Low Nanofiller Concentrations Research Articles

Characterization of UV Light Curable Piezoelectric 0-0-3 Composites Filled with Lead-Free Ceramics and Conductive Nanoparticles

Lead-free piezoelectric materials are essential for our healthy future but offer lower performance than lead-based materials. Different material combinations are explored to improve the performance of lead-free materials. By filling the UV light curable photopolymer resin with 30 vol.% lead-free piezoelectric ceramics and with up to 0.4 wt.% conductive nanofillers, thin and flexible piezoelectric 0-0-3 composites are formed. Two particle sizes of Potassium Sodium Niobate (KNN) and Barium Titanate (BTO) ceramics were used with four conductive nanofillers: Graphene Nanoplatelets (GNPs), Multi-Walled Carbon Nanotubes (MWCNTs), and two types of Graphene Oxide (GO). Resulting high viscosity suspensions are tape-cast in a mold as thin layers and subsequently exposing them to UV light, piezoelectric composite sensors are formed in 80 s. Even low nanofiller concentrations increase relative permittivities, however, they strongly reduce curing depth and increase undesirable dielectric losses. Non-homogeneous dispersion of nanofillers is observed. In total, 36 different compositions were mixed and characterized. Only six selected material compositions were investigated further by measuring mechanical, dielectric, and piezoelectric properties. Results show KNN composite performance as piezoelectric sensors is almost six times higher than BTO composite performance.

Epoxy-based/BaTiO3 nanodielectrics: Relaxation dynamics, charge transport and energy storage

Epoxy/BaTiO3 nanocomposites developed at low nanofiller concentrations with their dielectric relaxations, charge transport dynamics and capacitive energy storage were investigated via dielectric spectroscopy and dc charge-discharge experiments. Two relaxation processes were observed, namely the α- and β-relaxations, attributed to the dynamic Tg process and local motions, respectively. Another process located at low frequencies and high temperatures was identified as interfacial polarization. The charge transport properties were examined via the ac conductivity and impedance formalisms, indicating a beneficial effect with the increase of the nanofiller content. The dc conductivity was calculated from the ac spectra and exhibited Arrhenius temperature dependence. The theoretical energy density was found to increase up to 3.5 times comparing to the neat epoxy resin, highlighting the reinforcing dielectric/capacitive effect of the BaTiO3 nanoparticles on the epoxy resin. Comparisons between the theoretical energy densities and experimentally determined values were also discussed in detail.

Nanocomposites for Food Packaging Applications: An Overview.

There is a strong drive in industry for packaging solutions that contribute to sustainable development by targeting a circular economy, which pivots around the recyclability of the packaging materials. The aim is to reduce traditional plastic consumption and achieve high recycling efficiency while maintaining the desired barrier and mechanical properties. In this domain, packaging materials in the form of polymer nanocomposites (PNCs) can offer the desired functionalities and can be a potential replacement for complex multilayered polymer structures. There has been an increasing interest in nanocomposites for food packaging applications, with a five-fold rise in the number of published articles during the period 2010–2019. The barrier, mechanical, and thermal properties of the polymers can be significantly improved by incorporating low concentrations of nanofillers. Furthermore, antimicrobial and antioxidant properties can be introduced, which are very relevant for food packaging applications. In this review, we will present an overview of the nanocomposite materials for food packaging applications. We will briefly discuss different nanofillers, methods to incorporate them in the polymer matrix, and surface treatments, with a special focus on the barrier, antimicrobial, and antioxidant properties. On the practical side migration issues, consumer acceptability, recyclability, and toxicity aspects will also be discussed.

Development of Approaches for Producing Polymeric Composite Materials with Higher Strength

In laboratory conditions, oriented polypropylene composite materials containing various concentrations of anisotropic carbon nanoparticles (nanofibers, nanotubes) were obtained. The change in the mechanical properties of oriented composites is determined. Based on structural studies, it was shown that the increase in strength in oriented composites is associated with the formation of a more perfect supramolecular structure of the polymer matrix due to the introduction of low concentrations of nanofillers.

Flexible piezoelectric PVDF/NDs nanocomposite films: improved electroactive properties at low concentration of nanofiller and numerical simulation using finite element method

In the present work, flexible poly (vinylidene fluoride)/Diamond nanoparticles nanocomposite films with improved electroactive properties at low filler concentration were developed. The combination of nanofiller doping and mechanical stretching was employed to obtain the films with significantly improved electroactive phase at low nanodiamond (ND) concentration, making them the interesting materials for several applications in the electronic devices. The nanocomposite films with different nanofiller concentration were prepared and then stretched under different stretch ratios. The polar phase content of all films was calculated and compared. It was found that the polar phase fraction of the films was significantly enhanced by increasing the nanofiller concentration and the stretch ratio. Moreover, a finite element model was constructed to determine the true value of the strain during the tensile process and to calibrate the stretch ratio. Development of such nanocomposite films with improved piezoelectric properties at low nanofiller concentration can extend their applications for practical usage.

