Molding processes microstructure

The plastic molding process may be combined with deep etch X-ray lithography to fabricate microstructures with different shapes in the third dimension" In the first step, only the upper part of a very thick resist layer is patterned with the embossing technique using a mold insert fabricated by the standard LIGA process. The relief structure obtained by this first patterning process is subsequently exposed to synchrotron radiation through a precisely... 

Crystallization from an oriented melt may occur during extrusion and injection molding processes of crystallizable polymers. The crystalline microstructure which results is... 

Spennemann A, Michael W (2001) Process analysis and injection molding of microstructures. In Heim HP, Potente H (eds) Specialized molding techniques, plastic design library. Norwich, New York... 

The molding process represents the link between product development and a middle or large scale production. As mentioned earlier the injection molding of polymer microstructures is determined by the microstructure s aspect ratio as well as by the desired field of application and the resulting material requirements which determine the selection of the polymer. In the following some examples for successfully molded microcomponents are presented ... 

Microstructures that are typically observed in molded parts and extrudates include anisotropic textures. The higher orientation in extrusion can result in highly oriented rods or strands, at high draw ratios and/or small diameters, or in structures with an oriented skin and a less oriented central core in thicker strands. This skin-core texture is due to a combination of temperature variations between the surface and the bulk and the flow field in both extrusion and molding processes. For instance, the flow fields in a molded part are shown schematically in Fig. 1.7 [46]. Extensional flow along the melt front causes orientation. Solidification of the polymer on the cold mold surface freezes in this orientation. Flow between the solid layers is affected by the temperature gradient in the mold, and the resulting flow effects [57, 58] result in a rapidly cooled and well oriented skin... 

Esashi, M., and Watanabe, R. (1999) Lost sihcon mold process for PZT microstructures. Adv. Mater., 11 (10),... 

Re-entrant foam provides a counter-intuitive demonstration of processing (5). Polyurethane can be isotropically compressed in a mold and heated to about 170 °C. The microstructure of the resulting solid yields a material that bulges in cross section when stretched More information on polymers will be available from John Droske s complementary NSF-funded project (described in the preceding section). 

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