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SYNOPSISLow molecular weight poly (methylmethacrylate) and poly (methylmethacrylate-co-n-butylmethacrylate) emulsion-based polymers are developed for use as fugitive binders of high temperature powders to be used with the rapid prototyping method known as selective laser sintering. Kinetics of the homopolymerization of methylmethacrylate and n-butylmethacrylate are found to deviate from Smith-Ewart Type I1 predictions. Reactivity ratios for the monomer pair are determined and indicate the pair to yield random copolymers. Molecular weight was controlled by the addition of chain transfer agents. Several transfer agents were studied and one, Iso-octyl-3-mercaptopropionate, was selected for use with emulsion polymerizations. Glass transition temperatures of the homopolymers and copolymers were studied.

Lasers have been widely used in surface modi® cation. In the present research, a CO 2 continuous wave laser has been used to polish slot surfaces of silica rods. Strong absorption of 10 . 6 l m CO 2 radiation by the silica surface promotes softening of a very thin layer of material that¯ows under the action of surface tension forces. A smooth surface forms, which decreases the surface roughness without substantial change in surface geometry. The effect of laser ± surface inclination angle on the requisite power requirement has been assessed experimentally and theoretically. Using a computer controlled laser beam scanning system, reliability and reproducibility have been greatly improved compared with an alternative surface ® nishing method, manual ® re polishing.MST/5495

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