Progressive structure development

Figure 19.1 Stretching and folding by chaotic advection of initial melt bodies in a two component polymer melt give initially multilayer melts that transform by progressive structure development to a wide variety of polymer blend morphologies.

Progressive structure development Tapered circular stir Sc advection rods in oval barrel... 

Figure 19.7 Example of progressive structure development resulting from an initial multilayer blend morphology and the primary derivative morphologies producible in a PP/LDPE blend at a constant 70/30% volume composition.

Dispersions are obtained by specifying to the smart blender large values of the parameter N (Section 19.2). Even so, a variety of structural types are formed in the smart blender prior to the extrusion point due to progressive structure development. An extrusion with droplets such as Fig. 19.1 lA can be transformed to one having other blend morphologies such as depicted in the morphology map of Fig. 19.5. Similarly, extrusions with the platelet dispersion of Fig. 19.1 IB can be changed to extrusions have platelets localized within many layers such as the example in Fig. 19.10. 

Fig. 4. Schematic of continuous chaotic blender (CCB) showing progressive structure development and corresponding increasing platelet orientation.

In addition to the described above methods, there are computational QM-MM (quantum mechanics-classic mechanics) methods in progress of development. They allow prediction and understanding of solvatochromism and fluorescence characteristics of dyes that are situated in various molecular structures changing electrical properties on nanoscale. Their electronic transitions and according microscopic structures are calculated using QM coupled to the point charges with Coulombic potentials. It is very important that in typical QM-MM simulations, no dielectric constant is involved Orientational dielectric effects come naturally from reorientation and translation of the elements of the system on the pathway of attaining the equilibrium. Dynamics of such complex systems as proteins embedded in natural environment may be revealed with femtosecond time resolution. In more detail, this topic is analyzed in this volume [76]. 

The importance of resolution and determination of absolute configuration cannot be overemphasized. There was, in this writer s opinion, little significant progress in developing useful receptor models prior to the determination of the absolute configurations for the active enantiomers of apomorphine, I, certain N-substituted 5-hydroxy-2-amino-l,2,3,4-tetrahydronaphthalenes, and of 6,7-ADTN (X). It is very common to see structures drawn in the literature with their chiral center shown as a particular absolute configuration, for example similar to that of apomorphine. Yet, in many of these cases there is no evidence as to which isomer is active. The reversed stereochemistry for the active enantiomers of apomorphine and... 

The fabrication of composite laminates having a thermosetting resin matrix is a complex process. It involves simultaneous heal, mass, and momentum transfer along with chemical reaction in a multiphase system with time-dependent material properties and boundary conditions. Two critical problems, which arise during production of thick structural laminates, are the occurrence of severely detrimental voids and gradients in resin concentration. In order to efficiently manufacture quality parts, on-line control and process optimization are necessary, which in turn require a realistic model of the entire process. In this article we review current progress toward developing accurate void and resin flow portions of this overall process model. 

The paper is presented in three parts. First, the tests employed to determine the mixed mode fracture envelope of a glass fibre reinforced epoxy composite adhesively bonded with either a brittle or a ductile adhesive are briefly described. These include mode I (DCB), and mixed mode (MMB) with various mixed mode (I/II) ratios. In the second part of the paper different structural joints will be discussed. These include single and double lap shear and L-specimens. In a recent European thematic network lap shear and double lap shear composite joints were tested, and predictions of failure load were made by different academic and industrial partners [9,10]. It was apparent that considerable differences existed between different analytical predictions and FE analyses, and correlation with tests proved complex. In particular, the progressive damage development in assemblies bonded with a ductile adhesive was not treated adequately. A more detailed study of damage mechanisms was therefore undertaken, using image analysis combined with microscopy to examine the crack tip strain fields and measure adherend displacements. This is described below and correlation is made between predicted displacements and failure loads, based on the mixed mode envelope determined previously, and measured values. 

The organizational structure of the chemical industry in India has been an inherent element in its progress and development and has played a significant role in establishing India s self-reliance. To quote (S4) ... 

Let s begin by surveying some of the key physical and chemical properties of the transition-metal elements and interpreting trends in those properties using the quantum theory of atomic structure developed in Chapter 5. We focus initially on the fourth-period elements, also called the first transition series (those from scandium through zinc in which the 3d shell is progressively filled). Then we discuss the periodic trends in the melting points and atomic radii of the second and third transition series elements. 

Informative probe diffusion alone cannot reveal structural and intermolecular interaction details because the echo decay from a probe in a heterogeneous matrix is not imique and a large number of different structures and/or interaction possibilities may give rise to the same echo decay. One way to attack this problem is to use a similar approach to the one mentioned previously, regarding water diffusion in emulsions. In order to succeed with this, however, we believe that a three-dimensional gel structure must be used for diffusion simulations. For this reason work is in progress to develop a new combination of methods, NMR diffusometry, microscopy, mathematical reconstruction, image analysis and diffusion calculations/simulations by Monte Carlo and finite element methods (to be published shortly). 

---