Morphology and phase behaviour of blends of syndiotactic and isotactic polypropylene: 2. Differential scanning calorimetry, light transmission measurements, and PVT measurements

Thomann, Ralf; Kreßler, Jörg; Rudolf, Bernd; Mülhaupt, Rolf

doi:10.1016/0032-3861(96)87622-1

Cited by 61 publications

(63 citation statements)

References 7 publications

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“…This confirms the suggested edge-on crystallization of -form lamellae. The observation that the -form nucleated on preformed -form crystals is consistent with results reported by Lotz et al 79 and Thomann et al [80][81][82] At a later stage of crystallization (Figure 5e) secondary lamellae are formed at all primary lamellae. Many of them reveals branching angles of 40 AE 3 , but also some lamellae grow with a branching angle of 80 AE 5 referring to the additional formation of -phase lamellae.…”

Section: Scanning Force Microscopysupporting

confidence: 81%

Nucleation and Crystallization of Low Isotatic Polypropylenes with Statistically Distributed Stereoerrors

et al. 2009

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The time dependent crystallization of a low isotactic polypropylene with statistically incorporated stereoerrors was investigated by the combination of differential scanning calorimetry (DSC), wideangle X-ray scattering (WAXS) and scanning force microscopy (SFM). Owing to Scanning force microscopy (SFM) and WAXS experiments the crystallization of the sample in mixed =-form aggregates can be proposed. The nucleation and growth processes of crystallization in thin polypropylene films in real time were visualized with nanometer resolution by using SFM at variable temperature. During the isothermal crystallization from the melt initially crystals of the -form were developed. These lamellae act as nuclei for the further crystallization of -and mixed =-lamellae, which can be observed at longer crystallization times. Time dependent SFM and WAXS experiments showed that due to the low amount of crystallizable, regular sequences and its statistical distribution only slow crystallization rates can be observed. These results form the basis for a better understanding of the crystallization of low crystallinity polypropylenes. The investigations clearly show that the distribution of the regular isotactic segments influences the crystallization properties of propene based TEP's. This opens the possibility to tailor not only the mechanical but also the thermal properties of elastomeric polypropylenes by changing the polymer microstructure.

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Section: Scanning Force Microscopysupporting

confidence: 81%

Nucleation and Crystallization of Low Isotatic Polypropylenes with Statistically Distributed Stereoerrors

et al. 2009

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“…Indeed, the addition of s-PP to i-PP can improve impact characteristics over pure i-PP [222][223][224][225]. When s-PP is blended with i-PP, the resulting resin has a processability better than that of i-PP and impact and transparency properties better than those of pure i-PP.…”

Section: Additive S-pp/i-pp Blendsmentioning

confidence: 99%

Syndiotactic Polypropylene: Discovery, Development, and Industrialization via Bridged Metallocene Catalysts

Razavi¹

2013

Advances in Polymer Science

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This chapter covers the discovery that enabled, for the first time, the manufacturing of high molecular weight, highly stereoregular syndiotactic polypropylene polymers with narrow molecular weight distribution via the new class of metallocene molecules with bridged cyclopentadienyl-fluorenyl ligands. First, the salient crystal structural features of the neutral metallocene molecules and the crystal structure of the corresponding mono-alkyl-zirconocenium cation is introduced. Then, by employing the structural and geometrical data, a realistic working model for the active site precursor is developed and presented. The stereochemistry of the catalytic propylene poly-insertion reaction and the formation of syndiotactic polypropylene according to the enantiomorphic site control mechanism at the enantiotopic cationic active sites, formed after the activation of the prochiral metallocene dichloride with methylaluminoxane, MAO, is reviewed and further delineated. In the following sections, the impact of the introduction of substituents with proper size and composition at some selected positions of the ligand is discussed and the methods for increasing the molecular weight and stereoregularity of syndiotactic polypropylene polymers are elaborated. With the aid of computational calculations on real and hypothetical catalyst systems with substitutionally altered ligand structures, it is shown that the degree of enantioselectivity of syndiospecific catalyst systems can be determined and/or predicted for these systems quantitatively and with high precision. The calculations confirm that the introduction of substituent(s) reinforcing the preferential conformational orientation of the polymer chain enhances the overall enantioselectivity of the active site, and to certain extends stereoselectivity in general, by affecting the site epimerization processes. The computational calculations reveal that to account correctly for the frequency of the site epimerization-dependent m-type stereo-errors it is essential to include the counter-ion, as an integrated part of the A. Razavi (*) 35 Domaine de la Brisee, 7034 Obourg, Belgium e-mail: abbasrazavi@skynet.be catalyst system, into the calculations. The relevance of the symmetry and stereorigidity of the metallocene structure for the syndiospecificity of the final catalyst is debated by presenting a few "non-conforming" catalyst examples.Finally, the challenges involved in the manufacture of syndiotactic polypropylene in commercial scale continuous production processes are highlighted as well as the polymer's unique structural, physical, mechanical and rheological properties.

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“…c, sPP ) has been done as Equations (1) and (2): (1) (2) where $H f, iPP is the melting enthalpy of iPP (area of the melting endotherm of iPP), $H f, sPP is the melting enthalpy of sPP (area of the melting endotherm of sPP). $H [5,[23][24][25]. 'wt% iPP' and 'wt% sPP' are the mass composition of the mixture.…”

Section: Differential Scanning Calorimetry (Dsc)mentioning

confidence: 99%

Characterization of the morphology of iPP/sPP blends with various compositions

Bourbigot¹,

Garnier²,

Revel³

et al. 2013

Express Polym. Lett.

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Abstract. The paper investigates the morphology and the structural properties of blends of isotactic polypropylene (iPP) and syndiotactic polypropylene (sPP) having different compositions using different techniques. Solid-state nuclear magnetic resonance (NMR) permits via appropriate sequence to measure the composition, conformation and dynamics, and intimacy of mixing of polymeric materials. Measurement of relaxation times gives information on local structure of phases with different mobility. The morphology is directly related to the structural organization of the blends. The crystallization rate decreases as a function of the sPP content. The minor component is dispersed as a nodule in the main component of the blend and it plays the role of nucleating agent on it. Besides, morphology changes occur for the composition 50/50 (wt/wt) of the blend iPP/sPP. Different phases are identified, namely free amorphous, constrained amorphous and crystalline regions which exhibit different molecular mobilities. It is also shown at the interphase matrix-nodules, the nodules create a constrained amorphous zone.

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Morphology and phase behaviour of blends of syndiotactic and isotactic polypropylene: 2. Differential scanning calorimetry, light transmission measurements, and PVT measurements

Cited by 61 publications

References 7 publications

Nucleation and Crystallization of Low Isotatic Polypropylenes with Statistically Distributed Stereoerrors

Nucleation and Crystallization of Low Isotatic Polypropylenes with Statistically Distributed Stereoerrors

Syndiotactic Polypropylene: Discovery, Development, and Industrialization via Bridged Metallocene Catalysts

Characterization of the morphology of iPP/sPP blends with various compositions

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