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 ...

Abstract. To provide ethylene-propylene random copolymer (PPR) with balanced mechanical properties, !-nucleating agent and CaCO 3 nanoparticles are incorporated into PPR matrix by melt blending. It is found that crystallization rate and relative content of !-crystal increase with the addition of !-nucleating agent together with nanoparticles. Size of PPR spherulite is greatly reduced, and a specific morphology appears, in which #-crystal lamella is grown upon the !-nucleus. The results suggest that both !-nucleating agent and nano-CaCO 3 have heterogeneous nucleation and synergistic effects on !-nucleation of PPR. Mechanical characterization shows that mechanical properties of PPR can be tuned by incorporation of !-nucleating agent and nano-CaCO 3 particles. Under suitable compositions, low temperature impact strength and high temperature creep resistance of PPR, the bottlenecks of application of such material, can be simultaneously improved without sacrificing the Youngs'modulus and tensile strength.