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IP.com Disclosure Number: IPCOM000025721D
Original Publication Date: 1987-Aug-31
Included in the Prior Art Database: 2004-Apr-04

Publishing Venue

Xerox Disclosure Journal


Liquid resin casting offers many advantages over other techniques for fabricating prototype parts. It is much cheaper than machining and is a relatively fast process since all that is required is to make a silicone rubber tool from a pattern or master and cast the liquid resin. In making prototype parts for electrostatographic reproducing apparatus, it is necessary that the casted part be electrically conductive in order to dissipate the static charge that would otherwise buildup and interfere with transportation of the paper through the apparatus. A particularly effective liquid resin casting compound comprises Conap UC-30 plus 10% Ketjen carbon black. The Conap UC-30 available from Conap Inc, Olean, New York, is a thermosetting urethane casting compound made up of part A, a polyol and part B, an isocyanate which are mixed in a weight or volume ratio of 2/1, Part mart B. The Ketjen carbon black is a Vulcan XC72R available from Cabot Company. The casting is made by first mixing 10% by volume Ketjen black with part A of the Conap UC-30 for one to three minutes in a Waring Lab Blender at 1300 rpm after which the homogeneously blended mixture is added to the measured amount of part B for further mixing. The liquid may be degased if necessary and carefully poured into the mold to avoid air bubbles by baking at a 175°F for about two hours with a post cure at room temperature for about seven days. To ensure easy removal, a mold release agent may be used. While more than 10% Ketjen black may be employed, this is sufficient achieve a conductivity 108 ohmdsquare which in a static decay test dissi ated 5000 volts/static