Fractal Model of the Nanofiller Structure Affecting The Degree of Reinforcement of Polyurethane–Carbon Nanotube Nanocomposites

A percolation model of nanocomposite reinforcement is under study. It is shown that the degree of reinforcement of polyurethane–carbon nanotube nanocomposites depends on the structure of nanofillers, which are annular formations. This structure is most accurately characterized by its fractal dimension. It is established that the creation of a structure with negative percolation indices allows for a significant increase in the degree of reinforcement of considered nanocomposites at low nanofiller concentrations.

Dielectric Breakdown Strength of Polymer Nanocomposites-The Effect of Nanofiller Content

Insulation materials can be tailored by compounding nanofillers and polymer materials. The advantageous changes in properties of polymer nanocomposites can be explained by the large interface area of the nanofillers. Theoretical models developed in the field of nanodielectrics concentrate on the analysis of the interface volume.Dielectric breakdown strength (DBS) is one of the most important properties of an insulation material. The DBS of nanocomposites depends heavily on the nanofiller content and even small quantities can cause improvement. This is linked to the maximum interface volume achieved already at low nanofiller concentrations. Homogeneous nanodispersion is the key for DBS increase and reliable results. Often the most profitable nanofiller quantities are below 5 wt-%. The same kind of behaviour can be seen with different voltage shapes, but with dc voltage the increase is bigger. DBS has a maximum value with respect to nanofiller amount and decreases thereafter. Filler quantities around 5 wt-% and even lower are the most attractive considering DBS of nanocomposites.

Clay/carbon nanotube hybrid mixture to reduce the electrical percolation threshold of polymer nanocomposites

Creating electrically conductive polymer composites with extremely low nanofiller concentration by melt compounding is a major research challenge. At low nanofiller concentration, the valuable properties of polymers are preserved and the feasibility of the composite is promoted. In this work, an organically modified clay (OMC) was utilized to alter the structure and consequently the electrical resistivity of carbon nanotubes (CNT)/polypropylene (PP) composite. As a result of OMC incorporation, the electrical percolation threshold concentration (EPTC) was reduced from 1.0 wt% CNT for the CNT/PP composite to 0.5 wt% CNT for the CNT:OMC/PP composite, corresponding to 50% reduction in the amount of CNT. The macro-dispersion analysis did not reveal any significant difference between the dispersion of CNT in the CNT/PP and CNT:OMC/PP composites. However, the processing behavior analysis showed a significant decrease in mixing torque and consequently mixing energy due to the addition of OMC. The decrease in mixing torque and/or mixing energy decreases the destruction of CNT aspect ratio. In addition, the DSC analysis showed a decrease in composite crystallinity due to OMC addition. This finding reveals a thinner insulating crystalline layer at the surface of CNT particles and consequently higher electrical conductivity. Based on these experimental findings, it can be speculated that the addition of OMC promoted the conductivity of the composite by decreasing the mixing shear stress and/or polymer crystallinity.

Insulating property of polypropylene nanocomposites filled with nano-MgO of different concentration

Polypropylene (PP) has special advantages in replacing conventional crosslinked polyethylene (XLPE) to be insulation material of power cable. In order to reveal the effects of nano-filler addition on PP, five kinds of experiments, namely TEM, DSC, breakdown strengths (BDs), space charge and dielectric measurement were investigated to evaluate the insulating properties of PP and its nanocomposites with surface-treated nano-MgO of different concentration. It is revealed that, with the addition of nano-MgO, favorable dispersibility of nano-filler and significant increase of crystallinity of polymer are observed. BDs under dc voltage increase apparently with loading of nano MgO, but when the nano concentration reaches higher than 1 wt%, the BDs have a slight decline compared with 1 wt%. It is clarified that space charge and electric field distortion are well restricted with the addition of nano-MgO, while this effect is not obvious with the nano concentration reaches 6 wt%. Permittivity has trends of increase with the rise of temperature at first and then decrease when the temperature reaches about 333 K, and the addition of nano-filler MgO could also decrease permittivity. When the nano-filler concentration reaches high, dielectric loss increases to a high level. Low nano-filler concentration in MgO/PP shows better electrical insulation properties compared with PP and high nano-filler concentration composites.

