Crystalline part

Highest thermal performance with PPS compounds requires that parts be molded under conditions leading to a high level of crystallinity. Glass-filled PPS compounds can be molded so that crystalline or amorphous parts are obtained. Mold temperature influences the crystallinity of PPS parts. Mold temperatures below approximately 93°C produce parts with low crystallinity and those above approximately 135°C produce highly crystalline parts. Mold temperatures between 93 and 135°C yield parts with an intermediate level of crystallinity. Part thickness may also influence the level of crystallinity. Thinner parts are more responsive to mold temperature. Thicker parts may have skin-core effects. When thick parts are molded in a cold mold the skin may not develop much crystallinity. The interior of the part, which remains hot for a longer period of time, may develop higher levels of crystallinity. 

Polycarbonates. Polycarbonates (qv) are pardy crystalline thermoplastics with some disorder in the crystalline part and considerable order in the amorphous part. This disorder conveys high impact strength which, combined with its good transparency and outdoor exposure resistance, makes polycarbonates usefiil for vandal-resistant glazing and outdoor lighting. It is easily processed by extmsion and injection mol ding. Various uv and dame-retardant agents are often added. 

Meyer, K. H., Mark, H. (1928). Tiber den Bau des kristallisierten Anteils der Cellulose [About the Constitution of the Crystalline Parts of Cellulose]. Berichte der deutschen chemischen Gesellschcfft, 61, 592-615. 

Ozone diffuses readily into amorphous region of the polyethylene (32) and oxidation probably occurs much deeper in the solid sample. Ozone also attacks the crystalline part of polyethylene but it has a slow initiation stage followed by more rapid oxidation (13). Because ozone does not diffuse into the crystalline regions (13.32). oxidation is restricted to the surface. The resulting oxidized functional groups on the crystalline regions will remain at the surface, whereas those formed in the amorphous region can diffuse into the bulk. 

The mechanism of ion transport in such systems is not fully elucidated, but it is presumably dependent on the degree of crystallinity of the polymeric complex (which further depends on the temperature and the salt type). The ionic conductivity was initially attributed to cation hopping between fixed coordination sites in the depicted helical tunnel, i.e. in the crystalline part of the polymer. 

The volume inside the semicrystalline polymers can be divided between the crystallized and amorphous parts of the polymer. The crystalline part usually forms a complicated network in the matrix of the amorphous polymer. A visualization of a single-polymer crystallite done [111] by the Atomic Force Microscopy (AFM) is shown in Fig. 9. The most common morphology observable in the semicrystalline polymer is that of a spherulitic microstructure [112], where the crystalline lamellae grows more or less radially from the central nucleus in all directions. The different crystal lamellae can nucleate separately... 

It has grown increasingly apparent that the non-crystalline portions of cellulose structures may play as important a role in the properties and behavior of cellulosic materials as the crystalline parts. X-ray diffraction studies have greatly extended knowledge of crystalline cellulose but in the case of the amorphous or disordered fraction the methods of study have necessarily been indirect and not completely reliable. 

Sisson has traced the evolution of current concepts of the crystalline part of cellulose structures. The fiber diagram obtained by X-ray diffraction is now known to be produced by a series of elementary crystals, called crystallites, which have a definite arrangement with respect to the fiber axis. It is also known that the crystallites in regenerated cellulose may be oriented to varying degrees with respect to the fiber axis and that the crystallites in regenerated cellulose and mercerized cotton differ from those in native fibers. These hydrate type crystallites appear to be more reactive chemically than the native type. 

Evidence was presented that thallous ethylate did not penetrate or alter the crystalline parts of the fiber. Moreover, it was possible to conduct the thallation with different solvents for thallous ethylate. When this was done with normal ethers, the extent of methylation was observed to decrease as the molecular volume of the thallous ethylate solvent increased. These results suggested that accessibility is dependent upon the penetrating power of the ether solvent. Amorphous cellulose was, therefore, defined as the percentage of cellulose wetted by an ether of zero molecular volume and was estimated by determining methylation-molecular volume values for three or more straight-chain ethers, plotting the data and extrapolating to obtain methoxyl content for an ether of zero molecular volume. The amount of cellulose corre-... 

Physical properties to be controlled by these molecular factors include melting point, Tm (only the crystalline part shows a melting point) crystallisation temperature, glass transition temperature, Tg strength,... 

