Skin region

The blends of thermotropic LCPs and thermoplastics are generally two-phase systems where the dispersed LCP phase exists as small spheres or fibers within the thermoplastic matrix. Often a skin/core morphology is created with well-fibrillated and oriented LCP phases in the skin region and less-oriented or spherical LCP domains in the core. 

Figure 3 Twin-screw extruded PP-LCP blend processed at a melt temperature of 290°C with low- (left) and high-draw ratio (right). Upper micrographs are taken from the core and lower ones from the skin region.

Figure 4 Optical micrographs from the skin region of the single-screw extruded strands processed at cylinder temperatures of (a) ISO C, (b) 200°C, (c) 230°C, (d) 250°C, and (e) 280°C.

Figure 5 Optical micrographs of specimens injection molded at 180°C (a-d) and 280°C (e,t). Samples were taken from core (left) and skin region (right). (Sample codes as in Table 1.)...

Thus, the lighter nuclei are mostly skin and the heaviest nuclei still have substantial skin regions. These approximate models for the nuclear size and density distribution compare favorably to the measured distributions for typical nuclei (Fig. 2.11). 

Another question we might pose to ourselves is whether the neutron and proton distributions in nuclei are the same Modern models for the nuclear potential predict the nuclear skin region to be neutron-rich. The neutron potential is predicted to extend out to larger radii than the proton potential. Extreme examples of this behavior are the halo nuclei. A halo nucleus is a very n-rich (or p-rich) nucleus (generally with low A) where the outermost nucleons are very weakly bound. The density distribution of these weakly bound outermost nucleons extends beyond the radius expected from the R °c A1 /3 rule. Examples of these nuclei are nBe, nLi, and 19C. The most well-studied case of halo nuclei is 1 Li. Here the two outermost nucleons are so weakly bound (a few hundred keV each) as to make the size of 11 Li equal to the size of a 208Pb nucleus (see Fig. 2.12). 

Delineation of Skin Regions and Accuracy in their Dimensions from Factor Analysis... 

Experimental results. Some carbon fibre specimens reveal several orders of 001 particularly in electron diffraction patterns Figure 15 shows a plot of (3 against l2, equation (3), for an electron diffraction pattern from the skin region of a high-modulus material. L(oOl)> usually referred to as Lc, is 3.5 nm and a = 2%. A full description of electron-diffraction analysis in several similarly heterogeneous carbon fibres has been published (23). Figure 15 also includes a plot from the 001 electron diffraction profiles of a carbon whisker, an exceptionally perfect graphite material. This specimen, with an Lc of 10 nm, has zero distortion, and represents the only case where we have found no distortion in a fibrous specimen. 

Figures 11 to 13 are dark field micrographs of 66 polyamide monofilaments. Figure 11 show an Ag-S stained filament. Silver sulfide precipitates, which appear as black areas (as they did in bright field images) as well as polyamide crystallites (bright spots) are visible. Figure 12 corresponds to a type 4 fiber (with skin-core morphology) where there is a lower density of crystallites in the skin region. Figure 13 corresponds to the case of type 5 fiber which has smaller crystallites.

Fig. 13.12 Frozen skin profiles in two disk-shaped center-fed molds (a R = 6 cm, H — 0.5 cm b R = 6 cm, H — 0.3 cm). Rigid (unplasticized) PVC was considered in the simulation. The frozen-skin region is defined by T < 150°C (5). [Reprinted by permission from R C. Wu, C. F. Huang, and C. G. Gogos, Simulation of the Mold Filling Process, Polym. Eng. Set, 14, 223 (1974).]...

The targeted skin regions were cleaned with ethanol and distilled water 30 min before the start of measurement. Measurements were made at an ambient temperature of 21 to 23°C and relative humidity of 35 to 50% from December to February when the skin was apt to become dry. 

Within the skin region, the structures are rather fine and close and run more or less parallel to the right-hand edge of the image, respectively, along... 

The skin region is oriented along the direction of flow, as are the EPDM domains contained within the skin region. 

Fixed eruptions (drug exanthemas) with mostly few demarcated, painful lesions, usually located in intertriginous skin regions (genital area, mucous membranes). With repeated exposure, these typically recur at the same sites. 

In general, the basic architecture of the integument is similar in all mammals. However, differences exist in the thickness of the epidermis and dermis, the number of cell layers, and the blood flow patterns between species. Additionally, differences exist within the same species at different body sites. Skin is thickest over the dorsal and lateral surfaces and thinnest on the ventral and medial surfaces of the body. The stratum corneum is thickest in glabrous skin regions such as the palmar and... 

In spite of the better alignment of basal planes in the skin region, the surface of carbon fibers can show extremely fine-scale roughness. A scanning electron micrograph of AS4 carbon fibers is shown in Fig. 8.9a, while an atom-force microscope picture of the same fibers is shown in Fig. 8.9b. Note the surface striations and the roughness at a microscopic scale. 

Regional variations in percutaneous absorption contribute to differences in the systemic availability of a drug depending on the site of topical application. The Rhesus monkey Macaca mulatta) could probably serve as an animal model for human skin regional variation.f ° ... 

Anthracene is photosensitizing. It can cause acute dermatitis with symptoms of burning, itching, and edema, which are more pronounced in the exposed bare skin regions. Other symptoms are lacrimation, photophobia, edema of the eyelids, and conjunctival hyperemia. The acute symptoms disappear within several days after cessation of contact. Systemic effects of industrial anthracene manifest themselves by headache, nausea, loss of appetite, slow reactions, and adynamia. 

Also, the proportion of fibers in the skin (or shell) and those in the core depends on the rates of fiow." Low injection rates and low temperatures causes an expansion of the shell (skin) region These relationships also affect the orientation of polymer chains in filled and unfilled polymers during proc-essing Orientation of fiber in blow molding of bottles filled with fibers caused anisotropy of properties. Tensile strength was increased in the machine direction. At the same time, talc filled bottles had more uniform tensile properties than unfilled bottles. ... 

When (r — c)/a > 1, p(r) 0 and V)y(r) -> —Z/r, and the simple Coulomb potential may be used for r > lOR. Care is required in selecting an integration grid which is sufficiently dense over the nuclear skin region where the charge density is changing rapidly. An analytic Fourier-Bessel expansion which may be used in finite-difference calculations is presented in [75]. However, the complexity of (109) makes the calculation of the potential matrix required in (99)... 

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