Polymer Matrix Of Nanocomposites Research Articles

CO2-Philic Nanocomposite Polymer Matrix Incorporated with MXene Nanosheets for Ultraefficient CO2 Capture.

The incorporation of two-dimensional (2D) functional nanosheets in polymeric membranes is a promising material strategy to overcome their inherent performance trade-off behavior. Herein, we report a novel nanocomposite membrane design by incorporating MXene, a 2D sheet-like nanoarchitecture known for its advantageous lamellar morphology and surface functionalities, into a cross-linked polyether block amide (Pebax)/poly(ethylene glycol) methyl ether acrylate (PEGMEA) blend matrix, which delivered exceptional CO2/N2 and CO2/H2 separation performances that are critical to industrial CO2 capture applications. The finely dispersed Ti3C2Tx nanosheets in the blend polymer matrix led to an expansion of the free volume within the resultant mixed matrix membrane (MMM), giving rise to a substantially enhanced CO2 permeability of up to 1264.6 barrer, which is 102% higher than that of the pristine polymer. Moreover, these MXene-incorporated MMMs exhibited preferential sorption for CO2 over light gases, which contributed to an exceptional CO2/N2 and CO2/H2 selectivity (64.3 and 19.2, respectively) even at a small loading of only 1 wt %, allowing the overall performance to not only surpass the latest upper bounds but also exceed many previously reported high-performance nanosheet-based nanocomposite membranes. Long-term performance tests have also demonstrated the good stability of these membranes. This composite membrane design strategy reveals the remarkable potential of combining a blend copolymer matrix with ultrathin MXene nanosheets to achieve superior gas separation performance for environmentally important gas separations.

Panel flutter analysis of nano-hybrid laminated composite quadrilateral plates presuming curvilinear fibers

In the present article, the panel flutter behavior of nanocomposite hybrid laminated quadrilateral panel is studied. A three-phase carbon-nanotube (CNT)/polymer/fiber laminated composite is considered where the probable agglomeration of the CNT phase in the nano-matrix mixture is also addressed. Diverse use of fiber phase material in different plies is assumed in the context of hybrid laminated composite. A combination of nanocomposite polymer matrix, tow-steered curvilinear reinforcing fibers within the plies, and hybrid multi-material laminate is considered. The panel flutter behavior of the arbitrary quadrilateral hybrid laminated nanocomposite plate is formulated by a non-uniform rational B-splines-type isogeometric analysis method based on the first-order shear deformation plate theory. The nonideal mixture of the nanocomposite is also concerned about through applying a micromechanics approach. Representative results are obtained and compared with those available in the literature to demonstrate the quality of the proposed formulation. The effects of different parameters including the layup, mixture quality, boundary condition, geometry, and flow direction on the flutter behavior are investigated by performing parametric studies.

Triblock Superabsorbent Polymer Nanocomposites with Enhanced Water Retention Capacities and Rheological Characteristics.

Superabsorbent polymers (SAPs) are useful polymers in a wide range of application fields ranging from the hygiene industry to construction and agriculture. As versatility and high water absorption capacity are their important merits, SAPs usually suffer from low water retention capacity (fast release) and weak mechanical properties. To address these drawbacks, a set of new superabsorbent polymer–Halloysite nanotube (HNT) nanocomposites was synthesized via free radical polymerization of acrylamide, 2-acrylamido-2-methylpropane-1-sulfonic acid, and acrylic acid in the presence of vinyltrimethoxysilane (VTMS) as the crosslinker. FTIR and TGA characterizations confirm the polymerization of SAP and successful incorporation of HNTs into the SAP polymer matrix. The effect of the HNT nanofiller amount in the nanocomposite polymer matrix was investigated with swelling–release performance tests, crosslink density calculations, and rheology measurements. It was found that equilibrium swelling ratios are correlated and therefore can be tuned via the crosslink densities of nanocomposites, while water retention capacities are governed by storage moduli. A maximum swelling of 537 g/g was observed when 5 wt % HNT was incorporated, in which the crosslink density is the lowest. Among the SAP nanocomposites prepared, the highest storage modulus was observed when 1 wt % of nanofiller was incorporated, which coincides with the nanocomposite with the longest water retention. The water release duration of SAPs was prolonged up to 27 days with 1% HNT addition in parallel with the achieved maximum storage modulus. Finally, three different incorporation mechanisms of the HNT nanofiller into the SAP nanocomposite structure were proposed and confirmed with rheology measurements. This study provides a rapid synthesis method for SAP nanocomposites with enhanced water retention capacities and explains the relationship between swelling and crosslink density and water retention and mechanical properties of SAP nanocomposites.

