STUDY OF RESIN-BASED MATERIALS USING CO2-LASER STEREOLITHOGRAPHY

We present an experimental and theoretical analysis of i.r. (thermal) sintering of thermosetting resins used for stereolithography. In the e xperimental work an epoxy resin was chosen. The optimum mix (which was quite critical) was composed of 10 parts (by weight), 1.4 parts dieth ylene triamine and 0.7 parts of silica powder. Using a differential sc anning calorimeter (d.s.c.) we were able to determine reaction rates a s a function of temperature as well as the enthalpy (Delta H congruent to 368 J g(-1)) involved in the phase transition and the activation e nergy (21.7 +/- 0.9 kJ mol(-1)) of the sintering process. The solution of the heat equation simulating this process was in general agreement with our previous observations of the stereolithographic results. It was also found that the minimum radius of lateral confinement was limi ted to similar to 0.3 mm due to heat conduction. The absorption depth should be approximately the same (0.2 mm in this case) at the frequenc y of the laser. It was also noticed that the epoxy degrades rapidly at temperatures above similar to 280 degrees C. (C) 1997 Elsevier Scienc e Ltd.