Early stage crystallization

In this paper, we use SALS under cross-polarized Hy) alignment and USAXS to probe structural changes during of polymers. During early stage crystallization of polyethylene/olefin copolymers, fractal objects with diffuse interfaces are formed initially, and the interfaces of these domains sharpen with time. This compaction process is observed for both polyethylene/olefin copolymers, and the rates and pathways depend on both crystallization temperature and the chemical structure of the polymer. 

Figure 7.2 shows WAXS, SAXS and SALS results during isothermal crystallization of EH064. The crystallization kinetics is accurately resolved by X rays at temperatures below the peak melting temperature = 95° C (Fig. 7.3). As the crystallization temperature increases close to the peak melting temperature, both the changes in the SAXS invariant and crystallinity determined from WAXS are very small and close to the detection limits. This is because, at these high crystallization temperatures, large thermal fluctuations and the low density contrast between crystal and amorphous phase make it difficult to detect the changes in crystallinity and structure [27,29,39 1].To resolve early stage crystallization behavior without the influence of crystal...

Thus we can conclude that early stage crystallization is characterized by an increase in the magnitude of the limiting slope (from 2 to 4) while spherulite growth is characterized by a decrease (from 4 to 2.7). Our results demonstrate that small angle scattering (light and X-rays) can be used to probe the early... 

Fig. 10.4. Illustration of excess signals and their subtraction in typical small angle x-ray scattering experiment. The filled squares and open circles are SANS spectra of

Schmidt A. and Frischat G.H., "Atomic Force Microscopy of Early Stage Crystallization in Li20>Si02 Glasses," Phys. Chem. Glasses, 38, 161-66 (1997). 

Most materials scientists at an early stage in their university courses learn some elementary aspects of what is still miscalled strength of materials . This field incorporates elementary treatments of problems such as the elastic response of beams to continuous or localised loading, the distribution of torque across a shaft under torsion, or the elastic stresses in the components of a simple girder. Materials come into it only insofar as the specific elastic properties of a particular metal or timber determine the numerical values for some of the symbols in the algebraic treatment. This kind of simple theory is an example of continuum mechanics, and its derivation does not require any knowledge of the crystal structure or crystal properties of simple materials or of the microstructure of more complex materials. The specific aim is to design simple structures that will not exceed their elastic limit under load. 

MASSECUITE A mechanical mixture of crystals in mother liquor (molasses or heavy syrup), produced in a vacuum pan. The suspension of sugar crystals in mother liquor produced during the early stages of crystallization. 

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