposites were produced by melt compounding technique. The significant improvements in both toughness and impact strength values were obtained in PS/SIS blends containing 20%, 30%, and 40% SIS elastomer as compared to neat PS. Among them, PS-30SIS blend with a co-continuous morphology exhibited moderate tensile and impact properties and its nanocomposites having 3, 5, 7 and 10 phr Org-HNT were prepared through the melt mixing method. All the nanocomposites exhibited continuous/fibrillar morphologies with smaller elastomer domains and higher tensile modulus and toughness as compared to PS-30SIS blend. Among them, the nanocomposite having 7 phr Org-HNT and 30% SIS phase (7H-30SIS) exhibited the highest impact strength with enhanced tensile properties. The same nanocomposite exhibited about 21% and 100% increments in the modulus and toughness in comparison to its blend, respectively. The 7H-30SIS nanocomposite increased storage moduli of PS-30SIS blend at glass transition regions of both polyisoprene and PS phases and also at room temperature. Moreover, the rubbery storage moduli of the nanocomposites were found to be about 37% and 53% higher for 7 and 10 phr Org-HNT loaded nanocomposites, respectively, in comparison with that of PS-30SIS blend. The creep deformation and permanent deformation of the blend both decreased via introduction of the nanotubes which is in agreement with aforementioned improvements in the stiffness.

Electromagnetic interference shielding properties of graphene quantum‐dots reinforced poly(vinyl alcohol)/polypyrrole blend nanocomposites

AbstractGraphene quantum dots (GQDs) reinforced poly(vinyl alcohol) (PVA)/polypyrrole (WPPy) nanocomposite films with various GQDs loadings were synthesized using the versatile solvent casting method. The structural and morphological properties of PVA/WPPy/GQDs nanocomposite films were investigated by employing Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy. The thermogravimetric analysis revealed enhanced thermal stability of synthesized nanocomposites while enhanced dielectric properties were also observed. The maximum dielectric constant value for PVA/WPPy/GQDs nanocomposite films was observed to be ε = 6,311.85 (50 Hz, 150°C). The electromagnetic interference (EMI) shielding effectiveness (SE) of nanocomposite films was determined in the X‐band (8–12 GHz) and Ku‐band (12–18 GHz) frequency region. The EMI SE was found to be increased from 0.8 dB for the pure PVA film to 9.8 dB for the PVA/WPPy/GQDs nanocomposite film containing 10 wt% GQDs loading. The enhanced EMI shielding efficiency of nanocomposite films has resulted from the homogenous dispersion of GQDs in PVA/WPPy blend nanocomposites. Thus, the prepared nanocomposites are envisioned to utilize as a lightweight, flexible, and low‐cost material for EMI shielding applications.

Evaluation of air permeability characteristics on the hybridization of carbon black with graphene nanoplatelets in bromobutyl rubber/epoxidized natural rubber composites for inner‐liner applications

Nanotechnology has been explored recently as a means of enhancing the properties of conventional elastomers for engineering applications. In the current study, the effect of nanofillers on air impermeability properties of Brominated isobutylene‐isoprene rubber (BIIR)/Epoxidized natural rubber (ENR) blend has analyzed for automotive applications. The ENR chosen is ENR 25 and ENR 50 (25 and 50% epoxidation) and prepared the blends in a ratio of 75:25 (BIIR:ENR), and from both blend based composites, a part of carbon black replaced with graphene nanoplatelets (GNP). The physical and thermal properties were compared for both binary blend nanocomposites to study the level of exfoliation and reinforcement behavior of GNP. Morphology studies were employed to reveal the level of interaction between GNP and carbon black in both blends. The influence of epoxidation in the formation of nanostructures in both blends have been evaluated, and the effect of nanostructures on air permeability properties was studied. The air impermeability of BIIR‐ENR 50 nanocomposites were improved with increasing platelet concentration, a 30% improvement in air permeability is obtained for BIIR‐ENR 50 composites over BIIR ‐ENR 25.

