In this paper we report an experimental study on the conditions for droplet breakup in concentrated emulsions under simple shear flow. We present a set of experiments where the ratio between drop and matrix viscosity was varied from 0.1 to 22 and the volume fraction ranged from 0% to 70%. It was observed that the critical shear rate for breakup decreased by more than an order of magnitude for the most concentrated emulsions. Further, drops with viscosity ratio of 22 were seen to rupture in simple shear as soon as the emulsion concentration was raised to 40%. All these effects were conveniently explained by means of a mean field model which assumes simply that breakup of a droplet in a concentrated emulsion is determined by the average emulsion viscosity rather than the continuous phase viscosity.
In this paper a detailed study in investigating the effect of the chain flexibility in epoxy-amine crosslinked network is done. In order to introduce flexibility into the crosslinked network a homologous series of four aliphatic diamine curing agents varying only in the chain length and having a constant functionality (f=4) is taken and cured stoichiometrically with aromatic epoxy (f=2) resin. For each of the cured mixture the viscoelastic master curve and corresponding shift factors were determined. It is found the introduction of flexibility shifts the viscoelastic curves by 5 decades with respect to frequency scale. This shift in the viscoelastic curve is modeled with a parameterized Havriliak-Negami model for the master curve. The free volume contribution for the changes in the coefficient of thermal expansion at T g is also determined.
A new type of heating element was developed capable of changing the mold surface temperature by about 70 K in 0.2 s, thus enabling reduction of frozen‐in orientation and stresses in injection molded products without undue increase in cycle time. The heater, which consists of two insulation layers with a resistance layer in between, is discussed in this paper. The thickness of this insulation layer proves to be the most important design parameter. Too thick an insulation layer increases the cooling time too much, whereas with a thin layer the surface temperatures will stay too low. Temperature measurements at the heater surface and in the mold wall are reported and demonstrate the extreme fast response characteristics.
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