Polymer coefficient

Key Words Field-gradient NMR, Diffusion coefficient, Polymer network, Spatial inhomogeneity of cavities, 3D NMR imaging. 

Kim, K.J. Choi, K.Y. Alexander, J.C. Dynamics of a CSTR for styrene polymerization initiated by a binary initiator mixture. II. Effect of viscosity dependent heat transfer coefficient. Polym. Eng. Sci. 1992, 32 (7), 494-505. 

DEPENDENCE OF THE PROTEIN PARTITION COEFFICIENT POLYMER AND PROTEIN MOLECULAR WEIGHTS... 

Perez Gonzalez, M., Helguera Morales, A. and Diaz, H.G. (2004) A TOPS-MODE approach to predict permeability coefficients. Polymer, 45, 2073-2079. 

A TOPS-MODE approach to predict permeability coefficients. Polymer, 45, 2073. 

Nordmeier E (1993) Studies of polyelectrolyte solutions 111. Correlations between the second and the third virial coefficient. Polym J 25 1 17... 

A number of friction studies have been carried out on organic polymers in recent years. Coefficients of friction are for the most part in the normal range, with values about as expected from Eq. XII-5. The detailed results show some serious complications, however. First, n is very dependent on load, as illustrated in Fig. XlI-5, for a copolymer of hexafluoroethylene and hexafluoropropylene [31], and evidently the area of contact is determined more by elastic than by plastic deformation. The difference between static and kinetic coefficients of friction was attributed to transfer of an oriented film of polymer to the steel rider during sliding and to low adhesion between this film and the polymer surface. Tetrafluoroethylene (Telfon) has a low coefficient of friction, around 0.1, and in a detailed study, this lower coefficient and other differences were attributed to the rather smooth molecular profile of the Teflon molecule [32]. 

The lubricating properties of tears are an important feature in normal blinking. Kalachandra and Shah measured the coefficient of friction of ophthalmic solutions (artificial tears) on polymer surfaces and found no correlation with viscosity, surface tension or contact angle [58]. The coefficient of friction appears to depend on the structure of the polymer surfaces and decreases with increasing load and sliding speed. 

Povodyrev et aJ [30] have applied crossover theory to the Flory equation ( section A2.5.4.1) for polymer solutions for various values of N, the number of monomer units in the polymer chain, obtaining the coexistence curve and values of the coefficient p jj-from the slope of that curve. Figure A2.5.27 shows their comparison between classical and crossover values of p j-j for A = 1, which is of course just the simple mixture. As seen in this figure, the crossover to classical behaviour is not complete until far below the critical temperature. 

The general fomi of the expansion is dictated by very general synnnetry considerations the specific coefficients for the example of a polymer blend can be derived from the self-consistent field theory. For a... 

Theta conditions in dilute polymer solutions are similar to tire state of van der Waals gases near tire Boyle temperature. At this temperature, excluded-volume effects and van der Waals attraction compensate each other, so tliat tire second virial coefficient of tire expansion of tire pressure as a function of tire concentration vanishes. On dealing witli solutions, tire quantity of interest becomes tire osmotic pressure IT ratlier tlian tire pressure. Its virial expansion may be written as... 

Several ideas have been put forward to calculate tire diffusion coefficient of small molecules in polymers. Glasstone et al [M] proposed an expression based on transition-state tlieory... 

Otlier expressions for tire diffusion coefficient are based on tire concept of free volume [57], i.e. tire amount of volume in tire sample tliat is not occupied by tire polymer molecules. Computer simulations have also been used to quantify tire mobility of small molecules in polymers [58]. In a first approach, tire partition functions of tire ground... 

Material parameters defined by Equations (1.11) and (1.12) arise from anisotropy (i.e. direction dependency) of the microstructure of long-chain polymers subjected to liigh shear deformations. Generalized Newtonian constitutive equations cannot predict any normal stress acting along the direction perpendicular to the shearing surface in a viscometric flow. Thus the primary and secondary normal stress coefficients are only used in conjunction with viscoelastic constitutive models. 

Tetralluoroethylene polymer has the lowest coefficient of friction of any solid. It has remarkable chemical resistance and a very low brittleness temperature ( — 100°C). Its dielectric constant and loss factor are low and stable across a broad temperature and frequency range. Its impact strength is high. 

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