Перколяционная модель формирования высокомодульных нанокомпозитов полимер/углеродные нанотрубки

Production of the high-modulus nanocomposites polymer/carbon nanotubes and polymer/graphene at present is actual task and its solution is obviously important for such innovational industry sectors as air-, automobile industry, astronautics a.a. The general theoretical criterions of production of the indicated nanomaterials studied within the frameworks of percolative models of polymer nanocomposites reinforcement. These models assumed, that reinforcement degree or relative modulus of elasticity of polymer nanocomposites is defined by nanofiller structure in polymer matrix of nanocomposites. The structure of nanofiller (more exactly, its aggregates) can be characterized by fractal dimension of these aggregates. A various variants of percolative model of polymer nanocomposites reinforcement allow to taken into account such important for this class of nanomaterials parameters as the level of interfacial adhesion, relative content of interfacial regions (which are in the case of polymer nanocomposites the same reinforcing element of their structure as and actually nanofiller), aggregation degree of nanofiller a.a. Such approach allows to obtain functional interrelation between these characteristics and define conditions, which are necessary of production of high-modulus polymer nanocomposites. It was been found that for this goal achievement is necessary performance of the following conditions: realization of negative values of percolative index. Mathematically this condition is realized in the case, when aggregation degree is smaller, than volume content of nanofiller. Further, the usage of volume content of nanofiller larger than its percolation threshold and achievement of nanoadhesion effect are two following conditions. In the case of the indicated conditions performance percolative model predicts the possibility of production of polymer nanocomposites of the considered classes, which have mechanical characteristics, compared by its value with similar parameters for steel, but essentially smaller by weight.

SIMULATION OF REINFORCEMENT DEGREE OF NANOCOMPOSITES ELASTOMER/2D-NANOFILLER

Three schemes of modeling of reinforcement degree of nanocomposites polymer/2D-nanofiller with elastomeric matrix were proposed, differing principally from used ones earlier. These schemes do not used nominal characteristics of nanofiller (its modulus of elasticity, anisotropy degree), yet allow to obtain real (effective) values of these parameters. It has been shown, that modulus of elasticity of 2D-nanofiller aggregates in polymer matrix of nanocomposite is a function of stiffness of the indicated matrix. The other analogous model assumes the dependence of modulus of elasticity of 2D-nanofiller on its aggregation degree in polymer matrix, expressed by number of nanofiller separate platelets per one aggregate (“packet” or tactoid). The combination of these approaches allows to predict the real degree of nanofiller anisotropy and then reinforcement degree of nanocomposite. One more scheme uses the structure of nanofiller aggregates, characterized by its fractal dimension, for modeling of reinforcement degree of nanocomposites. The obtained real modulus of elasticity of 2D-nanofiller is in 5 orders of value smaller relatively to its nominal magnitude. The application of real (effective) characteristics of nanofiller allows to simulate reinforcement degree of nanocomposite within the framework of simple mixtures rule. Nanocomposites elastomer/2D-nanofiller are enough conservative systems, for which real anisotropy degree and structure of nanofiller aggregates do not depend on its content. This circumstance simplifies perceptibly prediction of mechanical properties of these nanocomposites.

