Crosslinked Side-chain Polyurethane with Shape-memory Effect

• Main Authors: Hsin-Chih Liu, 劉信志
• Other Authors: 鄭紀民
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/76q8jw

碩士 === 國立中興大學 === 化學工程學系所 === 100 === A hydroxyl group-containing [3-(4-(4-(3,3-dimethyl-2,4- dioxoazetidin-1-yl)benzyl)phenyl)-1,1-bis(2-hydroxyethyl)urea] with reactive azetidine-2,4-dione group was prepared and introduced into polyurethane backbone. The polyurethanes with reactive pendent azetidine-2,4-dione groups were further crosslinked by short-chain aliphatic diamine or modified by silane coupling agent (3-aminopropyltriethoxysilane; APS) following by a sol-gel reaction to bring about Si–O–Si crosslinked organic/inorganic hybrid polyurethanes with shape memory function. X-ray diffraction (WXRD) and differential scanning calorimeter (DSC) showed that the crystallinity of polyurethane decreased with the increase of crosslinking density. The glass transition temperatures (Tg), tensile strength and storage modulus increased with increasing crosslinking density and hard-segment rigidity. Dynamic mechanical analysis (DMA) and shape recovery tests revealed the close relationship between shape memory behaviors and polymeric structures. The high ratio of storage moduli below and above transition temperature accounted for excellent temporary shape fixing at low temperatures and faster shape recovery speed at high temperatures. In addition, phase separation was characterized by atomic force microscopy (AFM). By introducing the chemically crosslinked structures, the deformed samples completely recovered to their original shape in less than 6 second without any deficiency during shape recovery tests. Shape recovery went up to 99% during cyclic thermomechanical tensile tests, indicating that the polyurethanes with chemical crosslinking effects exhibited higher impact than did the linear and dendritic side-chain polyurethanes. Consequently, these novel crosslinked polyurethanes with excellent shape-memory effect have been successfully developed in this work.