Fractionated Crystallization in Incompatible Polymer Blends

Frensch, H.; Harnischfeger, P.; Jungnickel, B.‐J.

doi:10.1021/bk-1989-0395.ch005

Cited by 79 publications

(63 citation statements)

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“…Furthermore, exotherm (A) disappears completely in those blends with PP contents ≤ 10%. This indicates, as has been previously reported by other authors [11,12,[29][30][31][32], that the usual heterogeneous nucleation of the PP component is nearly completely suppressed as indicated by the marked decrease in the crystallization enthalpy in the temperature region where the PP homopolymer crystallizes. From scanning electron micrographs (SEM) obtained from these samples (see an example in Fig.…”

Section: Resultssupporting

confidence: 86%

“…Several phenomena that influence the crystallization behaviour of the system have been reported. Among these phenomena, the following can be mentioned: nucleation and epitaxial crystallization [4][5][6][7][8], migration of heterogeneities from one phase towards the other [9,10], fractionated crystallization [11,12], rejection, engulfing or deformation of the dispersed phase by the growing superstructures of the matrix [13][14][15], and induction of crystal modifications [16]. Although crystallizability of the components induces immiscibility in the solid state in most cases, if a good residence time in the barrel was about 5 min.…”

Section: Introductionmentioning

confidence: 99%

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Nucleation versus melting point depression of the polycaprolactone phase in polypropylene/polycaprolactone blends

Balsamo

Gouveia²

2004

E-Polymers

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Polypropylene/poly(ε-caprolactone) (PP/PCL) blends were prepared by melt mixing. The thermal behaviour of the blends was investigated using differential scanning calorimetry (DSC) and dynamical rheology in the solid state (RSA). Both non-isothermal and isothermal crystallizations were performed. The Avrami equation was applied to the latter case. DSC and RSA results demonstrated in agreement with morphological observations that PP/PCL blends are immiscible in the whole composition range. PP acts as a nucleating agent for PCL, and when PP forms the disperse phase, it crystallizes in a fractionated fashion. When PCL is the disperse phase, it exhibits an unexpected melting point depression after cooling at 10 °C/min. Such depression was not observed after isothermal crystallizations, indicating that under non-isothermal crystallization kinetic problems show up. Thus, global crystallization is governed by a competition between nucleation and diffusion, which depends on crystallization conditions and composition.

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Section: Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Nucleation versus melting point depression of the polycaprolactone phase in polypropylene/polycaprolactone blends

Balsamo

Gouveia²

2004

E-Polymers

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“…The phenomenon is similar to the fractionated crystallization exhibited by many polymers when they are finely dispersed into droplets. 8,[11][12][13][14][15][16][17][18] The bulk PET contains a number of heterogeneous nuclei which are responsible for nucleation and crystallization at the lowest undercoolings possible (which will be denoted "type A" heterogeneities) depending on the cooling rate from the melt (i.e., for PET the dynamic peak crystallization temperature upon cooling from the melt at 10°C/min will be around 175°C; see Fig. 4).…”

Section: Thermal Behavior Of Bulk Pet and Dispersed Pet In The Pc/petmentioning

confidence: 99%

“…This means that many PET droplets will not contain any type A heterogeneity; therefore, the polymer inside the droplet cannot crystallize at the same undercooling, and will crystallize at larger undercoolings only if another type of heterogeneity (say, "type B," active at larger undercoolings) is present or by creating its own nuclei in a homogeneous crystallization process that usually occurs at the largest possible undercooling. 8 Because these nucleation events are time-dependent, and given the relatively low crystallization rate of PET, it is possible that at the cooling rate used here the crystallization could be almost completely suppressed (as in the 40-rpm blend) or only partially suppressed (as in the 10-rpm blend). The differences in the ability to crystallize upon cooling could then be due to the degree of dispersion in the blend.…”

Section: Thermal Behavior Of Bulk Pet and Dispersed Pet In The Pc/petmentioning

confidence: 99%

“…This phenomenon is known as fractionated crystallization and occurs when the number of heterogeneities originally present in the bulk polymer is much smaller than the number of dispersed polymer droplets. 8,18 For this work we used differential scanning calorimetry (DSC) to study the nucleation and crystallization processes of PET dispersed in an immiscible PC matrix, at two different extrusion rates. We compared the behavior of bulk PET with that of dispersed PET in the blends under dynamic crystallization conditions.…”

Section: Introductionmentioning

confidence: 99%

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Nucleation and crystallization of PET droplets dispersed in an amorphous PC matrix

Molinuevo

Mendez

Müller

1998

J. Appl. Polym. Sci.

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ABSTRACT:The present work compares the nucleation and crystallization process of poly(ethylene terephthalate) (PET) in bulk and when it is finely dispersed in a polycarbonate (PC) matrix. Two types of 80/20 PC/PET immiscible blends were prepared by twin-screw extrusion at different screw rotation rates in order to produce fine dispersions of PET. The results indicate that the finer the dispersion, the greater the inhibition of the crystallization of the PET droplets. These results are explained by demonstrating (through self-nucleation experiments) that a fractionated crystallization process was developed in the dispersed PET, since the number of PET particles was much greater than the number of heterogeneities originally present in the bulk polymer. The dispersion of PET into droplets also affects its crystallization rate during isothermal crystallization at high temperatures and its reorganization capacity during heating.

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Rheological and calorimetric evidences of the fractionated crystallization of iPP dispersed in ethylene/?-olefin copolymers

Manaure¹,

Morales

Sánchez³

et al. 1997

J. Appl. Polym. Sci.

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ABSTRACT:In this work, the melt crystallization of immiscible blends of isotactic polypropylene (iPP) and branched polyethylenes (PE) was followed by oscillatory shear measurements during controlled cooling. All the blends contained 20% iPP finely dispersed in several ethylene/ a-olefin copolymer matrices (with and without a nucleating agent) with densities ranging from 0.88 to 0.92 g/cm 3 (linear low, very low, and ultra low density polyethylenes: LLDPE, VLDPE, and ULDPE). The rheological results were compared with parallel differential scanning calorimetry (DSC) measurements at the same cooling rate. During preliminary evaluations of the neat resins, no effect was found of the variation of the frequency of oscillation or the applied shear strain on their crystallization (at least in the range explored in this work). In the case of the blends, when the iPP crystallized in a fractionated fashion, only one sudden increase in the storage modulus ( G) was observed during cooling due to the partial coincident crystallization of both iPP and the PE matrix. In the presence of a nucleating agent, an almost complete separation between the crystallization of both components in the blend was achieved and two increases in G were clearly observed upon cooling. A close match between the dynamic crystallization kinetics obtained by DSC and torsion rheometry was demonstrated by a direct comparison between calorimetrically measured solid conversion and G during cooling from the melt.

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Fractionated Crystallization in Incompatible Polymer Blends

Cited by 79 publications

References 0 publications

Nucleation versus melting point depression of the polycaprolactone phase in polypropylene/polycaprolactone blends

Nucleation versus melting point depression of the polycaprolactone phase in polypropylene/polycaprolactone blends

Nucleation and crystallization of PET droplets dispersed in an amorphous PC matrix

Rheological and calorimetric evidences of the fractionated crystallization of iPP dispersed in ethylene/?-olefin copolymers

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