In the present study a comprehensive experimental investigation on the batch and semi-batch emulsion terpolymerization of methyl methacrylate/butyl acrylate/acrylic acid (MMA/BuA/AA) is reported. Batch experiments were carried out in a fully automated pilot-scale reactor system to analyze the effect of polymerization temperature, anionic surfactant and initiator concentrations on the polymerization rate, average particle size, copolymer composition and glass transition temperature of the polymer. In addition, a series of semi-batch experiments were performed under monomer starved conditions to assess the effect of seven process variables, (e.g., concentrations of anionic, nonionic surfactants and initiator, polymerization temperature, agitation rate, impeller type and addition time of initiator/pre-emulsion mixture) on the polymerization rate, average particle size, copolymer composition, glass transition temperature and MWD of the polymer.