A facile and easily industrialized approach for preparing highly dispersed MMT/polymer nanocomposites is developed by combining the latex compounding method and a spray‐drying process. Clay particles are successfully delaminated into layers, and layer re‐stacking is effectively prevented. HR‐TEM and XRD results confirm that MMT layers achieve exfoliated or nearly exfoliated dispersion in both MMT/styrene‐butadiene rubber and MMT/PS nanocomposites. Compared with melt‐blended MMT/SBR composites, MMT/SBR nanocomposites prepared by this new strategy exhibit extremely high dynamic modulus.
A “green” processing method, dual‐melt extrusion, was used to prepare thermoplastic starch/montmorillonite nanocomposites without organic reactions in the solution. XRD demonstrates that sorbitol enlarged the interlayer distance of MMT during the first step. MMT‐sorbitol, formamide and starch were used to obtain TPS/MMT nanocomposites in the second step. XRD and TEM reveal that TPS intercalated the layers of MMT. With increasing MMT content, improvements in thermal stability, tensile strength, Young's modulus and energy break, and a slight decrease of elongation at break, appeared. The effect of water content on the tensile strength and elongation at break was also studied.
Two novel cationic RAFT agents, PCDBAB and DCTBAB, were anchored onto MMT clay to yield RAFT‐MMT clays. The RAFT‐MMT clays were then dispersed in styrene where thermal self‐initiation polymerization of styrene to give rise to exfoliated PS/clay nanocomposites occurred. The RAFT agents anchored onto the clay layers successfully controlled the polymerization process resulting in controlled molecular masses and narrow polydispersity indices. The nanocomposites prepared showed enhanced thermal stability, which was a function of the clay loading, clay morphology, and slightly on molecular mass.
A diacrylate polysulfone oligomer is synthesized and used as the acrylic oligomer for the in situ synthesis of noble metal/PSU nanocomposites through UV‐induced simultaneous radical polymerization of acrylic functionalities and NP formation by reduction of their precursors. Thus, silver or gold NPs are formed in situ during polymer network formation. FESEM analysis of the morphology of the cured systems demonstrates that the nanoparticles of the noble metals are homogeneously distributed in the network without macroscopic agglomeration.
PA6 nanocomposite films with different nanoclay dispersion degrees are prepared by melt compounding and cast extrusion. The dispersion of the MMT platelets (homogeneity and degree of exfoliation) is evaluated qualitatively by TEM and quantitatively by rheology and NMR; it ranges from microcomposites to highly exfoliated nanocomposites. Compared to neat PA6, the optical properties (clarity, gloss, haze) are worse for the microcomposites and better for the nanocomposites. The mechanical properties depend strongly on the exfoliation level. Better exfoliation leads to higher stiffness. The strain at break decreases compared to neat PA6 films even in the case of highly exfoliated nanocomposites films. At low MMT content, the microcomposite has a higher ductility than well exfoliated nanocomposites films.
Fully exfoliated PS/clay nanocomposites were prepared via FRP in dispersion. Na‐MMT clay was pre‐modified using MPTMS before being used in a dispersion polymerization process. The objective of this study was to determine the impact of the clay concentrations on the monomer conversion, the polymer molecular weight, and the morphology and thermal stability of the nanocomposites prepared via dispersion polymerization. DLS and SEM revealed that the particle size decreased and became more uniformly distributed with increasing clay loading. XRD and TEM revealed that nanocomposites at low clay loading yielded exfoliated structures, while intercalated structures were obtained at higher clay loading.
To understand the effect of the percolated clay network structure formed by the exfoliated clay layers in nanocomposites, the clay network structure in nylon‐6‐based nanocomposites is characterized using TEM and FFT analyses. A MMT volume fraction between 0.013 and 0.014 is the percolation threshold for strong network formation. The volume spanning MMT network leads to a very high flow activation energy as compared with that of neat nylon 6, resulting in the pseudo‐solid like response under molten state in N6CNs. A canonical NVT‐MD simulation was conducted in the system made up by nylon 6 molecules/Si(OH)4 molecules. The formation of the strong interfacial interaction between nylon 6 molecules and Si(OH)4 molecules induced by OH groups is suggested.
