RHEOLOGY OF CONFINED POLYMER MELTS UNDER SHEAR-FLOW - WEAK ADSORPTION LIMIT:Weak Adsorption Limit

The dynamics of a confined polymer melt between weakly adsorbing surfaces is considered theoretically. The finite chain extensibility is taken into account explicitly, and the tangential stress and the first and the second normal-stress differences are calculated as functions of shear rate gamma. For small shear velocities (u <u**) the surface slip is large, and the apparent viscosity, eta(app), is proportional to the layer thickness h and is independent of the shear rate. For very high shear rates, the surface slip is small and the tangential stress increases with velocity to the power 1/3. Alternatively, the apparent viscosity eta decreases as a function of gamma with a characteristic -2/3 power law

THERMAL STEAM PLASMA DECOMPOSITION OF ORGANOCHLORINE COMPOUNDS

The report considers the decomposition of carbon tetrachloride and chlorobenzene by the plasma obtained in an AC plasma torch with separate supply of shielding gas and reaction components.171-17

USAGE OF AC PLASMA TORCH FOR PRODUCTION OF OXIDE POWDERS

The report deals with the synthesis of oxide materials in a plasma torch with separate injection of plasma-forming gas and solid aerosol of precursors. Thus, it is possible to provide a stability of the plasma torch operation and high degree of mixing of thermal plasma and precursors.188-18

HIGH VOLTAGE AC PLASMA TORCH OPERATING ON VAPORS OF ORGANIC SUBSTANCES

The report deals with a three-phase high-voltage plasma torch with separate supply of gases and vapors during its operation on a mixture of steam, carbon dioxide, methane and chlorobenzene vapors. Increase in the chlorobenzene flow rate leads to increase in the arc voltage drop and electric power from 100 to 140 kW.99-9

Phase equilibria in random multiblock copolymers

A mean-field theory for domain structures in random multiblock copolymer melts is developed. We focus on the finite molecular weight effects resulting in a competition between macroscopic phase separation and microdomain formation in the system. We identify an essential parameter $N\left|\epsilon\right|$ controlling the phase behavior of the system, where $N$ is the number of blocks per chain and $\epsilon$ is the composition asymmetry parameter $(=$ the difference between the mean copolymer composition and its critical value). The phase diagram involving $N\left|\epsilon\right|$ and the reduced temperature as variables is obtained. The regions of coexistence of two or more phases are identified. We show that a superstructure formation on cooling is always pre-empted by a macroscopic phase separation of the macroscopically homogeneous (disordered) system yielding two homogeneous phases: $\rm H_0\to H_1+H_2$. The third (lamellar) phase separates on further cooling. Then hexagonal and body-centred-cubic phases take over if $N\left|\epsilon\right|\gtrsim 1$. As the Flory interaction parameter $\chi$ increases further, the standard transitions ${\rm BCC}\to {\rm HEX}\to \rm LAM$ take place

Nanorheology of adsorbed diblock copolymer layers

We investigate the mechanical properties of ultra-thin layers of polystyrene/poly (2-vinylpyridine) (PS/P2VP) block copolymers by means of a Surface Forces Apparatus adapted to operate asa rheometer at the molecular level. Two systems are studied: ''brush/wall'' and ''brush/brush''. A comparison of the normal force curves shows that when brushes are compressed against each other, they contract rather than interpenetrate. Nanorheological experiments have been carried out on both systems but reliable measurements have been obtained only on the brush/wall system. The complex shear modulus, characterizing the confined medium, has been measured as a function of separation. Its distance dependence is compared with a scaling model describing the linear shear behaviour of a brush confined by a neutral surface.</p

Nanorheology of adsorbed diblock copolymer layers

We investigate the mechanical properties of ultra-thin layers of polystyrene/poly (2-vinylpyridine) (PS/P2VP) block copolymers by means of a Surface Forces Apparatus adapted to operate asa rheometer at the molecular level. Two systems are studied: ''brush/wall'' and ''brush/brush''. A comparison of the normal force curves shows that when brushes are compressed against each other, they contract rather than interpenetrate. Nanorheological experiments have been carried out on both systems but reliable measurements have been obtained only on the brush/wall system. The complex shear modulus, characterizing the confined medium, has been measured as a function of separation. Its distance dependence is compared with a scaling model describing the linear shear behaviour of a brush confined by a neutral surface