Development of Hashin-Shtrikman model to determine the roles and properties of interphases in clay/CaCO3/PP ternary nanocomposite

The Hashin-Shtrikman model underpredicts the bulk, shear and Young's moduli of the prepared clay/CaCO3/PP ternary polymer nanocomposite (TPN) by ignoring the interphase between polymer matrix and nanoparticles. In this study, the Hashin-Shtrikman model was developed assuming the thickness and strength of interphases. Also, the thickness and strength of interphases in the ternary samples could be calculated by the developed Hashin-Shtrikman and Pukanszky models, respectively using the experimental results of mechanical properties.The predictions of the developed model showed good agreement with the experimental data at different Mt and CaCO3 contents assuming the interphase role which validate the current approach. According to the calculations, the strong and thick interphases were formed in the TPN at low nanofiller concentrations. This occurrence for the present samples was explained by the material and processing parameters. However, the thickness and strength of interphases weakened by increasing in clay content, probably due to the poor dispersion of nanoparticles and reduced interfacial area/adhesion at this condition.

Study on interfacial properties in polymer blend ternary nanocomposites: Role of nanofiller content

In this work, the interfacial properties in polymer blend nanocomposites are calculated by micromechanical modeling of experimental tensile strength and modulus. Also, the effects of nanofiller content on the interfacial properties are determined. The calculated results demonstrate the good interfacial properties in the samples containing low nanofiller concentrations. However, the incorrect calculations of interfacial parameters are reported in the ternary nanocomposites which show the decreased tensile strength at high nanofiller concentrations. It is concluded that some undesirable phenomena at high nanofiller contents such as the aggregation of nanoparticles may deteriorate the predictability of the micromechanical models.

Influence of zinc oxide nanoparticles on structural and electrical properties of polyvinyl alcohol films

This study has been conducted with the objective of investigating the effects of zinc oxide nanoparticles on the structural and electrical properties of polyvinyl alcohol films. The fabricated nanocomposites were characterised by Fourier transform infrared spectroscopy, UV–visible (vis) spectra, X-ray diffraction and SEM techniques. UV–vis spectra showed that the addition of ZnO nanoparticles did not affect the absorbance in the visible region of nanocomposites. The SEM image showed that ZnO nanoparticles were homogeneously dispersed throughout the entire film’s polymeric matrix. The dielectric properties were found to be strongly dependent on frequency and nanofiller content. AC conductivity σac of polyvinyl alcohol/ZnO nanocomposites increased with increasing frequency. The dissipation factor tan δ also increased with nanoparticle addition and decreased with frequency. At low nanofiller concentrations, nanocomposites exhibited low dielectric values at higher frequency, thus behaving like a lossless material, making them suitable for utilisation in microwave applications.

LLDPE/Proton Exchanged Layered Niobate K4Nb6O17 Nanocomposites

Abstract The potassium hexaniobate was synthesized by reacting, in stoichiometric proportions, Nb2O5 and K2CO3 at 1100°C and modified with octadecylamine from an acid-base reaction. Through X-ray diffraction, an interlayer space of 4.27 nm was observed in comparison with 0.79 nm of unmodified oxide; this was also shown by SEM microscopy. The hybrid nanofiller previously obtained was incorporated into LLDPE by melt intercalation (0 up to 10 wt.%) using a twin screw extruder and LLDPE-g-MAH as compatibilizer. From TGA results, all nanocomposites (LLDPE/LLDPE-g-MAH/lamellar oxide) have increased the onset degradation temperature, while the oxide lost during processing for LLDPE/LLDPE-g-MAH/lamellar oxide nanocomposites was higher for the highest content in comparison with LLDPE matrix. According to the Eyring equation, the activation volume of the samples could be calculated using the relationship between the yield strength and strain rate from tensile stress-strain curves. The activation volume decreased with increase of nanofiller concentration, suggesting a good adhesion between the layered oxide and the polymeric matrix for high concentration. This can be attributed to the restricted segmental motion near the nanofiller/polymeric interface, while a poor interaction between them was observed for low concentration. However, the Young's modulus showed a 50% improvement for low nanofiller concentration, especially in the case of 1 wt.% of nanofiller, which was also confirmed by modulus and toughness balance. Considering all the results, it has been revealed that the proton exchanged layered niobate can improve the thermal and mechanical properties of LLDPE/LLDPE-g-MAH/lamellar oxide nanocomposites.

