Orientation and properties

Halpin (1) and Tsai (2) have presented treatises that address the effects of fiber content, orientation and properties on the composite s mechanical performance. A numerically controlled filament winding machine is capable of placing fiber in precise, three dimensional, engineered patterns. Future research addressing the molecular role of the resin s infrastructure on mechanical performance, will couple filament wound composite... 

Jabarin SA (1991) Orientation and properties of acrylonitrile copolymers. Polym Eng Sci 31 644-51. 

Mascia, L. Zhao, J. Transverse orientation dies for solid state extrusion of polymers. Part II. Orientation and properties of extrudates. Polym. Eng. Sci. 1991, 31 (9), 677. 

Orientation and Properties of Ionic Liquids at the Solid-Liquid Inteface 165... 

Finally, the forming ratio is the ratio of the TUR to the BUR. This quantity provides an indication of the balance of stretching, and so orientation, between MD and TD. If a film has identical mechanical properties in MD and TD, it is said to have isotropic properties. When a blown film is processed so that the FR approaches one, it is an indication that the properties of the film approach isotropy. There is not an exact relationship between forming ratio, molecular orientation, and property balance however, the general trends are in the same direction. Employing TUR, BUR, and FR provides extrusion personnel with convenient measures of processing conditions. 

A list of tensile properties of various LCP fibers in comparison with those of typical thermoplastic fibers is made in Table 8.4. It should be noted that the fiber properties of TLCPs in Table 8.4 are not for commercial fibers and should be used only for a comparison purpose. The fiber spinning, orientation, and properties of TLCP fibers have been well reviewed in the literature [121,122],... 

In spite of the promising performances of the liquid-crystalline polymers, their use is limited to few practical application. This is due to the high pronounced anisotropy of orientation and properties of LCP processed in the pure state. The apparent contraddiction can be avercome by blending the mesomorphous polymer with ordinary engineering thermoplastics. 

Bartczak Z and Martuscelli E (1997) Orientation and properties of sequentially drawn films of an isotactic polypropylene hydrogenated oligocyclopentadieue blends. Polymer 38 4139-4149. 

Mechanical properties of polymer nanocomposites can be predicted by using analytical models and numerical simulations at a wide range of time- and length scales, for example, from molecular scale (e.g., MD) to microscale (e.g., Halpin-Tsai), to macroscale (e.g., FEM), and their combinations. MD simulations can study the local load transfers, interface properties, or failure modes at the nanoscale. Micromechanical models and continuum models may provide a simple and rapid way to predict the global mechanical properties of nanocomposites and correlate them with the key factors (e.g., particle volume fraction, particle geometry and orientation, and property ratio between particle and matrix). Recently, some of these models have been applied to polymer nanocomposites to predict their thermal-mechanical properties. Young s modulus, and reinforcement efficiency and to examine the effects of the nature of individual nanopartides (e.g., aspect ratio, shape, orientation, clustering, and the modulus ratio of nanopartide to polymer matrix). 

Ananikov VP, Makarov AV, Beletskaya IP (2011) Catalytic hydrofiinctionalization of aUtynes through P-H hond addition the unique role of orientation and properties of the phosphmus group in the insertimi step. Chem Eur J 17(45) 12623-12630... 

The orientation and properties of polyethylene films produeed by the blown-film technique have been studied by many researehes in literature [2-6]. The correlation between orientation and morphology of oriented polyethylene (mostly blown film) has been studied thoroughly as well [7-10]. Mechanieal and viseoelastic properties of biaxially oriented films produeed by double bubble method were also investigated [11-13]. 

There is a large volume of contemporary literature dealing with the structure and chemical properties of species adsorbed at the solid-solution interface, making use of various spectroscopic and laser excitation techniques. Much of it is phenomenologically oriented and does not contribute in any clear way to the surface chemistry of the system included are many studies aimed at the eventual achievement of solar energy conversion. What follows here is a summary of a small fraction of this literature, consisting of references which are representative and which also yield some specific information about the adsorbed state. 

Van der Waals complexes can be observed spectroscopically by a variety of different teclmiques, including microwave, infrared and ultraviolet/visible spectroscopy. Their existence is perhaps the simplest and most direct demonstration that there are attractive forces between stable molecules. Indeed the spectroscopic properties of Van der Waals complexes provide one of the most detailed sources of infonnation available on intennolecular forces, especially in the region around the potential minimum. The measured rotational constants of Van der Waals complexes provide infonnation on intennolecular distances and orientations, and the frequencies of bending and stretching vibrations provide infonnation on how easily the complex can be distorted from its equilibrium confonnation. In favourable cases, the whole of the potential well can be mapped out from spectroscopic data. 

