Crystallization and melting behavior

Even though the first report about the synthesis of crystallizable ABC triblock copolymers was published in 1978 for PS-h-PB-h-PCL copolymers [114], in that work only a preliminary study of the tensile properties was performed, without considering the crystallizability of the materials. It was only 20 years later, when the preparation of these materials was reconsidered and optimized, that triblock copolymers with relatively narrow molecular weight distributions were obtained [115], a requisite which is indispensable for the generation of well-defined morphologies. To illustrate the complexity and richness of semicrystalline ABC triblock copolymers, PS-h-PB-h-PCL triblock copolymers have been chosen. These copolymers have been prepared with a wide composition range (with PCL contents from 11 to 77%) and they have been compared with PS-h-PCL and PB-fc-PCL diblock copolymers [29,98, 115-118]. 

Calorimetric measurements and morphological observations showed that PS-h-PCL, PB-h-PCL and PS-h-PB-h-PCL copolymers exhibit microphase separation and crystalhzation if the molecular weight is high enough. Only in PS-h-PCL diblock copolymers, a shift of the PS glass transition to lower temperatures has been observed. In PS-fc-PB-fc-PCL, the crystallizable block (Le., PCL) is covalently linked to a rubbery block and it has a free end. For these reasons there is no significant reduction in the melting temperature and 

As mentioned in Sect. 3, for PEO it has been found that the crystalHzation temperature is often a function of the MD volume. The examples quoted in Sect. 3 referred to PEO dispersed in droplets or to PEO that was a component within diblock copolymers. Eor other block copolymer components like PCL the variation in Tc encountered upon MD size increase is not as pronounced. Nojima et al. [22] found that the variation of Tc for PB-fo-PCL block copolymers with spherical PCL MDs of increasing sizes, ranging from 10.3 to 17.4 nm, was of about 5 °C for crystallization at very large supercoolings (Tc fluctuated between - 50 and - 45 °C approximately). For ABC triblock copolymers, Muller et al. [29], Schmalz et al. [101,119] and Balsamo et aL [118] foimd, by studying copolymers with minority components of PEO or PCL blocks linked to a rubbery block, that the Tc associated with fractionated 

The data of Table 4 clearly indicate that the PEO block within PB-fo-Pl-fo-PEO triblock copolymers exhibits fractionated crystalhzation when it constitutes a minority component. B11I70EO19 and B24I56EO20 show only one crystallization exotherm, whereas B17I57EO26 has two crystalhzation exotherms. 

Lam(Lamellar) Cyl(Cylinders) Sph(Spheres) CiC core shell cylinders, 11 lamellar-lamellar, Ic lamellar-cylindrical. 

Even though the nonisothermal crystallization leads to just small changes in the subsequent melting behavior of different types of triblock copolymers, isothermal experiments employed to calculate the equilibrium melting temperature, T, have shown that this parameter can exhibit significant changes depending on composition. It has been reported that in PS-fo-PB-fo-PCL tri- 

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Although each of these cyclic siloxane monomers can be polymerized separately to synthesize the respective homopolymers, in practice they are primarily used to modify and further improve some specific properties of polydimethylsiloxanes. The properties that can be changed or modified by the variations in the siloxane backbone include the low temperature flexibility (glass transition temperature, crystallization and melting behavior), thermal, oxidation, and radiation stability, solubility characteristics and chemical reactivity. Table 9 summarizes the effect of various substituents on the physical properties of resulting siloxane homopolymers. The... 

Buchner, S Wisme, D. and Zachmann, H. G., Kinetics of crystallization and melting behavior of poly(ethylenenaphthalene-2,6-dicarboxylate), Polymer, 30, 480-488 (1989). 

Zhang Z, Mo Z, Zhang H, Wang X, Zhao X (2003) Crystallization and melting behaviors of PPC-BS/PVA blends. J Macromol Chem Phys 204(12) 1557-1566... 

Dynamic mechanical property (DMP) measurements are used to evaluate the suitability of a polymer for a particular use in sound and vibration damping. Since the dynamic mechanical properties of a polyurethane are known to be affected by polymer morphology (4), it is important to establish the crystallization and melting behavior as well as the glass transition temperature of each polymer. Differential scanning calorimetry (DSC) was used to determine these properties and the data used to interpret the dynamic mechanical property results. 

