Solidification of syndiotactic polystyrene by a continuous cooling transformation approach

Carrubba, Vincenzo La; Piccarolo, S.; Brucato, V.

doi:10.1002/polb.21254

Cited by 7 publications

(6 citation statements)

References 45 publications

(135 reference statements)

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“…Density dependence on cooling rate is one such relationship defined in this frame as the “Solidification curve” since it brings an overall information of how stable, metastable and amorphous phases combine to the overall apparent state variable of the material under the conditions of solidification experienced after cooling. Mapping density with an adequately defined cooling rate33 has been reported to be a signature of the solidification behavior discriminating not only different materials behavior, but even small compositional differences in the material, presence of nucleating agents,43 differences in molecular weight or even tacticity index,44 or finally the influence of pressure can be accounted for. Certainly density hides too many subtle mechanisms arising even with time after solidification on samples that are metastable as much as an injection molded item on demoulding is thus implying a request for further accuracy even manipulating during the characterization 45.…”

Section: Discussionmentioning

confidence: 99%

The solidification behavior of a PBT/PET blend over a wide range of cooling rate

Stocco

Carrubba

Piccarolo

et al. 2009

J Polym Sci B Polym Phys

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In recent years, much attention has been paid to the development of high‐performance polyester blends, among which blends of polybutylene terephthalate/polyethylene terephthalate (PBT/PET) are expected to exhibit remarkable properties as far as their crystallization behavior is concerned. Through trial and error, appropriate commercial compositions have been chosen which could not be otherwise explained by a suitable interpretation of the mechanisms determining their solidification behavior. The solidification behavior of a 60/40 w/w PBT/PET blend was studied in a wide range of cooling conditions, according to a continuous cooling transformation (CCT) procedure developed previously, aiming at emulating the typical conditions encountered in polymer processing. Several samples characterized by a homogeneous structure were solidified from the melt at various cooling rates and the resulting structure and properties were subsequently evaluated by analyzing the density, microhardness (MH), and wide angle x‐ray diffraction (WAXD). The resulting solidification behavior was then compared to that exhibited by the individual constituents of the blend (i.e., PBT and PET). The blend displayed a unique solidification behavior, conversely to those of the pure components which showed characteristics not recognized in the blend except at certain restricted cooling rates ranges. The cooling rate dependence observed in the blend does not bring similarities to the crystallization behavior of individual constituents since the fall down of density with cooling rate should be related to the rate controlling demixing stage of the two moieties just before crystallization occurs. The kinetics observed is thus a measure of the kinetics of demixing. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 799–810, 2009

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Section: Discussionmentioning

confidence: 99%

The solidification behavior of a PBT/PET blend over a wide range of cooling rate

Stocco

Carrubba

Piccarolo

et al. 2009

J Polym Sci B Polym Phys

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“…Again in the two cases just discussed, as well in the case of the peculiar features of crystallization of syndiotactic polypropylene17 or of the peculiar mechanical toughness of β nucleated iPP as a function of cooling rate,18 one observes an isolated effort for tracing some clues on the solidification behavior at high cooling rates by the CCT method, efforts often isolated also in terms of low sophistication of the techniques adopted for characterization because interest on this technique by other teams has been very limited. Clearly less awkward morphologies being more traceable and understandable.…”

Section: The Solidification Curvementioning

confidence: 84%

“…In other cases, experimental limitations related with the small size of the sample obtained from the CCT procedure to ensure its homogeneity was of prejudice for obtaining any reliable information 26. In other cases, the limited stability of the samples, a potential source of inaccuracy, is also indicative of a clear departure from equilibrium able to eventually reveal a wealth of information on the underlying mechanisms 16–18…”

Section: Hints On Polymer Crystallization From Solidification Under Ementioning

confidence: 99%

Influence of plasticizers suggests role of topology in polymer solidification at high cooling rates

