The bulk polymerization of vinyl chloride is still at the present time far from being well understood. In spite of the economic importance of the process, the detailed quantitative behavior of the reactor has not been elucidated. Immediate reasons for this, are given by the physical complexities of particle formation (arising from oligomer precipitation in solution), and heterogeneous polymerization kinetics, recalling that the process starts with one liquid monomer phase and finishes with three phases: liquid and gaseous monomer, and solid polymer.