Direct incorporation of inorganic nanoscale building blocks into polymers represents a typical way for preparing polymeric nanocomposites. The most important aspect in preparation of nanocomposites through dispersive blending is surface modification of the nanofillers. It is able to increase hydrophobicity of the fillers, enhance interfacial adhesion via chain entanglement or chemical bonding and eliminate the loosen structure of filler agglomerates. The present paper reviews the state of the art of nanoparticles/polymer composites, including the specific surface pretreatment techniques and their applications. Especially, the role of treated nanoparticles and the mechanisms involved in the improvement of mechanical properties and wear resistance of the composites are highlighted.

Polymer nanocomposites have formed an interesting field of materials research because considerable performance improvement can be achieved by the addition of trace amount of the nano-scale fillers. [1][2][3][4][5][6][7][8] Compared to the substantial experimental attempts, however, theoretical consideration of the mechanisms involved with adequate predictability is relatively less reported. Design and production of polymer nanocomposites have to be mostly conducted on a trial and error basis. Empirical extrapolation of the parameters related to components selection and processing technique is not very successful.Recently, Gersappe has made molecular dynamics simulations and suggested that the mobility of the nanofillers in a polymer controls their ability to dissipate energy, which would increase toughness of the polymer nanocomposites in the case of proper thermodynamic state of the matrix.[9] By examining elongation to break and area under stress-strain curve of treated nanoclay filled poly(vinylidene fluoride) (PVDF) composites, Giannelis and his co-workers evidenced the above hypothesis.[10] They showed that the incorporation of the nanoclay brought about significant toughening effect when the tensile test was carried out above the glass transition temperature (T g ) of the matrix polymer, whereas embrittlement was detected at a temperature below the matrix' T g . It was believed that mobility of the polymer matrix is a precondition for this mechanism, which dictates the mobility of the nanoparticles. However, verification with the literature data reveals that for the polymer composites consisting of nanoparticles without layered structure, toughness increase is not bound to be perceived even if the matrix possesses higher mobility. The room temperature ductility of natural rubber reinforced by nano-Fe, nano-Ni, nano-SiC particles and singlewalled carbon nanotubes (SWNT), for example, is lower than that of the matrix. [11,12] In this work we prepared nano-silica/ thermoplastics composites. The results demonstrate that the concept of nanoparticles mobility is still valid for toughening non-layered nanoparticles/polymer composites if both reduced interparticulates interaction and enhanced nano-filler/ matrix interaction are guaranteed besides sufficient mobility of the polymer matrix. These guidelines are applicable to formulation of technical route for manufacturing nanoparticles/ polymer composites with increased toughness, or for increasing the degree of improvement in toughness of the nanocomposites. Silica nanoparticles, either untreated or grafted by poly(dodecafluoroheptyl acrylate) (PDFHA, percent grafting = 13.3 %, number average molecular weight = 1.5 × 10 4 ), were melt compounded with crystalline isotactic polypropylene (PP) and amorphous polystyrene (PS) at a constant particle concentration of 1.36 vol %, respectively. Differential scanning calorimetry study and dynamic mechanical analysis indicate that crystallinity of PP nanocomposites and T g 's of both PP and PS nanocomposites remain nearly unc...

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Abstract. By mixing macromolecular blowing agent grafted nano-SiO2 with polypropylene (PP) melt, the nanoparticle agglomerates can be pulled apart due to the in-situ bubble-stretching resulting from gasification of the side foaming groups on the grafted polymer. The present work evaluated the interfacial effect in the PP based nanocomposites prepared using the aforesaid technique through introducing rubbery components to the backbone of the grafted polymer chains. The results indicated that deagglomeration of the nanoparticles was not bound to yield the highest properties of the composites. The positive effect of the nanoparticles was brought into full play because of the joint contributions of particles dispersion status and interfacial interaction. An interlayer with proper flexibility ensured an overall enhancement of mechanical properties, especially impact strength, of the nanocomposites. : nanomaterials, processing technologies, nanoparticles, nanocomposites, interfacial effect eXPRESS Polymer Letters Vol.1, No.1 (2007) [2][3][4][5][6][7] Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2007.2 defoaming of the compounds was not necessary prior to injection molding. It implies that this technique could lead to deagglomeration of the nanoparticles when nanocomposites are being manufactured, without side effect that might deteriorate performance. For polymer-based nanocomposites, an appropriate surface treatment of inorganic nanoparticles should not only improve dispersion of the fillers, but also bring about notable influence on the interfacial characteristics, and subsequently enhance the mechanical properties of the ultimate composites [6]. Considering that graft treatment of nanoparticles leads to specific interfacial structures that can be tailored by changing graft monomers and graft conditions [7], the authors of the present work planned to introduce polymer chain units with relatively higher molecular mobility (i.e., poly(butyl acrylate)) into the aforesaid grafted polymeric foaming agent poly(p-vinylphenylsulfonylhydrazide) through copolymerization. It is hoped that the stiffness of the interlayer in the nanocomposites originally constructed by the grafted poly(p-vinylphenylsulfonylhydrazide) containing rigid phenyl groups can be somewhat balanced. In accordance with this idea, poly(p-vinylphenylsulfonylhydrazide-co-butyl acrylate) grafted nanosilica was synthesized. Afterwards, the treated nanoparticles were melt compounded with PP. With the help of in-situ bubble-stretching effect and the flexible interphase, agglomerated silica nanoparticles should be disconnected from each other and adhered to the matrix polymer via the grafted copolymer chains (Figure 1). In this paper, the feasibility of this technical route was analyzed by characterizing the grafted nano-silica and their influence on the structure and properties of PP based composites. Keywords Experimental MaterialsSilica (Aerosil 200) was supplied by Degussa Co., Germany with an average diameter of 12 nm and ...

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