Crystallinity chemical methods improving

Methods were discussed to reveal texture in plant materials in situ by X-ray diffraction. A uniform texture in plant materials is generally confined to areas of microscopic dimensions, and the oriented materials are normally of poor crystallinity. Special methods are therefore needed to obtain fibre diffraction from such areas. They may be distinguished as microbeam techniques, artificial orientation of micro-areas, chemical methods improving crystallinity in oriented but poorly crystalline materials, and combinations of these possibilities. 

NMR spectroscopy has developed during the last few years into a very powerful method to establish both the conformation of an oligosaccharide in solution and in the crystalline state. The solution conformation of a saccharide can be determined generally by the combination of 13C-NMR and H-NMR techniques. 2-d methods became available in the last few years and are prerequisites for the elucidation of the three dimensional structure of an oligosaccharide [7]. Both NOE measurements [21] as well as traditional determination of coupling constants and chemical shifts are important tools for the determination of preferred conformations. 2-dimensional methods have greatly improved the accessibility of these parameters from complex molecules. 

Toraya s WPPD approach is quite similar to the Rietveld method it requires knowledge of the chemical composition of the individual phases (mass absorption coefficients of phases of the sample), and their unit cell parameters from indexing. The benefit of this method is that it does not require the structural model required by the Rietveld method. Furthermore, if the quality of the crystallographic structure is poor and contains disordered pharmaceutical or poorly refined solvent molecules, quantification by the WPPD approach will be unbiased by an inadequate structural model, in contrast to the Rietveld method. If an appropriate internal standard of known quantity is introduced to the sample, the method can be applied to determine the amorphous phase composition as well as the crystalline components.9 The Rietveld method uses structural-based parameters such as atomic coordinates and atomic site occupancies are required for the calculation of the structure factor, in addition to the parameters refined by the WPPD method of Toraya. The additional complexity of the Rietveld method affords a greater amount of information to be extracted from the data set, due to the increased number of refinable parameters. Furthermore, the method is commonly referred to as a standardless method, since the structural model serves the role of a standard crystalline phase. It is generally best to minimize the effect of preferred orientation through sample preparation. In certain instances models of its influence on the powder pattern can be used to improve the refinement.12... 

Thermoplastic materials often have a lower surface energy than do thermosetting materials. Thus, physical or chemical modification of the surface is necessary to achieve acceptable bonding. This is especially true of the crystalline thermoplastics such as polyolefins, linear polyesters, and fluoropolymers. Methods used to increase the surface energy and improve wettability and adhesion include... 

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