Electrostatic dissipation rate

Styrene acrylonitrile copolymers can be rendered to be antistatic by adding a copolymer composed from epichlorohydrin and ethylene oxide and PMMA (7). The mixture is compounded in a Banbury mixer and then injection molded at 220°C. The surface resistivity, the percent of tensile elongation and the electrostatic dissipative rate from 5 kV to 0 V at 15 and 50% relative humidity have been measured. The results are given Table 9.2. 

We would expect intuitively that tan 0 emd the Deborah number De are related, since both refer to the ratio between the rates of an imposed process and that (or those) of the system. The exact shape of this relationship depends on the number and nature(s) of the releixation process(es). So let us anticipate [3.6.4 la] for the loss tangent of a monolayer in oscillatory motion, which describes a special case of [3.6,12], namely -tan0 = t]°(o/K°. Here, (o is the imposed frequency, equal to the reciprocal time of observation, t(obs) =< . The quotient K° /t]° also has the dimensions of a time in fact it is the surface rheological equivalent of the Maxwell-Wagner relaxation time in electricity, (Recall from sec. 1.6c that for the electrostatic case relaxation is exponential ith T = e/K where e e is the dielectric permittivity and K the conductivity of the relaxing system. In other words, T is the quotient between the storage and the dissipative part.) For the surface rheological case T therefore becomes The exponential decay that is required for such a... 

Handbook). Nevertheless, a number of phenomena unique to micro-conduits still prevail, causing pressure drops, flow rates, and/or friction factors to differ from results obtained for macrochannels [2]. Examples include dominant entrance effects because the conduits are very short, significant surface roughness effects due to the closeness of the channel walls, earlier onset of turbulence because of induced instabilities, measurable viscous dissipation effects resulting from steep velocity gradients, possible fluid-slip on channel walls depending upon the physical-chemical characteristics of the (coated) surfaces, and significant effects of low-level forces usually not relevant in macro-devices, such as surface tension and electrostatics. 

The dynamics of a nematic gel are assumed to be governed by the viscoelasticity of the gel, the rotational viscoelasticity of the director, and electrostatics. The governing equations for the dynamics are derived from the balance between the rates of free-energy release and viscous dissipation. In the present case, strain rates and stresses are spatially uniform because of the unconstrained geometry. Therefore, the governing equations for the dynamics of the strain and the director are obtained from the free energy as [31] ... 

Another method with similar effects is the use of anti-static matericds and additives to increase the rate of dissipation of electrostatic charges. Nitrogen compoimds, sulfonic acids, polyglycols, and polyhydric alcohols are examples of anti-static materials. They can be sprayed or wiped on surfaces or added to bulk materials. 

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