Crystalline index

Bleached cotton stalk pulp is treated with different concentrations of ethylene diamine (50-100%) for 20 min. It is clear that the crystallinity index (CrI) of these treated pulps is decreased by increasing the concentration of ethylene diamine that is, the decrystallization increases. The degree of polymerization is nearly the same, but some increase is shown in the sample treated with 100% ethylene diamine. This indicates that 100% ethylene diamine may act as a dissolving agent for low degree of polymerization (DP) of cellulosic chains and hemicellulose. 

A relative crystallinity or "crystallinity index" has been used as an approximate method [55,56]. The simplest procedure involves determination of the intensity at a single scattering angle (26), in reference to the value for the amorphous halo at the same angular reflection. This method, for example, was useful to follow the variation of crystallinity of an iPP during isothermal melting [57]. 

A simple phenomenological method can be used to describe changing crystallinity from WAXS data of isotropic materials. It is based on the computation of areas in Fig. 8.2. First we search the border between first-order and second-order amorphous halo. For PET this is at 29 37° (vertical line in the plot). Then we integrate the area between the amorphous halo and the machine background. Let us call the area Iam. Finally we integrate the area between the crystalline reflections and the amorphous halo, call it Icr, and compute a crystallinity index... 

Figure 4.7 Measurement of crystallinity index from IR spectrum of bone apatite. Reprinted from Journal of Archaeological Science 17, Weiner, S. and Bar-Yosef, O., States of preservation of bones from prehistoric sites in the Near East a survey , pp. 187-96, copyright 1990, with permission from Elsevier.

The estimation of the crystallinity index (Cl) of bone is based on one of the four vibrational modes associated with the apatite phosphate group. In amorphous calcium phosphate, the absorption band at 550-600 cm-1 appears as a single broad peak, whilst in hydroxyapatite it is split into bands of unequal intensity by the apatite crystal field (Sillen and Parkington 1996). Based on the splitting factor introduced by Termine and Posner (1966), Weiner and Bar-Yosef (1990) proposed the use of a crystallinity index to measure the crystallinity of bone mineral. As illustrated in Fig. 4.7, the Cl is estimated by drawing a base line from 750 to 495 cm 1 and measuring the heights of the absorption peaks at 603 cm-1 (measurement a), 565 cm 1 (measurement b) and the distance from the base line to the lowest point between the two peaks (c). Cl is calculated from the formula ... 

Measurement of crystallinity index from IR spectrum of bone apatite 88... 

Keywords infrared spectroscopy, transmitted light petrography, illite crystallinity index, 4-acid digestion ICP-MS, orogenic gold... 

Figure 2. Illite crystallinity index. Illite crystallinity is defined as the ratio of the depth of the water feature to the depth of the AI-OH feature.

Important characteristics of chitosan are its MW, viscosity, DD (Bodek, 1994 Ferreira et al., 1994a,b), crystallinity index, number of monomeric units, water retention value, pKa, and energy of hydration (Kas, 1997). Chitosan has a high charge density, adheres to negatively charged surfaces, and chelates metal ions. 

Careful work is necessary to remove all preferred orientation from powder samples. Figure 1 shows results obtained with polyethylene terephthalate (PET) fibers. Curve is a typical azimuthal scan of the 010 peak (20 = 17,5°) for a bundle of parallel fibers placed perpendicularly to the x-ray beam. Curve b is the same scan carried out on a "powder" sample, showing that all preferred orientation is removed in our conditions of moulding (350 kg/ m2). For each kind of fiber, it is necessary to do preliminary trials to find the best experimental conditions. For PET fibers, we show on Figure 2 the relative crystallinity index and the residual orientation plotted against the cut-lengh. (5). 

Figure 2. Effect of cross-section length on crystallinity index (------------) and on...

Preferential orientation increases rapidly when the cut-length is greater than 80 pm, and the crystallinity index goes through a maximum at the same cut-length. To explain such results we suggest ... 

Variations of k must be compared with variations in a Perfection Crystalline Index (IPC) obtained according to Dumbleton s method, from the 010 and 100 peaks (7). IPC increases rapidly after heat treatments. An increase of this index is proof of a progressive transformation from a pseudohexagonal phase in the initial sample (disturbed as seen from the k value) decreasing to give a less disturbed triclinic phase after thermal treatment ... 

The crystallinity index, as obtained using the "amorphous" diffraction pattern (by destruction of local order under the electron beam) gives reliable information, i.e., in agreement with dark field images. 

Si02 A12Q3 K20 Fe2Q3 Ti02 Montmoril- lonite Crystallinity index Quartz Mica Kaolinite books... 

An X-ray crystallinity index method -with application to poly (ethylene terephthalate). J. Appl. Polymer Sci. 7, 803—815 (1963). 

Some unexpectedly complex liquid solid interactions have been detected and studied by ultrasonic impedance measurements (ultrasonic impedometry). Small amounts of water and alcohols have pronounced effects on the physical state of hydrophilic polymers specifically, the high frequency shear modulus and crystallinity index of a poly (vinyl alcohol) film increases with water content to a maximum before normal solution phenomena occur. These effects are attributed to the increased molecular order owing to water hydrogen bonded between polymer chains. The unusual effects of moisture on a novel poly(vinyl chloride)/plasticizer system and on hydrophilic polymers other than poly (vinyl alcohol) are also described. 

Infrared Crystallinity Index. A measure of the relative degree of crystallinity was determined from the infrared spectra obtained in the preceding section by reporting the ratio of the optical density of the band at 1372"1 (7.29/mi) to that at 2900 cm 1 (3.45/xm). According to Nelson and O Connor (15), the crystallinity index measured in this way compares well with data from x-ray diffraction, density measurements, and accessibility measured by moisture sorption. 

DP Turnbull s Blue Test (Arb. Units) Infrared, (A OD) Infrared Crystallinity Index... 

DP Infrared COOH Content Injrared Crystallinity Index... 

Figure 10. Relationship between crystallinity index and the tensile strength of degraded cotton print cloths and archaeological fibers...

FIGURE 5.21 Infrared (IR) crystallinity index (Cl) 1429 versus accessibility by the Br2 method for different cellulose fiber. 

Cellulosic materials usually form crystal structures in part, and water cannot penetrate the inside of crystalline domains at room temperature. Native celluloses form crystalline microfibrils or bundles of cellulose chains 2-5 nm in width for higher plant celluloses and 15-30 nm for algal celluloses, which are observable by electron microscope. Almost all native celluloses have X-ray diffraction patterns of cellulose I with crystallinity indexes (Cl) 13] of about 40-95 %. 

CRYSTALLINITY Index. The crystallinity indexes for specimens heated under each set of conditions (LO, DO, LN, and DN) at each temperature from the first exposure time (ti) to the last or seventh exposure time ( 7) in hours at 190 °C and in days at 160, 130,100 °C were not significantly different. The crystalline reference was untreated cloth, and the amorphous or least crystalline reference was a sample heated at 200 °C for 14 days. The 112 samples representing seven exposure times at each temperature for the four conditions were of intermediate crystallinity. By using this system, measurement of the crystallinity index did not reveal differences among samples that could be used to show changes in structural order with aging. 

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