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High-pressure crystallization of isotactic polypropylene droplets.

Zapala K, Piorkowska E, Hiltner A, Baer E - Colloid Polym Sci (2012)

Bottom Line: Only the largest PP droplets, with average sizes of 170 μm, crystallized predominantly in the γ form.The results showed that the γ phase formed only in the droplets sufficiently large to contain the most active heterogeneities nucleating PP crystallization under atmospheric pressure.It is concluded that the presence of nucleating heterogeneities is necessary for crystallization of PP in the γ form under high pressure.

View Article: PubMed Central - PubMed

Affiliation: Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90 363 Lodz, Poland.

ABSTRACT
Dispersions of isotactic polypropylene (PP) particles in polystyrene (PS) were produced by interfacially driven breakup of nanolayers in multilayered systems that were fabricated by means of layer-multiplying coextrusion. The droplet size was controlled by the individual PP layer thickness ranging from 12 to 200 nm. In addition, PP was melt blended with PS to produce PP droplets larger than those formed by breakup of nanolayers. The dispersions of PP particles in the PS matrix were melted and annealed under high pressure of 200 MPa. Only the largest PP droplets, with average sizes of 170 μm, crystallized predominantly in the γ form. In the 42-μm droplets obtained by breakup of 200 nm layers, a minor content of the γ form was found whereas the smaller droplets obtained by breakup of the thinner nanolayers contained the α form and/or the mesophase. The results showed that the γ phase formed only in the droplets sufficiently large to contain the most active heterogeneities nucleating PP crystallization under atmospheric pressure. It is concluded that the presence of nucleating heterogeneities is necessary for crystallization of PP in the γ form under high pressure.

No MeSH data available.


Related in: MedlinePlus

SEM micrographs of cryo-fracture surfaces of PP/PS systems, in which PP droplets formed during heating and annealing at 230 °C
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Fig1: SEM micrographs of cryo-fracture surfaces of PP/PS systems, in which PP droplets formed during heating and annealing at 230 °C

Mentions: SEM micrographs of cryo-fracture surfaces of PP/PS systems after the breakup of the PP layers into droplets are compared in Fig. 1. As expected, the PP layers broke into droplets of sizes increasing with increasing individual PP layer thickness as in the previous studies of Jin et al. [30]. However, even in PP/PS-200, the droplet size (diameter) did not exceed 125 μm. Larger droplets, with sizes up to 360 μm, formed only in PP/PS melt blend, which is also shown in Fig. 1.Fig. 1


High-pressure crystallization of isotactic polypropylene droplets.

Zapala K, Piorkowska E, Hiltner A, Baer E - Colloid Polym Sci (2012)

SEM micrographs of cryo-fracture surfaces of PP/PS systems, in which PP droplets formed during heating and annealing at 230 °C
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3472077&req=5

Fig1: SEM micrographs of cryo-fracture surfaces of PP/PS systems, in which PP droplets formed during heating and annealing at 230 °C
Mentions: SEM micrographs of cryo-fracture surfaces of PP/PS systems after the breakup of the PP layers into droplets are compared in Fig. 1. As expected, the PP layers broke into droplets of sizes increasing with increasing individual PP layer thickness as in the previous studies of Jin et al. [30]. However, even in PP/PS-200, the droplet size (diameter) did not exceed 125 μm. Larger droplets, with sizes up to 360 μm, formed only in PP/PS melt blend, which is also shown in Fig. 1.Fig. 1

Bottom Line: Only the largest PP droplets, with average sizes of 170 μm, crystallized predominantly in the γ form.The results showed that the γ phase formed only in the droplets sufficiently large to contain the most active heterogeneities nucleating PP crystallization under atmospheric pressure.It is concluded that the presence of nucleating heterogeneities is necessary for crystallization of PP in the γ form under high pressure.

View Article: PubMed Central - PubMed

Affiliation: Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90 363 Lodz, Poland.

ABSTRACT
Dispersions of isotactic polypropylene (PP) particles in polystyrene (PS) were produced by interfacially driven breakup of nanolayers in multilayered systems that were fabricated by means of layer-multiplying coextrusion. The droplet size was controlled by the individual PP layer thickness ranging from 12 to 200 nm. In addition, PP was melt blended with PS to produce PP droplets larger than those formed by breakup of nanolayers. The dispersions of PP particles in the PS matrix were melted and annealed under high pressure of 200 MPa. Only the largest PP droplets, with average sizes of 170 μm, crystallized predominantly in the γ form. In the 42-μm droplets obtained by breakup of 200 nm layers, a minor content of the γ form was found whereas the smaller droplets obtained by breakup of the thinner nanolayers contained the α form and/or the mesophase. The results showed that the γ phase formed only in the droplets sufficiently large to contain the most active heterogeneities nucleating PP crystallization under atmospheric pressure. It is concluded that the presence of nucleating heterogeneities is necessary for crystallization of PP in the γ form under high pressure.

No MeSH data available.


Related in: MedlinePlus