Influence of nanoparticle weight fraction on morphology and thermal properties of HDPE/SiO2 composite films

High-density polyethylene (HDPE) composite films with di erent amounts of SiO 2 nanoparticles ( 1 - 20 % vol.) were prepared by melt blending using a high-pressure thermal pressing technique. The morphological characterization, surface topology and distribution of nanoparticles in polymer matrix of nanocomposites were investigated by using Scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal characterization of the nanocomposites were investigated by di erential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). SEM and AFM results revealed that silica nanoparticles aggregates were distributed mainly homogeneously. The nano-fillers change supramolecular structure and surface morphology of HDPE strongly. DSC results showed addition of nano-SiO 2 particles slightly decrease the melting temperature by 3-4 degree but strongly decrease the crystallization temperature by 7-8 degree. And crystallinity degree of the HDPE decrease. The thermal stability of the composite films was measured using Thermo Gravimetric analysis (TGA). Polymer nanocomposite showed higher thermal stability as compared with pure HDPE. Composites with 20% vol. of nano-SiO 2 have maximum thermal degradation temperature of 498.4 ◦ C.

Structure and magnetic properties of PP+Fe3O4 nanocomposites depending on manufacturing techniques

The structures and magnetic properties of the PP[Formula: see text]+[Formula: see text]Fe3O4 nanocomposites manufactured by different technological techniques were studied in this work. Polymeric nanocomposite materials based on PP[Formula: see text]+[Formula: see text]Fe3O4 were obtained by two technological methods: hot pressing and extrusion. Scanning electron microscopy (SEM) and AFM investigations of nanocomposites were carried out for structure analysis. It was found that the distribution of Fe3O4 nanoparticles in the polymer matrix for nanocomposites obtained by the hot pressing method is uniform and monodisperse. Compared to this, the heterogeneous and inhomogeneous distribution of nanoparticles in the polymer matrix for the samples that were produced through extrusion method was observed. Furthermore, the nanocomposite samples produced via the extraction method have a lower surface regularity rather than those obtained by hot pressing. M(H) and M(T) studies of polymer nanocomposite samples synthesized through both technological methods were performed. Studies have shown that for relatively low concentrated samples — PP[Formula: see text]+[Formula: see text]10% Fe3O4, the values of the saturation magnetization were close, but the magnetization of nanocomposites obtained by heat pressing was slightly higher than the other samples. This is because the samples obtained by hot pressing method are characterized by higher uniformity and structure that is called “flat packaging”.

STRUCTURAL MODEL OF EFFICIENCY OF COVALENT FUNCTIONALIZATION OF CARBON NANOTUBES

Functionalization of carbon nanotubes (covalent and noncovalent ones) is effective and often applied method of enhancement of their interaction with polymer matrix of nanocomposites. In present work the treatment is proposed, for the first time allowing quantitative estimation of efficiency (quality) of this nanofiller functionalization. For this purpose proposed earlier generalized model was used, taking into consideration characteristics of matrix polymer and nanofiller and also type of the last. Application of the indicated model allows to obtain quantitative characteristic of functionalization efficiency and also elucidation of interconnection of the indicated efficiency with structure of carbon nanotubes in polymer matrix of nanocomposite, namely, with radius of their annular structures. It has been found that the same method of functionalization from the chemical point of view can be changed its efficiency in 20 times that is dependent upon structure (radius) of annular formations of carbon nanotubes. Their specific surface is the more precise characteristic of these formations. This surface serves as indicator of intensity of contact of polymer matrix and surface of nanotubes, which in the end forms mechanical and other properties of the considered nanocomposites. The equation has been obtained, showing the dependence of functionalization efficiency on two parameters: effective specific surface and content of carbon nanotubes. The sharp discrete reduction of functionalization occurs at reaching of percolation threshold of nanofiller. This means that functionalization of local structures of carbon nanotubes is more effective than functionalization of uninterrupted structures of this nanofiller. The most important mechanical property of polymer nanocomposites, namely, the reinforcement degree, is defined unequivocally by efficiency of functionalization. This approach allows making structural prediction of mechanical properties of nanocomposites polymer/carbon nanotube depending of efficiency of nanofiller functionalization.