Characterization and radiation modification of low density polyethylene/polystyrene/maleic anhydride/magnesium hydroxide blend nanocomposite

Preparation of Low density polyethylene/polystyrene/maleic anhydride/nano Magnesium hydroxide LDPE/PS/MA/Mg(OH)2 blend nanocomposite was carried out. The Mg(OH)2 nanoparticles were investigated by XRD and TEM. The effects of different contents of polystyrene, maleic anhydride and nano magnesium hydroxide on the properties of the prepared blends and blend nanocomposite were investigated. From the mechanical properties the LDPE/PS/MA/Mg(OH)2 blend nanocomposite with composition 70/30/10/5 wt % has higher tensile strength compared with pure LDPE. PS and other blend films. Since polymers used in the biomedical and packaging sectors exposed to ionizing radiation such as gamma rays for sterilization purposes, therefore the selected LDPE/PS/MA/Mg(OH)2 blend nanocomposite films subjected to gamma irradiation at doses 0 up to 40 kGy. The FTIR, TGA analyses and the mechanical properties were used for monitoring changes in properties evaluated by radiation. The selected LDPE/PS/MA/Mg(OH)2 blend nanocomposite films characterized by high chemical, thermal and stable structure against gamma irradiation up to 35 kGy than ordinary LDPE film. The limiting oxygen index (LOI) show that the selected irradiated blend nanocomposite has higher LOI value compared to original PS and nonirradiated blend nanocomposite films. The Field emission- SEM show the accumulation of the nano Mg(OH)2 on the surface of selected LDPE/PS/MA/Mg(OH)2 blend nanocomposite film then reduces to average particle size 153.5 nm by effect of gamma irradiation. The presence of Mg(OH)2 nanoparticles did not alter the mechanical properties of the selected prepared LDPE/PS/MA/MgOH2 blend nanocomposite film, also it increase thermal stability and enhance fire retardency which is better than traditional additives.

Mechanical behavior of additively manufactured nanoclay/HDPE nanocomposites

Nanoclay (NC) has blended with relatively inexpensive, widely consumed HDPE (high density polyethylene) for the development of filament to be used in 3D printers. NC/HDPE blends are prepared by varying NC wt. % (0.5, 1, 2, and 5) and are subjected to melt flow index (MFI) measurements. MFI has noted to be decreasing with NC loadings. NC/HDPE nanocomposite blends are further extruded using a single screw extruder. Developed nanocomposites filaments are fed to the fused filament fabrication (FFF) based 3D printer for realizing NC/HDPE nanocomposite prints. The density of printed sample increases with filler content. Filament and printed samples thermal study is carried out using differential scanning calorimeter (DSC). NC addition increases crystallinity and crystallization temperature without significant change in melting peak temperature. Freeze fractured prints reveal the uniform distribution of NC in HDPE. The tensile test is conducted on the filaments and prints. Further printed nanocomposites are subjected to flexural investigations. Tensile modulus and strength of filament increase with NC additions in HDPE matrix. Tensile and flexural properties (modulus and strength) of the nanocomposite prints increases with NC content. Finally, results obtained from the tensile and flexural tests of prints are compared with different HDPE composites available in the literature.

The effect of filler localization on the properties of biopolymer blends, recent advances: A review

