JOURNAL OF MATERIALS SCIENCE LETTERS 22, 2 0 0 3, 1225 – 1228 New polyurethane-type rigid foams from liquified wood powders M. H. ALMA ∗ , M. ALTAY BASTURK Department of Industrial Engineering of Forestry, Faculty of Forestry, University of Kahramanmaras Sutcu Imam, 46060 Kahramanmaras, Turkey E-mail: alma@ksu.edu.tr M. DIGRAK Department of Microbiology, Faculty of Art & Science, Kahramanmaras Sutcu Imam University, 46100 Kahramanmaras, Turkey Polyurethanes (PUs) are one of the most useful three- dimensional polymers because they can be used in various forms of materials such as sheets, foams, elas- tomers, adhesives and paints, etc. PUs are a large va- riety of polymer with quite different compositions and correspondingly different properties. They can be pro- duced through interaction between polyols and poly- isocyanate via poly addition polymerization (Fig. 1) [1]. Since lignocellulosic materials including agricultural and or forestry wastes contain natural polymers (e.g., cellulose, lignin, hemicellulose and tannins) with more than two hydroxyl groups per molecule, they can be used as polyol for PUs preparation [2–13]. Recently, large amounts of industrial and domestic wood wastes have motivated the researchers to evaluate the wastes in the production of various materials such as molding materials, foams, adhesives, etc. The aim of this study was to produce PU-type rigid insulation foams from the two kinds of wood wastes as polyols. The wood powders (20–80 mesh) of Anatolia chestnut (Cestanea sativa L) and Calabrian pine (Pinus brutia L.) were used as a primary natu- ral polyols for making the polyurethane-type foams. Poly(ethylene glycol)-400, (PEG-400, polyols), ethy- lene glycol (polyols), 98% sulfuric acid (catalyst in the liquefaction) and 1,4-dioxan (solvent) have reagent grade. The ingredients used in the making of foam are as follows: Polyethylene glycol (PEG-400, commercial polyol), triethylene diamine (TEDA-D33LV, foaming catalyst), silicon-glycol copolymer (L3001, nonionic surfactants for rigid foams) and polymeric diphenyl- methane diisocyanate (PMDI-TED-31, crosslinking agent). All these ingredients were donated by Ispol Foam Ltd., Turkey. All the other chemicals used were of analytical grade and obtained from Carlo Erba (Carlo Erba Reagenti Co., Italy). For the laboratory-type biodegradation test, the fol- lowing microorganisms provided from department of Biology, Elazig University, Turkey were used. A mixture of oven-dried wood powders, PEG-400, gylcerin and sulfuric acid was heated in a three-necked round bottom glass at 150 ◦ C for 60 and 120 min. The resulting mixture was dissolved in a binary solvent (1,4- ∗ Author to whom all correspondence should be addressed. dioxane/water: 8/2) and then filtrated. And the dioxan- insoluble part was oven dried and weighed. Finally, percent dioxan-insoluble part (DIP) was determined by the following equation: DIP(%) = w B0 - w B w B0 × 100 (1) where w B0 and w B are the oven-dry weight of starting wood powders (g) and the oven-dry weight of unliqui- fied wood determined after the liquefaction (g), respec- tively. In addition, the acid and hydroxyl values of the liqui- fied products were as described elsewhere [10]. A definite amount of the concentrated liquified wood, the foaming catalyst, surfactant and blowing agent (water) were uniformly premixed in a paper cup. And then a certain amount of PMDI (isocyanate index: 130) was added to the premixed components and stirred at a speed of 8000 rpm for about 20 s. The foam was allowed to form at an ambient tem- perature, and allowed to be cured for two days be- fore cutting them into specimens (50 mm × 50 mm × 50 mm) for measurements of the mechanical prop- erties and densities. The mechanical properties (i.e., compressive strength and its elastic modulus) of the foam specimens were measured according to JIS K7220 using a universal testing machine (Instron, DCS-500R). Two bio-assay tests were conducted to evaluate the biodegradabilities of the PU foams. One of them is ser- vice test. Another one is laboratory test. For the for- mer, the oven-dried foam blocks (2 cm × 2 cm × 2 cm) were buried in culture soil (sand: 48.8; clay: 27%; silt: 24.2; pH: 7.8; organic matter: 1.8%; total nitrogen: 0.15%; phosphorous, 17.8 ppm; exchangable K + ions, 1.08 m.e./100 g soil; exchangable Mg 2+ ; 6.96 m.e./100 g soil) and then incubated at 30 ◦ C for 6 months. Water content of the soil was maintained at 60% by occasional addition of water. At the end of incubation period, impurities on the samples were com- pletely removed and oven dried. Eventually, the percent weight loss was calculated by conventional methods [14]. 0261–8028 C  2003 Kluwer Academic Publishers 1225