A remarkable manifestation of slow dynamics in dense polymeric systems is that their viscosity scales with their molecular weight as a power-law, with the “viscosity exponent” mη, experimentally measured to be 3.4 ± 0.2. Following De Gennes’ work in 1971, current understanding of this slow dynamics is based upon an effective single-polymer theory that pictures every polymer in such systems movi...

a series of ethylene-propylene-2-ethylidenebicyclo [2.2.1] hept.5-ene terpolymers (epdm) have been prepared using a vocl3/al2et3cl3 catalyst under various al/v ratios and diene concentrations via solution polymerization and characterized by ftir, mooney viscosity (ml1+4,125oc), and thermal gravimetery analyzing. the polymerization yield was seen to increase with augmentation of the al/v ratio a...

Synthetic polymer fluids are becoming a popular replacement for bentonite slurries to support excavations for deep foundation elements. However, the rheological properties of the polymer fluids used in excavation support have not been studied in detail, and there is currently confusion about the choice of mathematical models for this type of fluid. To advance the current state of knowledge, a l...

rhelogical properties of mucilage extracted from garden cress (lepidium sativum l.) seeds as influenced by gum concentration (0.4, 0.6, 0.8 and 1.0 % w/w), temperature (5, 25 and 40 ?c), as well as ph (2.5, 4, 7 and 10) were investigated. non-newtonian shear thinning flow behavour was observed with the power law model well describing the rheological behavior of the solutions. increasing the sol...

A new theoretical model based on the local composition concept (TNRF-mNRTL model) was proposed to express the short-range contribution of the excess Gibbs energy for the solutions containing polymer and electrolyte. This contribution of interaction along with the long-range contribution of interaction (Pitzer-Debye-Hückel equation), configurational entropy of mixing (Flory-Huggins relation)...

Polymers for hot melt extrusion must exhibit thermoplastic characteristics in order to permit the melt extrusion process and they must be stable at extrusion temperatures. Other relevant characteristics are: suitable glass transition temperature (Tg) of 50–180 °C, low hygroscopicity and no toxicity since larger amounts of polymer are used [1]. Extrudability of a polymer is mainly determined by ...

The aim of this work was to study the properties of the carboxylated polyelectrolyte obtained from guar gum. The C-6 alcohol functions of galactose units side chains were oxidized first by GO-ase to aldehyde groups and then to carboxylic groups by halogen oxidation. The enzymic oxidation step was followed by the Dische method, by viscosity and light scattering measurements. With regard to previ...

Xanthan is a polysaccharide secreted by Xanthomonas campestris that contains pentameric repeat units. The biosynthesis of xanthan involves an operon composed of 12 genes (gumB to gumM). In this study, we analyzed the proteins encoded by gumB and gumC. Membrane fractionation showed that GumB was mainly associated with the outer membrane, whereas GumC was an inner membrane protein. By in silico a...

In this study, synthetic sulfonated polymers were used in order to enhance the rheological properties of drilling fluids. The capability of these polymers in reducing the effects of environmentally friendly, but harmful, pollutants such as cement, calcium chloride, gypsum as well as pH changes were investigated. In the present work, two sulfonated synthetic polymers, namely Polythin and Polydri...

Monodisperse and size-controlled polymer particles were produced without surfactant or washcoat from O/W monomer emulsions and “on the fly” polymerization under UV irradiation in a very simple needle/tubing system. The effect of the viscosity of the continuous phase on the size of final particles was investigated. The capillary number ratio was found to be relevant to predict the size of the dr...