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Crystalline/amorphous ratio

The smart response capability of polysaccharides upon application of stress allows polar and apolar domains to easily form or disintegrate due to variation of the order/disorder ratio at the molecular level. This finally results in variation of specific crystallinity index or crystalline/amorphous ratio at the macroscopic level. Significant variation of interactive properties may even be achieved by minor variation of branching characteristics, which changes surface/volume ratio and, hence, preferences for inter- or intramolecular stabilization. Additionally, a rather effective response option is variation of relative percentages of molar and mass fractions by limited degradation/ reorganization or precipitation/dissolution transition. [Pg.2349]

Other. As a result, the difference between the crystalline and amorphous phases appears in the relaxation times and chemical shifts. Fyfe et al. [1] and Earl and VanderHart [2] independently observed the chemical shift difference between the crystalline and amorphous phases for polyethylene. Figure 7.1 shows a spectrum of polyethylene measured by the CPMAS method. If all of the methylene units in polyethylene are identical, the NMR spectrum gives only one peak. However, a strong peak and shoulder are observed in the real spectrum, which means that there exists two inequivalent methylene units in the solid polyethylene. From measurements on polyethylenes with various crystalline/amorphous ratios, peaks at about 33 and 31 ppm are attributed to the crystalline and amorphous phases, respectively [3]. Figure... [Pg.268]

The most important structural changes concern the changes of the crystalline/amorphous ratio. [Pg.139]

Because PLA is a semi-crystalline polymer, thermal history affects the physical properties of PLA, inducing changes in the crystalline/amorphous ratio, as well as large physical aging effects on the glassy amorphous phase (Gelli and... [Pg.255]

Plastics and their composites are permeable to gases at different degrees and this permeability depend on the internal architecture of the polymer such as its crystallinity, crystalline amorphous ratio, thermal and mechanical... [Pg.79]

Fig. 7. Variation of a/y PA6 crystal ratio and crystalline/amorphous ratios as a function of the CCB processing parameter N. Fig. 7. Variation of a/y PA6 crystal ratio and crystalline/amorphous ratios as a function of the CCB processing parameter N.
Figure 2. Glow curves of various polyethelenes with different ratios of crystallinity-amorphous components. Temperature rises from left to right. Peaks 0, y, where a is caused hy crystalline component, and y by amorphous... Figure 2. Glow curves of various polyethelenes with different ratios of crystallinity-amorphous components. Temperature rises from left to right. Peaks 0, y, where a is caused hy crystalline component, and y by amorphous...
ZrOz-H -Zeolite catalytic systems were synthesized in the following way H -Zeolite suspension was added to aqueous suspension of zirconium hydrogel washed off from salts, and the resulting mixture was then vigorously stirred for 45 min to achieve more homogeneous sample. The deposit was then squeezed and dried at 100 °C, and calcinated at 500 °C for 3 hours. To vary the amorphous and crystalline phases ratio, carriers with diverse compositions were obtained. [Pg.427]

With this much interest in polyethylene, many attempts have been made to use low frequency NMR in either the time domain or frequency domain to monitor and control the production more rapidly. Auburn International (now part of Oxford Instruments) developed a widely adopted system based on the time domain spectrometers [21]. In this case, sample preparation is no longer an issue since the system accepts either powder or pellets and no solvent is used. The Auburn systems determine crystalline and amorphous ratios, viscosity, melt index and molecular weight For other types of polymers, the list of advertised measurements include tacticity, rubber content, copolymer analysis, and various rheological properties. These values are determined by correlating several routine but laborious methods with the decay of the NMR signal under various pulse sequences. The man-hours... [Pg.901]

The semi-crystalline HDPE being modeled is initially of a sphernlitic morphology described in Chapter 2. It is made up of a 3D packing of crystalline lamellae and their attached amorphous layers as idealized in Fig. 9.25(a). The basic elements of the spherulite are two-phase composite inclusions that consist of integrally coupled crystalline lamellae and their associated amorphous layers between lamellae. Owing to their large aspect ratio, the composite inclusions are modeled as infinitely extended sandwiches with a planar crystalline/amorphous interface as shown in Fig. 9.25(b). Each composite inclusion I is characterized by its interface normal rt and the relative fractional thicknesses and / = 1 / of... [Pg.309]

One approach to determining the crystalline-to-amorphous ratio is to use conventional quantitative analysis methods. Non-overlapped X-ray diffraction peaks are chosen for the phase to be analyzed. Either peak height or peak area is used for quantitative analysis. Standards of known concentration are then used to prepare a calibration curve. [Pg.699]

Wide angle X-ray scattering (WAXS) provides information on the unit cells where the data obtained can be utilized in determination of the lattice parameters, hkl reflection planes and hence the lattice structure i.e. face centred cubic, hexagonal, etc. In addition to the unit cell information, the level of crystallinity can be determined by considering the polymer as a two-phase material, amorphous and crystalline. The ratio of the second moment of the data corresponding to the sharp... [Pg.55]

Totally new types of thermoresponsive gels have also been s)mthe-sized. The copol)mier gel made of stearqyl acrylate (SA) and acrylic acid (AA) (copolymer ratio SA AA=1 4) exhibits a crystalline-amorphous... [Pg.685]

The crystalline-to-amorphous ratio can be determined by wide-angle X-ny scattering, by density measurements, and also by differential scanning calorimetry (DSQ. [Pg.634]

Poly(vioyUdeoe fluoride). (C jCF])u is a polycrysuUine polymer with repetition units n of the order of 30,000 and a crystalline-to-amorphous ratio mut 0.6. The crystalline part may exist in several polymorphic modificalioos depending on the method of preparation. Details of its structure are discussed elsewhere in this volume. [Pg.937]


See other pages where Crystalline/amorphous ratio is mentioned: [Pg.246]    [Pg.384]    [Pg.2357]    [Pg.267]    [Pg.166]    [Pg.73]    [Pg.69]    [Pg.293]    [Pg.313]    [Pg.278]    [Pg.31]    [Pg.40]    [Pg.384]    [Pg.293]    [Pg.248]    [Pg.246]    [Pg.384]    [Pg.2357]    [Pg.267]    [Pg.166]    [Pg.73]    [Pg.69]    [Pg.293]    [Pg.313]    [Pg.278]    [Pg.31]    [Pg.40]    [Pg.384]    [Pg.293]    [Pg.248]    [Pg.242]    [Pg.282]    [Pg.219]    [Pg.50]    [Pg.78]    [Pg.79]    [Pg.211]    [Pg.217]    [Pg.123]    [Pg.50]    [Pg.78]    [Pg.79]    [Pg.328]    [Pg.820]    [Pg.233]    [Pg.699]    [Pg.726]    [Pg.659]   
See also in sourсe #XX -- [ Pg.313 ]




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