Gamma polymorph and branching formation as inductors of resistance to electron beam irradiation in metallocene isotactic polypropylene

Cerrada, María L.; Pérez, Ernesto; Benavente, Rosario; Ressia, Jorge Aníbal; Sarmoria, Claudia; Vallés, Enrique M.

doi:10.1016/j.polymdegradstab.2010.01.013

Cited by 24 publications

(31 citation statements)

References 48 publications

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“…The corresponding values obtained at room temperature are listed in Table 1. The degree of crystallinity is within the range of that found in analogous quenched metallocenic iPP specimens [26][27][28][29][30]. Under the quenching conditions imposed during film preparation, crystallization takes place at conditions far from equilibrium and the fast cooling applied limits even more the development of crystallites and their perfection.…”

Section: Resultssupporting

confidence: 54%

“…These features can be ascribed to the relatively high cooling rate used during processing of these films since the γ form is attained in other similar metallocenic iPP homopolymers when crystallization is performed at very slow rate [26]. In fact, the profiles at room temperature (depicted in the Figure 4b) obtained after crystallizing at a rate of 8ºC/min during real-time variable-temperature WAXS experiments with synchrotron radiation show the deep effect that cooling rate has on the development of this γ polymorph.…”

Section: Resultsmentioning

confidence: 99%

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Rheological and structural details of biocidal iPP-TiO2 nanocomposites

Serrano

Cerrada

Ressia

et al. 2012

European Polymer Journal

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Nanocomposites obtained from incorporation of TiO 2 nanoparticles in different amounts, ranging from 0.5 to 5 wt.%, into an isotactic polypropylene (iPP) matrix are achieved via a straightforward and cost-effective melting process. These materials exhibit a powerful germicide capability over a wide variety of regular bacteria and other microorganisms widely present in the environment that cause infections and serious illness.The iPP-TiO 2 nanocomposites show similar or improved structural characteristics than those of the pure iPP matrix and aspects as important as processability and final mechanical performance seem to be not affected because of the incorporation of these TiO 2 nanoparticles.Validation of time-temperature superposition of the molten polymers is observed within the temperature range analyzed. On the other hand, the α polymorph is the one primarily attained for these specimens. Crystallinity and most probable crystallite size are slightly dependent on TiO 2 content, both increasing as oxide composition is enlarged.

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Section: Resultssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

Rheological and structural details of biocidal iPP-TiO2 nanocomposites

Serrano

Cerrada

Ressia

et al. 2012

European Polymer Journal

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“…Other important factors to be considered are those related to knowing how the interfacial agent content and the thermal history imposed on these nanocomposites affect their final crystalline structure. Figure 6 clearly shows the coexistence at room temperature of the α and γ polymorphs in the whole series of the slowly cooled samples (S) in the press 40. The most typical and the most stable crystalline structure is the monoclinic α form that was first characterized by Natta and Corradini 41.…”

Section: Resultsmentioning

confidence: 98%

Efficient Rhodium‐Catalyzed Installation of Unsaturated Ester Functions onto Porphyrins: Site‐Specific Heck‐Type Addition versus Conjugate Addition

Baba

Chen

Shinokubo

et al. 2008

Chemistry A European J

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A facile introduction of alpha,beta- or alpha,beta,gamma,delta-unsaturated ester functions onto porphyrins was achieved through rhodium-catalyzed addition of beta-borylporphyrins to acrylate or 2,4-pentadienoate esters. The reaction of meso-borylporphyrins with acrylates exclusively afforded saturated esters by 1,4-conjugate addition under the same reaction conditions. Thus, the reaction mode (Heck-type versus conjugate addition) is highly dependent on the reaction site (beta versus meso). This functionalization has a significant impact on the electronic properties of the pi system of porphyrins, which induces a substantial redshift and broadening in the absorption spectra by effective conjugation through the beta positions. The coplanar structure of the unsaturated ester moieties with respect to the porphyrin core has been unambiguously elucidated by X-ray crystallographic analysis.

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“…The J‐integral based on the multiple specimen method was used to measure the fracture toughness of the specimens by following ESIS and ASTM protocols . A set of identical specimens for each type of material were loaded to various displacements at a 1 mm/min cross‐head speed using an Instron‐8872 machine.…”

Section: Methodsmentioning

confidence: 99%

“…The initial and final stable crack lengths for each specimen were measured physically from the fracture surfaces. Great care was taken during the crack length measurements according to the standards . The J values were calculated from the total energy required ( U ) to extend the crack, which was determined from the area under the load–displacement curve obtained from the Instron‐8872 data acquisition system.…”

Section: Methodsmentioning

confidence: 99%

Fracture toughness of rotationally molded polyethylene and polypropylene

Saifullah¹,

Thomas

Cripps³

et al. 2017

Polymer Engineering & Sci

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In this work, the fracture toughness of rotationally molded polyethylene (PE) and polypropylene (PP) was measured using J integral methods at static loading rates and at room temperature. Two different commercially available rotational molding grades PE and PP were tested in this study which have been used in various rotationally molded products such as small leisure craft, water storage tanks, and so on. Scanning electron microscope (SEM), optical microscope, differential scanning calorimetry (DSC), solidstate nuclear magnetic resonance (solid-state NMR), and X-ray scattering were used to investigate the microstructure, fracture surfaces, and compare toughness properties of these materials. In PE, higher molecular weight and broader molecular weight distribution, larger amorphous and crystal region thicknesses are found to be related to higher toughness values. High molecular weight favors higher number of entanglements that improve fracture energy and broader distribution increases long chain branching of higher molecular weight fractions which creates higher entanglements at the branch sites. Larger amorphous regions promote microvoiding more easily compared to thinner amorphous regions, leading to greater plastic deformation and energy absorption. Higher crystal thickness also contributes to microvoiding in the amorphous region. For PP, greater plastic deformation observed in the fracture surfaces is related to higher fracture toughness values. POLYM. ENG. SCI., 58:63-73, 2018.

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Gamma polymorph and branching formation as inductors of resistance to electron beam irradiation in metallocene isotactic polypropylene

Cited by 24 publications

References 48 publications

Rheological and structural details of biocidal iPP-TiO2 nanocomposites

Rheological and structural details of biocidal iPP-TiO2 nanocomposites

Efficient Rhodium‐Catalyzed Installation of Unsaturated Ester Functions onto Porphyrins: Site‐Specific Heck‐Type Addition versus Conjugate Addition

Fracture toughness of rotationally molded polyethylene and polypropylene

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