2016, Mir, Seyed Mohammad, Jafari, Seyed Hassan, Khonakdar, Hossein Ali, Krause, Beate, Pötschke, Petra, Taheri Qazvini, Nader

Electrical conductive poly(methyl methacrylate) (PMMA) nanocomposites with low percolation threshold are very challenging to be prepared. Here, we show that the miscibility between poly(ethylene oxide) (PEO) as matrix for predispersions of multi-walled carbon nanotubes (MWCNTs) and PMMA represents an efficient approach to achieve very low electrical percolation threshold. PMMA/PEO-MWCNTs nanocomposites were prepared by a two-step solution casting method involving pre-mixing of MWCNTs with PEO and then mixing of PEO-MWCNTs with PMMA, resulting in a PMMA/PEO ratio of 80/20 wt%. The electrical percolation threshold (EPT) value was determined to be ~ 0.07 wt% which is significantly lower than most of the reported EPT values in the literature for PMMA/CNT composites. The very low electrical percolation threshold was attributed to the effectual role of PEO in self-assembly of secondary structures of nanotubes into an electrically conductive network. This was further confirmed by transmission electron microscopy and by comparing the obtained EPT value with the prediction of the excluded volume model in which statistical percolation threshold is defined based on uniform distribution of high-aspect ratio sticks in a matrix. Moreover, based on UV–Vis measurements and linear viscoelastic rheological measurements, optical and rheological percolation thresholds were obtained at nearly 0.01 wt% and 0.5 wt%, respectively.

2020, Avid, Arezoo, Jafari, Seyed Hassan, Khonakdar, Hossein Ali, Ghaffari, Mehdi, Krause, Beate, Pötschke, Petra

Multiwalled carbon nanotubes (MWCNTs) were modified by an organo-silane in order to improve their dispersion state and stability in paraffin wax. A family of paraffin-based phase change material (PCM) composites filled with MWCNTs was prepared with different loadings (0, 0.1, 0.5, and 1 wt%) of pristine MWCNTs and organo-silane modified MWCNTs (Si-MWCNT). Structural analyses were performed by means of Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and rheological studies using temperature sweeps. Moreover, phase change transition temperatures and heat of fusion as well as thermal and electrical conductivities of the developed PCM nanocomposites were determined. The SEM micrographs and FTIR absorption bands appearing at approximately 1038 and 1112 cm−1 confirmed the silane modification. Differential scanning calorimetery (DSC) results indicate that the presence of Si-MWCNTs leads to slightly favorable enhancement in the energy storage capacity at the maximum loading. It was also shown that the thermal conductivity of the PCM nanocomposites, in both solid and liquid phases, increased with increasing the MWCNT content independent of the kind of MWCNTs by up to about 30% at the maximum loading of MWCNTs. In addition, the modification of MWCNTs made the samples completely electrically nonconductive, and the electrical surface resistivity of the PCMs containing pristine MWCNTs decreased with increasing MWCNTs loading. Furthermore, the rheological assessment under consecutive cyclic phase change demonstrated that the samples containing modified MWCNTs are more stable compared to the PCM containing pristine MWCNTs. © 2019 Wiley

2020, Karimpour-Motlagh, Navid, Moghadam, Abolfazl Salehi, Khonakdar, Hossein Ali, Jafari, Seyed Hassan, Wagenknecht, Udo, Kasbi, Sina Farahani, Shojaei, Shahrokh, Mirzaee, Ramin

Poly (lactic acid) (PLA)-based compounds are widely used in thin-film and food packaging industries. Herein, PLA/ethylene vinyl acetate copolymer (EVA)/nanoclay nanocomposites are prepared in various compositions by melt blending. The gas permeability against N2, CO2, and O2 gases is determined as a function of composition and morphology of the nanocomposites. Inclusion of high aspect ratio of platelet-like nanoclay to the blend reduces the gas diffusion. The best barrier properties against all gases is observed on introducing 5 wt% poly(ethylene/n-butyl acrylate glycidyl methacrylate) copolymer as compatibilizer to the PLA/EVA/nanoclay (75/25/5) system. The scanning and transmission electron microscopic analyses and wide-angle X-ray scattering studies reveal that inclusion of compatibilizer to the filled-blends improves the blend morphology, dispersion state, and intercalation level of clay platelets which are preferably localized at the interface of the blend. Analysis of selectivity parameter (a) shows the lowest O2 permeability and the highest aCO2/N2 and aO2/N2 values for the compatibilized filled-blend (75/25/5/5). In situ aspect ratio of clay and the degree of intercalation are theoretically evaluated based on the permeability data using various empirical models. It is found that the compatibilized filled-blend has the highest aspect ratio and intercalation level that are responsible for the optimum perm-selectivity performance. © 2020 The Authors. Published by Wiley-VCH GmbH

2022, Mousavi, Seyed Rasoul, Estaji, Sara, Kiaei, Hediyeh, Mansourian-Tabaei, Mohammad, Nouranian, Sasan, Jafari, Seyed Hassan, Ruckdäschel, Holger, Arjmand, Mohammad, Khonakdar, Hossein Ali

Epoxy (EP) resins exhibit desirable mechanical and thermal properties, low shrinkage during cuing, and high chemical resistance. Therefore, they are useful for various applications, such as coatings, adhesives, paints, etc. On the other hand, carbon nanotubes (CNT), graphene (Gr), and their derivatives have become reinforcements of choice for EP-based nanocomposites because of their extraordinary mechanical, thermal, and electrical properties. Herein, we provide an overview of the last decade's advances in research on improving the thermal and electrical conductivities of EP resin systems modified with CNT, Gr, their derivatives, and hybrids. We further report on the surface modification of these reinforcements as a means to improve the nanofiller dispersion in the EP resins, thereby enhancing the thermal and electrical conductivities of the resulting nanocomposites.

2019, Bhagavatheswaran, Eshwaran Subramani, Das, Amit, Rastin, Hadi, Saeidi, Hoda, Jafari, Seyed Hassan, Vahabi, Henri, Najafi, Farhood, Khonakdar, Hossein Ali, Formela, Krzysztof, Jouyandeh, Maryam, Zarrintaj, Payam, Saeb, Mohammad Reza

Rubber technology experiences a new age by the use of biowaste or natural fillers. In this regard, taking properties of reinforcing agents from biowaste fillers remains as the challenging matter. Chicken eggshell (ES) biowaste has recently been introduced to substitute calcium carbonate (CaCO3) duo to its superior properties and low price. In this work, composites based on acrylonitrile butadiene rubber (NBR) reinforced with ES and CaCO3 microfillers at various loading levels were prepared and characterized. To improve the interactions between fillers and the NBR matrix, ES and CaCO3 were surface-functionalized using a terpolymer, namely poly(vinyl 2-pyrrolidone-co-maleic acid-co-acrylic acid). Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to characterize the modified fillers. The incorporation of the functionalized fillers resulted in a significant rise in the maximum torque according to the rheometric measurements. The Young’s modulus of the ES-based and CaCO3-based compounds showed a mild improvement over a wide range of filler contents. The elongation at break of the NBR composites, however, was dependent on the filler content. This work provides exciting opportunities for the design of novel and innovative coupling agents to be used in rubber applications. © 2019, The Author(s).

2017, Vaezi, Javid, Nekoomanesh, Mehdi, Khonakdar, Hossein Ali, Jafari, Seyed Hassan, Mojarrad, Alireza

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.