The polarization properties of single-molecule fluorescence excitation spectra have been explored and utilized to detennine botli tlie molecular transition dipole moment orientation and tlie deptli of single pentacene molecules in a /7-teriDhenyl crystal, taking into account tlie rotation of tlie polarization of tlie excitation light by tlie birefringent... 

The program uses two ASCII input files for the SCF and properties stages of the calculation. There is a text output file as well as a number of binary or ASCII data files that can be created. The geometry is entered in fractional coordinates for periodic dimensions and Cartesian coordinates for nonperiodic dimensions. The user must specify the symmetry of the system. The input geometry must be oriented according to the symmetry axes and only the symmetry-unique atoms are listed. Some aspects of the input are cumbersome, such as the basis set specification. However, the input format is documented in detail. 

The most notable studies are those of Ingold, on the orienting and activating properties of substituents in the benzene nucleus, and of Dewar on the reactivities of an extensive series of polynuclear aromatic and related compounds ( 5.3.2). The former work was seminal in the foundation of the qualitative electronic theory of the relationship between structure and reactivity, and the latter is the most celebrated example of the more quantitative approaches to the same relationship ( 7.2.3). Both of the series of investigations employed the competitive method, and were not concerned with the kinetics of reaction. 

FIGURE 27 1 Electro static potential maps of the 20 common amino acids listed in Table 27 1 Each ammo acid is oriented so that Its side chain is in the upper left corner The side chains affect the shape and properties of the ammo acids... 

Acrylonitrile (AN), C H N, first became an important polymeric building block in the 1940s. Although it had been discovered in 1893 (1), its unique properties were not realized until the development of nitrile mbbers during World War II (see Elastomers, synthetic, nitrile rubber) and the discovery of solvents for the homopolymer with resultant fiber appHcations (see Fibers, acrylic) for textiles and carbon fibers. As a comonomer, acrylonitrile (qv) contributes hardness, rigidity, solvent and light resistance, gas impermeabiUty, and the abiUty to orient. These properties have led to many copolymer apphcation developments since 1950. 

Mechanical Properties. Polyester fibers are formed by melt spinning generally followed by hot drawing and heat setting to the final fiber form. The molecular orientation and crystalline fine stmcture developed depend on key process parameters in all fiber formation steps and are critical to the end use appHcation of the fibers. 

Terephthahc acid (TA) or dimethyl terephthalate [120-61 -6] (DMT) reacts with ethyleae glycol (2G) to form bis(2-hydroxyethyl) terephthalate [959-26-2] (BHET) which is coadeasatioa polymerized to PET with the elimination of 2G. Moltea polymer is extmded through a die (spinneret) forming filaments that are solidified by air cooling. Combinations of stress, strain, and thermal treatments are appHed to the filaments to orient and crystallize the molecular chains. These steps develop the fiber properties required for specific uses. The two general physical forms of PET fibers are continuous filament and cut staple. 

When drawdown is high, the film may be uniaxially oriented and the properties of the final film isotropic. In the manufacture of strapping tape this effect is accentuated. If the cast or quenched film is to be used to feed an orientation tine, additional attention must be given to the amorphous—crystalline nature of the film ia the draw processes so that maximum strength can be achieved and uniform gauge and optical quality maintained. Slot casting is used for the orientation of these resins, polyesters, polyamides, and a variety of others. 

BiaxiaHy oriented films have excellent tensile strength properties and good tear and impact properties. They are especially well regarded for their brilliance and clarity. Essentially all poly(ethylene terephthalate) film is biaxiaHy oriented, and more than 80% of polypropylene film is biaxiaHy oriented. Polystyrene film is oriented, and a lesser amount of polyethylene, polyamide, poly(vinyl chloride), and other polymers are so processed. Some of the specialty films, like polyimides (qv), are also oriented. 

Theoretical studies of diffusion aim to predict the distribution profile of an exposed substrate given the known process parameters of concentration, temperature, crystal orientation, dopant properties, etc. On an atomic level, diffusion of a dopant in a siUcon crystal is caused by the movement of the introduced element that is allowed by the available vacancies or defects in the crystal. Both host atoms and impurity atoms can enter vacancies. Movement of a host atom from one lattice site to a vacancy is called self-diffusion. The same movement by a dopant is called impurity diffusion. If an atom does not form a covalent bond with siUcon, the atom can occupy in interstitial site and then subsequently displace a lattice-site atom. This latter movement is beheved to be the dominant mechanism for diffusion of the common dopant atoms, P, B, As, and Sb (26). 

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