Space Charge Trapping and Conduction in Low-Density Polyethylene/Silica Nanocomposite

The high field conduction and space charge distribution were investigated in low-density polyethylene (LDPE) and LDPE/silica nanocomposites filled with various concentrations of nanosilica. The results indicate that nanosilica could effectively suppress space charge accumulation at nanofiller concentrations from 0.1 to 5.0 wt %. However, the conduction current at a high field significantly increases at low concentrations from 0.1 to 0.5 wt % and remarkably reduces at high concentrations from 0.5 to 5.0 wt %. It is shown that the trap depth corresponding to the time from 2 to 3600 s significantly decreases at low nanofiller concentrations from 0.1 to 0.5 wt %. However, the depth of deep traps corresponding to the time from 100 to 3600 s increases with the increase in nanofiller concentration from 0.5 to 5.0 wt %. Moreover, the depth of shallow traps corresponding to the time from 2 to 100 s increases at concentrations from 0.5 to 2.0 wt %, and then it decreases at concentrations from 2.0 to 5.0 wt %. In addition, the apparent mobility varies with the modification of trap depth caused by the introduction of nanofiller. The threshold field EΩ–t for remarkable charge injection and Et–c proportional to the total trap density H are significantly lower in the nanocomposite with a low nanosilica concentration, i.e., 0.1 and 0.5 wt %, while both of them increase at concentrations from 0.5 to 5.0 wt %. It is considered that the impurity effect is greater than the nanofiller effect at a low nanofiller concentration. The deep trap is speculated as the chemical trap in the interface of the nanofiller bonding strongly with the polymer chain, while the shallow trap may be related to the chemical trap in the weakly bonded interface. It is clear that the space charge behavior and conduction are significantly affected by modification of the trap depth and density distribution owing to the introduction of nanofiller.

Thermal stability, crystallization and mechanical properties of nylon11/montmorillonite nanocomposites

AbstractNylon 11 nanocomposites with different montmorillonite loadings were successfully prepared by melt compounding. XRD and TEM show the exfoliated nanocomposites are formed at low montmorillonite concentration (less than 2 wt%) and the intercalated nanocomposites are obtained at higher montmorillonite contents. TGA shows that the thermal stability of the nanocomposites is improved by 27 °C when the montmorillonite content is only 2wt%. At the same time, The crystallization behavior of nylon11/montmorillonite nanocomposites has been studied by means of XRD, DSC.The Avrami equation described well the isothermal crystallization behavior of nylon11 and nylon11/montmorillonite nanocomposites. The results showed that the montmorillonite acted as the nucleating agent and facilitated the crystal growth rate of nylon 11 matrix. The incorporation of montmorillonite did not change the crystal morphology of nylon 11 but increased the crystallization temperature and decreased the crystallization activation energy, which lead to a easy crystallization of nylon11. Mechanical testing shows that the Izod impact strength of all nanocomposites are higher than that of the neat nylon 11, but the tensile strength of the nanocomposites decrease at low nanofiller concentrations (less than 8wt%) and then increased, when the montmorillonite content is 10wt% ,the tensile strength of the nanocomposite is 5% improved than neat nylon 11. This is may be due to the strong interaction between the nylon 11 matrix and the montmorillonite interface.

Study on the Morphology and Properties of Nylon11/Montmorillonite Nanocomposites

nylon 11 nanocomposites with different montmorillonite loadings were successfully prepared by melt compounding. XRD and TEM show the exfoliated nanocomposites are formed at low montmorillonite concentration(less than 2wt%) and the intercalated nanocomposites are obtained at higher montmorillonite contents. TGA shows that the thermal stability of the nanocomposites is improved by 27°C when the montmorillonite content is only 2wt%. Mechanical testing shows that the Izod impact strength of all nanocomposites are higher than that of the neat nylon 11, but the tensile strength of the nanocomposites decrease at low nanofiller concentrations (less than 8wt%) and than increased, when the montmorillonite content is 10wt% ,the tensile strength of the nanocomposite is 5% improved than neat nylon 11. This is may be due to the strong interaction between the nylon 11 matrix and the montmorillonite interface.

Comparative rheological studies of polyamide-6 and its low loaded nanocomposite based on layered silicates

We study some rheological properties for polyamide-6 (PA-6) and a low concentrated clay nanocomposite melt based on polyamide-6 and montmorillonite. Simple shear experiments, carried out for both the neat system and nanocomposite at two different temperatures, include start up shear flows, stress relaxation after cessation of steady flow and oscillatory shear. The dynamic data for the neat PA-6 matrix differ markedly from that of the nanocomposite system, even if it has very low nanofiller concentration. Thermal stability of the PA-6 matrix imposed many restrictions on rheological studies of our systems. Therefore an experimental window was established via rheological and thermal characterization of the materials, wherein the polymer matrix was confirmed to be thermally stable. The relaxation spectra for both polymer systems were determined from linear dynamic experiments using the Pade’-Laplace procedure. A rough estimation of nanocomposite volume fraction at percolation allowed us to attribute the occurrence of extra (relative to the neat polymer) Maxwell modes observed for the nanocomposite to the formation of a particulate network above the percolation threshold.