INDUSTRIAL PHOTOCHEMISTRY .20. 3-DIMENSIONAL MACHINING WITH LASER-POLYMER DEFORMATION INDUCED BY SHRINKAGE PHENOMENA

One of the main restrictions to the industrial development of the manufacturing process of three-dimensional objects by photopolymerization induced by laser (which is briefly described in the appendix) derives from the variation in volume between the liquid monomer and the solidified polymer. This results in the warping of the object. The shrinkage depends on the polymerization kinetics and, more particularly, on the light flux. The relationship between the shrinkage and the warping of the object is analysed. Before the gel point is reached, the reactive medium is fluid and the warping is directly related to the shrinkage. After the gel point, the reactive medium is solid and shear stresses appear which induce additional warping of the object. The notion of a gel point is illustrated by a model in which concepts from percolation theories are used. A semi-quantitative model, based on a kinetic model, is proposed to predict the volume variations in the reactive medium. This model will be used in further papers related to this subject. Our aim is to predict the warping of objects manufactured by laser photopolymerization using these simulation models.