Crystallization of Polypropylene

Pawlak, Andrzej; Gałęski, Andrzej

doi:10.1007/978-3-030-12903-3_4

Cited by 11 publications

(12 citation statements)

References 159 publications

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“…According to Guinier approximation, if N groups of voids with different sizes exist in material, the intensity of scattering may be described by the equation: 3,48

normalI = K \sum_{i = 1}^{N} v_{i} italicexp ((), - h^{2} R_{i}^{2} / 3),

where K is a constant, v i the volume of voids in the i th group, Ri the radius of gyration, and h the scattering vector. For rod‐like scattererrs, the radius of gyration R g of the microvoids is obtained according to the following relationship: 3,29,48,49

\ln I = italicconst - \frac{q^{2} R_{g}^{2}}{4}

…”

Section: Methodsmentioning

confidence: 99%

“…During deformation process, semi‐crystalline polymers generally produce superstructures. The evolution of superstructures involves the variation of crystalline and amorphous phases, including orientation‐induced crystallization, crystal transition, chain orientation, fibrillary formation and cavitation and so forth 1–7 . Therefore, it is of great significance to study superstructure transformation and its correlations with stress–strain curves for preparing microporous membrane by dry process 8–11 …”

Section: Introductionmentioning

confidence: 99%

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The cavitation development of poly(4‐methyl‐1‐pentene) casting films studied by in situ small angle X‐ray scattering

Jiang

Wang³

et al. 2020

J of Applied Polymer Sci

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In this paper, the on‐line small angle X‐ray scattering/wide‐angle X‐ray scattering (SAXS/WAXS) characterization method was adopted to study the morphology evolution of poly(4‐methyl‐1‐pentene) casting films during stretching. In this process, the lamellae structure was destroyed. And “bridge structure” was generated in the amorphous region. The scattering pattern changed obviously before and after cavities orientation. Stretching temperature and stretching speed mattered for the size of micropores. Low temperature helped generate more and larger voids. The faster stretching speed can improve the generation of cavities, enlarged cavitation number and helped its reorientation. These results provide the basic knowledge of how to produce poly(4‐methyl‐1‐pentene) microporous membranes with high electrochemical performance.

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“…According to Guinier approximation, if N groups of voids with different sizes exist in material, the intensity of scattering may be described by the equation: 3,48

normalI = K \sum_{i = 1}^{N} v_{i} italicexp ((), - h^{2} R_{i}^{2} / 3),

\ln I = italicconst - \frac{q^{2} R_{g}^{2}}{4}

…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The cavitation development of poly(4‐methyl‐1‐pentene) casting films studied by in situ small angle X‐ray scattering

Jiang

Wang³

et al. 2020

J of Applied Polymer Sci

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“…Pure PP, similar to HDPE, is a PO with a strongly crystalline structure. The uniform isotactic architecture of the investigated PP allows packing of the polymer chains into strong chain-folded crystalline structures, which are mostly spherulitic [78]. The presence of the methyl group results in a stiffer and stronger material compared to PE.…”

Section: Deformation Of Contaminated Pp Matrix Blendsmentioning

confidence: 99%

Macromolecular Insights into the Altered Mechanical Deformation Mechanisms of Non-Polyolefin Contaminated Polyolefins

et al. 2022

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Current recycling technologies rarely achieve 100% pure plastic fractions from a single polymer type. Often, sorted bales marked as containing a single polymer type in fact contain small amounts of other polymers as contaminants. Inevitably, this will affect the properties of the recycled plastic. This work focuses on understanding the changes in tensile deformation mechanism and the related mechanical properties of the four dominant types of polyolefin (PO) (linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP)), contaminated with three different non-polyolefin (NPO) polymers (polyamide-6 (PA-6), polyethylene terephthalate (PET), and polystyrene (PS)). Under the locally elevated stress state induced by the NPO phase, the weak interfacial adhesion typically provokes decohesion. The resulting microvoids, in turn, initiate shear yielding of the PO matrix. LLDPE, due to the linear structure and intercrystalline links, is well able to maintain high ductility when contaminated. LDPE shows deformation similar to the pure material, but with decreasing ductility as the amount of NPO increases. Addition of 20 wt% PA-6, PET, and PS causes a drop in strain at break of 79%, 63%, and 84%, respectively. The typical ductile necking of the high-crystalline HDPE and PP is strongly disturbed by the NPO phase, with a transition even to full brittle failure at high NPO concentration.

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“…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%

“…Up to date, four main crystal modifications were reported for isotactic PP, including the monoclinic α phase, the trigonal β phase, the orthorhombic γ phase, and the ordered mesomorphic mesophase. [26][27][28] Various research groups reported multiple distinct melting endotherms associated with different crystalline forms of PP, depending on the processing conditions. [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.…”

mentioning

confidence: 99%

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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Crystallization of Polypropylene

Cited by 11 publications

References 159 publications

The cavitation development of poly(4‐methyl‐1‐pentene) casting films studied by in situ small angle X‐ray scattering

The cavitation development of poly(4‐methyl‐1‐pentene) casting films studied by in situ small angle X‐ray scattering

Macromolecular Insights into the Altered Mechanical Deformation Mechanisms of Non-Polyolefin Contaminated Polyolefins

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

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