Characterization of Polymer Morphology in Polyurethane Foams Using Atomic Force Microscopy
Q. Lan1 and G. Haugstad2
1Huntsman Polyurethanes, 8600 Gosling Road, The Woodlands, Texas 77381
2Characterization Facility, University of Minnesota, Minneapolis, Minnesota 55455
One of the most important challenges in polyurethane (PU) science is characterization of foam morphologies, which provides information to help understand material properties and improve synthesis conditions. Atomic force microscopy (AFM) is a very useful technique to obtain such information. A key challenge is to apply this technique to PU foams without destroying their cell structure. In this article, we describe the development of a methodology to characterize different types of PU foams using AFM while keeping the foam cells intact. Epoxy resin was used to impregnate the foams and was cured afterwards. Smooth surfaces were created using a microtome to minimize topographic effects during AFM examination. Phase information was obtained on the PU matrix and differentiated from the epoxy in AFM. This technique is demonstrated using several different foams including a flexible foam, two different elastomeric foams, and a rigid foam nanocomposite. Comparison with compression techniques reveals that the proposed method does not modify foam morphology.