Piccarolo

Poulose

Luzio

2012

J of Applied Polymer Sci

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Although solidification in processing determines short-and long-term properties, methods for understanding polymer crystallization mostly rely on real time experiments. Their evidences being drawn on time scales farther apart with respect to those experienced in processing. Nor significant outcomes have been so far drawn with approaches mimicking the typical processing times, the Continuous Cooling Transformation methods. Use of these techniques has indeed been limited to a heuristic interpretation of the structure developed under extreme solidification conditions without suggesting alternative routes to the understanding or even clues to the many open questions on polymer crystallization under realistic solidification conditions. If the mechanisms inferred from realtime methods cannot in principle be translated to processing conditions the oxymoron is not overcome. In this work, we compare the influence of a plasticizer on the density drop with cooling rate, and therefore on the disappearance of any long range order crystalline phases, observed after fast controlled quenching of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT).The plasticizer enhances significantly the maximum cooling rate at which PET still shows long range order crystalline phases, whereas barely modifies the situation for PBT. On the basis of a series of concurrent clues, we suggest that the complex inherent topology of macromolecular melts introduces a timescale on polymer crystallization lying in the range of the solidification conditions experienced in processing. Although melt topology is known to determine in many instances polymer solidification, all approaches so far proposed to describe the development of polymer crystallization overlook or even neglect any explicit dependence of such mechanisms on parameters like the molecular weight between entanglements. Albeit the arguments are feeble they all concur to raise several questions even on the contradictory role of nucleating agents under the extreme conditions experienced in processing. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: [4233][4234][4235][4236][4237][4238][4239][4240][4241][4242] 2012

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“…Details related to the choice of solvents have already been reported for iPP, 39 PET, 18,44 and sPS. 45 As far as the density measurements for PA6 are concerned, although the two liquids used in this work (n-heptane and carbon tetrachloride) are those almost universally used for PA6, the thin film samples did not achieve a stable position inside the gradient column, even by extending the observations to a few weeks. Obviously, the long residence time in the column can bring about density changes due to annealing of the sample and/or to sorption of the solvents used.…”

Section: Materials and Characterizationmentioning

confidence: 96%

“…• C (characteristic temperatures of iPP, PA6, PET, and sPS, respectively, 3,13,14,18,30,39,42,45 and depth in the sample can be calculated based on the conduction heat transfer problem (Eq. (5)), as shown in Fig.…”

Section: Rapid Cooling Under Pressurementioning

confidence: 99%

The continuous cooling transformation (CCT) as a flexible tool to investigate polymer crystallization under processing conditions

et al. 2009

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An experimental route for investigating polymer crystallization over a wide range of cooling rates (from 0.01 to 1000◦C/s) and pressures (from 0.1 to 40 MPa) is illustrated, using a method that recalls the approach adopted in metallurgy for studying structure development in metals. Two types of experimental setup were used, namely an apparatus for fast cooling of thin films (100–200 μm thick) at various cooling rates under atmospheric pressure and a device (based on a on-purpose modified injection molding machine) for quenching massive samples (about 1–2 cm3) under hydrostatic pressure fields. In both cases, ex situ characterization experiments were carried out to probe the resulting structure, using techniques such as density measurements and wide-angle x-ray diffraction (WAXD) patterns. The cooling mechanism and temperature distribution across the sample thickness were analyzed. Results show that the final structure is determined only by the imposed thermal history and pressure. Experimental results for isotactic polypropylene (iPP), poly(ethylene terephthalate) (PET), polyamide 6 (PA6), and syndiotactic polystyrene (sPS) are reported, showing the reliability of this experimental approach to assess not only quantitative information but also a qualitative description of the crystallization behavior of different classes of semicrystalline polymers. The present study gives an opportunity to evaluate how the combined effect of the cooling rate and pressure influences the crystallization kinetics for various classes of polymer of commercial interest. An increase in the cooling rate translates into a decrease in crystallinity and density, which both experience a sudden drop around the specific “crystallizability” (or “critical cooling rate”) of the material examined. The exception is sPS where competition among the various crystalline modifications determines a minimum in the plot of density vs. cooling rate. As for the effect of pressure, iPP exhibits a “negative dependence” of crystallization kinetics upon pressure, with a decrease of density and degree of crystallinity with increasing pressure, owing to kinetic constraints. PA6 and PET, on the other hand, due to thermodynamic factors resulting in an increase in Tm with pressure, exhibits a “positive dependence” of crystallization kinetics upon pressure. Finally, recent original results concerning sPS have shown that the minimum in the density vs. cooling rate curve shifts toward larger cooling rates upon increasing pressure

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Solidification of syndiotactic polystyrene by a continuous cooling transformation approach

Cited by 7 publications

References 45 publications

The solidification behavior of a PBT/PET blend over a wide range of cooling rate

The solidification behavior of a PBT/PET blend over a wide range of cooling rate

Influence of plasticizers suggests role of topology in polymer solidification at high cooling rates

The continuous cooling transformation (CCT) as a flexible tool to investigate polymer crystallization under processing conditions

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