Crystal ordering of α phase isotactic polypropylene

Naiki, Masahiro; Kikkawa, T.; Endo, Y.; Nozaki, Koji; Yamamoto, Takashi; Hara, Takehisa

doi:10.1016/s0032-3861(00)00848-x

Cited by 45 publications

(59 citation statements)

References 23 publications

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“…Irreversible transition from the 1 form to the 2 form is observed by annealing at high temperature. [12][13][14][15][16][41][42][43][44] The helical arrangement (right and left handed helix) in the 2 form is the same as that in the 1 form. For the up or down arrangement (the projected direction of methyl group onto the c-axis), the 1 form is the limit-disordered structure while the 2 form is the limit-ordered structure.…”

Section: Resultsmentioning

confidence: 99%

“…It has been already reported in many papers that the 2 fraction increases with crystallization temperature 46 and/or annealing temperature. [41][42][43][44] On annealing, the 2 form fraction rapidly increases with time and saturates within 10 min. 44 This indicates that the structural ordering (transformation from 1 to 2 ) is completed early on in the annealing process.…”

Section: Resultsmentioning

confidence: 99%

“…[41][42][43][44] On annealing, the 2 form fraction rapidly increases with time and saturates within 10 min. 44 This indicates that the structural ordering (transformation from 1 to 2 ) is completed early on in the annealing process. Also, the lattice parameters for a-axis and c-axis of the 1 form increase slightly on heating.…”

Section: Resultsmentioning

confidence: 99%

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Temperature Dependence of Crystal Growth Rate for α and β Forms of Isotactic Polypropylene

Nakamura

Shimizu

Umemoto

et al. 2008

Polym J

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The crystal growth rate of the 1 , 2 and forms of isotactic polypropylene (iPP) and their morphological changes were studied in a wide range of crystallization temperatures. The temperature dependence of the crystal growth rate of the 1 form showed a bell-shaped curve with the maximum growth rate (G max ) at 70 C. The crystal growth rate of the form induced by calcium pimelate also showed a bell-shaped curve with G max at 79 C. Two crossover points on the growth rate curve from the 1 form to the form or vice versa were observed at 90 C and 133 C, respectively. Tear-drop shaped spherulites were observed at temperatures between the two crossover points. Electron diffraction patterns showed the high ordered structure of the 2 form for thin films crystallized at 140 C. The 2 fraction became detectable in X-ray diffraction pattern for temperatures above 110 C. The 2 fraction increased with crystallization temperature and saturated to 100% at about 140 C. In the temperature region from 110 C to 140 C, several crystal growth rates were found at the same crystallization temperature. The growth rate variations could be associated with the co-crystallization of the 1 and 2 forms. Above 140 C, the growth rate variations disappeared, since the fraction of the 2 reached to 100%. The extrapolated G max of the 2 showed at 72 C.KEY WORDS: Isotactic Polypropylene / -Form / -Form / Crystal Growth Rate / Crossover / Isotactic polypropylene (iPP) is one of the most widely used commercial polymeric materials and has been extensively investigated for it academic and industrial interest. iPP displays different structural polymorphism, such as form (monoclinic), form (trigonal), form (orthorhombic) and smectic form, which all consist of 3 1 helical conformations with a 0.65 nm chain axis periodicity. The form is the most common crystal structure, which is produced by crystallization from the melt or solution.1-5 The form can be obtained from temperature gradient crystallization, 6 crystallization under molecular orientation 7 or can be induced by selective -nucleating agent. 8-10The crystal structure of the form was first determined by Natta and Corradini. 11 Mencik 12 and Hikosaka and Seto 13showed that the structure has two limiting modifications named 1 and 2 forms. Extensive works on these crystalline forms have been also reported. 14-16 The 1 form space group (C2/c) is the limit-disordered structure and the 2 form (P2 1 /c) is the limit-ordered structure. They are characterized by either regular alternation of the up and down orientations of the methyl group along the chain ( 2 ) or random orientation. A transition from the 1 form to the 2 form is observed by annealing at a higher temperature. [17][18][19][20][21][22] The crystal structure of the form has been analyzed by Meille et al. 23 and refined by D. L. Dorset et al. 9Many studies about the crystallization behavior and morphology of iPP have been reported. When iPP was crystallized from the melt in a wide temperature range, Keith and Padden found four distinct spherulites,...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Temperature Dependence of Crystal Growth Rate for α and β Forms of Isotactic Polypropylene

