The University of Texas System

Neal K Vail

Joel W Barlow

Joseph Jefferson Beaman, Jr

Harris L Marcus

Richard H Crawford

David L Bourell

James R Tobin

Balasubramanian Badrinarayan

The development of polymer binder compositions that provide novel binders for high temperature inorganic particulates, especially metal and ceramic particulates is described. These materials are especially useful in a laser beam sintering process known as SLS.TM. that forms accurately shaped high strength green objects. The new binders may be thermally removed in post-shaping operations without significant residual ash. The resulting structures contain only metal, ceramic, or metal ceramic materials. The inventive methods developed for producing the new polymeric binder materials are based in part on using emulsion forms of selected polymers at controlled low molecular weights and high melt flow. An important aspect of the process is the semi-batch addition of selected chain transfer agents to the reacting emulsion. This optimizes coating characteristics of the polymer binder and results in high part strengths of the prototype parts produced in the SLS.TM. process.

Binder compositions for laser sintering processes

A mold useful for injection molding, comprising: a porous network of metal and oxidized metal and a cured epoxy resin dispersed in the porous network. The mold can be prepared by a process comprising the sequential steps of (a) forming a mixture of a metal powder and a polymer binder; (b) heating the mixture at a temperature in the range from about 100.degree. C. to about 300.degree. C. to remove a majority of the polymer binder from the mixture; (c) heating the mixture resulting from step (b) at a temperature greater than about 300.degree. C. and less than the melting point of the metal in the presence of oxygen to oxidize at least a portion of the metal to form a self-adhering porous network of metal and oxidized metal; (d) contacting the self-adhering porous network with an epoxy resin to fill at least a portion of the porous network with epoxy resin; and (e) curing the body resulting from step (d) to form the mold. The shape of the mold can be performed by selective laser sintering of the mixture.

Mold useful for injection molding of plastics, and methods of production

A method of producing high temperature parts by way of relatively low temperature sintering is disclosed. A powder is produced, for example by spray drying a slurry, in which particles of a high temperature material such as a ceramic are partially coated with a low temperature material such as a polymer. The powder is subjected to selective laser sintering, or another heat-based layerwise additive process, to form a green part where the ceramic particles are bound by the polymer. The green part is permeated with a cementing agent having high temperature properties when cured; the cementing agent binds the exposed ceramic surfaces in the green part. The polymer is then removed, leaving the high temperature part. Additional cementing agent, or another high temperature material, may then be added to the part after removal of the polymer.

Method of producing high-temperature parts by way of low-temperature

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Austin, TX, United States of America

Neal K Vail