Crystalhte extended-chain

Tsuji, H. and Ikarash, K. (2004) In vitro hydrolysis of poly(L-lactide) crystalline residues as extended-chain crystalhtes II. Effects of hydrolysis temperature. Biomacromolecules, 5, 1021-1028. 

Different types of crystalline structures develop Fibrillar or extended-chain crystals and lamellar crystalhtes. Development of the first mentioned stractures is an equilibrium process. We do not have an amorphous phase since both segments and chains are ordered. Extended-chain crystals develop only in polymers of low molecular mass M < 10 kg/mol) and in the range of low undercoolings, that is AT = T - T is small. 

A common feature of highly oriented fibers is poor compressive properties, demonstrated by kink bands that can be seen in the OM and the SEM. Kink bands have been studied [677,679-682] and a mechanism for their formation, consistent with tensile loss, was proposed. Martin [693, 705, 706] addressed this issue by use of HREM, imaging the deformation and disorder in extended chain polymer fibers [705], showing that deformation occurs by strain localization into kink bands. High resolution EM images revealed the crystalhte size, shape, orientation, and internal perfection. The nature of the disorder within a kink band was imaged, modeled, and compared with diffraction data. Kinks were observed [706] by TEM investigation of PBZT... 

Polyurethanes show many of the same features as the copolyesters and copolyamides with respect to both hard and soft segment crystallinity. One substantial difference between polyurethanes and the previous two materials is that not all commercial polyurethane TPEs show hard segment crystallinity MDI-based polyurethanes show crystallinity while TDl-based urethanes do not. Two crystalline structures have been found for MDl-BD hard segments in the unoriented state with another distinct form found in the oriented state [86,87]. Other studies have examined the effect of chain extender length on the crystal structure [88]. The differences between polyurethanes with chain-folded and chain-extended hard segment crystalhtes has been extensively studied by Eisenbach et al. [89]. 

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