Properties of Rigid Polyurethane Foams Prepared from Recycled Aircraft Deicing Agent with Hexamethylene Diisocyanate Bao Wang, 1,2 Yan-Ling Cheng, 1,3 Yuhuan Liu, 1,4 Paul Chen, 1 Dong Li, 2 Roger Ruan 1 1 Center for Biorefining and Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota 55108 2 Department of Agricultural Engineering, College of Engineering, China Agricultural University, Beijing 100083, China 3 Department of Biological Medicine, College of Biochemical Engineering, Beijing Union University, Beijing 100023, China 4 Biomass Energy Center and State Key Laboratory of Food Science, Nanchang University, Jiangxi 330047, China Correspondence to: R. Ruan (E-mail: ruanx001@umn.edu) ABSTRACT: Polyurethane (PUR) rigid foams were prepared from recycled aircraft deicing agent (aircraft deicing fluid) with reaction of hexam- ethylene diisocyanate at temperature of 55  C. The effect of [NCO]/[OH] ratio on properties of microscopic structure, cell size distribution, compressive strength, apparent density, as well as thermal conductivity (k) was studied. Higher [NCO]/[OH] ratio helped achieve better micro- morphology, higher apparent density, and compressive strength of the PUR foams. With the [NCO]/[OH] ratio of 0.75 and 0.8, some shrink- ing happened during foam rising, causing a decrease in total volume of the PUR foam, and leading to higher apparent density as well as sharply increased compressive strength. All PUR foams displayed good thermal insulation properties in this study. With [NCO]/[OH] ratio increased from 0.7 to 0.8, the k value increased significantly from 34.3 to 42.2 mW m 1 K 1 . The k value here was chiefly governed by the apparent den- sity of the foams, which was in turn a function of the ratio of [NCO]/[OH]. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 000: 000–000, 2012 KEYWORDS: compression; foams; microstructure; polyurethanes; thermal conductivity Received 4 October 2011; accepted 19 February 2012; published online DOI: 10.1002/app.37525 INTRODUCTION Polyurethane (PUR) rigid foam is one of the most important thermal insulating materials used in constructions and other areas. The PUR foam works more effectively than fiberglass in thermal insulation. 1 Nowadays, PUR foams are generally pro- duced by polymerization of polyols/diols and isocyanates, both of which are produced mostly from petroleum-based products. 2 Due to the increasing consumption as well as limited availability of fossil resources, many researchers are seeking alternative raw materials for oil-based polyols, such as bio-based polyols from vegetable oils, including soybean oil, castor oil, rape oil, linseed oil, safflower oil, and palm oil 3–5 or from biomasses such as sto- ver, wood, and dried distiller grains. 1,6,7 During the formation of the PUR foam, generally two kinds of reactions take place. One reaction is between isocyanate and polyol/diol, which produces urethane links (ANH(CO)OA) and polymerizes PUR [as shown in Eq. (1)]. Another reaction is between isocyanate and water, which can be divided into two steps, and the reaction equations are given in eqs. (2) and (3). As shown in Eq. (2), water first reacts with isocyanate and pro- duces a carbamic acid, which is very unstable and quickly decomposes into amine and carbon dioxide (appears as foam bubbles). Then quickly the amine from Eq. (2) reacts with iso- cyanate and produces urea links [Eq. (3)]. Therefore, the two kinds of reactions cause an increase in apparent viscosity and form the cross-linking framework of the PUR foam subse- quently. Due to increase in the apparent viscosity of the mixed reaction agents, a lot of the carbon dioxide diffuses into the ‘‘solution,’’ which then helps form the cell structures and causes the foam to rise. (1) V C 2012 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM WILEYONLINELIBRARY.COM/APP J. APPL. POLYM. SCI. 2012, DOI: 10.1002/APP.37525 1