13C CP/MAS NMR studies of morphological changes in polypropylene: 2. The double melting endotherm of spunbonded fabrics

Caldas, V.; Brown, G. R.; Nohr, Ronald S.; MacDonald, John

doi:10.1002/(sici)1099-0488(19960915)34:12<2085::aid-polb14>3.0.co;2-y

Cited by 17 publications

(31 citation statements)

References 3 publications

(4 reference statements)

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“…Relatively unchanged mechanical properties of the PE monolayer control and the concurrent 20 J/g increase in melting enthalpy for the PP control indicate that changes in mechanical properties and thermal behavior before and after aging are not controlled directly by PE component in the multilayered films. Note that the significant increase in modulus upon annealing shown by PP was in agreement with literature . Indeed, as confirmed also by XRD and NMR results (vide infra), in these samples, PP crystallization appears to be much more sensitive than the crystallization of PE to the increase in the number of the layers.…”

Section: Resultssupporting

confidence: 88%

“…The melting point of PP, reported at 143 °C in all samples, is very distant from typical values of isothermally crystallized iPP (mp 163 °C). The difference is too wide to be attributed to kinetic effects, since even melt‐spun fibers and quenched iPP films that could theoretically be more similar to the present material melt around 155 °C . A melting point depression of 10 °C was observed also in PE compared with a metallocene HDPE .…”

Section: Resultsmentioning

confidence: 61%

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Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Mauri¹,

Ponting

Causin

et al. 2017

J Polym Sci B Polym Phys

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Shortly after processing, Polyethylene/Polypropylene (PE/PP) multilayer films demonstrate an increase in tensile modulus and other mechanical properties when the individual layer thickness is below 0.5 mm. Subsequent annealing at 60 8C for 16 h brings the properties of all other samples to similar values. WAXD characterization of the layered films identified a prevalence of mesophase in the thicker PP layers. In samples with increased layer numerosity or subjected to annealing, WAXD detected its conversion to a crystalline phase that correlates with improved mechanical properties. SSNMR and DSC detailed the defective nature of a iPP crystallites. Comonomers, detected by NMR in the commercial polymers used for the films, are the source of "tunable disorder" that dictates the formation of the PP mesophase and the low temperature of conversion to the mechanically stronger defective a phase. Soft intrafilm layer interfaces instead enable nucleation and localized polymer chain rearrangement even without annealing.

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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 61%

Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Mauri¹,

Ponting

Causin

et al. 2017

J Polym Sci B Polym Phys

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“…The isothermal temperature causes the distributions of two melting endotherms of iPP have been extensively discussed. [22][23][24][25][26] Figure 3 shows the crystallization behavior of iPP/POSS nanocomposites as a function of POSS contents during the cooling trace. The crystallization temperature (T c ) and latent heat of crystallization (DH c ) of all iPP/POSS nanocomposites increase evidently with the increase in POSS molecules, respectively.…”

Section: Resultsmentioning

confidence: 99%

Crystallization behavior and morphological development of isotactic polypropylene blended with nanostructured polyhedral oligomeric silsesquioxane molecules

Chen

Chiou

2006

J Polym Sci B Polym Phys

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The thermal properties and morphological development of isothermally crystallized isotactic polypropylene (iPP) blended with nanostructured polyhedral oligomeric silsesquioxane (POSS) molecules at very small loading of POSS were studied with differential scanning calorimeter (DSC), thermal gravimetric analysis, dynamic mechanical analysis, polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The result of DSC indicated that the crystallization rate of iPP increases with the increase in POSS contents during crystallization; moreover, the melting temperature of iPP/POSS nanocomposites slightly decreases, while the heat of fusion increases with the addition of POSS molecules at melting and remelting traces. The storage modulus and thermal stability, respectively, remarkably decrease, while the glass transition temperature of isothermally crystallized iPP/POSS nanocomposites increases slightly with the increase in POSS contents. The morphologies results of WAXD and POM show that the POSS molecules form about 35 nm sized nanocrystals and aggregate to form thread-like and network structure morphologies, respectively, in the molten state even when the POSS content is very small. These results, therefore, suggest that the interaction force between the POSS molecules should be larger than the force between POSS molecules and iPP matrix; however, those interactions depend on the chain length of functionalized substituents on the POSS cage. Therefore, the POSS molecules aggregate forming nanocrystals and act as an effective nucleating agent for iPP and influence the thermal properties of iPP/ POSS nanocomposites due to the shorter chain length of functionalized substituents, methyl, on the POSS cage.

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“…The intensities of all functional group related to the α 2 signals increase and become narrower with increasing annealing temperatures. The observed doublets are related to the ordering of the packing structure [18,19]. This observation is well consistent with previously reported NMR results [5,17,20].…”

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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13C CP/MAS NMR studies of morphological changes in polypropylene: 2. The double melting endotherm of spunbonded fabrics

Cited by 17 publications

References 3 publications

Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Crystallization behavior and morphological development of isotactic polypropylene blended with nanostructured polyhedral oligomeric silsesquioxane molecules

Influence of Tacticity on Structural Ordering of Isotactic Polypropylene under Annealing

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