Crystalline Areas

These materials are segmented copolyether esters formed by the melt transesterification of dimethyl terephthalate, poly(tetramethylene ether) glycol and 1,4-butane diol. As with the thermoplastic polyurethanes, one can describe a hard segment and a soft segment, the hard segments forming crystalline areas which act as pseudocrosslinks . 

Scattering from Thin Crystals. The simple arguments given above hold only if samples are amorphous. Although some catalyst supports are non-crystalline, such as charcoal and silica, others such as alumina are not. Furthermore, the metal catalyst clusters themselves are generally crystalline and thus the above arguments must be modified to account for Bragg reflections from crystalline areas. 

The data in Lake Erie, Lake Ontario and of the Swedish lakes were measured only in surface waters. The Swedish lakes are in crystalline area and have somewhat lower pH values. In these lakes and in Lake Baikal there is no CaC03 precipitation. 

The combination of water and hexylamine forms only an isotropic liquid phase. In combination with octanoic acid, a large liquid crystalline area is found. 

Effects of Crystallinity on Properties. In polymers that can crystallize, the ratio of crystalline to amorphous material has a profound effect on properties. Because the chains arc packed more tightly and efficiently in the crystalline areas Ilian in the amorphous, the cryslalline phase lias a higher density and greater mechanical strength. In fact, density is a common measure of degree of crystallinity,... 

TOPOCHEMICAL REACTION. Any chemical reaction that is not expressible in stoichiometric relationships. Such reactions are characteristic of cellulose they can take place only at certain sites on the molecule where reactive groups are available, i.e., in the amorphous areas or on the surfaces of the crystalline areas. 

Based on conceptions of work [105] the specific dielectric relaxation in PPX with M nanoparticles is supposed to be connected with reorientation of dipoles in polymer environment of M nanoparticles that accompanies the electron transfer between M nanoparticles of percolation cluster. Dipole centers in PPX are (Tv-units of polymer chains on a surface of lamellar PPX crystallites. Such centers are characteristic, in particular, for extended polymer defects (dislocations, grain boundaries, interfaces between amorphous and crystalline areas) where, most probably, M nanoparticles are formed. 

The structure of starch granules is of essential importance. Amoiphous zones of irradiated granules undergo hydrolysis prior to hydrolysis in their crystalline areas.104 Irradiation of granules of maize starch causes them to break along radial and concentric lines. An increase of dose makes the granules more crunchy. These... 

FIGURE 2.5 The stacked bilayers of the skin barrier are envisioned as composed of crystalline domains separated by fringes of lipids in the liquid crystalline state.38 The fringe zones may actually oscillate in a very small time scale between a liquid crystalline state and a crystalline (gel) state. Such a tentative idea would mean that the barrier is open just temporarily at a certain location since penetration must occur in the liquid crystalline areas. Thus, the action of a penetration enhancer would be to stabilize a liquid crystalline state or transform it into another type of structure, for example, a cubic phase. 

In general, acid hydrolysis produces similar degradation. Since acids usually involve a much smaller molecule as the attacking agent, however, acids penetrate the amorphous area of cellulose more easily than enzymes and produce a faster drop in DP. Diffusion into the crystalline areas proceeds more slowly. Because acid hydrolysis is more easily controlled and is faster than enzymatic attack, acid hydrolysis was selected as the second aging system to be examined. 

MW and density affect the optical properties of LDPE. High MW molecules produce a rough, low gloss surface HDPEs contain more or larger crystalline areas that scatter light and cause a hazy appearance. 

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