Self-nucleation applications

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. 

A special case of interest is reinforced polypropylene with various fibers. Often transcrystallinity in polypropylene occurs which is due to dense heterogeneous nucleation by a substrate. The occurrence of transcrystallinity depends on the type of fiber and the temperature. In contrast to transcrystallinity in quiescent crystallization, the application of stress at the interface between a fiber and a PP melt results in the crystallization of polypropylene on a row-nuclei around a fiber. This effect is caused by strain-induced nucleation via some self-nucleation mechanism and is independent of the type of fiber and less dependent on the temperature of crystallization [5,6]. Axial stress arises also during cooling of two materials with a large difference in thermal expansion coefficients. As such, the stress-induced nucleation in reinforced PP depends also on the cooling rate, fiber length, position along the fiber and viscoelastic properties of the PP melt [5]. 

Blimdell D, Keller A, Kovacs A (1966) A new self-nucleation phenomenon and its application to the growing of polymer crystals from solution. J Polym Sci B Polym Lett 4(7) 481-486... 

Self-nucleation can be used as the basis of comparison to determine the nucleation power of additives, nanofillers, or nucleating agents. This is a very useful application in order to quantify the efficiency of nucleation of a foreign additive into any polymer. The idea was proposed by Fillon et al. [34], The first step would be to self-nucleate the polymer of interest, just like in Figure 5.4, to determine its self-nucleation domains. 

The SSA technique is now being used rather frequently for all the applications quoted above. Unfortunately, in many recent references, the authors do not perform a previous self-nucleation study to determine the ideal self-nucleation temperature. Therefore, they start their SSA protocol at an arbitrary value that will have an important impact on the fractionation profile. Any attempt to quantify the data and calculate SCB or MSL distributions will not be correct unless the first value employed to perform SSA is the ideal self-nucleation temperature. 

Analytical solutions of the self-preserving distribution do exist for some coalescence kernels, and such behavior is sometimes seen in practice (see Fig. 40). For most practical applications, numerical solutions to the population balance are necessary. Several numerical solution techniques have been proposed. It is usual to break the size range into discrete intervals and then solve the series of ordinary differential equations that result. A geometric discretization reduces the number of size intervals (and equations) that are required. Litster, Smit and Hounslow (1995) give a general discretized population balance for nucleation, growth and coalescence. Figure 41 illustrates the evolution of the size distribution for coalescence alone, based on the kernel of Ennis Adetayo (1994). 

Paul van der Schoot, Nucleation and Co-Operativity in Supramolecular Polymers Michael J. McPherson, Kier James, Stuart Kyle, Stephen Parsons, and Jessica Riley, Recombinant Production of Self-Assembling Peptides Boxun Leng, Lei Huang, and Zhengzhong Shao, Inspiration from Natural Silks and Their Proteins Sally L. Gras, Surface- and Solution-Based Assembly of Amyloid Fibrils for Biomedical and Nanotechnology Applications... 

Major topics include rate equations, reactor theory, transition state theory, surface reactivity, advective and diffusive transport, aggregation kinetics, nucleation kinetics, and solid-solid transformation rates. The theoretical basis and mathematical derivation of each model is presented in detail and illustrated with worked examples from real-world applications to geochemical problems. The book is also supported by online resources self-study problems put students new learning into practice and spreadsheets provide the full data used in figures and examples, enabling students to manipulate the data for themselves. 

Shur, V. 2004. Correlated nucleation and self-organied kinetics of ferroelectric domains., in Nucleation Theory and Applications. Schmelzer, J.W.P., Editor. Wiley-VCH. Ch. 6, pp. 178-214. 

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