AbstractIn recent times, the field of biopolymer (BP) blends has been the focus of intensive fundamental and applied researches. Such BP combinations possess unique properties that are different from those of the individual components. However, most polyester polymers are thermodynamically immiscible because of their poor interactions. In the past, a third component, known as a well‐defined diblock or triblock copolymer, whose chemical structure is identical to that of the main components, was usually used as a compatibilizer in order to emulsify the interfacial phase, decreasing the interfacial tension and refining the phase size. Currently, nanofillers are used to improve the phase morphologies of immiscible BP blends. The main advantage of using nanofillers, when compared to copolymers, is that the former can simultaneous act as nano‐reinforcements and compatibilizers. In this review, the addition of nanofillers as the third component in the BP blend systems are reported in relation to their morphologies, barrier properties, shape memory, thermal, and mechanical properties. The effects of selectively localized nanofillers on the properties of the BP blends are also explored, with the aim of establishing the relationships between the localization of the fillers and the overall properties of the BP blends. Furthermore, the effect of the processing techniques on the localization of the nanofillers/BP blend is also reported. The review article discusses recent progress from 2014 up to 2019 on filler localization of BP blend nanocomposites.

Organic modifier induced interfacial transformation, morphology and physico-mechanical properties of PP/NR based blend nanocomposites

The influence of incorporating organic modified nanoclay (Cloisite 10A) (C 10A) on the morphology, interfacial characteristics, and physico-mechanical properties of polypropylene (PP) melt blended with natural rubber (NR) is investigated here. Melt-mixing technique was employed to prepare nanocomposites with varying amounts of C 10A (1, 3, 5, 7 phr). Nanoclay, depending on its concentration, ‘instigated dramatic transformation of phase morphology from a co-continuous type to a non-uniform sea-island type leading to well-defined matrix-droplet morphology. Besides, addition of nanoclay refined the phase morphology and effectuated synergistic improvement in physico-mechanical properties, where 3 wt% nanoclay modified system exhibited optimal properties for end use application in automotive industry thereby establishing the morphology-property correlation.

Degradation and stability of polymer: A mini review

Observations of alterations in the structural and chemical properties have been commonly performed to understand the process by which polymers degrade. The validity of each observational procedure depends primarily on the test material and type of degradation. An appropriate method for the characterization of polymers can often be utilized to examine the properties of degradation. The service life of a polymer depends strongly on the conditions to which the material is subjected. On the other hand, the stability of the material, including nanocomposite polymer blends, often dictates its usefulness. Thus, this review was aimed to evaluate the degradation of nanocomposite polymer blends, with specific focus on the role of the fillers and the composition of the blends. The factors that could significantly affect the degradation of the same were the presence of a filler, as well as the morphology and composition of the blends.

Shear-Induced Carbon Nanotube Migration and Morphological Development in Polylactide/Poly(vinylidene fluoride) Blend Nanocomposites and Their Impact on Dielectric Constants and Rheological Properties

Polymer composites featuring high dielectric constants are known to be useful materials for the development of modern transducers, piezo- and thermal-sensors, and energy storage devices. In this study, blend nanocomposites of carbon nanotube (CNT)-containing (0.25, 0.75, and 1.0 wt %) polylactide (PLA)/poly(vinylidene fluoride) (PVDF) (70/30 w/w) are developed by melt-mixing PVDF-CNT composite with PLA in a twin-screw extruder. The novelty of this process lies in the fact that the CNTs can migrate from the PVDF to the interface between PVDF and PLA, which could potentially improve the dielectric constant (eᵣ) and elastic moduli G′of the composites. For purposes of comparison, the PLA/PVDF/CNT composite is processed using melt extrusion of all three components together. Furthermore, the effects of CNT network formation are understood using high (L) and low (S) CNT aspect ratios. The dielectric and rheological properties of the composite are measured under different shearing and annealing conditions using a dielectro-rheological device. The results show that the dielectric properties are temperature sensitive, exhibiting higher values at higher temperatures, and that L-CNTs form stronger networks than S-CNTs in nanocomposites. Moreover, the CNTs can migrate toward the interface and coarsen the morphologies of the composite when annealing at a temperature of 200 °C. Such phenomena enhance the eᵣ of the PLA/(PVDF + 0.75 wt % L-CNT), from eᵣ ≈ 22 × 10³ at t = 0 to eᵣ ≈ 3 × 10⁴ after 2 h of annealing at 1 kHz. In contrast, under constant shear rates the eᵣ value of the same composite reduces from eᵣ ≈ 22 × 10³ to eᵣ ≈ 8.2 × 10³ after 1 h. However, under the specific measurement conditions of a 0.001 s–¹ shear rate applied for 300 s, there is a resulting overshoot in both the viscosity and dielectric constant. Such an observation indicates the suitability of these composites for potential application in highly sensitive strain sensors.

