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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Abstract:In this investigation surface treatment of titanium is carried out by plasma ion implantation under atmospheric pressure plasma in order to increase the adhesive bond strength. Prior to the plasma treatment, titanium surfaces were mechanically treated by sand blasting. It is observed that the

Moulding compounds are used as encapsulation materials for electronic components. Their task is to protect the components from mechanical shocks and environmental effects such as moisture. Moulding compounds are epoxy resins filled with inorganic (silica) particles, carbon black and processing aids. They shows a clear viscoelastic behaviour which is not only temperature but also cure dependent. Due to both thermal and reaction shrinkage moulding compounds introduce residual stresses which may eventually result in product failure.Therefore they can be considered as key materials for the overall thermomechanical reliability. This paper deals with the characterization and modeling of the mechanical behaviour of such moulding compound. The focus will be on the effects of the degree of cure and the filler concentration.

One type of polymer EPN1 180 is selected for the Hygroscopic swelling tests and the sample is made in the thickness of 30ktm. Coefficient of thermal expansion is tested by using DMA Q800 and coefficient of moisture expansion is tested by using DMA Q800 jointed with a humidity generator. Three conditions temperature, 50°C, 60°C, and 70°C, and different relative humidity with 20RH% steps are used for the tests and moisture induced expansion is characterized. The characterized equation can be used to expect the moistureinduced expansion at temperature between 0°C and 100°C, at relative humidity between ORH% and 100RH% for this epoxy. This new method is convenient than that of the old method and easily is used to characterize other polymers. In addition, hygroscopic effect on the viscoelasticity is tested and characterized. The storage modulus is linear decreased with the increase of relative humidity at certain temperature.