General Premises

As distinct from almost all polymer materials, the kinetics of IPN formation is a governing factor in development of the system morphology. For traditional polymeric materials their structure and morphology depend on the ways of processing, heat treatment, and other physical, not chemical, factors, while for IPNs all depends on the kinetic conditions. One may say that thermodynamics gives the general rules of the equiUbrium state and determines the path to equilibrium, whereas the kinetics allows the reahzation of the path and predetermines the real structure far from equilibrium. This specific feature of the IPN formation is connected with the fact that in the reaction system two processes proceed simultaneously the chemical process of network formation and the physical process of phase separation. As will be shown below, these processes are interconnected. 

By considering the reaction kinetics of the individual network or linear polymer formation in IPNs, one should also bear in mind that the data on the kinetics obtained for pure components could not be used to describe the IPN synthesis for three main reasons [51]  

In the case of sequential IPNs the reaction from the very beginning proceeds by definition in the medium of the first matrix networks. In the case of simultaneous IPNs the network that is formed earlier, due to the difference in reaction kinetics, also forms the mediiun for the development of the second network and serves as a matrix. The matrix network changes the reaction conditions at the expense of the variation in the ratio of the rates of elementary reactions (chain propagation, transfer, and termination), and due to the possibility of chain transfer or termination on the chains of another network leading to grafting. 

The matrix network changes the diffusion parameters of the reaction and influences the reaction proceeding in the diffusion region. 

In the course of the synthesis of both the sequential and the simultaneous networks, microphase separation of the system occurs as a result of the appearance of immiscibihty of growing chains of both network components. During IPN synthesis the kinetics of the formation of each network is different, primarily because of different formation mechanisms—in general, these mechanisms are polymerization and polyaddition. Usually one network is formed first and serves as a matrix for the formation of the second network. 

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These results fit with the general premises of mixing. Motor power requirements will increase with increasing time and RPM. In addition the increase in surface area of the rotor (i.e., that area... 

Generally, the primary objective of parameter estimation is to generate estimates of rate parameters that accurately predict the experimental data. Therefore, once estimates of the parameters are obtained, it is essential that these parameters be used to predict (recalculate) the experimental data. Comparison of the predicted and experimental data (whether in graphical or tabular form) allows the goodness of fit to be assessed. Furthermore, it is a general premise that differences between predicted and experimental concentrations be randomly distributed. If the differences do not appear to be random, it suggests that the assumed rate law is incorrect, or that some other feature of the system has been overlooked. 

Diolefins also occur in relatively small concentrations in olefin feed streams. Their concentration increases as cracking severity increases, such as in fluid coking. As in the case of ethylene, the butadienes do not appear to react with isobutane in the presence of strong sulfuric acid. The dienes are believed to form reaction products, most of which are acid soluble, and if this general premise is accepted the fresh acid make-up rate for a dilution range of 98.5 to 90.0% (wt.) can be calculated to be 2465 pounds of acid per barrel of butadiene. Industry practice is to use rates in the range of 1890 to 4200 pounds per barrel. 

Moffitt and Ballhausen,41 and the application of the molecular orbital theory to electron-deficient compounds, particularly the hydrides of boron, by Eberhardt, Crawford, and Lipscomb has been fully described by these authors in their original papers.14 The present review will, therefore, be devoted entirely to those developments in the molecular orbital theory which have been associated with its application to the electronic spectra of unsaturated hydrocarbons. These developments form in themselves a relatively coherent story, the main lines of which are now clear, and it seems a suitable moment at which to put the history of the subject into perspective. Before doing this, however, it will be convenient to outline the general premises of the molecular orbital theory. 

Describe the general premise behind cancer chemotherapeutics. 

In this section we will discuss briefly some theoretical aspects related to the design and realization of compartmentalized reactions, mainly derived from our experience with biochemical systans. As a general premise, we remade that although an ever inoeasing number of published work on this subject (mono- or multi-enzymatic reactions inside liposomes, fatty add vesicles, polymersomes, as well as w/o or w/o/w compartments ) a full understanding of the physico-chemical details of compartmentalized reactions has not been reached. A related field, which has a longer tradition, i.e. that one of enzymes in reverse micelles has revealed interesting compartmentation-dependent mechanisms. ... 

Figure 9.6 I A bomb calorimeter is a feirly complicated piece of equipment, as shown in the diagram on the left. But the general premise of the device is simply to carry out a reaction at constant volume and with no heat flow between the calorimeter and the outside world. The diagram on the right shows the standard choice of system and surroundings for a bomb calorimetry experiment. The system consists of the contents of the bomb itself. The surroundings include the bomb and the water bath surrounding it. We assume that no heat is exchanged with the rest of the universe, outside the insulated walls of the apparatus.

In cleaning operations this false general premise is most commonly adopted. Many-to-most operators of cleaning systems accept that the only variable cost of their solvent cleaning system is their purchase of virgin solvent and/or their only fixed cost is their purchase of the vapor degreaser (or perhaps not) ... 

Another general premise of the clonal selection theory is that an-... 

A rule that can be derived theoretically from general premises likely to be valid for polymer melts and solutions is the Lodge-AfeicSfrier relationship (L ge and Meissner, 1972) between the shear stress and the first nomml stress difference after a step shear strain ... 

The general premise of using hydrogen bonds to constmct low-molecular weight [25] mesogenic supramolecules (e.g., dimers and trimers) has been demonstrated in a number of accounts and was initially evoked to explain the mesomorphic... 

As summarized in the previous section, laboratory tests of ceramic biomaterials have demonstrated substantial advantages over CoCr for articulation against UHMWPE. The harder ceramic surfaces should theoretically be more scratch resistant than CoCr femoral heads [125, 126]. Unfortunately, it has thus far proven difficult to conclusively establish, as a general premise, the clinical benefit of ceramic femoral heads in patients. For reasons noted previously associated with in vivo phase transformation and surface roughening of zirconia, clinical wear studies pubUshed in the past 5 years with zirconia heads have reported nuxed results in the literature, ranging from no significant difference to inferior performance relative to CoCr heads. 

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