Hybrid Rubber Nanocomposites Based on XNBR/EPDM: Select the Best Dispersion Type from Different Nanofillers in the Presence of a Compatibilizer

Hybrid rubber nanocomposite blends based on (80/20) XNBR/EPDM containing 5 phr Cloisite 10A, 15A 20A, 25A, 93A, 30B, carbon black and silica nanofiller and two types of EPDM-g-MA and ENR 50 containing 5 phr was prepared by a two roll mill. A rheometer test was used to study the curing of the blends, the tensile test was used to study the mechanical strength of the nanocomposite and XRD, FESEM and TEM tests were used to evaluate and observe the morphology of the nanocomposite blends prepared. The results of the rheometer test show that the Cloisite 30B nanofiller, in addition to increasing the torque and optimum cure time, decreased compared to other nanofillers. The results of the XRD test showed that the ENR50 compatibilizer with the Cloisite 30B nanofiller compared to other nanofillers, compared to the EPDM-g-MA compatibilizer, significantly increased the openness of the layers by 2.21 nm. The results of FESEM and TEM confirmed the better distribution of Cloisite 30B nanoparticles in the XNBR/EPDM sample containing ENR 50 compatibilizer. Also, XRD evidence showed that the opening of the nanofiller layers of Cloisite 30B was higher the other nanofillers. This result is consistent with microscopic observations. In addition, all nanoparticles are located in the XNBR phase. The results of the tensile test showed that the modulus and tensile strength of nanocomposite containing Cloisite 30B nanofiller and ENR 50 compatibilizer with other nanocomposites increased.

Membranes for hydrogen separation: a significant review

Hydrogen (H2)-selective membranes involve significantly less energy and generally a better way to manage them. Partial inlet/outlet pressure of H2, as well as temperature, are the best parameters for membrane processes. Membrane processes are appropriate for portable applications and small scale as opposed to other separation techniques. The membrane can also be performed at different pressure and temperature ranges. The critical purpose of the separation membrane is the suitable usage in membrane reactors that permit the purification and production of synchronous H2. Observations of alterations in the structural and chemical properties have been commonly performed to understand the process by which polymers degrade. The validity of each observational procedure depends primarily on the test material and type of degradation. An appropriate method for the characterization of polymers can often be utilized to examine the properties of degradation. The service life of a polymer depends strongly on the conditions to which the material is subjected. On the other hand, the stability of the material, including nanocomposite polymer blends, often dictates its usefulness. Thus, this review was aimed to evaluate the degradation of nanocomposite polymer blends, with specific focus on the role of the fillers and the composition of the blends. The factors that could significantly affect the degradation of the same were the presence of a filler, as well as the morphology and composition of the blends.

Phase-selective conductivity enhancement and cooperativity length in PLLA/TPU nanocomposite blends with carboxylated carbon nanotubes

