Recently, polymer nanocomposites reinforced with lower volume fraction of nanoceramics and carbon nanotubes have attracted steadily growing interest due to their peculiar and fascinating properties as well as their unique applications in commercial sectors. The incorporation of nanoceramics such as layered silicate clays, calcium carbonate or silica nanoparticles arranged on the nanometer scale with a high aspect ratio and/or an extremely large surface area into polymers improves their mechanical performances significantly. The properties of nanocomposites depend greatly on the chemistry of polymer matrices, nature of nanofillers, and the way in which they are prepared. The uniform dispersion of nanofillers in the polymer matrices is a general prerequisite for achieving desired mechanical and physical characteristics. In this review article, current development on the processing, structure, and mechanical properties of polymer nanocomposites reinforced with respective layered silicates, ceramic nanoparticles and carbon nanotubes will be addressed. Particular attention is paid on the structure–property relationship of such novel high-performance polymer nanocomposites.

Structural and mechanical properties of polymer nanocomposites

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Structuration, selective dispersion and compatibilizing effect of (nano)fillers in polymer blends

The structure and physical properties of polypropylene and thermoplastic olefin nanocomposites containing nanosilica

This review provides a rationale for polymer nanocomposites, emphasizing layered (smectic) silicate reinforcements, particularly montmorillonite clay with various surfactant treatments. Considerable attention is given to processing techniques for synthesizing such nanocomposites via compounding in the melt. While briefly covering structural characterization, it focuses on physico‐mechanical properties, using examples of nylon as a polar polymer matrix and polypropylene, the continuous phase in a thermoplastic vulcanizate (TPV), as a non‐polar polymer matrix. Both polar and non‐polar rubber components are considered for the TPV. Thus, the thermodynamic compatibility between a surfactant‐treated clay and the polymer matrix as well as the partitioning of the clay reinforcement in a two‐phase heterogeneous polymer blend are addressed. Finally, functional performance is reviewed, with an emphasis on automotive applications.

Layered Silicate Reinforced Polymer Nanocomposites: Development and Applications

Thermoplastic vulcanized (TPV) nanocomposites were prepared in a laboratory mixer using EPDM, polypropylene of different viscosities, maleic anhydride modified polypropylene, an organo-clay, and a sulfur-based curing system. Based on the obtained results from X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimeter, and mechanical properties, the microstructure of the prepared nanocomposites was found to be sensitive to the viscosity difference between the two phases and the clay content. X-ray diffraction and TEM images of the TPV nanocomposites showed that clay was nearly exfoliated and randomly distributed into the polypropylene phase. The SEM photomicrographs of the dynamically vulcanized thermoplastic elastomer samples showed that the rubber particles were dispersed through the polypropylene in form of aggregates and their size increased with the introduction of clay. The nanoscale dimensions of the dispersed clay resulted in a significant improvement of the tensile modulus of the TPV nanocomposite samples, from 20 to 90% depending on clay content and the viscosity ratio of PP/EPDM. In the PP nanocomposites, the clay layers act as nucleating agents, resulting in higher crystallization temperature and reduced degree of crystallinity. Moreover, the oxygen permeability in the TPV nanocomposites was found to be lower than in unfilled but otherwise similar materials. POLYM. ENG. SCI., 47:207–217, 2007. © 2007 Society of Plastics Engineers.

Microstructure-properties correlations in dynamically vulcanized nanocomposite thermoplastic elastomers based on PP/EPDM

Nanocomposites comprising nanoscale platelets derived from layered silicates treated with an organic modifier in thermoplastic vulcanizates (TPV) and PP/EPDM blends were prepared by direct melt intercalation. The interlayer spacing and dispersion of the nanoclay are greatly affected by polar forces between the nanoclay and the polymeric matrix material. The mechanical properties strongly depend on the structure and morphology of the nanocomposites, which can be modified by phase partitioning of the reinforcements. Morphology characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM) provides the basis for understanding the observed structure-property relationships in this class of materials. With the increase of organoclay loading, the tensile modulus of TPV/clay nanocomposites increases by up to 170% at 8 wt% organoclay loading, while tensile strength gradually decreases with increase of organoclay loading. In the physical blend systems, the tensile modulus increases for all PP/EPDM blend compositions and generally shows higher values in the case of selectively reinforced phases in blends having a continuous PP matrix. The tensile strength of those blends decreases at higher nanoclay content no matter how blending is performed. However, the tensile strength may increase when sufficient selectively reinforced EPDM phase is present.

Structure‐property relationships in polymer blend nanocomposites

Nanocomposites with organically treated montmorillonite derived from layered silicates in various PP/EPDM blends were prepared by direct melt intercalation in an internal mixer. In these nanocomposites, the nanoclay reinforcement is constrained to lie selectively either in the continuous matrix or in the dispersed phase or both phases of a thermoplastic olefin. The morphology as well as mechanical properties of the nanocomposite blends are strongly affected by the selective reinforcement of each phase. Morphology characterization by x-ray diffraction (XRD) and transmission electron microscopy (TEM) provide the basis for understanding the observed structureproperty relationships in this class of materials.

Synthesis and properties of polymer blend nanocomposites. Part II. Thermoplastic olefins (TPO)

Wind turbine blades are prone to damage by airborne particulate matter; hence, periodic blade inspection is necessary for maintenance. However, quantitative data on wind turbine performance reduction due to erosion are lacking. Herein, erosion conditions were classified into four levels based on the erosion area in long-term operated wind turbine blades. Transient three-dimensional computational fluid dynamics analysis was performed by applying the suction side erosion shape to the tip airfoil of the National Renewable Energy Laboratory’s 5 MW blade. In the early stage, irregular erosion of the airfoil’s leading edge resulted in the development of a reverse pressure gradient inside the boundary layer and a larger recirculation area of the trailing edge. Thus, the lift coefficient of the airfoil decreased by up to 30%, whereas the drag coefficient increased by over 100%. The wind turbine output curve calculated using aeroelastic software showed that the worst erosion condition decreased output by 2.54%. Annual energy production had declined by up to 2% based on the annual average wind speed; therefore, immediately repairing erosion can minimize the loss of energy production. 

Analysis of variations in annual energy production based on types of suction side erosion at the blade tip of a wind turbine using numerical simulation

Keun Yong Lee

Papers

Structure‐property relationships in polymer blend nanocomposites

Synthesis and properties of polymer blend nanocomposites. Part II. Thermoplastic olefins (TPO)

Analysis of variations in annual energy production based on types of suction side erosion at the blade tip of a wind turbine using numerical simulation