Between the asbestos diaphragms, asbestos with polymer or only polymer for use in the chlor-alkali industry, the diaphragm technology is still known for contributing the most in industrial production being responsible for the operational security and energetic efficiency. The objective of this work is the quantitative understanding of the influence of the effects that the variables involved in the diaphragms manufacturing have on the performance of this process. The major variables considered in this work are: the specific weight, the relationship between the length of the asbestos fibers and the concentrations of NaCl, NaOH and the SM2 (TM) polymer. From a statistical mathematical model, it was possible to establish quantitative relationships between these variables and the parameters that characterize the diaphragm, such as the MacMullin number and permeability associated to a phenomenological model proposed by Van Zee [Van Zee, J.W., 1984. Sodium-Hydroxide Production in Diaphragm-Type Electrolyzers, Ph.D. Dissertation, Texas A&M University]. Therefore, it was possible to compare experimental and calculated data from this model for current efficiency and the concentration of NaOH produced for a group of 34 industrial cells in operation. Finally, it was possible established a mathematical relationship between the variables involved in the manufacturing process with the performance of the diaphragm in an industrial electrolytic cell. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.