Nakamura

Shimizu

Umemoto

et al. 2008

Polym J

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“…the amount of crystalline phase, crystal type, the thickness of lamellae, etc. Isotactic polypropylene (iPP) crystallizes into several crystalline modifications, such as monoclinic (), hexagonal () and triclinic () form, depending on the conditions of crystallization and molecular characteristics [1][2][3][4][5][6][7][8][9][10]. Thermodynamically the most stable  crystalline phase originates under common crystallization conditions that occur in industrial practice during manufacturing of different iPP-based products.…”

Section: Introductionmentioning

confidence: 99%

The correlation between structure and β-nucleation efficiency of Ba, Sr, Ca and Mg pimelates in isotactic polypropylene

Janevski

Bogoeva‐Gaceva

Stefov

et al. 2015

Maced. J. Chem. Chem. Eng.

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The pimelates of the earth-alkaline elements and pimelic acid have been synthesized and studied. All prepared pimelates are crystallohydrates and Ba and Sr pimelates are isotypic. The obtained compounds have been characterized using infrared spectroscopy and X-ray diffraction, and it was found that, near and above the melting temperature of polypropylene, the pimelates of Ba and Sr are crystalline, whereas the ones of Ca and Mg are amorphous. The nucleation activity of these pimelates has been studied in the process of crystallization of polypropylene in non-isothermal conditions and followed by differential scanning calorimetry (at cooling rate V c = 1-20 K min -1 ). It was found that their nucleation activity, even at concentration of 0.1 %, differs considerably with regards to the cooling rate, and they induce different polymorphic composition of the polymer. The nucleation activity was mostly exhibited by Ca pimelate, and when it was used the content of the β crystalline phase (U β ) in polypropylene ranged from 0.90 to 0.94, depending on the cooling rate, compared to 0.18-0.35 when Mg pimelate was used. In the polymer crystallized by using Ba and Sr pimelate as nucleators, U β ranged from 0.47 to 0.77. Based on the theoretical concepts for nucleation activity of solid substrates, an attempt was made to correlate the structurаl features of the synthesized pimelates with their β-nucleation activity in the process of nonisothermal crystallization of iPP. ). Беше најдено дека нивната нуклеациона активност и при концентрации од 0,1 % значително се разликува во зависност од брзината на ладење и се добива различен однос на полиморфните модификации на полимерот. Најизразена беше нуклеационата активност на пимелатот на Ca, а во случајот кога тој беше употребен, содржината на β-кристалната фаза (U β ) во полипропиленот беше од 0,90 до 0,94, во  Dedicated to Academician Gligor Jovanovski on the occasion of his 70 th birthday.A. Janevski, G. Bogoeva-Gaceva, V. Stefov, M. Najdoski Maced. J. Chem. Chem. Eng. 34 (1), 189-199 (2015) 190 зависност од брзината на ладење, споредено со 0,18-0,35 кога беше употребен пимелат на Mg. Во полимерот кристализиран со употреба на пимелати на Ba и Sr како нуклеатори, U β е од 0,47 до 0,77. Имајќи ги предвид теоретските концепти за нуклеационата активност на супстратите, беше направен обид да се корелираат структурите на синтетизираните пимелати со нивната β-нуклеациона активност во процес на неизотермална кристализација на iPP.

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“…In case of   phase, the orientations of methyl group are statistically ordered, and it is random for   phase. The helical structure of both   and    form are well known [9][10][11]. It was reported that the commercial iPPs has various degrees of disorder in the orientation of the methyl groups [4,9] indicating the presence of both  1 and  2 phases.…”

Section: Introductionmentioning

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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Crystal ordering of α phase isotactic polypropylene

Cited by 45 publications

References 23 publications

Temperature Dependence of Crystal Growth Rate for α and β Forms of Isotactic Polypropylene

Temperature Dependence of Crystal Growth Rate for α and β Forms of Isotactic Polypropylene

The correlation between structure and β-nucleation efficiency of Ba, Sr, Ca and Mg pimelates in isotactic polypropylene

Influence of Tacticity on Structural Ordering of Isotactic Polypropylene under Annealing

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