Static sensitization, effect

BXL Plastics ERP Division is to introduce new grades of antistatic and conductive closed-cell crosslinked PE and ethylene copolymer foam at the Internepcon Exhibition to meet a growing demand from the electronics industry, for ways of minimising the effect of static electricity on circuits embodying static-sensitive devices, particularly using metal oxide/silicone technology. Very brief details are noted of Evazote C conductive closedcell, crosslinked ethylene-vinyl acetate copolymer foam. 

Probably, the most commonly known LA/LS mixture for detonators is the ASA composition. It contains 68 % dextrinated LA, 29 % LS, and 3 % aluminum. The small amount of aluminum was added to overcome the tendency of the LA/LS mixture to buUd up on the punches during pressing. On the other hand, aluminum unfortunately has a sensitizing effect on the composition. The possible problems with this mixture caused by static discharge between the leading wires and the tube of electric detonators have been discussed in detail by Medlock and Leslie [44]. These problems led to a number of accidents in the past [44]. The ASA mixture has been subsequently discontinued. 

Fig. 5.16. The relative, shock-induced magnetization change is determined at a given pressure by the ratio of peak current to that at full magnetization change. Various sensitivities with pressure are indicated in agreement with static high pressure data. Offsets at zero magnetization change are typical and may be due to magnetic or mechanical effects (after Edwards [90E01]).

In Table 3 we have listed the results of a basis set and correlation study for the hyperpolarizability dispersion coefficients. In a previous investigation of the basis set effects on the dispersion coefficients for the first hyperpolarizability (3 of ammonia [22] we found quite different trends for the static hyperpolarizability and for the dispersion coefficients. While the static hyperpolarizability was very sensitive to the inclusion of diffuse functions, the dispersion coefficients remained almost unchanged on augmentation of the basis set with additional diffuse functions, but the results obtained with the CC2 and CCSD models, which include dynamic electron correlation, showed large changes with an increase of the... 

The mixing sensitivity of (fast) polymerizations is known and frequently described in literature. This is due to the fact that radical polymerizations typically take 1 s until chain termination [125]. However, typical mixing times of large-scale mixers, including conventional static mixers, are longer. Accordingly, the course of mixing has an effect on the product quality, i.e. the polymer-chain distribution. 

These compounds have been the subject of several theoretical [7,11,13,20)] and experimental[21] studies. Ward and Elliott [20] measured the dynamic y hyperpolarizability of butadiene and hexatriene in the vapour phase by means of the dc-SHG technique. Waite and Papadopoulos[7,ll] computed static y values, using a Mac Weeny type Coupled Hartree-Fock Perturbation Theory (CHFPT) in the CNDO approximation, and an extended basis set. Kurtz [15] evaluated by means of a finite perturbation technique at the MNDO level [17] and using the AMI [22] and PM3[23] parametrizations, the mean y values of a series of polyenes containing from 2 to 11 unit cells. At the ab initio level, Hurst et al. [13] and Chopra et al. [20] studied basis sets effects on and y. It appeared that diffuse orbitals must be included in the basis set in order to describe correctly the external part of the molecules which is the most sensitive to the electrical perturbation and to ensure the obtention of accurate values of the calculated properties. 

In static headspace sampling [301,302] the polymer is heated in a septum-capped vial for a time sufficient for the solid and vapour phases to reach equilibrium (typically 2 hours). The headspace is then sampled (either manually or automatically) for GC analysis, often followed by FID or NPD detection. Headspace sampling is a very effective method for maintaining a clean chromatographic system. Changing equilibrium temperature and time, and the volumes present in the headspace vial can influence the sensitivity of the static headspace system. SHS-GC-MS is capable of analysing volatile compounds in full scan with ppb level... 

To separate the effects of static and dynamic disorder, and to obtain an assessment of the height of the potential barrier that is involved in a particular mean-square displacement (here abbreviated (x )), it is necessary to find a parameter whose variation is sensitive to these quantities. Temperature is the obvious choice. A static disorder will be temperature independent, whereas a dynamic disorder will have a temperature dependence related to the shape of the potential well in which the atom moves, and to the height of any barriers it must cross (Frauenfelder et ai, 1979). Simple harmonic thermal vibration decreases linearly with temperature until the Debye temperature Td below To the mean-square displacement due to vibration is temperature independent and has a value characteristic of the zero-point vibrational (x ). The high-temperature portion of a curve of (x ) vs T will therefore extrapolate smoothly to 0 at T = 0 K if the sole or dominant contribution to the measured (x ) is simple harmonic vibration ((x )y). In such a plot the low-temperature limb is expected to have values of (x ) equal to about 0.01 A (Willis and Pryor, 1975). Departures from this behavior indicate more complex motion or static disorder. 

Luminescence is often much more sensitive to molecular dynamics than other optical techniques where temperature, viscosity, pH and solvent effects can have a significant influence on the emission response. Analyte degradation for light sensitive fluors and photobleaching for static measurements also influence the emission signal. Because of the wide variety of potential matrix effects, a thorough investigation should be conducted or the sample matrix well understood in terms of its potential impact on emission response. A complete discussion on the fate of the excited states and other measurement risk considerations can be found elsewhere. ... 

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