Giant single crystal of isotactic polypropylene showing near-equilibrium melting temperature

Asakawa, Harutoshi; Nishida, Koji; Kanaya, Toshiji; Tosaka, Masatoshi

doi:10.1038/pj.2012.136

Cited by 13 publications

(9 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…35 In addition, the melting temperature-annealing temperature line of isotactic polypropylene reported by Asakawa et al also showed the slope around 1. 36 However, the authors did not discuss this observation. 35,36 In contrast to our results, in the range of low T c , the melting point of the copolymer used by Kim et al did not increase much with increasing crystallization temperature.…”

Section: ■ Materials and Sample Preparationcontrasting

confidence: 99%

Stabilization of Nuclei of Lamellar Polymer Crystals: Insights from a Comparison of the Hoffman–Weeks Line with the Crystallization Line

Heck

et al. 2016

Macromolecules

View full text Add to dashboard Cite

We have studied melting of poly(butylene succinate), isothermally crystallized over a wide temperature range, employing a combination of the Hoffman–Weeks plot and the Gibbs–Thomson crystallization line, determined by small-angle X-ray scattering measurements. A change in the slope α of the Hoffman–Weeks (H–W) line, accompanied by a change of the slope of the crystallization line, was observed for crystallization temperatures higher than 110 °C. α was reaching a value of 1, implying that no intersection point between the H–W line and the T m = T c line could be obtained. (T m is the measured melting temperature and T c is the temperature at which the sample was crystallized). This observation was corroborated by the crystallization line, which was found to be parallel to the melting line for T c > 110 °C. We relate these changes in slope to different stabilization mechanisms of the secondary nuclei at the growth front of polymer lamellar crystals. For T c > 110 °C, secondary nuclei are proposed to be stabilized by coalescence of neighboring nuclei, all having a small width. By contrast, for T c > 110 °C, the number density of secondary nuclei is low and thus their coalescence is rare. Accordingly, nuclei are stabilized by growing in size, mainly increasing their width.

show abstract

Section: ■ Materials and Sample Preparationcontrasting

confidence: 99%

Stabilization of Nuclei of Lamellar Polymer Crystals: Insights from a Comparison of the Hoffman–Weeks Line with the Crystallization Line

Heck

et al. 2016

Macromolecules

View full text Add to dashboard Cite

show abstract

“…Asakawa et al took 24 h to obtain crystals with a melting temperature 183.7°C by crystallizing iPP at 166°C. 20 Our results suggest an effective approach to achieve iPP sample with ultrahigh melting temperature. The ultrahigh melting temperature means formation of thick lamellae or other unique crystalline architecture, which are undoubtedly attributed to the mutual effect of pressure and shear flow.…”

Section: Resultsmentioning

confidence: 91%

Flow and Pressure Jointly Induced Ultrahigh Melting Temperature Spherulites with Oriented Thick Lamellae in Isotactic Polypropylene

et al. 2015

View full text Add to dashboard Cite

In practical processing, polymer melts generally experience flow and pressure fields simultaneously, but their flow-induced crystallization behavior under pressure was barely investigated. For this reason, we provided an insight into the crystallization behavior and crystalline morphology and structure of isotactic polypropylene (iPP) obtained under the combination of flow (2.5−22.5 s −1 ) and high pressure (200 MPa) by using self-designed pressurizing and shearing device. Unprecedented iPP spherulites were observed, which are composed of oriented thick lamellae (18 nm) with ultrahigh melting temperature (179.5°C). Such spherulitic crystals with lamellae aligning perpendicular to flow have never been reported. All samples have a double melting peak behavior including an additional low temperature peak (165−169°C) apart from the ultrahigh melting peak. The in situ synchrotron X-ray measurements show that the parents of cross-hatched structure are responsible for the ultrahigh melting temperature and the daughters give rise to the low temperature melting peak because the parents crystallized much earlier and had a higher growth rate than the daughters. Moreover, the parents are all in α-form while the daughters consist of α-and γ-forms. Our results afford a new method to obtain thick lamellae in a relatively short time.

show abstract

“…Indeed, the total melting enthalpy measured in the final melting step was ≈126 J g −1 , while exothermic 102 J g −1 was obtained in the first isothermal step conducted at 145 °C. Furthermore, the relatively large fraction of the polymer melting in the range 180–190 °C, obtained practically from an isothermal crystallization at a relatively low temperature of 145 °C points toward the possibility that the equilibrium melting temperature of iPP is often underestimated …”

Section: Resultsmentioning

confidence: 99%

Molecular and Thermal Characterization of a Nearly Perfect Isotactic Poly(propylene)

Tranchida

Mileva

Resconi

et al. 2015

Macro Chemistry & Physics

View full text Add to dashboard Cite

The structure formation upon cooling of the quiescent melt of a nearly defect-free isotactic poly(propylene) (iPP) homopolymer is investigated in this study. This iPP, having a molecular weight of 1 × 10 6 g mol −1 and a narrow molecular weight distribution, has been produced with a C2 symmetric hafnocene complex. Information about the crystallization kinetics is collected in a broad range of cooling rates. Standard differential scanning calorimetry is used for cooling rates in the range 3-100 °C min −1 and FSC is employed to analyze the solidifi cation process at cooling rates larger than 100 °C s −1 . The near absence of regio-and stereo-defects allows this iPP to crystallize at signifi cantly high temperatures and to form crystals at cooling rates higher than commonly observed for standard Ziegler-Natta iPP. The data reveal that the iPP homopolymer with close-to-perfect stereo-regularity form crystals at high cooling rates as, e.g., α-nucleated iPP. The defect-free polymer chain allows the formation of relatively thick lamellar crystals which resulted in a relatively high tensile modulus of 2088 ± 8 MPa.

show abstract

Giant single crystal of isotactic polypropylene showing near-equilibrium melting temperature

Cited by 13 publications

References 38 publications

Stabilization of Nuclei of Lamellar Polymer Crystals: Insights from a Comparison of the Hoffman–Weeks Line with the Crystallization Line

Stabilization of Nuclei of Lamellar Polymer Crystals: Insights from a Comparison of the Hoffman–Weeks Line with the Crystallization Line

Flow and Pressure Jointly Induced Ultrahigh Melting Temperature Spherulites with Oriented Thick Lamellae in Isotactic Polypropylene

Molecular and Thermal Characterization of a Nearly Perfect Isotactic Poly(propylene)

Contact Info

Product

Resources

About