Interfacial effects in polypropylene–silica nanocomposites

Abstract

Grafted inorganic nanoparticles can greatly improve the mechanical performance of polymers. To examine the effects of the interfacial characteristics generated by the grafting polymer bonded to nanoparticle surfaces, we chemically grafted nano-silica with different polymers and then melt-mixed it with polypropylene (PP). We extracted the homopolymers produced during the graft polymerization from the grafted products before the composites were manufactured to get rid of the side effects of the nongrafting polymers. We tailored the interfacial interaction between the grafted nano-SiO 2 and PP matrix by changing the amount of the grafting polymers on the nanoparticles, that is, the grafting percentage. Mechanical tests indicated that all the composites incorporated with grafted nano-SiO 2 particles possessed much higher impact strength than untreated SiO 2 /PP composites and neat PP. The greatest contribution of the particles was made at a low grafting percentage. Tensile measurements showed that the treated nanoparticles could provide PP with stiffening, strengthening, and toughening effects at a rather low filler content (typically 0.8 vol %) because of the enhanced interfacial adhesion resulting from molecular entanglement and interdiffusion between the grating polymers on the nanoparticles and matrix macromolecules. The presence of grafting polymers on the nanoparticles provided the composites with a tailorable interphase. The tensile performance of the composites was sensitive to the nature of the grafting polymers. Basically, a hard interface was beneficial to stress transfer, whereas a soft one hindered the development of cavities in the matrix.

Interfacial effects in nano-silica/polypropylene composites fabricated by in-situ chemical blowing

“…The procedure of grafting of poly(p-vinylphenylsulfonylhydrazide-co-butyl acrylate) onto nanosilica was similar to that of grafting poly (p-vinyl-3 Cai et al -eXPRESS Polymer Letters Vol.1, No.1 (2007) [2][3][4][5][6][7] Figure 1. Schematic drawing of the proposed route for making nano-SiO2/PP composites…”

“…For poly(p-vinylphenylsulfonylhydrazide-co-butyl acrylate) grafted SiO 2 /PP composite, its notched impact strength is higher than that of poly(p-vinylphenylsulfonylhydrazide) grafted SiO 2 /PP system. According to Rong et al [7], the grafted polymer, especially the one with higher molecular mobility, might play the role of a bumper interlayer around the fillers, while absorbing impact energy and preventing initiation of cracks. The data in Figure 5 coincide with the above conclusion.…”

“…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.…”

Effects of ultrasound on the morphology and properties of propylene-based plastomer/nanosilica composites

“…In view of the cost-effectiveness and feasibility of the available processing techniques, melt blending of polymers with nanoparticles is still the optimum method of compounding. To achieve homogeneous dispersions of nanoparticles in polymeric matrices and to enhance the interactions between fillers and polymer matrices during the melt-blending process, several methods are generally applied: 4,[9][10][11][12][13] (1) the surface modification of nanoparticles with coupling agents or active monomers; (2) the polar group functionalization of polymers with partial oxidation, g-rays, electron beams, microwaves, UV irradiation or polar grafting; (3) the addition of a bifunctional component (compatibilizer) that can interact with both fillers and polymer matrices; and (4) the mechanochemical modification of nanoparticles.…”