The Different Fractal Structure of Oxide Nanopowders Depending on Method of Production

This study was undertaken to compare chemically identical nanoparticles that have been synthesed by different methods. The methodology applied allows the identification of different characteristics in the structure and surface parameters of nanoparticles. The study shows that the structural parameters of nanoparticles are to a great extend related to the conditions in which nanoparticles are formed. This is demonstrated through the comparison of three oxides and their different methods of synthesis. The results show that the method of synthesis defines the structure of the nanoparticles; the surface and qualitative and quantitative parameters of the crystaline phases, energy shifts and changes in the internal electron levels. The examples of nanoliquids and the associated polymer strength identify that the interaction of nanoparticles with the environment is also depends on the synthesis method. It is proposed that a fractal dimension may be used as a basic parameter to classify nanoparticles and predict the properties in their interaction with various media.

The Synthesis and Properties of the Modified Bentonite-Starch Absorbent Polymer

The composite absorbent polymer was synthesized by the solution polymerization method with acrylic acid, starch and bentonite as raw materials, N, N-methylene-bis-acrylamide as cross-linking agent, and ammonium persulphate as initiator. The whole process was under nitrogen protection. Factors including amount of starch, crosslinker, initiator, monomer, and neutralization degree and reaction temperature were investigated in terms of their influences on water absorbency. Effect of bentonite amount on polymer strength and water absorption rate was also tested. The modified polymer, with the composition of 10% corn starch, 0.15% initiator, 0.05% crosslinking agent and 8% bentonite, showed a significant strength enhancement at 65°C and 80% neutralization degree (molar ratio) with water absorption of 1012g/g in deionized water and 92g/g in 0.9% NaCl solution.

Rheological Characteristics of Ethylene Vinyl Acetate (EVA)/Silane Nanocomposites

EVA/tetraethylorthosilane(silane) nanocomposites were prepared. Rheological properties were studied in both dynamic and steady modes at 150oC. The rheological properties of the nanocomposites are strongly affected by silane dispersed in EVA matrix. As silane content incresed, the polymer strength increased due to interconnections between filler clusters which can be disrupted by high shear rate (in steady mode). The degree of silane dispersion in the EVA matrix decreased with increasing silane content, leading to a “pseudo-solid-like” behaviour. The samples showed viscous and elastic behaviour at low- and high-shear rate regions, respectively. The nanocomposite films were almost as clear as EVA film.

Molecular Theory of Strength

Polymer strength depends on the nature of the constituting elements and their mechanical, thermal, and otherwise physical, but also chemical interaction. Some of these mechanisms are discussed in this paper; special attention is given to disentanglement and chain scission.

Viscoelastic Behaviour and Rupture of Linear Flexible Chain Polymers at Elevated Temperatures

It is shown that T11 is the relaxation transition that corresponds to the maximum of the dynamic loss modulus G″(T). Simple relations are found between the fracture strains, the long-term durability and the initial values of parameters characterizing polymer rheology at deformation rates and stresses approaching zero. Fracture regimes are determined by two groups of parameters. Linear polymer strength is uniquely determined by the storage of recoverable deformation. There exists a relationship between the maximum value of recoverable strain in the transition region from the rubber-like to the leather-like state and extensibility of macromolecules for polymers with various molecular weight for each polymer. Quenching of polymer near the maximum recoverable strain makes it possible to obtain high-strength samples. Over-spurt regimes for polymer flow have been studied.