Rendering polyureas melt processible
2011
Kang, Jungmee | Erdodi, Gabor | Kennedy, Joseph P.
Because of the presence of extensive H-bonding in the hard segments, polyureas are processed by solution techniques (e.g., dry spinning) by the use of relatively costly and environmentally unfriendly solvents. Thus, the objective of this research was to render polyureas melt processible, (i.e., to reduce their flow temperature, Tflow) without compromising their excellent mechanical properties. We hypothesized and herein demonstrate that by using conventional chain extenders (CEs) in combination with small amounts of H-bond acceptor chain extenders (HACEs), the Tflow of polyureas can be significantly reduced from ∼230 to ∼180 °C, and thus melt processible products with excellent mechanical properties can be obtained. We document the synthesis of conventional polytetramethylene oxide-based and novel polyisobutylene (PIB)-based polyureas with Tflows ∼ 180 °C and excellent mechanicals by the addition of few percents of commercially available HACEs. Products were characterized by various techniques, including Instron (tensile strengths, elongations), durometer (Shore A Hardness), dynamic mechanical thermal analysis (Tflow), and thermal gravimetric analysis (TGA) (thermal weight loss). According to TGA, a polyurea with Tflow of ∼180 °C did not degrade up to ∼234 °C in air. A micromorphology for melt processible polyureas is proposed that emphasizes flexibilized hard segments in the presence of HACEs.
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