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Crystallization in polymer systems actually is a process that transfers the entangled melts into a semi-crystallinelayered structure. Whether or not a chain disentangles may result in different crystallization mechanism. When compared tothe crystal thickness (d_c), the volume occupied by the chain in the melt, i.e., the radius of gyration (R_g), plays a veryimportant role in polymer crystallization. When d_c≤R_g, crystallization does not necessitate a chain disentangling. Theentanglements are just shifted into the amorphous regions. However, as d_c>R_g, i.e., as the crystal thickness ges larger thanthe radius of gyration of the chain in the melt, it becomes necessary for a chain to disentangle. Then a change ofcrystallization mechanism occurs. Such change has been experimentally observed in the crystallization of poly(1-butene). Achange in the crystal morphologies from spherulite to quadrangle, is seen via PLM, as crystalliation temperatures increase.Even more, such a change is molecular weigh dependent and shifts to lower temperature as molecular weigh decreases.There exists a jump of crystal thickness and crystallinity associated with morphological change, as seen via SAXS. A changeof crystallization kinetics and crystallinity is further evidenced via dilatometry. The unique feature of P1b crystallization hasbeen discussed based on the radius of gyration of chain in the melt (R_g), and very good agreement is obtained.
Crystallization in polymer systems actually is a process that transfers the entangled melts into a semi-crystalline crystalline structure. Whether or not a chain disentangles may result in different crystallization mechanisms. When compared tothe crystal thickness (d_c), the volume occupied by the chain in the melt, ie, the radius of gyration (R_g), plays a very important role in polymer crystallization. When d_c≤R_g, the crystallization does not necessitate a chain disentangling. However, as d_c> R_g, ie , as the crystal thickness ges larger thanthe radius of gyration of the chain in the melt, it becomes necessary for a chain to disentangle. Then a change of crystallization process mechanism occurs. Such change has been experimentally observed in the crystallization of poly (1-butene) . Achange in the crystal morphologies from spherulite to quadrangle, is seen via PLM, as crystalliation temperatures increase. Even more, such a change is is molec ular weigh dependent and shifts to lower temperature as molecular weight determination. There exists a jump of crystal thickness and crystallinity associated with morphological change, as seen via SAXS. A change of crystallization kinetics and crystallinity is further evidence via via dilatometry. The unique feature of P1b crystallization hasbeen discussed based on the radius of gyration of chain in the melt (R_g), and very good agreement is obtained.