Transmission electron microscopy, temperature-modulated differential scanning calorimetry, and broadband dielectric spectroscopy were employed to characterize ternary nanocomposites consisting of carboxylated carbon nanotubes (CNT) dispersed in a blend of two immiscible polymers, poly(L,lactide) (PLLA) and thermoplastic polyurethane (TPU). The nanocomposite blends were obtained by melt-compounding of PLLA and TPU in the presence of 0.2 wt-% CNT, either in the presence or absence of a Joncryl® ADR chain extender for PLLA, leading to reactive and non-reactive melt mixed samples. In both cases, the binary PLLA/TPU blend is characterized by phase separation into submicron TPU droplets dispersed in the PLLA matrix, and displays two separate glass transition temperatures. The carbon nanotubes are present either inside the TPU phase (samples obtained without chain extender), or at their boundaries (reactive-melt mixed samples). The effect of the sub-micron confinement of the TPU component is to decrease the cooperativity length of the primary segmental relaxation of this polymer, which is accentuated by the presence of the CNT fillers. Depending on the type of sample, five or six distinct relaxations are observed by means of dielectric spectroscopy, which we are able to assign to different dielectric phenomena. Our dielectric data show that the CNT fillers do not contribute directly to the long-range charge transport in the nanocomposite blends, consistent with the nanocomposites morphology, but rather result in a shift of the Maxwell-Wagner-Sillars space-charge frequency associated with charge accumulation at the PLLA/TPU boundary. Such shift testifies to a selective conductivity enhancement of the TPU phase due to the filler.

Development of SWCNTs-reinforced EPDM/SBR matrices for shock absorbing applications

The present research investigates the effects of various concentrations of single-walled carbon nanotubes (SWCNTs) on the viscoelastic and thermomechanical characteristics of styrene-butadiene/ethylene propylene diene polymer (SBR/EPDM) blended polymeric matrices (60:40). Standard elastomeric methods are used to synthesise SWCNTs-reinforced EPDM/SBR nanocomposite blends. The results reveal that high SWCNTs concentrations offer remarkable thermal stability enhancement. SWCNTs reinforced with 0.6 mass% EPDM/SBR become 20% harder, with Tangent Delta values boosted by 70% with maximum cross-linking, elongation enhanced by 38% and tensile strength improved by 35%. With the 38% elongation enhancement, storage modulus is increased by 80%, whereas compressive strain is reduced by 20%. The planned hybrid nanocomposites exhibit viscoelastic characteristics against applied shock, in which the viscous component is associated with spongy structure, whereas the elastic component is associated with spring-like response.

Effects of EVA-g-MA and EVACO compatibilizers/tougheners on morphological and mechanical properties of PP/EVA/HNT blend polymer nanocomposites

A series of polypropylene (PP)/poly(ethylene- co-vinyl acetate) (EVA) blend nanocomposites was produced by utilizing different amounts of organophilic halloysite nanotube (Org-HNT) and EVA-based compatibilizers/tougheners. They were prepared by using either only EVA elastomer or using EVA with the compatibilizers which are maleic anhydride grafted EVA (EVA-g-MA) and poly(ethylene-vinyl acetate-carbon monoxide) (EVACO) as well as maleic anhydride grafted PP (PP-g-MA). The morphology–mechanical property relationship was investigated as a function of nature of the compatibilizer and the amount of aluminosilicate nanotube/compatibilizer. The composites prepared without using the EVA-based compatibilizers in all nanotube loading degrees (1%, 3%, 5%) exhibited nanotube aggregates as evidenced by scanning electron microscope analyses. On the other hand, EVA-g-MA and EVACO provided a good dispersion of HNTs at both PP–EVA interface and in the PP matrix. The use of compatibilizers together with 3% Org-HNT resulted in PP/EVA blend nanocomposites with higher tensile modulus and toughness when compared to PP/EVA blend. Particularly, EVACO compatibilizer having highly polar carbonyl group at its backbone provided the highest toughness and Young’s modulus as well as impact resistance for the 3% Org-HNT loaded nanocomposite while retaining the yield strength as an indication of a good balance between stiffness/toughness.

