GOALI: New Generation of Acrylic Resins Produced through Spontaneous Thermal Polymerization

Drexel University, Philadelphia PA

Investigators

Abstract

ABSTRACT PI: Masoud Soroush Institution: Drexel University Proposal Number: 0651706 Title: GOALI: New Generation of Acrylic Resins Produced through Spontaneous Thermal Plymerization Intellectual Merit: North American regulations on volatile organic content (VOC) of coatings require the reduction of allowable VOC's from 480 g/L of paint in 1990 to below 300 g/L by 2010. These and similar regulations are driving change in the basic nature of resin in coatings. Low molecular weight, highly functionalized polymer and oligomer solutions at 60 to 80 weight percent solids have replaced high molecular weight, non-functional polymer solutions at 30 to 40 weight percent solids as key components in coatings formulas. A promising method of producing low molecular-weight polymer solutions is to carry out the polymerization at high temperatures. At these high temperatures, secondary reactions, that are insignificant at low temperatures, have very strong effects on the polymerization rate and molecular structure formation. For example, alkyl acrylates undergo significant, sustained, reproducible, spontaneous homo- and co-polymerization at temperatures above 140.C, which was first reported by this team in 2002 methacrylates and styrene have been known for several decades to undergo reproducible spontaneous polymerization at high temperatures. The species that initiate the chain reactions in spontaneous thermal polymerization of alkyl acrylates and the initiation mechanism are yet unknown. A quantitative understanding of these secondary reactions allows one to design safer and environmentally-friendlier polymerization processes that produce a new generation of higher quality, solvent-borne resins. In this project, an effective experimental method is first designed to identify (a) the trace species that initiate the spontaneous polymerization of alkyl acrylates and (b) the mechanism of the initiation process. The experiment method should ensure the identifiability of the initiating species and the reaction parameters. Second, under carefully controlled conditions, high-temperature spontaneous polymerization of alkyl acrylates such as butyl acrylate is carried out according to the experiment method, and the polymer structure is characterized. Third, these results are combined with mathematical modeling to refine the mechanistic pathways and quantify the kinetics of the secondary reactions. Fourth, the identifiability of the parameters of the developed reaction network is investigated to ensure the sufficiency of the type, number and quality of measurements. Fifth, a general model applicable for high-temperature free radical polymerization of alkyl acrylates is constructed and tested against lab-scale experimental data. Finally, by using the developed mechanistic models, reactor design configurations such as semi-batch, continuous stirred tank (CST), and hybrid (CST followed by semi-batch) are screened using a novel game-theory-based method, and an optimal recipe for each optimal design configuration is calculated. Broader Impact: The potential impacts of the project are environmental, economic and educational, among others. The improved quantitative understanding of the secondary reactions leads to the production of a new generation of higher quality, environmentally-friendlier solvent borne paints and coatings at lower operating costs. Low molecular weight, polymer and oligomer solutions even at high weight percent solids have adequately low viscosity, thus requiring the addition of less organic solvents. The use of less or no added thermal initiators (normally the most expensive component of a resin formula) and the adequacy of shorter reaction times at higher temperatures lower the operating costs. The presence of less residual groups from thermal initiators (which adversely affect polymer properties such as resistance to UV radiation) in the final product and the use of the quantitative understanding in optimal control of molecular properties improve the resin quality. The resin and coating industries including DuPont benefit primarily from the scientific outcomes of this project. The project provides one Ph.D. and two undergraduate students with an invaluable opportunity to gain research experience in an industrial environment. Its results are released to the public at conferences and in journal papers.