Growth sector boundaries

Figure 6.4. Forms of growth sector boundaries depending on the relation between and Rj.

Figure 3.6 Sketch of top views of lozenge-shaped (left, as in Fig. 3.1) and truncated lozenge-shaped (right, as in Fig. 3.16) crystals of polyethylene. The crystallographic a-axis it to the right and 6-axis is vertical up. Adjacent reentry folding is assumed along each growth face. Solid lines represent successive fold planes, while dotted lines indicate sector boundaries that separate distinct fold domains. From Wunderlich [6] with kind permission from the author.

Figure 3.28 Transmission electron micrograph of polyethylene crystals grown from dilute tetrachloroethylene solution. The spiral growth in the upper part of the central crystal is believed to have originated from a tear at the growth face. The larger spiral in the top left of the figure is centered on a sector boundary. Reproduced from Geil [1] with kind permission from the author.

Another approach to the problem of curved edges is based on a solution of Frank s equations in the case of moving boundaries by Mansfield [139], Figure 3.14 shows the ellipitical profile which would arise if the sides of a crystal sector move outwards with a constant velocity, h, which is of comparable size to the spreading rate, g. The magnitude of h is supposed to be determined by the growth rate of the adjoining dominant sector.10... 

Growth rates in the various market sectors and the changing boundary conditions, such as more economical manufacture and higher quality, affect product development and applications to a great extent. The principal area of application for PC is still the electrical sector in which it has replaced classical materials like ceramics, metals, and thermosets, because of an advantageous combination of properties such as electrical insulation, impact strength, stiffness, heat resistance, and transparency. This process is essentially complete even if isolated substitution events take place [94],... 

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