Evaluation of the structural state of carbon nanotubes in the polymer matrix of nanocomposites

By virtue of high degree of anisotropy and small transverse stiffness, carbon nanotubes are known to form ring-shaped annular structures (fractal objects) in the polymer matrix of nanocomposites. We used the fractal dimension for quantitative and physically strict characterization of the nanofiller structure (carbon nanotubes) in the polymer matrix of nanocomposites. Two methods of calculation based on the models of irreversible aggregation and fractal analysis are proposed. The results obtained using both approaches match each other within 6%. It has been shown that formation of the annular structures occurs according to the cluster-cluster mechanism (i.e., by combining small formations into larger ones, rather than individual nanotubes). Moreover, the method of fractal analysis takes into account the effect of the polymer matrix on the structure of ring-shaped formations and, hence, on the properties of polymer nanocomposites. The correctness of the methods thus used was proved using the percolation model, which showed good agreement between the theory and experiment when using fractal dimensions determined by both methods. This means that for a fixed nanofiller content, the properties of nanocomposites are determined only by the nanofiller structure. In other words, a significant change in the properties (for the degree of reinforcement more than by an order of magnitude) is possible even at a low content of a nanofiller, which is realized only through change in the nanofiller structure using various methods of nanofiller treatment (ultrasound, functionalization, construction of special types of nanofiller frame, etc.).

The structure of graphene oxide in polymer matrix and its effect on reinforcement degree of nanocomposite

The methodics of characterization of 2D-nanofiller tactoids structure in polymer matrix of nanocomposite was proposed, which shown that the indicated tactoids are fractal objects with dimension of 1.75-2.16. This variation of tactoids structural state is due to interfacial interactions. It has been shown within the framework of reinforcement percolation theory, that structure of tactoids is single factor, defining reinforcement efficiency is characterized by its ability to create interfacial regions.

The Role of Nanoparticle Network in 2D Nanofiller-Reinforced Polymer Nanocomposites

The paper presents the fractal analysis which shows that the distribution or dispersion of 2D nanofiller (graphene oxide) particles in the polymer matrix of nanocomposite determines the critical index in the percolation model of nanocomposite reinforcement. The structure of the particle network or tactoidal aggregates of 2D nanofiller is connected with the finite structure of nanocomposite as a whole and also with the interface effects occurred. Correctness of proposed approach shows good agreement between theoretical calculations and experimental data.

Delocalization of π electrons and trapping action of ZnO nanoparticles in PPY matrix for hybrid solar cell application

Polypyrrole (PPY)-Zinc Oxide (ZnO) nanocomposites with varying concentration of ZnO (1:1–1:4) were prepared via in-situ polymerization technique by using pyrrole monomer in the presence of ammonium persulphate (APS) as oxidant. Globular morphology of PPY and sheet like structure of ZnO was examined using FESEM and EDAX. FTIR showed the presence of vibration modes in fingerprint region (1500 cm−1–500 cm−1) for metal oxides confirming the presence and interaction of ZnO with the polymer matrix in nanocomposites. Amorphous nature of PPY and hexagonal wurtzite structure of ZnO was confirmed using XRD with average crystallite size within 20 nm–30 nm. PANI-ZnO (1:1) exhibited blue shift in comparison to PPY (neat) and optimized optical band gap ∼ 1.81 eV. The effect of carrier concentration was investigated using electrochemical analyzer and maximum current was recorded for PANI-ZnO (1:1). The highest conductance was calculated for PANI-ZnO (1:1) ∼ 7.3242 × 10−3 S using current –voltage characteristics. Thermal stability was found to be increasing with the increase in ZnO concentration PANI-ZnO nanocomposite.

