Poly spherulite nucleation rate

Fig. 9.26 Plot of spherulite nucleation rate in poly(hexamethylene adipamide), Mn = 14 600, at indicated crystallization temperatures. (From McLaren (108))...

Fig. 9.71 Spherulite growth rates of isotactic poly(propylene) with different sorbitol compounds as nucleation catalysts, o pure polymer dibenzylidene sorbitol o- (p-chloro, p-methyl) dibenzylidene sorbitol, -o bis (p-ethylbenzylidene sorbitol. (Data from (249))...

Table 9.8 compares the influence of different nucleating agents on the spherulite growth rate of poly(ethylene terephthalate).(254) The growth rate at 237 °C for the pure polymer is 3.9 0.3 gm min. Except for CaO, the spherulite growth rates are... 

Table 9.8. Spherulitic growth rates (fim/min) of poly(ethylene terephthalate) samples containing indicated nucleating agents for crystallimtion...

Attapulgite reinforced poly(butylene succinate-co-butylene adipate) nanocomposites were prepared by melt mixing and thermoforming. Attapulgite acted as the nucleating agent. The crystallization rate was increased and the size of the spherulites was reduced with the attapulgite added into PBS A matrix. ... 

In LCP blends with PBT, the increase in crystallinity is associated with the decrease in crystallite size (nucleation favored) when LCP concentration is low (20%). At high LCP content the increase in crystallinity is associated with the increasing crystallite size suggesting the favored growth of crystal domain. Poly(ethylene 2,6-naphthalate), PEN, spherulite dimensions decrease in the presence of LCP. This is caused by a heterogeneous nucleation by the crystallized LCP particles on the molten PEN matrix. Also presence of LCP nucleates poly(ether imide) increasing its crystallization rate. ... 

The overall crystallinity, crystalhzation rate, nucleation density, and spherulite number increased, and the crystallization time decreased, indicating the heterogeneous nucleating effect of zinc oxide and phenylphosphonic acid zinc salt on the crystallization of PLA. The synergistic effect of zinc oxide and phenylphosphonic acid zinc salt on the crystallization behavior of poly (lactic acid) was observed. ... 

In a few cases, the addition of minor amounts of immiscible or miscible polymers results in the nucleation of a crystalline polymer. The nucleation of PP by PE and polyamides (e.g., PAl 1) (immiscible) as well as the addition of PP to poly(butene-l) (miscible) has been noted in the literature [138-141 ]. The addition of LDPE to PP showed a reduction in the spherulite size of PP, attributed to an increase in nucleation density of the a-crystalline form along with an increase in the rate of growth of the -crystalline form [141]. The nucleation of polycarbonate by the zinc salt of sulfonated polystyrene ionomers was noted to occur with both miscible and phase separated blends [142]. Nanometer sized ionic aggregates appeared to contribute to the polycarbonate nucleation. A liquid crystalline copolyesteramide (Vectra-B950 ) was shown to accelerate the crystallization of poly(phenylene sulfide) [143]. This effect was not concentration dependent and did not change the level of crystallinity. 

The results of Rory and McIntyre (22) for the rate of formation of spherulitic centers in molten poly(decamethylene sebacate) provide a good set of data to examine whether Eq. (9.170) or (9.171) is operative. In these experiments the undercooling ranges from 11 °C to 16 °C. Concomitantly the initiation rate increases by a factor of 10. This result is clearly indicative of nucleation control. The log of the rate of spherulite formation, log N, for this polymer is plotted against (T / T)(l/ AT) and (Tra/T)(l/ AT) in Fig. 9.38. Excellent straight lines are obtained with either plot. Thus, it is not possible to discriminate between the two distinctly different initiation nucleation processes by analysis of the temperature coefficient. 

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