A high degree of exfoliation of MMT in NR is achieved by using the so‐called “propping‐open approach” in which a stepwise expansion of the interlayer spacing of MMT takes place. The nanostructure is characterized by WAXD and TEM which indicate different extents of clay dispersion depending on the fatty‐acid chain length. Curing kinetics of different nanocomposites is studied and interestingly low activation energies of the vulcanization process are observed in the case of NR/EMMT nanocomposites. The incorporation of EMMT dramatically affects composite properties whereas DMA indicates significant reduction of tan δ peak height and the tensile strength approximately doubles from 14 to 30 MPa with only 5 phr EMMT.
Novel fluoroalkyl end‐capped oligomer/hydroxyapatite nanocomposites have been easily prepared by the reaction of disodium hydrogenphosphate and calcium chloride in the presence of self‐assembled molecular aggregates formed by fluoroalkyl end‐capped oligomers in aqueous media. The fluorinated hydroxyapatite nanocomposites thus obtained were found to exhibit a good dispersibility in a variety of media, and were applied to the surface modification of glass.
PA nanocomposites are prepared from clays organophilized with a phosphonium and an ammonium salt, and sodium montmorillonite is used as reference. The analysis of mechanical and micromechanical properties of the composites reveal that several micromechanical deformation processes occur in the PA/MMT composites. The matrix cavitates at relatively small stress. Processes related to non‐exfoliated clay structural units are initiated at larger stresses. Sound is emitted mainly by the fracture of particles, but debonding may also occur. The plastic deformation of the matrix dominates at larger stresses and deformations. The various local deformations are independent of each other and composite properties are not determined by silicate related processes but by the deformation of the matrix.
PCL‐based nanoclay (layered silicate) nanocomposites are prepared using a small scale intermeshing co‐rotating twin‐screw extruder. Improving the level of nanoclay dispersion in PCL nanocomposites is obtained by changing the extrusion parameters. Increasing the screw speed and decreasing the throughput leads to an improved dispersion quality, as observed from the improved mechanical properties of the nanocomposites as well as from their clearly affected rheological and crystallization behavior. Furthermore, a commercially available software that simulates the twin‐screw extrusion process (LUDOVIC) is used to asses the processing parameters applied for making the nanocomposites.
Sunflower oil‐based HBTPU/Ag and LTPU/Ag nanocomposites have been prepared by in situ catalytic reduction of a silver salt. The virgin polymer and their nanocomposites are soluble in various polar organic solvents and amenable for both solution‐casting and hot pressing. XRD, TEM, and UV spectroscopic analyses ascertained well‐dispersed, narrow‐sized Ag nanoparticles. Tensile testing, dynamic mechanical, thermogravimetric, and DSC analyses showed desirable mechanical and thermal features with improvement upon incorporation of Ag nanoparticles and the presence of a hyperbranched component in the nanocomposites. RSM has been used to evaluate the catalytic efficacy of the nanocomposites.
A two‐level factorial experimental design was used to examine the combined effects of o‐MMT gallery polarity, surface modification of MDH, MA‐g‐PP and antioxidant addition, together with processing variables, on the burning behaviour and thermal stability of ternary composites based on PP, MDH and o‐MMT. Regression equations highlighted the detrimental effect of o‐MMT intercalants and possible improvement in the dispersion of o‐MMT at higher MDH levels. A polar gallery environment (providing quat OH groups) led to increased char formation, and MA‐g‐PP combined with o‐MMT led to a higher oxidation onset temperature. Addition of o‐MMT to PP/MDH composites can lead to a reduction in the level of MDH required for effective flame retardation.
Organoclay–polyolefin nanocomposites have been shown to exhibit slightly increased thermal stability and decreased flammability, compared to unfilled polyolefins. In contrast, we find that when the clay has not been organically modified, the resulting polyolefin nanocomposites are less thermally stable and, unexpectedly, also much less flammable. In this contribution, we investigate the mechanistic origins of these effects. Clay–polyolefin nanocomposites were prepared by in situ polymerization of ethylene or propylene, using a catalyst adsorbed onto the clay. Decreased thermal stability is attributed to clay‐catalyzed polymer decomposition, while decreased flammability arises in part from clay‐catalyzed formation of a polyaromatic char from olefins trapped in the material by the dispersed nanofiller.
