Crystallinity weight fraction

For the one-parameter model, crystalline weight fraction, X, at any temperature is given by ... 

Equations 11-12,11-19, and 11-20 form the basis for calculating the percent crystallinity as a function of temperature for the one-parameter model. Calculations of crystalline weight fraction based on the above equations gave values at each temperature which were considerably higher than those found experimentally. 

The isotherms of crystallization were obtained by plotting the crystalline weight fraction at time t Xt) versus t. The half-time of crystallization, to.5 (defined as the time taken for half of the crystallinity to develop), is obtained from the curves and plotted against blend composition, for some T, in Fig. 6.2. 

Table 6.4 Crystallization Temperature T, Melting Temperature I m, and Crystalline Weight Fraction wq of PB-l/HOCP Blends.

During the conversion process, the melting temperatures (I m) of the two crystalline forms were quite constant at all the aging temperatures. The mean values for I m are reported in Table 6.4. The values decreased as the HOCP fraction increased in the blends due to the different values adopted and the interference by HOCP. The apparent enthalpies of fusion (A//n) were calculated from the area under the endothermic peaks of form II, obtained by DSC. The crystalline weight fractions of form II, am, referred to the amount of PB-1 present in the blends, were calculated from the relation ... 

Table 6.8 Amorphous and Crystalline Weight Fractions, cuam and u>a, and Crystallinity of iPP Components, Wcrpp, of Pure iPP and iPP/HOCP Blends Isothermally Crystallized and Annealed.

For quantitative analysis of largely amorphous composites, an analysis based on the diffraction-absorption method was also developed. In this approach, the intensity scale factor and the microabsorption parameter are obtained by a calibration procedure based on the diffraction data of different samples of pure crystalline and mixtures. This information is used to calculate the crystalline weight fraction. 

The specific heat above the melting point increases slowly with temperature. The area under the melting peak of the Cp, T curve equals the heat of fusion AH, multiplied with the crystalline weight fraction. Both the heat of fusion and the percent crystallinity are dependent on the thermomechanical history of the polymer, as discussed in the previous section. 

If an amorphous phase is present in the sample, it is still possible to perform the quantitative analysis by introducing a small amount of crystalline powder with the known weight fraction 1 that will be the iV+ 1 phase in the sample, so the equation becomes ... 

Heat capacity measurements at the glass transition temperature, Tg, are based on the same differential concept. The weight fraction of amorphous phase is calculated as the ratio of changes of heat capacity of the semi-crystalline sample ACp(S) over the change in heat capacity of the melt (ACp(m)) at the glass transition. For a two-phase system, the degree of crystallinity is given as ... 

Another double-crystalline system that has recently been studied is that of PLLA-fo-PCL diblock copolymers [110]. Kim et al. synthesized rather broad molecular weight distribution PLLA-fc-PCL diblock copolymers with polydis-persities ranging from 1.3 to 1.6. They reported that a diblock copolymer with a Mn value of 77 000 and a PCL weight fraction of 0.32 was phase-separated... 

The carboxylic acids were combined with hexylamlne and water in order to study the association structures formed. The hexyl-amine was chosen because it did not by Itself form a liquid crystalline phase with water. Fig. 3A. Water dissolves in the amine to a maximum of 60% to form an isotropic solution. The liquid crystal is formed first at a certain octanoic acid amine ratio, approximately 0.1. The liquid crystalline phase forms a large region reaching to a weight fraction of 0.61 of the acid, corresponding to a 1 1 molar ratio of the two species. 

The pore size of the membrane could also be controlled independently of the porosity by altering the size of the salt particles (Fig. 5a). Membranes with high surface area/volume ratios were produced and the ratio was dependent on both salt weight fraction and particle size (Fig. 5b). In addition, the crystallinity of PLLA membranes can be tailored to that desired for each application. These characteristics are all desirable properties of a scaffold for organ regeneration. The major disadvantage of this technique is that it can only be used to produce thin wafers or membranes (up to 2 mm in thickness). A three-dimensional scaffold cannot be directly constructed. This problem may be circumvented however, by membrane lamination. 

Each of the glass transitions has the appearance as given in Fig. 1. From the magnitude of the increase in heat capacity at the transition it should be possible to obtain information on the total amount of mobility gained, as outlined in Sect. 2. For well characterized systems, the glass transitions can also be used for the approximate determination of the weight fraction of crystallinity wc... 

Colloidal boehmite nanorods have been included in a PA-6 matrix to yield a homogeneous dispersion by in situ polymerization.91 At weight fractions up to 9%, improvements in the Young s modulus of the composite and changes in the crystalline morphology of the PA-6 matrix were observed, although fire properties were not reported. 

The low intensity of the x-ray lines found in the diffraction pattern of the terpolymer compared with the high intensity observed for PE signified that the level of crystallinity in the former was significantly below that of PE. In spite of this, an amorphous sample could not be prepared by quenching. The presence of crystalline regions was indicated in many mixtures, but crystallinity decreased markedly as the weight fraction of the terpolymer decreased. 

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