Identification and Quantitation of Urea Precipitates in Flexible Polyurethane Foam Formulations by X-ray Spectromicroscopy

E. G. Rightor,* ,† S. G. Urquhart, ‡, A. P. Hitchcock, § H. Ade, ‡ A. P. Smith, ‡,| G. E. Mitchell, † R. D. Priester,A. Aneja, # G. Appel, ‡ G. Wilkes # and W. E. Lidy ^

† Analytical Sciences, The Dow Chemical Company, 1897 Building, Midland, Michigan 48667
‡ Department of Physics, North Carolina State University, Raleigh, North Carolina 27695
§ Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON L8S 4M1 Canada
^ Polyurethanes, Dow Chemical, Building B-1608, 2301 N. Brazosport Blvd., Freeport, Texas 77541
# Department of Chemical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061

Received December 28, 2001

ABSTRACT: Scanning transmission X-ray microscopy (STXM) and atomic force microscopy have been used to study the morphology and chemical composition of macrophase-segregated block copolymers in plaque formulations based on water-blown flexible polyurethane foams. Although there has been a large body of indirect evidence indicating that the observed macrophase-segregated features in water-rich polyurethane foams are due principally to urea components, this work provides the first direct, spatially resolved spectroscopic proof to support this hypothesis. The STXM results are consistent with a segregation model where urea segments segregate, forming enriched phases with the majority of the polyether- polyol and urethane groups at the chain ends of the urea hard segments. Chemical mapping of the urea, urethane, and polyether distribution about the urea-rich segregated phases showed that the urea concentration changes gradually (across several hundred nanometers) in a butylene oxide-based foam. This mapping also showed the urea-rich segregated phases present as a partial network in an ethylene oxide/propylene oxide sample.

10.1021/ma0122627 CCC:© 2002 American Chemical Society