Polymeric Composites Based on Polyurea Matrix Reinforced with Carbon Nanotubes

This paper deals with the synthesis of polyurea and its use as polymer matrix for nanocomposites reinforced with multi-walled carbon nanotubes (MWCNT). Two types of materials were obtained during this research, the first cathegory uses the polyurea as matrix and the second one uses a mixture between epoxy resin and polyurea. The nanocomposites were characterized by Thermogravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMA), Scanning Electron Microscopy (SEM) and Tensile Tests .The elastomeric features of nanocomposites were highlighted by the results which showed low value of Tg. Also higher thermal stability with ~40oC compared with commercial products (M20) were observed, but lower mechanical properties compared to neat polyurea.

Effect of processing conditions on the thermal and electrical conductivity of poly (butylene terephthalate) nanocomposites prepared via ring-opening polymerization

Successful preparation of polymer nanocomposites, exploiting graphene-related materials, via melt mixing technology requires precise design, optimization and control of processing. In the present work, the effect of different processing parameters during the preparation of poly (butylene terephthalate) nanocomposites, through ring-opening polymerization of cyclic butylene terephthalate in presence of graphite nanoplatelets (GNP), was thoroughly addressed. Processing temperature (240°C or 260°C), extrusion time (5 or 10min) and shear rate (50 or 100rpm) were varied by means of a full factorial design of experiment approach, leading to the preparation of polybutylene terephthalate/GNP nanocomposite in 8 different processing conditions. Morphology and quality of GNP were investigated by means of electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry and Raman spectroscopy. Molecular weight of the polymer matrix in nanocomposites and nanoflake dispersion were experimentally determined as a function of the different processing conditions. The effect of transformation parameters on electrical and thermal properties was studied by means of electrical and thermal conductivity measurement. Heat and charge transport performance evidenced a clear correlation with the dispersion and fragmentation of the GNP nanoflakes; in particular, gentle processing conditions (low shear rate, short mixing time) turned out to be the most favourable condition to obtain high conductivity values.

Silver nanoparticles decorated lipase-sensitive polyurethane micelles for on-demand release of silver nanoparticles

In order to improve the antibacterial activities while decrease the cytotoxity of silver nanoparticles, we prepared a novel nanocomposites composed of silver nanoparticles decorated lipase-sensitive polyurethane micelles (PUM-Ag) with MPEG brush on the surface. The nanocomposite was characterized by UV–vis, TEM and DLS. UV–vis and TEM demonstrated the formation of silver nanoparticles on PU micelles and the nanoassembly remained intact without the presence of lipase. The silver nanoparticles were protected by the polymer matrix and PEG brush which show good cytocompatibility to HUVEC cells and low hemolysis. Moreover, at the presence of lipase, the polymer matrix of nanocomposites is subject to degradation and the small silver nanoparticles were released as is shown by DLS and TEM. The MIC and MBC studies showed an enhanced toxicity of the nanocomposites to both gram negative and gram positive bacteria, i.e. E. coli and S. aureus, as the result of the degradation of polymer matrix by bacterial lipase. Therefore, the nanocomposites are biocompatible to mammalian cells cells which can also lead to activated smaller silver nanoparticles release at the presence of bacteria and subsequently enhanced inhibition of bacteria growth. The satisfactory selectivity for bacteria compared to HUVEC and RBCs make PUM-Ag a promising antibacterial nanomedicine in biomedical field.

Considering Viscoelastic Micromechanics for the Reinforcement of Graphene Polymer Nanocomposites.

There has been much recent work investigating the reinforcement of glassy polymers with nanoparticles, and much excitement has been generated by some apparent synergies that suggest reinforcements greater than expected from elastic bound models. Here we show that it is necessary to consider the thermoviscoelastic response of the polymer matrix in nanocomposites (PNCs) to fully understand the reinforcement of the filler. This is especially so because polymer nanocomposites are frequently used at high fractions of the glass transition temperature Tg, where the time dependence of the polymer is significant. Therefore it is a conceptual error to examine the modulus behavior of PNCs via only elastic micromechanics. When the glass transition temperature increases due to the interactions between reinforcement and polymer, it is more reasonable to use a viscoelastic micromechanics approach to estimate the bounds on modulus behavior of PNCs. Here we use new results for grapheme oxide reinforced poly(ethyl methacrylate) (PEMA) and literature results for reinforced poly(methyl methacrylate) (PMMA) and show that the ultralow loading of graphene oxide raises the Tg of PEMA and PMMA significantly and leads to a large shift of the frequency-temperature properties of the polymer matrix. Our thermoviscoelastic approach shows that apparent extreme reinforcements can be attributed to the changing Tg of the polymer, and the corrected mechanical reinforcement from graphene oxide is much weaker than previously reported.