Comparative study of some mechanical properties of nanocomposites based on the polymer’s blends used for dentures base applications

Recently, high mechanical and physical properties of PMMA material have encouraged many researchers to work in the denture’s applications. However, it is a weak material in terms of fatigue loads and impact strength. In the present research, two types of polymer blend nanocomposite samples were manufactured by utilizing a hand lay-up method used to produce the complete or partial dentures base. Polymer blends containing (poly methyl methacrylate resin and 2% natural rubber (NR)) were used as matrix; it was strengthened by two kinds of natural powder in the nanometer size of clove powder and pomegranate peels powder (PPP) individually, with a chosen weight fraction percent of (0.0, 0.1, 0.3, 0.5 and 0.7% wt). The results manifested appreciably the advanced values of flexural strength, flexural modulus, maximum shear stress, fracture toughness and impact strength for both kinds of hybrid composites specimens compared to matrix material (PMMA: 2%NR). Composite specimens of polymer blend (PMMA: 2%NR) matrix reinforced by (PPP) elucidated the highest values for these properties as compared with their counterpart of nanocomposites, which reinforced by clove nanoparticles. The highest values for the flexural strength and maximum shear stress reached to 144 MPa and 3 MPa, respectively at 0.5% ratio of PPP, whereas the highest values of flexural modulus, impact strength and fracture toughness reached to 3.3 GPa, 10 KJ m−2 and 5.74 MPa.m½, respectively at 0.7% ratio of PPP for polymer blend nanocomposite (PMMA: 2%NR: 0.7% PPP). Depending on these results, it can be concluded that the addition of natural fillings in a nanometer size of pomegranate peels or clove powders individually to the polymer blend (PMMA: 2% NR) material is one of the promising materials that can be used to improve the mechanical properties, especially the fracture strength for the complete or partial dentures base.

Ductility improvements of PLA-based binary and ternary blends with controlled morphology using PBAT, PBSA, and nanoclay

In this study, binary and ternary immiscible blends of polylactide (PLA) with poly[(butylene adipate)-co-terephthalate] (PBAT) and poly[(butylene succinate)-co-adipate] (PBSA) were prepared through an injection-molding (IM) process. Blend nanocomposites of PLA/PBAT/nanoclay were also prepared using a twin-screw extruder (TSE) followed by IM. An amorphous PLA (A-PLA), a semicrystalline PLA (SC-PLA), and their mixture were used as the matrix to investigate the matrix crystallization effect on blend morphology evolution and ductility enhancements. The results showed that in PLA/PBAT blends with 75/25 wt ratio, the increase in PLA crystallization capability caused finer and more homogenous blend morphology and hence the ductility increased significantly from around 5% to ~205%. In contrast, the ductility enhancements of co-continuous PLA/PBAT blends with 50/50 wt ratio became more profound when the PLA matrix was more amorphous. In PLA/PBSA blends, however, no ductility improvement was observed as the vitrification of PLA could hinder the PBSA crystallization which resulted in a non-uniform blend structure. In ternary blends, a matrix-core shell morphology was obtained and led to the improvements of the flexural strength and modulus. The use of nanoclay also significantly promoted the ductility of PLA/PBAT blends with 75/25 wt ratio, specifically in blends with A-PLA.

Construction of hexagonal boron nitride@polystyrene nanocomposite with high thermal conductivity for thermal management application

Hexagonal boron nitride (BN) hold great promise as emerging building blocks for thermal interface materials owing to their outstanding heat transfer performance. Herein, we report a carboxylated polystyrene-coated hydroxylated BN (BN–OH@PS-COOH) nanocomposite with highly thermal conductivity (TC) and extraordinary mechanical properties for thermal management. The exfoliated BN-OH nanosheets were obtained via molten alkali hydroxide pretreatment and sonication. Subsequently, PS-COOH nanospheres were grew on the surface of BN-OH nanosheets by in situ polymerization. Noncovalent interactions between PS-COOH and BN-OH are favor to reduce interfacial thermal resistance, which contributes to accelerate heat transport. As a result, the TC of the resultant BN-OH@PS-COOH nanocomposite with 12 wt% BN-OH addition is 1.131 W/mK, which is much higher than that of neat PS (0.186 W/mK) and BN/PS blend nanocomposite (0.312 W/mK). Moreover, the BN-OH@PS-COOH nanocomposite exhibits outstanding mechanical properties. Our study may stimulate novel perspectives on the design of high-performance polymer-based thermal interface materials.

