Solid State Polymorphism of Isotactic and Syndiotactic Polypropylene

Auriemma, Finizia; Rosa, Claudio De; Malafronte, Anna; Scoti, Miriam; Girolamo, Rocco Di

doi:10.1007/978-3-030-12903-3_2

Cited by 20 publications

(28 citation statements)

References 216 publications

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“…The excellent and inimitable properties of syndiotactic polypropylene due to its exclusive crystallization performance as well as many researchers have concentrated on normal commercial isotactic polypropylene, the two mentioned factors encouraged the proposed study to take advantage and rely on syndiotactic polypropylene as a major material to accomplish current research [15][16][17][18]. The characteristics of raw syndiotactic polypropylene which was used in the present study can be summarized in Table 1.…”

Section: Methodsmentioning

confidence: 99%

Correlation between Parameters of Extrusion Technique and Both of Optical and Physical Characteristics of Reinforced Polypropylene Composites

Saleh

2020

Egypt. J. Chem.

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Section: Methodsmentioning

confidence: 99%

Correlation between Parameters of Extrusion Technique and Both of Optical and Physical Characteristics of Reinforced Polypropylene Composites

Saleh

2020

Egypt. J. Chem.

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“…We analyzed the distance between the lattice planes and the corresponding Miller indices [hkl] of the main Bragg reflections relative to the α, β, γ and mesomorphic forms of isotactic PP according to the literature data. 35,43 The related analysis method by the Scherrer and Bragg equations (Equation S1 and Equation S2) are given in the Supplementary Information.…”

Section: Characterization By Differential Scanning Calorimetry and Wide-angle X-ray Diffractionmentioning

confidence: 99%

“…The mesomorphic mesophase can form at cooling rates high enough to prevent the crystallization of the more stable monoclinic α form. 27,35 We investigated the crystal structure of the produced MB fiber mats and hot-pressed sheet to analyze the influence of the processing conditions (Figure 14). The hot-pressed sheet showed Bragg reflection peaks (Figure 14A obtained by the WAXD analysis of the PP hot-pressed sheet suggest that lamellar branching occurred with two different crystal forms that suggest α crystals act as a nucleus for the γ crystals.…”

Section: Waxd Testsmentioning

confidence: 99%

“…[29][30][31] The related models explain the multiple melting endotherms in different ways, including the existence of primary and secondary crystallization, two crystal phases of PP (e.g., α and β), recrystallization and reorganization, crystalline perfection, development of the up/down disorder in the crystals of the α form, iPP degree of stereoregularity. 26,[32][33][34][35][36] However, very little work is done on the evaluation of the PP melt-blown fibers and their crystalline structure development.…”

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confidence: 99%

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Revealing of process–structure–property relationships of fine polypropylene fiber mats generated via melt blowing

Kara

Molnár

2021

Polymers for Advanced Techs

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In this study, we presented systematic and comparative investigations on the structure of polypropylene fibers generated using different processing conditions via melt blowing. Increasing air pressure, die-to-collector distance, and air temperature reduced the average fiber diameter nearly 3-fold, 2-fold, and 1.75-fold, respectively.An average of 1.4 μm Feret-diameter was observed as the smallest pore size, while the fiber mat solidities ranged from 8 to 13%. Differential scanning calorimetry results showed single melting peaks in the 1st heating cycle and double melting peaks in the second one, due to the phase transition at melt blowing. The fiber crystallinities varied between 43 and 52% by changing the processing conditions. The X-ray diffraction study revealed that the MB fibers exhibited α and mesomorphic crystals depending on the processing parameters. The reference polypropylene sheet made of the same fiber grade polypropylene resin, on the other hand, exhibited a mix of α and γ crystalline forms. The polypropylene fiber mat tensile strength improved by 48% and by 13% with increasing air pressure and air temperature, respectively.Decreasing fiber collection distances resulted in 2.5-fold higher tensile strength while strain at break reduced eightfold. A new factor, mat consolidation coefficient, was introduced and used to efficiently summarize melt-blown fiber mats' process-property-structure relationships. This study details how to control the melt blowing parameters to tailor the polypropylene fiber mat features for the respective application field. It also presents an insight into fiber formation mechanisms during melt blowing for generating self-bonded, defect-free, fine fiber mats.

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“…12 As typical semicrystalline polymers applied in industry and in everyday life, [17][18][19][20][21][22][23] iPP homopolymer and iPP-⊍-olefin copolymers exhibit polymorphic behavior and can crystallize in monoclinic ⊍, trigonal ⊎ and orthorhombic γ forms, and in a new trigonal form under different crystallization conditions. [24][25][26][27][28][29][30][31] Moreover, a mesomorphic form, 32 whose degree of ordering is intermediate between that of the crystalline phase and the amorphous phase, can be obtained via rapidly cooling from melt to temperature above the glass transition temperature or by annealing completely amorphous iPP. 33 Several factors affect the formation of the mesophase of iPP, including cooling rate, 34,35 comonomer content, [36][37][38][39][40] isotacticity 41,42 and nucleating agent.…”

Section: Introductionmentioning

confidence: 99%

Structural evolution of mesomorphic propylene–1‐butene random copolymer during heating process

Qian

Zhao

Wang

2021

Polymer International

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The study of the transition of mesophase to ⊍-crystal (meso-⊍ transition) is of great significance for understanding the crystallization, morphology as well as processability of polypropylene materials. The structural evolution of mesomorphic isotactic propylene-1-butene (iPPBu) random copolymer during the continuous heating process was investigated using in situ Fourier transform infrared spectroscopy, differential scanning calorimetry, wide-angle X-ray diffraction and dynamic mechanical analysis. The presence of the butene comonomer influences the meso-⊍ transition behavior. Compared with the mesomorphic iPP homopolymer, the presence of butene comonomer reduces both onset temperature (T onset ) and end temperature (T end ) of the meso-⊍ transition, and narrows the transition temperature range. The content of the 3 1 helical sequence with 12 monomers remains invariant during the meso-⊍ transition, differing from that of mesomorphic iPP homopolymer. Similar to mesomorphic iPP homopolymer, the 3 1 helical sequence with monomer number n ≤ 12 is found to exist in the rigid amorphous fraction of iPPBu, but is different from that of a mesomorphic propylene-ethylene random copolymer. In the meso-⊍ transition (from 60 to 100 °C), the redshift of the peak position of the band at ca 841 cm −1 provides new information for the approaching of adjacent stems at the molecular level. Moreover, a new peak at around T end is found in the tan(⊐)-T plot, and is correlated with the meso-⊍ transition. The activation energy of the meso-⊍ transition of mesomorphic iPPBu is 32.5 kJ mol −1 , which is slightly lower than that of mesomorphic iPP homopolymer. This work sheds new light on further understanding of the meso-⊍ transition mechanism of iPPBu copolymer at the molecular level and elucidates the effect of butene comonomer on the meso-⊍ transition.

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Solid State Polymorphism of Isotactic and Syndiotactic Polypropylene

Cited by 20 publications

References 216 publications

Correlation between Parameters of Extrusion Technique and Both of Optical and Physical Characteristics of Reinforced Polypropylene Composites

Correlation between Parameters of Extrusion Technique and Both of Optical and Physical Characteristics of Reinforced Polypropylene Composites

Revealing of process–structure–property relationships of fine polypropylene fiber mats generated via melt blowing

Structural evolution of mesomorphic propylene–1‐butene random copolymer during heating process

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