Shear-Induced Orientation in Well-Exfoliated Polystyrene/Clay Nanocomposites

We report measurements of shear-induced particle orientation in highly exfoliated polystyrene/clay nanocomposites. Samples were prepared using an in situ polymerization technique, in which native clay is organically modified with a cationic surfactant that incoporporates a polymerizable vinylbenzyl moiety. Controlled radical polymerization was used during the synthesis to limit the molecular weight and polydispersity of the nanocomposite polymer matrix. Flow-induced orientation was measured in the flow-gradient plane of shear flow using synchrotron-based small-angle X-ray scattering. Despite the small rotational diffusivity expected for the clay particles, significant particle orientation was only observed at relatively high rates in steady shear or at high frequencies in large-amplitude oscillatory shear. Measurements of orientation upon flow cessation provided direct evidence of a structural relaxation process that was orders of magnitude faster than estimates of rotational Brownian motion. It is suggested that this fast relaxation arises from either relaxation of shear-induced distortion of partially flexible exfoliated clay sheets in a highly entangled nanoparticle network or coupling of particle and polymer dynamics.

Clay‐induced Preferred Orientation in Polyethylene/Compatibilized Clay Nanocomposites

Nanocomposites of the organically modified clay Cloisite® 15A (CL15A) dispersed in HDPE‐g‐MA were prepared by melt‐compounding. Microcomposites of the same clay with HDPE were also obtained with similar procedures. The spherulitic morphology of the polymer matrix was evidenced by optical microscopy in thin films, whereas the structure of the up to 2‐mm–thick, compression‐molded samples was investigated by WAXD and SAXS. Preferred orientation of both the clay and the HDPE crystallites were evidenced in the microcomposites and, to a greater extent, in nanocomposites, whereas in HDPE and HDPE‐g‐MA control specimens hardly any anisotropy was detected. The degree of orientation of PE crystals increases with CL15A concentration, but also with clay exfoliation, with lower cooling rates and decreasing sample thickness. The orientation of the clay platelets parallel to the compression‐molded surface appears to be determined by the platelets anisotropy and by shear in the mixing and the compression‐molding procedures. In turn, it determines the preferred uniaxial orientation of HDPE crystals, which have their crystallographic a axis orthogonal, while b and c are coplanar, to the sample surface, as already reported in the literature for melt‐crystallized HDPE films with thickness below 0.3 μm. It is proposed that the HDPE orientation results from confined crystallization between parallel clay platelets which are on average less than 0.1 μm apart. Simple models, qualitatively accounting for the observed orientation of HDPE, are discussed. Organized architectures resulting from confined crystallization of the polymer matrix in nanocomposites with appropriate anisotropic fillers may be a general feature, important in determining key properties of these systems.

On the fate of carbon nanotubes: Morphological characterisations

Single-walled and multi-walled carbon nanotubes (SWNTs and MWNTs) were characterised as-produced, after exfoliation and purification, and imbedded in the polymer matrix of nanocomposites by using various microscopic techniques. Transmission electron microscopy (TEM) shows thickness distribution as well as catalyst presence of as-produced carbon nanotubes (CNTs); scanning electron microscopy (SEM) and atomic force microscopy (AFM) are helpful tools to better understand the influence of post-treatment during exfoliation and purification, e.g. on the length distribution of CNTs; and finally SEM operated in charge contrast mode offers the potential to monitor the organisation of CNT networks in the polymer matrix of conductive nanocomposites.