Mechanical behavior diffusion effects

Unlike the influence of morphology on mechanical behavior, the effect on biological behavior is a less mature area of endeavor. For absorbable polymers, the effect of crystalline structure on diffusion and reaction rates provides insight. The relative amount of crystalline phase influences the rate of diffusion of water into a hydrolytically unstable polymer. Furthermore, the rate of hydrolysis of a given ester group in the polymeric chain will depend on whether the group resides in a self-protecting crystal or whether it exists in an unprotected, easily accessed, amorphous phase. 

M 90] [P 82] As expected, the decay of intensity is not equal for the two different fluorescent dyes having different molecular masses and hence different diffusion coefficients [164]. In a sense, this indicates also that diffuse mixing is effective and is a major contribution to mixing. However, some deviations from diffusion as the only mixing mechanism seem to take place, since the theoretical models are not fully able to describe the experimental behavior. This indicates the presence of other secondary-flow mechanisms besides diffusion. 

In the present study, the effects of composition, molecular weight, and heat treatment on the relaxation behavior of styrene—butadiene-styrene (SBS) block polymers are investigated. There is evidence (e.g., 6,7,8) that these types of multicomponent multiphase systems exhibit unusual phenomena in their dynamic mechanical behavior and in other physical properties. These are apparently related to the presence of the so-called interphase mixing region between the elastomeric and glassy domains. Similar evidence has been obtained by gas diffusion and sorption studies on the copolymer samples used in this investigation (9). 

Several researches have been carried out to understand the mechanism of moisture movement in clay during drying. Newitt et al. [12] and Wakabayashi [13] investigated the moisture movanent in clay by liquid diffusion and vapor diffusion, which affect the drying characteristics particularly the falling rate. They concluded that the liquid diffusion dominates the movement until about 20%-dry basis in moisture content for stoneware clay and 30% for the mixture of 80% Kibushi clay and 20% feldspar. Wakabayashi [14] also evaluated the effective moisture diffusion coefficient of some sorts of clay such as Kibushi, Gairome, stoneware, feldspar, and their mixtures. The effective diffusion coefficient is available for the brief description of the moisture movement behavior. The effective diffusion coefficient D can be defined by... 

Many electrocatalytic processes involve a complex combination of surface charging processes (H or OH or O deposition and removal) and net Faradaic reactions, in which the surface species are themselves involved and cause effects associated with inhibition of the main reaction sequence or of coreactions. The Faradaic reactions may also be partly diffusion controlled, which leads to the most complex behavior. In cases where surface oxide films arise which are substantially thicker than a monolayer, e.g., as at Ni or Ag electrodes, the time-dependent current in a sweep experiment reverts to a square root dependence on sweep rate and this effect arises either because of a dissolution-precipitation mechanism of oxide layer growth or because of solid state diffusion effects. 

The second part is devoted to the characterization of polymers properties. Effective utilization of a polymeric material in agriculture and the food industry depends on their physical form, porosity, solvation behavior, diffusion, permeability, surface properties, chemical reactivity and stability, deterioration and stability, and mechanical properties. Any such features are crucial and depend on the conditions employed during preparation and must be considered during the design of a new reactive polymer. 

For better understanding the diverse relaxation behavior of confined polymers, researchers have utilized models or simulation tools to capture the kinetic features of the material at the molecular level, aiming to represent the results observed in experiments. The FVHD model, which has been widely employed in characterizing physical aging in bulk polymers, is reformulated to describe the relaxation behavior of polymers under nanoconfinement. A dual mechanism combines the effect of vacancy diffusion and lattice contraction, and was recently applied with time-dependent internal length scales to characterize the free volume reduction in the aging process [169]. The dual mechanism model (DMM) fits the data of thin film permeability fairly well. The potential predictive capability of the DMM model depends on the accuracy of the relationship between the internal length and time scale on the description of complex material dynamics [161]. 

While there have been several studies on the synthesis of block copolymers and on the molecular weight evolution during solution as well as bulk polymerizations (initiated by iniferters), there have been only a few studies of the rate behavior and kinetic parameters of bulk polymerizations initiated by iniferters. In this paper, the kinetics and rate behavior of a two-component initiation system that produces an in situ living radical polymerization are discussed. Also, a model that incorporates the effect of diffusion limitations on the kinetic constants is proposed and used to enhance understanding of the living radical polymerization mechanism. 

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