Nanoparticles of the standard pyrogenic Aerosil 1380 (Degussa) pregrafted by ã-irradiation with styrene were melt-compounded with the general purpose isotactic polypropylene (PP) homopolymer by a single-screw extruder. Storage G¢(w) and loss G²(w) shear moduli of the neat PP (PP-0) and of the nanocomposite with the filler volume content 4.68 % (PP-4.68) were treated to derive the relaxation times spectra h (t) using the NLREG computer program based on Tikhonovs method of non-linear regularisation. Drastic changes in the pattern, and broadening of the h (t) to longer relaxation times for the PP-4.68 were attributed to the onset of plastic yield of a spatial network of filler particles coated with polymer boundary layer, preceding the macroscopic melt flow.

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ABSTRACT:The rheological and mechanical properties of the blends of liquid-crystalline polyester (LCP) and poly(methyl methacrylate) (PMMA) filled with aluminum borate whiskers have been studied. It was established the combined action of reinforcing LCP and filler onto the property of PMMA matrix leads to marked reinforcing of PMMA. At 10% of filler and 30% of LCP, the tensile strength of PMMA increases by 30% and elasticity modulus by 110%, the processability being no worse. The viscosity of the blend PMMA ϩ 30% LCP ϩ 10% filler practically is the same as the PMMA melt viscosity at 220°C. With increasing concentration of LCP up to 30%, the filler effect in binary matrix becomes more essential. The possible reason is the preferential adsorption of LCP at the filler interface (surface segregation) and additional ordering of LCP near the surface, possible, due to additional stretching of nematic phase in the convergent flow zone.

SynopsisViscoelastic properties of polymer blend melts of polystyrene-polycarbonate were investigated in a wide range of temperatures, frequencies, and compositions. It was established that the more essential changes in viscoelastic characteristics took place a t small concentrations of one of the components and at low frequencies, probably because of a putting down of the slow relaxation processes. The marked decrease in the viscosity of the melts takes place in the region of phase separation due to thermodynamic incompatibility of the components and is in a good correlation with the appearance of excess free volume in the system.

International audienceThe viscoelastic characteristics of the blends of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) (PMMA/SAN) were investigated at various temperatures below, near, and above the phase separation temperature. The investigated polymer system is characterized by a lower critical solution temperature. Rheological behavior of the blends in the region of a phase separation was compared with change of the light scattering intensity. The presence of nanofillers in the blend results in that the phase separation occurs at a higher temperature. At the isothermal conditions, the phase separation begins earlier and proceeds with a higher rate as compared with the same blend without filler. The results of the study show the considerable change of the viscoelastic characteristics of PMMA/SAN when the polymer system passes from the homogeneous state to the heterogeneous one. Such characteristics as the dependence of the storage modulus (G (')) on the loss modulus (G (aEuro3)), the dependence of the loss viscosity (eta (aEuro3)) on the dynamic viscosity (eta (')), the dependences of the complex viscosity (eta*), and the free volume fraction (f) on the blend composition are the most sensitive to the phase separation. The phase separation affects the characteristics G (')(omega), where omega is the frequency only in a low-frequency range. Temperatures of phase separation were estimated using dependence G (')(T) at omega, which is the constant in the range of low frequencie

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