Comparison of Adipic Versus Renewable Azelaic Acid Polyester Polyols as Building Blocks in Soft Thermoplastic Polyurethanes

In this study, novel polyester diols of 2000 molecular weight (MW) were synthesized by reacting azelaic acid (AZ) with 1,3-propanediol (1,3-PDO) and diethylene glycol (DEG) in the esterification reaction catalyzed with a small amount of butyltintris(2-ethylhexanoate). As a reference, polyester polyols of 2000 MW were synthesized from adipic acid (AA) with 1,3-PDO and DEG. The properties of polyester polyols were evaluated. The polyester polyol based on AZ and 1,3-PDO is 100 % renewable polyol; 1,3-PDO used in the syntheses is renewable product produced by fermentation process of sugar. Both 1,3-PDO-polyester polyols exhibited crystalline transition above room temperature, while DEG-polyester polyols were liquid at room temperature. The polyester polyols were chain-extended with 4,4′-diphenylmethane diisocyanate (Mondur M) and 1,4-butanediol (BDO) to form thermoplastic polyurethanes (TPU). TPU were evaluated for mechanical and water resistance properties, and their morphology were studied via differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and atomic force microscope (AFM). TPU based on azelate and adipate polyols were relatively soft elastomeric materials with high melting temperatures. AFM analyses of TPU indicated better phase separation in 1,3-PDO polyester polyols with the highest phase separation observed in TPU based on 1,3-PDO/azelaic acid polyols. Water resistance of TPU based on azelate polyols was improved as compared to TPU based on adipate polyols. © 2016, AOCS.