Novel Polybutadiene Diols for Thermoplastic Polyurethanes

Krasol® polybutadiene diols are anionically polymerized products characterized by very narrow molecular weight distribution, linear structure of polymer chains and the absence of species with functionality higher than 0.2. These unique features make them suitable as hydrophobic polyol components for use in thermoplastic polyurethanes (TPUs). Various TPU formulations were developed using polybutadiene diols with either primary (Krasol LBH-P) or secondary terminal OH groups (Krasol® LBH), adopting a one-shot or prepolymer procedure. The TPU elastomers thus obtained may be classified as soft grade TPUs. The elastomers were characterized by measuring their physical and mechanical properties. Special attention was focused on the hydrolytic and chemical resistance of these TPUs. A hydrolysis study was performed in aqueous media (acetic acid, sulfuric acid, nitric acid, caustic soda), in methanol and ethanol. Contrary to a TPU based on a conventional polyether polyol, which was tested simultaneously, the stability of polybutadiene TPUs was outstanding even in very aggressive solutions of inorganic acids. TPUs manufactured from Krasol® polybutadiene diols have excellent electrical properties. The measurements of volume and surface resistivity of the polybutadiene-urethanes showed values several orders higher than those of polyether based TPUs. Based on their mechanical, chemical and electrical properties, polybuladiene TPUs have great potential for applications where excellent moisture resistance, chemical stability and electrical insulation characteristics are required. Introduction Thermoplastic polyurethanes (TPUs) are formed by linear polymeric chains of segmented structure. They are prepared by the addition reaction of bifunctional isocyanates, chain extenders and longchain polyols. Most of conventional TPUs are based either on polyester or polyether polyols, 4,4diphenylmethane diisocyanate (MDI) as an isocyanate component and 1,4-butanediol (BDO) as a chain extender(1). Development of soft grades of TPUs (having hardness about 70-85 Shore A) has been reported among the latest trends that are taking place in the TPU market. The main interest of researchers is focused on the polyol components(2). Polyurethanes based on polybutadiene polyols could fall into this category. Moreover, they are known for excellent hydrophobicity, hydrolytic and chemical resistance, electrical insulation properties and low-temperature elasticity(3-5). However, most of the commercially available large-scale hydroxyl terminated polybutadienes are manufactured by a free radical polymerization technology, e.g. Poly bd®. This technology yields polyols with functionality exceeding the value 2.0, that are not applicable in TPU systems(6). Polybutadiene polyols with a functionality of 2.0 designated Difol were developed by Amoco Chemicals several years ago(7). These polybutadiene diols proved to be suitable components used for 4880 01/10 APPLICATION BULLETIN Oaklands Corporate Center, 468 Thomas Jones Way, Suite 100, Exton, PA 19341 Toll Free 877-871-2729