Nearly pure α2 form crystals obtained by melt crystallization of high tacticity isotactic polypropylene

Radhakrishnan, J.; Ichikawa, Kazuhiko; Yamada, Koji; Toda, Akihiko; Hikosaka, Masamichi

doi:10.1016/s0032-3861(97)00617-4

Cited by 35 publications

(41 citation statements)

References 10 publications

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“…The absolute value of ordered fraction depends on the crystallization process, tacticity, temperatures, and may even differ with the technique used for estimation. For example, a much higher ordered fraction (~100% [21] and 90-95% [10]) were obtained for isothermal crystallization of iPP measured by XRD analysis. The higher reported values might be related to isothermal crystallization process where the crystallization process approaches from molten state.…”

Section: Temperature Dependent Ordered Fractionmentioning

confidence: 99%

Influence of Tacticity on Structural Ordering of Isotactic Polypropylene under Annealing

2014

Can Chem Trans

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Abstract:Influence of tacticity on phase transition from disordered to ordered state was investigated for isotactic polypropylenes (iPPs) synthesized using Ziegler-Natta (ZN) and metallocene (M) catalysis method. The less stable and disordered   rich iPPs samples were annealed at higher temperature for few days. The more stable and ordered  2 fraction, average lamellae thickness () and melt temperature (T m ) as a function of annealing temperature (T a ) were studied by using solid state NMR, small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) techniques. The  2 fraction, crystals lamellae thickness and melt temperatures were strongly influenced by annealing temperature and tacticity of the iPPs. The less stable and thinner  1 crystal having relatively lower melting temperature shows a significant increase of stability and thickening with annealing. The ordered fraction starts to increase with temperatures while the disordered phase partially melted. Thus, the melting of the disordered phase and simultaneous reorganization and/or re-crystallization into more ordered phase is considered for structural ordering and thickening of iPPs under annealing conditions.

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Section: Temperature Dependent Ordered Fractionmentioning

confidence: 99%

Influence of Tacticity on Structural Ordering of Isotactic Polypropylene under Annealing

2014

Can Chem Trans

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“…We assume that ln G " has a linear dependence on X s ; thus we can write Equation (12) (12) Since we know the dependence of ln G " on the amount of regio-defects (Equation. (11)) and stereodefects (Equation (12)), it is possible to combine these equations as was done for the !-phase (see Equation (9) and (10)) resulting in Equation (13) and (14):…”

Section: Growth Rates Of the "-And !-Phasesmentioning

confidence: 99%

“…Morphology changes on the spherulitic level for iPP involve variations in the crosshatched structure of the !-phase and the frequency of branching in the "-phase [5,9]. Naturally, changes in the morphology on the spherulitic level take place due to variations in the relative amounts of the "-and #-phases compared to the commonly existing !-phase.…”

mentioning

confidence: 99%

The influence of chain defects on the crystallisation behaviour of isotactic polypropylene

Meer¹,

Varga²,

Vancso³

2015

Express Polym. Lett.

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“…The X-ray diffraction reflections of the annealed fibers of this investigation show (h þ k), an even number revealing the presence of only a 1 crystalline form whereas a 2 crystalline form exhibits (h þ k) odd numbers. 50 Equatorial X-ray diffraction trace shown in Figure 3 can be fitted with at least six crystalline peaks indexed as 110, 040, 130, 060, 200, and 220, respectively. The indexed peaks corresponds to a-monoclinic phase.…”

Section: X-ray Diffraction Measurementsmentioning

confidence: 99%

The influence of annealing treatment on the molecular structure and the mechanical properties of isotactic polypropylene fibers

Karacan

Benli

2011

J of Applied Polymer Sci

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An investigation was carried out on the effects of annealing treatment on the molecular structure and the mechanical properties of isotactic polypropylene fibers annealed in an air heated environment at temperatures ranging from 60 to 140 C. Analysis of the equatorial Xray diffraction traces showed the presence of a three phase system of amorphous-smectic-monoclinic forms and revealed the transformation of the metastable smectic form to the highly stable monoclinic form as the annealing temperature is increased, resulting in an enhanced degree of crystallinity and the crystallite size. The improvements in the degree of crystallinity and the crystallite size became more remarkable above 120 C. Evaluation of the crystallinity was carried out using an analysis of density, infrared spectroscopy, and X-ray diffraction methods whereas the state of the molecular orientation was evaluated using polarized infrared spectroscopy measurements only. Polarized infra-red spectroscopy measurements after the curve fitting procedure showed a slight increase of the molecular orientation of the helical chain segments present in the crystalline phase represented by the IR bands at 841 and 998 cm À1 whereas the amorphous structure represented by the IR band at 974 cm À1 showed no significant change with increasing annealing temperature. The improvement in the molecular orientation of the crystalline phase became more remarkable above 120 C. Tensile strength of the annealed fibers increased with increasing annealing temperature but the elongation at break and the initial modulus were not affected as much as the tensile strength.

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Nearly pure α2 form crystals obtained by melt crystallization of high tacticity isotactic polypropylene

Cited by 35 publications

References 10 publications

Influence of Tacticity on Structural Ordering of Isotactic Polypropylene under Annealing

Influence of Tacticity on Structural Ordering of Isotactic Polypropylene under Annealing

The influence of chain defects on the crystallisation behaviour of isotactic polypropylene

The influence of annealing treatment on the molecular structure and the mechanical properties of isotactic polypropylene fibers

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