New infrared stereolithography: control of the parameters of the localized curing thermosensitive materials

Abstract

In normal practice, stereolithography has been used for photosensitive resins where ultraviolet light (HeCd laser 2=O.352j.tm) initiates the curing process for prototypes construction. In this work we developed a new aspect of stereolithography, using CO2 laser (=1O.6jtm) in thermosensitive materials where no shrinkage and post-cure treatment was observed. The bulk curing process in resins, epoxy unlike, has been proved useful in a new tethnique for fabrication of prototypes. Control of the laser parameters appears as an important tool for localized cure in the material. Our resin basic sample is composed by the thermosensitive epoxy resin proved to be (in weight) I 0 parts, I ,4 parts diethilene triamine (the cunng agent) and 0.7 parts silica powder. Silica play an important hole in the curing process Tests with fumed silica and non treated fumed silica showed considerable difference in the obtained final product We also developed a physical and chemical models of the setting process determine the time delay for onset of curing as a function of temperature and the profiles of the isotherms in the sample. In order to model the flow of the heat in laser-induced cunng we used theoretical approach to solve the time dependent heat equation in cylindrical coordinator. The data show the curing rate as function of temperature. Activation energy results were derived from differential scanning calorimetry (d.s.c.).