| Inorganic nanoparticle is a particle with smaller characteristic latitudinal dimension than 100 nm, being a substance between macroscopic solid and sub-stable immediate of molecule. It possesses small-dimension effect, quantum dimensional effect and surface effect. Polymer/nanoparticles nanocomposites become very active domain at present, displaying good exploitation and application foreground. But because of inorganic particles'smaller dimension, bigger specific surface area, higher interfacial energy, they agglomerate very easily, and consequently can't exert nanometric effect to full extent. Thus lowering the interfacial energy of nanoparticles, improving compatibility between nanoparticles and polymer, and weakening interfacial polarity of nanoparticles become the most important technological problems for surface modification of nanoparticles.In this paper, we use the Stober method to produce silica nano-particles (SiO2) of mono-dispersity, and, in order to get SiO2-g-PBA hybrid particles, atom transfer radical polymerization (ATRP) was used to graft Poly (n-butyl acrylate) (PBA) from the surface of silica nanoparticles to establish an inorganic core and organic shell structure. The results of Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), Gel permeation chromatograph (GPC) and thermogravimetric analysis (TGA) show that we are succeeded in bonding PBA with SiO2 and getting a polymer brush from its surface. Furthermore, as is shown from Thermogravimetric analysis (TGA), the grafting density of initiator is about 150μmol per gram, and the grafting ratio of PBA is around 40 percent (weight ratio) which is calculated from the measurement result.Polyoxymethylene (POM)/ SiO2-g-PBA composites were prepared by melting mix process. The results of TEM, scanning electron microscope (SEM), and mechanical properties testing show that SiO2-g-PBA hybrid particles are more easily dispersed in the matrix than bare nano-SiO2. The impact property of POM/ SiO2-g-PBA composites is apparently improved, while the content of SiO2-g-PBA hybrid particles is 2%, the impact strength of composited materials amounts to 71.2 kJ·m-2, which is 7 times more than that of pure POM. Meantime, the tensile strength can also reach 68.1MPa.The effect of the addition of SiO2 and SiO2-g-PBA particles on the crystallization and thermal stability properties of POM were studied by the characteristics of polarized light microscopic (PLM), wide-angle X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The results show that the addition of SiO2 and SiO2-g-PBA particles did not change the hexagonal system of POM crystal, just decreased the micro-crystal size of the polymer. Moreover, the spherulite size becomes smaller as the addition of fillers while the crystallinity becomes higher, which verified that the fillers of bare SiO2 and SiO2-g-PBA particles serve as a nucleating agent for the crystallization resulting in a higher crystallinity. TGA result shows that the resistance of thermal degradation of POM-based nanocomposites is clearly higher than that of POM. The incorporation of inorganic fillers enhanced the thermal stability property of POM. It is obvious that SiO2-g-PBA particles play a more important role in the influence on the thermal stability of POM than SiO2 particles.The nonisothermal crystallization kinetics of POM based nano-composites was studied by means of DSC, and Jeziorny method is used to analyze the data. The results of crystallization rate constant (Zc), half crystal period (t1/2) and crystallization activation energy (ΔE) show that both SiO2 and SiO2-g-PBA particles can promote the crystallization process, especially SiO2-g-PBA particles.Poly (vinyl Chloride) (PVC) based nanocomposites were prepared by melting mix process. The results of TEM, SEM, TGA, Vicat softing point (VSP) and mechanical properties testing show that the dispersibility of SiO2-g-PBA in the PVC is greatly improved, and accordingly the mechanical properties of PVC/ SiO2-g-PBA are apparently improved. It is noted that the impact strength increases with the increasing filling contents until 5%, which reaches a maximum value (9.5 kJ/m2) , and the tensile strength also amounts to 65.3 MPa, moreover, the elongation at break of PVC/ SiO2-g-PBA composite comes up to 34 percent. In comparison with SiO2 particles, SiO2-g-PBA particles plays a more important role in the enhancement of the VSP of PVC, however, the thermal stability of PVC nearly does not change as the filling of SiO2-g-PBA nanoparticles.The theological properties of pure PVC and PVC based composites were studied by the torque theometer. The result shows that SiO2 particles can reduce the melting time of PVC because of the effect of the abrasion among SiO2 particles which can easily produce much thermo-energy in a short time, but the torque becomes too higher. However, SiO2-g-PBA particles may prolong the time of melting process of PVC, but, apparently, the balance torque are much lower. |
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