Green Chemistry Approach to Synthesize Polyurea Elastomer

• Main Authors: Wen Chen Pan, 潘玟蓁
• Other Authors: Shenghong A. Dai
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/00407604632870981823

博士 === 國立中興大學 === 化學工程學系所 === 103 === In an effort to develop green processes to produce elastomeric polyurethane-urea Elastomer (PUaE) through non-isocyanate routes (NIR), highly practical methods of utilizing diphenyl carbonate (DPC) instead of diisocyanate as the carbonylation agents have been developed. The trans-esterification of several representative aliphatic diamines with DPC under different combinations and solvents has resulted in new processes which produced segmented PUaEs with consistent high molecular weights and mechanical performances. In the evolution of our NIR process developments, it began with the preparation and isolation of pure bis-carbamates from diamines such methylene dianiline (MDA) or 1,6-hexamethylene diamine (HDA) with DPC which was followed by trans-esterifications with long-chained and short-chained diamines carried out in tetramethylene sulfone (TMS) solution leading to PUaEs. Then, in the subsequent improvement, a one-pot sequential addition of three different diamines, HDA, polypropylene ether diamine of 2,000 molecular weight, and isophorone diamine were added to DPC sequentially in TMS to form the second generation PUaEs. Finally, non-VOC solvent trans-esterification processes were developed simply using the pure DPC under its molten state. The key to the present successful development lies in the realization of timing and sequence of the diamine additions to form initial biscarbamate intermediates in-situ and then in shifting the equilibrium towards polyurea product formation by phenol removal from the solution so that high molecular weight polyurea could be formed favorably. Furthermore extension of the approach through replacing partial hard segment with water dispersants groups such as ESA (3-[(2-aminoethyl) amino]-1-propane sulfonic acid sodium salt) or APTES ((3-Aminopropyl) triethoxysilane) in making water-based PUaE also have been achieved. The optimized NIR polyurea films made in this study consistently have the ηinh of over 0.6, with high performance characteristics showing tensile strength ranges of 15~30 MPa and elongation exceeding 400 %. Ultra-high molecular weight of polyurea (NS-P7) and the highest heat properties with Td of > 315 ℃ was achieved in the melt-process. Well-defined soft- and hard-segment domains were observed for the products as determined by AFM. These new improved NIR processes to produce segmented poly-aliphatic ureas thereby comply fully with the principles of green chemistry using safe and readily available chemicals.