Orientation, oriented thermal

Orientation, thermal characteristic These oriented plastics are considered permanent, heat stable materials. However, the stretching decreases dimensional stability at higher temperatures. This situation is not a problem since these type materials are not exposed to the higher temperatures in service. For the... 

Thermal Diffusivity - The thermal diffusivity [D = k/(pCp)] of S10C-N312 BN 2-D composites was determined by the laser flash method in which a laser is used as a heat source and the thermal pulse transmission speed is measured in the desired orientation. Thermal diffusivity measurements were made both in-plane and through-plane ofthe 2-D composite. The specimen size was 9x9x2 mm square. The thermal diffusivity was calculated from solution of the diffusion equation for heat flow with the known boundary conditions. Details of this procedure are found in ASTM Standard Test Method E37.05 (Thermal Diffusivity by the Flash Method). 

As the measurements have shown, thermal properties of filled polymers depend considerably on filler orientation. Thermal conductivity and specific heat of glass plastics with formaldehyde and epoxy binder increase with increasing temperature, whereas thermal diffusivity falls in inverse proportion with temperature. The direction of the heat flux and orientation of the filler are responsible for the conductance and thermal diffusion in a given direction. Specific heat does not practically depend on the heat flux direction, since it characterizes the scalar value, i.e., energy accumulation. 

Janietz et al. in a series of reports have studied the Langmuir monolayers as well as LB films with varying thickness of amphiphilic pentaynes 1 and 2 showing discotic nematic phases [89-92]. After successful aligmnent by the LB technique, they also studied the photophysical properties of the thin films. Interestingly, these compounds form discotic nematic phases in bulk however, in the LB films they form ordered columnar stacks with edge-on orientation. Thermal treatments cause irreversible destmction of the LB film stmcture of these discotic amphiplules. 

From the micro-mechanical point of view, the process modeling strategies must consider simultaneous interplay of the following intrinsic factors initial and boimdary conditions in terms of pressure and temperature, fiber content and stacking, sequence of layers (ie ply-to-ply orientation), thermal shrinkage, chemical shrinkage, time-temperature-degree of ciu-e dependent resin properties, and... 

If an c-wave is incident on a hybrid NLC cell, all three interaction mechanisms (orientation, thermal, and thermoorientation ) will occur simultaneously. We will use Eq. (17) and the corresponding expressions for the perturbation of the permittivity tensor to estimate the relative contributions of these mechanisms to the nonlinear phase shift. For the orientation and thermo-orientation mechanisms, Sen efe-k =Sa sin 10 S0. We readily find an expression for 30 for the orientation mechanism from Eq. (4a) by setting = 0, = const, and E z0 (for definiteness we consider a normally indicent e-wave). For the thermal mechanism of nonlinearity,... 

Assuming that the fracture system has an orientation, thermal conductivity must be formulated as a tensor. The tensor simplifies for the case that the axes of the ellipsoid coincide with the axes of the Cartesian coordinate system. For the assumption of peimy-shaped fracture with long ellipsoid axes a,b parallel x,y coordinate axis and a short ellipsoid axis c- = b parallel z coordinate axis, thermal conductivity components are the solutions of the following equations ... 

All revisions of the arrangement models afforded the NRPCT technical insight into the relationship between components, piping effects on pressure drop, component orientation, thermal concerns, manufacturability issues, and effects of mission on reactor and plant layout. Several other subsystems were to be incorporated, such as the Primary Support Structure, micrometeoroid protection, and aeroshell, which would lead to additional iterations and trade studies. 

To realize a process integrated quality control the conception shown in fig. 2 was followed. The casting process which is influenced by process parameters like thermal economy, alloy composition or black wash will be pursued with particulary to the problematic nature adjusted sensoring systems. On basic factors orientated sensoring systems like microfocus radioscopy, and tomography will be employed and correlated with sensoring systems which can be applicated under industrial conditions. 

Noncrystalline domains in fibers are not stmctureless, but the stmctural organization of the polymer chains or chain segments is difficult to evaluate, just as it is difficult to evaluate the stmcture of Hquids. No direct methods are available, but various combinations of physicochemical methods such as x-ray diffraction, birefringence, density, mechanical response, and thermal behavior, have been used to deduce physical quantities that can be used to describe the stmcture of the noncrystalline domains. Among these quantities are the amorphous orientation function and the amorphous density, which can be related to some of the important physical properties of fibers. 

In the spunbond process, the fiber is spun similarly to conventional melt spinning, but the fibers are attenuated by air drag appHed at a distance from the spinneret. This allows a reasonably high level of filament orientation to be developed. The fibers are directly deposited onto a moving conveyor belt as a web of continuous randomly oriented filaments. As with meltblown webs, the fibers are usually thermal bonded or needled (53). 

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. 

At HOY speeds, the rate of increase in orientation levels off but the rate of crystallization increases dramatically. Air drag and inertial contributions to the threadline stress become large. Under these conditions, crystallization occurs very rapidly over a small filament length and a phenomenon called neck-draw occurs (68,75,76). The molecular stmcture is stable, fiber tensde strength is adequate for many uses, thermal shrinkage is low, and dye rates are higher than traditional slow speed spun, drawn, and heat-set products (77). 

Biaxial Orientation. Many polymer films require orientation to achieve commercially acceptable performance (10). Orientation may be uniaxial (generally in the machine direction [MD]) or biaxial where the web is stretched or oriented in the two perpendicular planar axes. The biaxial orientation may be balanced or unbalanced depending on use, but most preferably is balanced. Further, this balance of properties may relate particularly to tensile properties, tear properties, optical birefringence, thermal shrinkage, or a combination of properties. A balanced film should be anisotropic, although this is difficult to achieve across the web of a flat oriented film. 

In conventional tenter orientation, the sequence of steps is as described above (MD—TD). In some cases it is advantageous to reverse the draw order (TD—MD) or to use multiple draw steps, eg, MD—TD—MD. These other techniques are used to produce "tensilized" films, where the MD tensile properties are enhanced by further stretching. The films are generally unbalanced in properties and in extreme cases may be fibrillated to give fiber-like elements for special textile appHcations. Tensilized poly(ethylene terephthalate) is a common substrate for audio and video magnetic tape and thermal transfer tape. 

Polymer Composition. The piopeities of foamed plastics aie influenced both by the foam stmctuie and, to a gieatei extent, by the piopeities of the parent polymer. The polymer phase description must include the additives present in that phase as well. The condition or state of the polymer phase (orientation, crystallinity, previous thermal history), as well as its chemical composition, determines the properties of that phase. The polymer state and cell geometry are intimately related because they are determined by common forces exerted during the expansion and stabilization of the foam. 

Mechanical Properties and Structural Performance. As a result of the manufacturing process, some cellular plastics have an elongated cell shape and thus exhibit anisotropy in mechanical, thermal, and expansion properties (35,36). Efforts are underway to develop manufacturing techniques that reduce such anisotropy and its effects. In general, higher strengths occur for the paraHel-to-rise direction than in the perpendicular-to-rise orientation. Properties of these materials show variabiUty due to specimen form and position in the bulk material and to uncertainty in the axes with respect to direction of foam rise. Expanded and molded bead products exhibit Httie anisotropy. 

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