Eor the discussion of the crystallization and melting behavior in immiscible polymer blends, a division into 3 main classes is proposed. 

Because the phases are physically separated in the melt, the theory concerning the crystallization behavior as discussed in Parts 3.4.3 (matrix crystallization) and 3.4.4 (dispersed droplet crystallization) can be combined to understand the crystallization and melting behavior of most crystalline/ crystalline polymer blends. In general, both crystal-lizable phases crystallize separately around then-characteristic bulk T-value (as long as the minor phase is not dispersed into very fine droplets). The T-values can be somewhat shifted due to... 

Pukansky et al. [1989] investigated both the crystallization and melting behavior, and the global blend morphology in PP/EPDM blends over the whole composition range. Blends quickly... 

Figure 3.48. Influence of compatibilization (10 wt%) on the crystallization and melting behavior of PA-6/PP blends with various blend compositions. Compatibilizer types used were EBA-g-FA (I), PP-g-MAH (II), SEBS-g-MAH (III) and E EA-GMA (IV) [Ikkala et al., 1993].

The crystallization and melting behavior of a dispersed phase is highly different from the behavior of the continuous phase and much more sensitive for changes. 

Varma-Nair, M. Handa, P. Mehta, A. Agarwal, P. (2003) Effect of Compressed C02 on Crystallization and Melting Behavior of Isotactic Polypropylene. Thermochim. Acta. Vol.396, No.1-2, pp.57-65... 

Kawai, X, Rahma, N., Matsuba, G. et al. (2007) Crystallization and melting behavior of poly (L-lactic acid). Macromolecules, 40, 9463-9469. 

Cao, D. and Wu, L. (2009) Poly(L-lactic acidj/sUicon dioxide nanocomposite prepared via the in situ melt polycondensation of L-lactic acid in the presence of acidic silica sol Isothermal crystallization and melting behaviors. Journal of Applied Polymer Science, 111, 1045-1050. 

Liu, S.L. and T.S. Chung. 2000. Crystallization and melting behavior of regioregular poly(3-dodecythiophene). Polymer 41 27SI. 

Causin, V., C. Marega, A. Marigo, L. Valentini, and J.M. Kenny. 2005. Crystallization and melting behavior of poly(3-butylthiophene), poly(3-octylthiophene), and poly(3-dodecylthiophene). Macromolecules 38 409. 

AlazidehA, SohnS.Quinn J, MarandH (2001) Influence of Structural and Topological Constraints on the Crystallization and Melting Behavior of Polymers 3. Bisphenol A Polycarbonate. Macromolecules 34 4066 078. 

The crystallization and melting behaviors of polymers are conventionally measured by the method of differential scanning calorimetry (DSC). One can obtain the heat flow or compensation power dQ/dt as a function of temperature, which is in principle proportional to the heat capacity of materials Cp and the scanning rate q, as given by... 

Papageorgiou, G.Z. and Bikiaris, D.N. (2005) Crystallization and melting behavior of three biodegradable poly(alkylene succinates). A comparative study. Polymer, 46, 12081-12092. 

Wu, L. and Hou, H. (2010) Isothermal cold crystallization and melting behaviors of poly(L-lactic acid)s prepared by melt polycondensation. J. Appl. Polym. Sci., 115, 702-708. 

Polypropylene Five samples, mm = 92.2-94.9% (NMR) M = 22000—947000 fractionation according to stereoregularity crystallization and melting behavior with IR tacticity studied. [154]... 

Varma-Nair, M., et al.. Effect of compressed C02 on crystallization and melting behavior of isotactic polypropylene. Thermochimica Acta, 2003. 396(1,2) p. 57-65. 

EPDM and EPR copolymers are crystalline if block copolymer and depending on the ethylene/propylene ratio in blends with PE or PP, they can extract to some extent (depending on the ethylene/propylene ratio) amorphous low molecular weight molecules from the PP or PE phase that slightly influence the crystallization and melting behavior Study done on fibers... 

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