Morphology semicrystalline

A major challenge in using interactive chromatography for polyamides is to find a suitable mobile phase (Mengerink et al., 2001, 2002 Weidner et al., 2004). Polyamides form semicrystalline morphologies that limit the solubility in organic solvents. Besides hot phenol, formic acid, and trifluoroethanol (TFE) (Mori and Barth, 1999), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) represents a suitable solvent for polyamides (Chen et al., 2002). These solvents are mainly used to analyze the molar mass distribution of polyamides by SEC. 

C), it has been observed that its crystallization from the melt is enhanced [103-106], Melt crystallized polymers nucleated with n-s polymer-CD-ICs crystallize more rapidly, evidence greater levels of crystallinity, higher melt crystallization temperatures, and semicrystalline morphologies characterized by crystals which are smaller and more uniformly distributed than in un-nucleated pure bulk samples. 

This chapter, related to the crystallization, morphological structure and melting of polymer blends has been divided into two main parts. The first part (section 3.1) deals with the crystallization kinetics, semicrystalline morphology and melting behavior of miscible polymer blends. The crystallization, morphological strucmre and melting properties of immiscible polymer blends are described in the second part of this chapter (section 3.4). 

In the following part, a discussion on the crystallization behavior in immiscible polymer blends is given, including the nucleation behavior, spheiuhte growth, overall crystallization kinetics, and final semicrystalline morphology. Each topic is illustrated with several examples from the literature, to allow the reader to find enough references on the discussed subject for further information. 

The discussion on the crystallization behavior of neat polymers would be expected to be applicable to immiscible polymer blends, where the crystallization takes place within domains of nearly neat component, largely unaffected by the presence of other polymers. However, although both phases are physically separated, they can exert a profound influence on each other. The presence of the second component can disturb the normal crystallization process, thus influencing crystallization kinetics, spherulite growth rate, semicrystalline morphology, etc. 

Blend system Comp. G(lim/min) (from O. M.) p C Final semicrystalline morphology Comments Reference... 

Some examples of the final semicrystalline morphology in several immiscible crystalline/ amorphous blend systems have already been given in Table 3.21 for the discussion of the spherulite growth rate (Part 3.4.3.2). Some more information about this topic can be found in the articles listed in Table 3.23. 

Table 3.23. Overview of literature in which the final semicrystalline morphology in immiscible crystaUine/amorphous polymer blends has been studied...

Influence of compositional variations on the semicrystalline morphology has been investigated Influence of different spherulite growth rates on semicrystalline morphology is discussed Final spherulite size has been evaluated... 

Several authors have investigated the influence of compatibilization on the global blend morphology. However, only a few authors really tried to understand the effect of compatibilization in crystalline/crystalline polymer blends on the crystallization kinetics, melting behavior and semicrystalline morphology of the components. In Table 3.29 some recent results on this topic are summarized. 

The scientific literature on crystallization in polymer blends clearly indicates that the crystallization behavior and the semicrystalline morphology... 

The most important chitin derivative is chitosan, obtained by its partial deacetylation under alkaline conditions or by enzymatic hydrolysis in the presence of chitin deacetylase. Because of the semicrystalline morphology of chitin, chitosan obtained by a solid-state reaction has a heterogeneous distribution of acetyl groups along the chain. On the other hand when chitin is treated with concentrated aqueous sodium hydroxide, N-deacetylation proceeds smoothly and homogeneously deacetylated samples are obtained [37]. 

Crevecoeur, G., and Groeninckx, G., Binary blends of peck and poly(clher-imide) miscibility, crystallization behaviour and semicrystalline morphology, Maeromoleeules (in press I 91 when received by me). 

The processes that occur in the spinline, between the exit of the polymer from the spinneret and the point of stress isolation on the first godet or roller at the base of the spin line, involve the changing of this fluid network to the solid-state molecular chain topology of the filament. Within a distance of 3 5 m, and under the influence of an applied force (take-up tension) and quench media, at speeds in excess of 100 miles per hour—less than 0.01 sec residence time—the fiber is transformed from a fluid network to a highly interconnected semicrystalline morphology, characterized by the amount, size, shape, and net orientation... 

Excellent work was reported by Balsamo et al. (2006) on the semicrystalline morphology of PCL/PSMA14 miscible blends as well as on their crystallization kinetics. The authors used a combination of dielectric, calorimetric, and microscopy characterization tools to investigate crystallization features of PCL in miscible PCL/PSMA14 blends over the whole composition range. The results achieved allowed to draw the following conclusions with respect to the miscibility effect on the blend relaxation dynamics and crystallization kinetics of PCL ... 

Semicrystalline morphology, i.e., shape, size, and texture of the spherulites, interspherulitic boundaries, etc. 

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