Elastic modulus, encapsulants

The chemical and mechanical stability of poly(n-butyl acrylate)(PnBA) to weathering, especially to solar radiation, is of interest for possible use of this material as an encapsulant/ pottant for silicon cell solar energy arrays. This application requires that the material retain an acceptable level of its desirable properties, such as transparency, elastic modulus, etc., over several years of exposure to intermittent moisture, temperatures ranging from -10 to 50 C, solar radiation, and other norms and extremes of exposure conditions. Knowledge of the dependence of changes in properties and composition of the material on exposure conditions is a requisite for establishing reasonable estimates of its prospective performance lifetime characteristics. 

Yet one has to keep In mind that stress of an encapsulant on chip and bonds is reduced by accommodating CTE and by lowering elastic modulus (17). As these two properties are not Independent and arbitrary, optimization work has to be done with resin matrix and filler reinforcement to keep stress within tolerable limits. 

Apart from these studies in stirred vessels, neural stem cell expansion, and differentiation has also been performed in rotary bioreactors (Lin et al., 2004 Low et al., 2001). In these cases, NSCs encapsulated in 3D collagen gels produced cell-collagen constructs containing, after 6 weeks in rotary culture, over 10-fold more Nestin-positive cells than those found in static cultures (Lin et al., 2004). In fact, the rate of proliferation of NSCs decreases with hydrogel stiffness, and a great enhancement in expression of neuronal markers can be achieved in soft hydrogels, which have an elastic modulus comparable to that of brain tissues (Banerjee et al, 2009). 

The protection of electronic devices has been a key application for specialty silicones, and this application continues to keep pace with the rate of device development (5). Silicones are used in various ways, ranging from resinous circuit board coatings to encapsulants, with the silicone gels representing a unique solution to a diflScult problem, stress relief These dielectric gels are prepared by hydrosilation and are lightly cross-linked poly(dimethylsiloxane)s. Their modulus is extremely low, but they are elastic in their behavior. They have the stress-relief characteristic of a liquid but the nonflow property of an elastomer. These jellylike materials maintain their physical profile over the broad temperature range of-80 to 200 °C. 

In contrast to ceramics, BC nematics are fluids therefore they require bulky elastic support or encapsulation to prevent cell leakage and electrical shorts. As noted above, the bending modulus of the substrate is cubic... 

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