Polymer crystallization crystal growth rate

Hu WB (2005) Molecular segregation in polymer melt crystallization simulation evidence and unified-scheme interpretation. Macromolecules 38 8712-8718 Hu WB, Cai T (2008) Regime transitions of polymer crystal growth rates molecular simulations and interpretation beyond Lauritzen-Hoffman model. Macromolecules 41 2049-2061 Jeziomy A (1971) Parameters characterizing the kinetics of the non-isothermal crystallization of poly(ethylene terephthalate) determined by DSC. Polymer 12 150-158 Johnson WA, Mehl RT (1939) Reaction kinetics in processes of nucleation and growth. Trans Am Inst Min Pet Eng 135 416-441... 

Hu W, Cai T. Regime transitions of polymer crystal growth rates Molecular simulations and interpretation beyond Lauritzen-Hoffman model. Macromolecules 2008 41 2049-2061. 

The overall rate of crystallization is determined by both the rate of nuclei formation and by the crystal growth rate. The maximum crystal growth rate lies at temperatures of between 170 and 190 °C [71, 72], as does the overall crystallization rate [51, 61, 75], The former is measured using hot stage optical microscopy while the latter is quantified by the half-time of crystallization. Both are influenced by the rate of nucleation on the crystal surface and the rate of diffusion of polymer chains to this surface. It has been shown that the spherulite growth rate decreases with increasing molecular weight due to the decrease in the rate of diffusion of molecules to this surface [46, 50, 55, 71, 74],... 

In all kinetic theories of polymer crystallization [8] the crystal growth rate G... 

In order to record the dynamic polymer crystal growth process in-situ, two factors are significantly important. One is the use of a very high resolution technique. Such a technique can repeatedly record the same area without damage to or significant interactions with the sample. AFM has been proved to be a successful tool to fulfill this task. The other key factor is that the polymers must have an appropriate crystallization rate. It generally takes an AFM several minutes to produce an image. This requires that the polymer has a very slow crystallization rate. The crystallization rates of most semicrystalline polymers at room temperature are too fast. 

Accordingly, the influence of MW on the crystallization behaviors of semicrystalline polymers has been studied in various articles. For example, linear crystal growth rates of poly(ethylene oxide) and poly(ethylene succinate) (PES) reach a minimum value at a critical MW. This value is related to the crystallization transition from an extended chain to a folded chain conformation [96,97], suggesting that high MW polymers require sufficient reconformation time to achieve an ordered structure. As evidence of this MW dependence of the semicrystalline polymer on... 

Incorporating the concepts discussed above, the equation describing the crystal growth rate in a miscible polymer blend can be expressed as ... 

Reprinted by permission of John Wiley Sons, Inc. from (a) Holland, V. F. and Lindenmeyer, P. H., Morphology and crystal growth rate of polyethylene crystalline complexes J. Polymer Sci. 57, 589 (1962) (b) Blundell, D. J., Keller, A. and Kovacs, A. I., A new self-nucleation phenomenon and its application to the growing of polymer crystals from solution , J. Polymer Sci. B 4, 481 (1966). Copyright 1962, 1966 John WUey Sons, Inc. 

The details of the polymer crystallization process can be quite complicated. Practically, one may not care about the details of crystal nucleation and the linear crystal growth rates, but just want to characterize the overall crystallization kinetics. The degree of crystallization process can be roughly defined as crystallinity, regardless of their detailed crystal morphologies. The conventional methods to characterize the crystallinity include DSC, X-ray diffraction and dilatometer. Depending on the measured quantity, crystallinity is also separated into the weight crystallinity... 

The recent development of video rate AFM has also been discussed and its first application to crystal melting has been shown. The possibility of obtaining images 1000 times faster than conventional AFM, with time resolution of milliseconds, should provide exciting new information in many areas of polymer crystal growth in the future. 

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