Compounds crystallized directly onto the carbon grid or with a defined orientation, due to other preparation methods, normally exhibit a suitable initial zone close to 0°. Samples from insoluble compounds are almost statistically oriented only biased by the particle shape. In this case, it is difficult to find a single crystalline part of appropriate thickness oriented with a suitable zone parallel to the surface. The best flexibility, and therefore the best possibility to orient a zone correctly, is given by a recently developed rotation-double tilt holder (Gatan Inc.). Through the combination of rotation and additional tilt (beta tilt) it is possible to orient the tilt axis exactly even if the crystal is not sitting flat on the support film (see Fig. 4). The tilt range, dependent on the pole piece distance of the objective lens, should be at least 40°. 

The fracture patterns of noncrystalline or partly crystalline, partly amorphous materials are unpredictable. Conchoidal fracture is typical of glass and yields odd-shaped flakes of various sizes. 

Comparison with the Crystalline Structure of A- and B-Type Starch. In the most recent crystallographic studies on the crystalline part of starch (14.15) the structure of both polymorphs are based on a parallel arrangement of left-handed double-helices. In the two observed structures the double-helices are slightly different since small variations away from the perfect six-fold symmetry are found. Nevertheless, they correspond closely to the model studied here. The essential result is that in these two structures the closest interactions between two neighboring double-helices correspond closely to the duplex described as PARA 1. 

Thermoplastic rubbers (TPE s) show rubbery behaviour at ambient temperature because the rubber phase plays the dominant part. In thermoplastics the behaviour of the glassy phase or of the crystalline part is dominant. 

Video microscopy with crossed polarizers permits the direct and non-invasive observahon of the nucleahon and growth process for many substances, and thus the study of the hme evoluhon of the spherulite radius R t). When the growth is controlled by diffusion the radius of the spherulites increases as R t) a while when the growth is determined by a nucleation-controlled process (incorporahon of atoms or molecules to the surface of the crystalline part) the radius increases linearly with hme, R t) a t. 

Gernat, C., Radosta, S., Anger, H., Damaschun, G. (1993). Crystalline parts of three different conformations detected in native and enzymatically degraded starches. Starch, 45, 309-314. 

The structure [17-19] consists of radiating fibrils with amorphous material, additives, and impurities between fibrils and between individual spherulites. The crystalline part of the spherulite might be a lamellar or other crystalline structure. 

For the PVN-PEO polyblends, volume changes at melting temperature (Figure 6) as well as x-ray data at room temperature (2) show that the 25% (PEO) blend is completely amorphous, and that the 50 and 75% blends contain significant amounts of amorphous PEO. Calculations based on specific volume data indicate that the crystalline part of both the 50 and 75% blends consists of PEO, whereas the amorphous part contains 46% PEO and 54% PVN. Another important result is that the unusual phenomenon of a well in the modulus temperature curves (Figure 1) was observed only for the blends which exhibit crystallinity. Based on these observations, the behavior of blends could be interpreted by postulating that the amorphous PEO forms a complex phase with PVN in the ratio of 3 to 1 monomer units (i.e., 46 wt. % PEO to 54 wt. % PVN), respectively. 

Taken from Ref.19 b taken from Ref.69 c taken from Ref. 8 d taken from Ref.67 taken from Ref, 731 r taken from Ref.,0) phr of sulfur h % of dicumyl peroxide number of crosslinking units per weight average PMA chain j average number of repeat units between crosslinks k concentration of chains between network joints, (mole/cm3)x 104 1 methyl group rotation m segmental motion motions within the crystalline part of the polymer... 

This operation, which removes the excess of toluene, may be carried out in the same flask and loss by transfer thus avoided (Note 2). The aqueous solution of aluminium chloride and hydrochloric acid, after thorough cooling, is decanted through a suction filter, the residue washed with a little cold water, and that collected on the filter returned to the flask. This residue consists almost solely of toluylbenzoic acid, partly crystalline, partly in oily lumps. 

A number of other investigations of the electrical properties of lipid mono- and multilayers were published recently. It is obvious from studies of the conductivity of thin Langmuir films that the electrical properties of metal-organic layer-metal structures can be described by well known concepts from solid state physics, like Schottky injection of electrons from the metal into the lipid film (45, 46, 47). Measurements of dielectric losses in calcium stearate and behenate indicate the presence of movements of dipoles in the organic molecules, and loss peaks connected with the amorphous and crystalline parts of the layers were identified (48). 

Infrared spectra and crystallinity. Part III. Polyethylene glycol. J. chem. 

Fig. 17.6. Maps of in-plane crystallographic orientation of the orthorhombic cell in the crystalline part of the polyethylene structure (a) short-term and (b) longterm implanted acetabular cups (cf. the central photographs). Compare the average direction of c-axis orientation and the motion direction shown on the respective maps and on the photographs of the acetabular cups, respectively...

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