The influence of the functionalization of fully condensed POSS cages on the properties of POM‐based nanocomposites is studied. POSS with different organic substituents [glycidylethyl, aminopropylisobutyl, and poly(ethylene glycol)] are taken into account and melt mixed with POM. Good dispersion was achieved upon the addition of amino functionalized POSS, leading to an increase on the thermal decomposition temperature under nitrogen atmosphere up to 50 °C. However, µm‐size aggregates were observed for other nanocomposites. There is no significant change in other thermal properties of the nanocomposites. The relationships among these effects and the morphological characteristics of the systems were analyzed.
The intercalation of cationic copolymer into a smectic clay, montmorillonite, has been used to produce polymerically modified organoclays. The organoclays of different lamellar morphology and content of quaternary ammonium groups have been prepared by altering the clay/polymer ratio. The organoclays prepared have been explored in the design of antimicrobial materials based on clay/polymer nanotechnology. Polyamide nanocomposites containing organoclays with incorporated cationic polymer showed an antimicrobial activity and improved mechanical properties. The antimicrobial efficiency and the mechanical properties of the nanocomposites were controlled by the variation of the content of the cationic polymer incorporated into the organoclay and organoclay loading.
Isotactic PP nanocomposites filled with Fe@FeO nanoparticles are fabricated by a facile ex situ method. The nanofillers are dispersed in a boiling PP/xylene solution. X‐ray diffraction is used to determine the nanofiller effects on the crystallinity of PP. The crystallinity along the (040) plane is found to decrease with the incorporation of nanoparticles. Thermal properties and crystallinity are studied by TGA and DSC, respectively. Enhanced thermal stability and influenced crystallinity are observed in the PP nanocomposites compared with those of pure PP. An increased dielectric property without percolation threshold is observed. In addition, the nanocomposites are found to exhibit ferromagnetic properties.
A simple, easily accessible solvent‐free method for the dispersion of MWCNTs into PET is proposed, based on the preparation of a microparticulate polymer/nanotube masterbatch via cryogenic impact‐milling and its subsequent melt blending with the bulk polymer. Thermal and mechanical properties of nanocomposites prepared using this method were evaluated as a function of nanotube concentration. Thermal stability was improved, and superior crystallization behavior of PET in the nanocomposites was observed. Significant improvements of around 25% in tensile strength and tensile modulus of the nanocomposites was achieved using this strategy, with only 0.25 wt.‐% MWCNT, compared to previous literature data where 1 wt.‐% MWCNT was employed.
PET/PE blends are prepared with and without different types of organo‐modified montmorillonites (OMMT) using a extrusion process. The droplet size of PE dispersed phase decreases upon organoclays addition, however without any direct dependence on the organoclay initial surface tension. To assess the effect of the organomodifier without MMT, PET/PE blends are then compounded adding solely the surfactants (similar to those used to modify the various organoclays). Whatever the chemical nature of the surfactant, a refinement of the PE droplets is observed, interestingly similar to those previously observed in presence of clay. This shows unambiguously that the key factor for organoclay compatibilization efficiency, in the case of PET/PE blends, is the surfactant modifier itself and not the MMT platelets.
Nanocomposites of poly(ethylene terephthalate) and two different montmorillonite‐based organoclays were prepared by a co‐rotating twin screw extruder. Dispersion of nanoclays in the polymer matrix was examined by TEM and XRD. Nanocomposites with lower content of organoclay showed exfoliated morphology while by increasing the amount of organoclay the intercalated morphology was more prevalent. Both organoclays had a good intercalation with PET and were uniformly dispersed within the polymer. Oxygen permeability of thin films of nanocomposites showed that the nanocomposites had better oxygen barrier properties than the neat PET. Tensile and impact properties of the nanocomposites also were measured.
