The effect of pristine silica nanoparticles on a model low-density polyethylene (LDPE)-ethylene vinyl acetate copolymer (EVA) thermoplastic elastomer blend system is explored in this article. Pristine silica nanoparticles were melt-blended with the LDPE-EVA system at 1.5, 3, and 5 wt % loadings through the variation of the sequence of addition. In one of the compositions, coupling agent bis [3-(triethoxysilyl)propyl] tetrasulfide (Si-69) was used to improve the interaction of hydrophilic silica fillers with the polymer matrix. The blends were compressionmolded, and their mechanical, dynamic mechanical, and thermal properties, X-ray diffraction patterns, and morphology were evaluated. The properties of the blends were found to be strong functions of the sequence of addition of nanofillers during their preparation. With Si-69 as a coupling agent, the dynamic storage modulus of nanosilica-based composites was found to increase up to 35%. An appreciable improvement in the tension set properties of the thermoplastic elastomer nanocomposites was observed in all the nanosilica-based films. Morphological studies and dynamic properties clearly indicated that the differential properties of these blend systems primarily stemmed from the extent of dispersion and alternation of crystalline morphology, which in turn was a strong function of preferential incorporation in the LDPE or EVA matrix and the agglomeration tendency of the nanofillers.

BACKGROUND: The technical properties of polyolefinic thermoplastic elastomer (TPE) systems can be modified significantly using fillers like nano-silica. Controlled irradiation can potentially be an effective way of tailoring the technical properties of such nano-silica-filled TPE systems. RESULTS: The effect of controlled electron-beam irradiation on the properties of a pristine silica nanoparticle-filled model low-density polyethylene/ethylene-(vinyl acetate) (LDPE/EVA) TPE system is explored in this paper. The morphology of such a filled system was investigated using scanning electron microscopy (SEM) and field-emission SEM. The dispersion of silica particles was analysed using transmission electron microscopy which clearly indicates that at low loading a fine dispersion of silica occurs in the polymer matrix. Swelling studies and Fourier transform infrared analyses indicate the occurrence of a favourable EVA-silica interaction. On the whole, it is observed that electron-beam irradiation induces a high degree ofreinforcement in all the silica-filled samples through interfacial crosslinking as well as controlled crosslinking in the two polymer phases. In a few samples the processing characteristics are remarkably preserved following concurrent nano-silica reinforcement and irradiation, while the technical properties of TPE systems, including set, solvent swelling and mechanical properties, are improved. However, the improvement in properties is a strong function of sequence of addition of filler in the LDPE/EVA blends. CONCLUSION:The green technique studied can be potentially extended for the improvement of the technical properties of conventional TPE systems.

The effect of pristine silica nanoparticles on the dynamic and capillary rheology of a model LDPE‐EVA thermoplastic elastomeric system is explored in this paper. The pristine silica nanoparticles were melt‐blended with the LDPE‐EVA system at 1.5, 3, and 5 wt% loadings, respectively, by varying the sequence of addition. In one of the compositions, coupling agent bis‐[3‐(triethoxysilyl)propyl] tetrasulphide (Si‐69) was used to improve the interaction of hydrophilic silica particles with polymer matrix. Results obtained reveal that the viscoelastic behavior of such composites is influenced remarkably by loadings of silica, variation of sequence, and addition of Si‐69. Upon addition of coupling agent, G′ value increases especially at higher strain levels due to increased polymer‐filler interactions. All systems with various loading of nanosilica represent an increase in elastic response with increasing frequency. Both the unfilled and filled blends exhibit rheological behavior of non‐Newtonian fluids. But interestingly, the viscoelastic response varies markedly with the temperature. The dynamic and steady shear rheological properties register a good correlation in regard to the viscous vs. elastic response of such systems. Finally, the rheological behavior is correlated with morphology of the present system processed at various shear rates. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

The pristine nanosilica particles were melt-blended with a model low-density polyethylene-ethylene vinyl acetate thermoplastic elastomers (TPE) system by varying the sequence of addition and nanosilica contents. Bis-[3-(triethoxysilyl)propyl] tetrasulfide (Si-69) was used to improve the state of dispersion of nanosilica particles in one of the compositions. The dielectric properties of the TPE systems are influenced remarkably by loadings of silica, variation of sequence of addition of ingredients during mixing, addition of Si-69, and controlled electron beam irradiation. The effects of interfacial and orientation polarization on the permittivity and the loss tangent were studied by dielectric analyses. These were correlated with the structures of various nanocomposites. An attempt has also been made to support the dielectric results by volume resistivity measurements, measurements of breakdown voltage, and swelling-deswelling kinetic results. POLYM. ENG. SCI.,

The effect of controlled electron beam irradiation on the rheological properties of a model LDPE-EVA thermoplastic elastomer (TPE) system filled with silica nanoparticles is explored in this article. The pristine silica particles were mixed with LDPE-EVA system in molten condition by varying the sequence of addition and amount of nanosilica. In one composition, Si69 was used to improve the state of dispersion of nanosilica. The rheological behavior of irradiated TPE systems is influenced remarkably by irradiation dose, loadings of silica, variation of sequence, and addition of Si69. All filled TPE systems register an increase in elastic response with increasing frequency and with increase in irradiation dose. Upon irradiation, melt viscosity increases when compared with the unirradiated samples because of the crosslinking effect and improvements in interfacial bonding. The viscoelastic response varies markedly with the temperature. The radiation sensitizing effect of silica is reflected from the rheological data. The dynamic and steady shear rheological properties do not follow a simple correlation. Finally, the rheological behavior is correlated with the morphology of the irradiated systems processed at various shear rates.