Poly spherulitic growth rates

Tant, M. R. and Culberson, W. T., Effect of molecular weight on spherulite growth rate of poly(ethylene terephthalate) via real-time small angle light scattering, Polym. Eng. Sci., 33, 1152-1156 (1993). 

Di Lorenzo, M.L. (2001) Determination of spherulite growth rates of poly(L-lactic acid) using combined isothermal and non-isothermal procedures. Polymer, 42, 9441-9446. 

FIGURE 3 Arrhenius plot for spherulite growth rate of poly(hydroxyl butyrate-co-... 

Spherulitic growth is a special case in crystallization. Spherulites form only within a specific temperature range for example, with it-poly(propylene) with a melting point of ITO C, they are first formed below IIS C. With spherulites, the rate of advance of the spherulite boundary is followed. This boundary encloses the crystalline portion of the spherulite. Since spherulites also contain noncrystalline material, however, the spherulite growth rate thus corresponds to the linear crystal growth rate. As the molecular weight increases, the rate of crystallization falls, since the rate of diffusion of segments and molecules decreases. 

Isotactic poly(2-vinyl pyridine) mm>98% Cystallization and melt behavior discussed. Mv = 400000 maximum spherulite growth rate at 7c = 165°C 7 °=212.5°C. [159]... 

Regime transition is presented when the data are analyzed with the Lauritzen and Hoffman kinetic theory. Di Lorenzo demonstrated that the discontinuity in the spherulite growth rate is not associated to any change in superstructural morphology. Tsuji et al. and Yuryev et al. also observed this unusual bimodal crystallization behaviour for pure PLLA, while the normal characteristic bell-shaped spherulite growth rate dependence was seen for poly(L/D-lactide) copolymers. 

In blends composed of immiscible polymers, amorphous polymer does not affect the crystallization of ciystallizable polymer, but if two polymers are miscible, amorphous polymer acts as diluent and affects crystallization of the second polymer. Poly( -caprolactone) is a ciystallizable component of the blend with poly(vi-nyl butyral), which is studied in compositions containing carbon black. Typically, blends of these two polymers form very large spherulites, and it is interesting to find out how carbon black affects crystallization and other properties of the blend as well as the distribution of carbon black in relationship to the spherulites. Figure 16.6 shows that spherulite growth rate is independent of carbon black presence (points of carbon black filled and carbon black free blend follow the same relationship). Additional data show that crystallization rate decreases with the amount of PVB increasing. Carbon black aggregates are mainly found in spherulites. 

PEO blends with poly(ether sidfone) (PES) exhibit miscibility with a lower critical solution temperature slightly above the PEO melting point [198, 199]. The addition of PES to PEO reduces the overall crystaUization rate and spherulitic growth rate as expected from the combination of miscibility and the high Tg of PES (220 °C) [200]. The phenolphthalein poly(ether ether sidfone) (PES-C) was also shown to be miscible with PEO with a lower critical solution temperature [201 ]. PEO crystaUinity was observed at PEO > 50 wt% and all films were transparent above the PEO melting point, but became turbid when heated above the lest phase boundary. 

PC yields lower crystallinity and reduced crystallization rate for PCL, as would be expected from the above discussion. A similar situation exists for miscible blends of poly(butylene terephthalate) (PBT) and the polyarylate based on Bisphenol A isophthalate (PARi) [126]. PBT with a much lower Tg than PARi exhibits decreased spherulitic growth rates with PARi addition. PARi, which is very difficult to melt crystaUize (imblended), showed increasing spherulitic growth rate with PBT addition. 

Du ZX, Yang Y, Xu JT, Fan ZQ. Effect of molecular weight on spherulite growth rate of poly(e-caprolactone) and poly(e-caprolactone)-h-poly(ethylene glycol). J Appl Polym Sci 2007 104 2986-2991. 

In order to evaluate the application of modulated-temperature differential scanning calorimetry (M-TDSC) to the study of the crystallisation kinetics of semicrystalline polymers, isothermal crystallisation kinetics in poly(e-caprolactone)-SAN blends are investigated. The temperature dependence of d In G/dT (G =crystal growth rate), determined by M-TDSC agrees approximately with previous experimental data and theoretical values. These were obtained from direct measurements of spherulite growth rate by optical microscopy. Here, theoretical and M-TDSC experimental results show that the d In G/dT versus temperature plots are not sensitive to the noncrystalline component in the poly(e-caprolactone)-SAN blends. 15 refs. 

Fig. 9.8 Plot of spherulite growth rates against time for poly(ethylene adipate), M = 9900, at indicated crystallization temperatures. (From Takayanagi (23))...

Fig. 9.45 Fit of experimental spherulite growth rate data, ( ) to theoretical plot for poly(ethylene oxide), M = 152000. (Data from Kovacs and Gonthier (168))...

Other polymers, as typified by poly(3,3-dimethyl thietane), show maxima in the overall crystallization rate.(218) The data can be analyzed in a manner comparable to that described for spherulite growth rates and the conclusions are the same. Whether a transition from Regime II to III is discerned depends on the values taken for the Vogel constants. 

Fig. 9.59 Plot of temperature of maximum spherulite growth rate, Tmax, against equilibrium melting temperature. I m, for indicated polymers. (1) isotactic poly(styrene) (a) (2) poly(tetramethyl-p-silphenylene siloxane) (b) (3) poly(cis-isoprene) (c) (4) poly(caproamide) (d,e) (5) poly(L-lactic acid) (f) (6) poly(phenylene sulfide) (g,h) (7) poly(R-epichlorohydrin), poly(S-epichlorohydrin), poly(I-RS-epichlorohydrin) (i) (8) poly(ethylene terephthalate) (j,k,l) (9) poly(aryl ether ether ketone) (m,n) (10) poly(ethylene-2,6-naphthalene dicarboxylate) (n) (11) poly(3-hydroxybutyrate) (o) (12) isotactic poly(methyl methacrylate) (q) (13) poly(dioxolane) (r) (14) New TPI poly(imide) (s) (15) poly(methylene oxide) (t) (16) poly(cis-butadiene) (u) (17) poly(propylene oxide) (v,w) (18) poly(imide) BPDA - - 134 APB (x) (19) poly(imide) BPDA - -C12 (x) (20) syndiotactic poly(propylene) (y) (21) poly(3-hydroxy valerate) (z) (22) poly(ethylene succinate) (aa) (23) poly(aryl ether ketone ketone) (bb) (24) poly(phenylene ether ether sulfide) (cc) (25) poly(tetramethylene isophtha-late) (dd) (26) poly(hexamethylene adipamide) (e,ee) (27) poly(tetrachloro-bis-phenol-A adipate) (fQ nylon 6-10 (ee).

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))...

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