Polymer Crystalligation under shear Flow-Aming to Reveal the Formation Mechanism pf Fiber Structure.

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In this project we have studied formation mechanism of the so-called shish-kebab structure, which is a molecular origin of ultra-strong and ultra-high modulus fiber. We have studied crystallization process of some polymers (1)as a function of many factors which control the crystallization of polymers such as molecular weight, its distribution, temperature, shear rate, shear strain, (2)using several experimental methods to cover a wide spatial scale, and (3)under a mild shear condition to observe the shish-kebab formation process clearly. The main results obtained here are :(1)there exists a critical shear rate for the shish formation2)the critical shear rate is closely related to relaxation time of polymer(3)there exists a critical shear rate for the kebab formation(4)the above two critical shear rates are almost the same, showing that kebab formation is dominated by the shish formation.(5)the shish is formed before the kebab(6)high molecular weight component in a sample play an important role in the shish formation(7)entanglements play important role in shish formationIn conclusion, it is essential to study the shish formation process on the basis of the relation between the relaxation time and crystallization rate.