One-way thermo-responsive shape memory polymer nanocomposite derived from polycaprolactone and polystyrene-block-polybutadiene-block-polystyrene packed with carbon nanofiber

Shape-memory polymer nanocomposite (SMPNC) blends with thermoresponsive shape memory capability have received increasing interests and have been a grooming research area due to its potential applications. In the present study, the polymer blend comprising of Polycaprolactone (PCL) and Polystyrene-block-Polybutadiene-block-Polystyrene (SBS) is prepared by melting and blending method, followed by the addition of carbon nanofibers (CNF), to provide the blend with excellent shape memory property stimulated by temperature. In this polymeric blend SBS, PCL, and CNF are acted as an elastomer, switch polymer and conductive filler, respectively. The two-phase morphology of components in the blend is confirmed using Scanning Electrode Microscopic (SEM) images, Polarised Optical Microscopic (POM) images, and stress-strain plots. The immiscibility between the microstructures is revealed from the Differential Scanning Calorimetric (DSC) results. Characterization techniques such as X-Ray Diffraction (XRD), Thermo Gravimetric Analysis (TGA) and shape memory test are also conducted. The crystallinity of the synthesized composite is influenced by the PCL content. As the PCL content increases, crystalline nature also increases. From TGA results, the thermal stability of the composites is found to be decreasing from PCL 5 to PCL 100. The tensile and shape memory results show an optimized one-way SMPNC system with good shape recovery and fixing performances.

Ion dynamics and dielectric relaxation behavior of PVA-PVP-NaI-SiO2 based nano-composites polymer blend electrolytes

In this paper we have reported the loading effect of SiO2 nano-particles on the electrical transport properties and dielectric relaxation behavior of the PVA-PVP-NaI based nano composite polymer blend electrolytes (NCPBEs). Solution cast technique has been used for the preparation of PVA-PVP-NaI-SiO2 based NCPBE films. AC impedance spectroscopic technique is used for the study of electrical conductivity and dielectric properties. The frequency dependence of AC conductivity with different SiO2 concentration for all prepared NCPBEs obeys the Jonscher power law (JPL) with exponent, n ≥ 1. The dielectric permittivity (ε′&ε″), electric modulus (M′&M″) vs. frequency plots at different concentrations and temperatures were reported. Mobility (μ), dc conductivity (σdc) and total number of charge carriers (N) were estimated and found that mobility varies with the SiO2 concentration. Sample containing 0.6 wt% of SiO2 shows optimum dc conductivity, σdc ~5.07 × 10−6 S/cm with μ ~4.60 × 10−7 and N ~6.98 × 1021. Dielectric relaxation peaks have been observed for all samples and relaxation time (τ) is minimum for 0.6 wt%SiO2 based NCPBE film.

Effect of shear rate and pressure on the crystallization of PP nanocomposites and PP/PET polymer blend nanocomposites

The effect of shear flow on the crystallization of homopolymers has been widely studied, however more complex systems such as nanocomposites or polymer blends nanocomposites (PBNANOs) have received less attention. In this work, the effect of pressure and shear flow on the crystallization process of polypropylene-based nanocomposites and polypropylene/polyethylene terephthalate PBNANOs have been studied employing dilatometry (PVT), X-ray, rheology, and DSC. The material systems used allow studying the effect of shear in the presence of nanoparticles that do not have a nucleating effect, as well as the combined effect of shear and nucleating nanoparticles. Nucleating nanoparticles increase the crystallization temperature more significantly because of the combined effect of nucleation and flow. For carbon nanotubes, nucleation is more pronounced due to stronger interactions with PP chains, as demonstrated by rheological measurements. For PBNANOs the effect of shear on crystallization is more significant due to the higher amount of available surfaces.