Sphemlite growth

Sphemlite growth of the crystallizable component in miscible blend (3.3.3) will be influenced by the type and molecular weight of the amorphous component (the former affecting the intermolecular interactions between both... 

Martuscelli [1984] studied the influence of the molecular weight of the crystallizable component (PEG) on the sphemlite growth rate of PEG/PMMA blend. In contrary to Calahorra et al. [1982] they found that the fold surface free energy, decreases with increasing PMMA content in the blend. It should be mentioned, however, that the... 

Figure 3.29. Temperature dependence of the diffusion driven displacement of the non-crystallizing component, v, and the sphemlitic growth rate, G [hi et al., 1991].

Figure 3.37. Theoretical estimation for sphemlite growth rate depression in immiscible PP-based blends in the case of REJECTION of particles influence of particle size, and volume concentration of the second component [Martuscelli, 1984].

The effect of blending on the overall crystallization rate is the net combined effect of the nucleation and sphemlite growth. Martuscelli [1984] observed that in blends of PP with LDPE, crystallized at a T high enough to prevent any LDPE crystallization, the overall rate of crystallization of the PP matrix... 

Sphemlite growth rate Finer dispersion of LLDPE can cause more o S ... 

The sphemlitic growth rate, the overall crystallization rate, and the melting temperature of PB-1 are depressed by the presence of HOCP. The verified HOCP interferences on the kinetics of PB-1 crystal transformation from form II to form I indicate that in the crystallized mixtures the HOC molecules are rejected in inter-lamellar and/or interfibriUar regions of PB-1 spherulites where, dependening on the blend composition, they can form a homogeneous mixture with uncrystaUized PB-1 molecules or a conjugated amorphous phase, one rich in PB-1 component and the other rich in HOCP component. 

The miscibility in the melt of iPP, PB-1, and HOCP has been evidenced by the presence of a single glass transition and by the interference of PB-1 and HOCP on sphemlite growth rate, overall crystallization rate, and melting equilibrium temperature of iPP. The addition of the HOCP component to iPP and PB-1 has been found to increase the stability of the blends. The demixing phenomena in the ternary blends occur during and/or after the crystallization of the PB-1 component. The possibility of preparing ternary blends where the PB-1 component directly crystallizes in form I, could offer new opportunities about their application. 

Bouapao, L., Xsuji, H., Xashiro, K. etal. (2009) Crystallization, sphemlite growth, and structure of blends of crystalline and amorphous poly(lactide)s. Polymer, 50, 4007 017. 

Plasticizers may slow down the formation of crystalline structures because they interfere in sphemlites growth since they are present in fold surfaces of crystalline lamel-lae. Sphemlites grown in the presence of tricresyl phosphate are coarser and less bire-fringent. In ionomers, the plasticizer helps to form aggregates (multiplets) and clusters in which polymer chains have restricted mobility. 

From the slope on the right graph of Fig. 99 an Avrami exponent of 3.2 results, close to the value expected for athermal nucleation followed by sphemlitic growth, but because of the many assumptions that went into the derivation of the Avrami equation still not proven without a detailed structural analysis. 

Armistead JP, Hoffman JD (2002) Direct Evidence of Regimes 1,11, and HI in Linear Polyethylene Fractions as Revealed by Sphemlitic Growth Rates. Macromolecules 35 ... 

Table 3.19 Expressions for the dissipation energy terms and corresponding sphemlite growth rates in a crystalline/amorphous polymer blend system (Martuscelli 1984 Bartczak et al. 1984) ...

Influence of compositional variations on the semicrystalline mmphology has heen investigated Inflnence of different sphemlite growth rales on semicrystallme morphology is discussed I inal sphemlite size has been evaluated... 

Flaris et al. (1993) investigated also the same blend system and reported that blending had a pronounced effect on the lamellar morphology. Eurthermore, the isothermal crystallization experiments indicated that the sphemlite growth rate, G, and the nucleation density of the PP phase were enhanced. The authors suggested that these observations could be related to the formation of additional nucleation sites, which arise from the polymer-polymer interfaces created by the blending. 

As observed under optical microscope with crossed polarizers, incorporation of up to 10 wt% EPDM into PPBC does not affect the nucleation density or ultimate size of PPBC spheruhtes (Fig. 10.19). The EPDM particles act as inert inclusions, constituting geometrical obstacles to the PPBC sphemlites growth, thus changing their morphology. Nevertheless, some interfacial interactions are observed in the case of a blend with 10 wt% EPDM. The spheruhtes of PPBC are found to nucleate from the interface with EPDM (Fig. 10.19c). This resembles the transcrystaUine structure observed in several glass or carbon fibers reinforced, semicrystalline polymers, such as PP, PE, PA-6, etc. (Xavier 1991). Such a stmcture was considered an indication of good interfacial interaction between the two constituents. 

Early studies on sphemlitic growth were sectioned in different subjects because they have investigated in numbers of material systems of various characteristics. Some well-established morphologies of sphemUte are presented in Fig. 1.15. Efforts have been made to propose a common feature of growth and mechanism of sphemlitic patterns. However, it observed that mechanism of spherulitic growth is not depends only on the molecular property and chemical stmctures of material systems. The morphologies and physical characteristics of a sphemlite from a system to other materials are varied drastically and found to be reliable on few key factors. 

The analysis of sphemlite growth-rate data over an extended temperature range thus presents a major dilemma. There are two conflicting results from the above... 

Figure 11.8b shows the LH plots and it is evident that the slope has decreased in value substantially after self-nucleation, when the self-nucleated and the neat sample data are compared. Also, from Table 11.4 we can observe the excellent correlation found between the values of Kg obtained by the LH treatment from sphemlitic growth rate data (PLOM) and those... 

The sphemlite growth rate and bulk crystallization kinetics of OBCs was studied. Rejection of the non-crystallizable soft block from the gro face decreases the crystallization kinetics of OBCs with increasing soft block content. The sphemlite growth rate conformed to the LH analysis and it was shown that a more disordered fold surface is obtained with increasing soft block content. Avrami analysis of bulk crystallization kinetics confirms sphemlitic growth and heterogeneous nucleation. It was also shown that statistical sequences crystallize much slower than ethylene blocks in OBCs. 

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