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Search Results (4)

Search Parameters:
Keywords = calcium pimelate

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19 pages, 3505 KiB  
Article
Crystallization of the β-Form of Polypropylene from the Melt with Reduced Entanglement of Macromolecules
by Justyna Krajenta and Andrzej Pawlak
Polymers 2024, 16(12), 1710; https://doi.org/10.3390/polym16121710 - 15 Jun 2024
Cited by 3 | Viewed by 2644
Abstract
The influence of decreasing the entanglement density of macromolecules on the crystallization of the β-form of polypropylene was investigated. Polypropylene with seven times less entanglement was obtained from a solution in xylene, and its properties were compared with those of fully entangled polypropylene. [...] Read more.
The influence of decreasing the entanglement density of macromolecules on the crystallization of the β-form of polypropylene was investigated. Polypropylene with seven times less entanglement was obtained from a solution in xylene, and its properties were compared with those of fully entangled polypropylene. To obtain a high β-phase content, the polymer was nucleated using calcium pimelate. In non-isothermal crystallization studies, accelerated growth of β-crystals was found, increasing the crystallization temperature. Also, the isothermal crystallization was fastest in the nucleated, partially disentangled polypropylene. Increased growth rate of spherulites and enhanced nucleation activity in the presence of more mobile macromolecules were responsible for the high rate of melt conversion to crystals in the disentangled polypropylene. It was also observed that the equilibrium melting temperature of β-crystals is lower after disentangling macromolecules. Better conditions for crystal building after reduction of entanglements resulted in enhanced crystallization according to regime II. Full article
(This article belongs to the Special Issue Crystallization Behavior and Mechanical Properties of Semi-crystalline Polymers)
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16 pages, 4369 KiB  
Article
Structural Characteristics and Improved Thermal Stability of HDPE/Calcium Pimelate Nanocomposites
by Christina Samiotaki, Evangelia Tarani, Dimitra Karavasili, Alexandra Zamboulis, Konstantinos Chrissafis and Dimitrios N. Bikiaris
Macromol 2024, 4(1), 42-57; https://doi.org/10.3390/macromol4010003 - 5 Feb 2024
Cited by 1 | Viewed by 2086
Abstract
In the present research work, calcium pimelate (CaPim) was synthesized and investigated as an additive for high-density polyethylene (HDPE). HDPE/CaPim nanocomposites were prepared by melt-mixing, with CaPim content ranging from 0.1% to 1%, affording white homogeneous materials. The chemical structure of the nanocomposites [...] Read more.
In the present research work, calcium pimelate (CaPim) was synthesized and investigated as an additive for high-density polyethylene (HDPE). HDPE/CaPim nanocomposites were prepared by melt-mixing, with CaPim content ranging from 0.1% to 1%, affording white homogeneous materials. The chemical structure of the nanocomposites and the incorporation of CaPim was confirmed by infrared spectroscopy. The surficial morphology and the additive distribution were examined by scanning electron microscopy. Differential scanning calorimetry and X-ray diffraction measurements showed that the thermal transitions and crystal structure of HDPE are not affected by the incorporation of CaPim, while the mechanical properties are retained overall. This study focuses on the thermal degradation of HDPE nanocomposites, investigating the degradation mechanism and kinetic parameters through various analytical methods. Isoconversional techniques, including the Friedman method, Vyazovkin analysis, and Ozawa Flynn Wall analysis, were employed to calculate activation energies (Eα). The degradation mechanism and kinetic triplet were determined based on a multivariate non-linear regression method (model-fitting). Finally, the presence of a CaPim additive was shown to increase the Eα of thermal degradation, consistent with the calculated dependence of Eα on the degree of conversion and the improved thermal stability of the HDPE matrix. Full article
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18 pages, 30733 KiB  
Article
The Friction of Structurally Modified Isotactic Polypropylene
by Natalia Wierzbicka, Tomasz Sterzyński and Marek Nowicki
Materials 2021, 14(23), 7462; https://doi.org/10.3390/ma14237462 - 5 Dec 2021
Cited by 4 | Viewed by 2975
Abstract
The purpose of studies was to analyse an impact of heterogeneous nucleation of modified isotactic polypropylene (iPP) on its tribological properties. The iPP injection molded samples, produced by mold temperature of 20 and 70 °C, were modified with compositions of two nucleating agents [...] Read more.
The purpose of studies was to analyse an impact of heterogeneous nucleation of modified isotactic polypropylene (iPP) on its tribological properties. The iPP injection molded samples, produced by mold temperature of 20 and 70 °C, were modified with compositions of two nucleating agents (NA’s), DMDBS creating α-form and mixture of pimelic acid with calcium stearate (PACS) forming β–phase of iPP, with a total content 0.2 wt.% of NA’s. A polymorphic character of iPP, with both, monoclinic (α) and pseudo-hexagonal (β) crystalline structures, depending on the NA’s ratio, was verified. The morphology observation, DSC, hardness and tribological measurements as test in reciprocating motion with “pin on flat” method, were realized, followed by microscopic observation (confocal and SEM) of the friction patch track. It was found that Shore hardness rises along with DMBDS content, independent on mold temperature. The friction coefficient (COF) depends on NA’s content and forming temperature—for upper mold temperature (70 °C), its value is higher and more divergently related to NA’s composition, what is not the case by 20 °C mold temperature. The height of friction scratches and the width of patch tracks due to its plastic deformation, as detected by confocal microscopy, are related to heterogeneous nucleation modified structure of iPP. Full article
(This article belongs to the Special Issue Structure–Physical Properties Relationship of Polymer and its Composites)
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20 pages, 12299 KiB  
Article
Supramolecular Structure of Polypropylene Fibers Extruded with Addition of Functionalized Reduced Graphene Oxide
by Jan Broda, Janusz Fabia, Marcin Bączek and Czesław Ślusarczyk
Polymers 2020, 12(4), 910; https://doi.org/10.3390/polym12040910 - 14 Apr 2020
Cited by 9 | Viewed by 3242
Abstract
An effective β-nucleating agent for polypropylene crystallization was obtained by the functionalization of reduced graphene oxide with calcium pimelate. The nucleating ability of the modified reduced graphene oxide (rGO-CP) was confirmed during non-isothermal crystallization. In further examinations, the rGO-CP was used as an [...] Read more.
An effective β-nucleating agent for polypropylene crystallization was obtained by the functionalization of reduced graphene oxide with calcium pimelate. The nucleating ability of the modified reduced graphene oxide (rGO-CP) was confirmed during non-isothermal crystallization. In further examinations, the rGO-CP was used as an additive to modify polypropylene fibers. The fibers were extruded in laboratory conditions. Gravity spun fibers containing three different concentrations of the rGO-CP and fibers taken at three different velocities were obtained. The supramolecular structure of the fibers was examined by means of calorimetric and X-Ray Scattering methods (DSC, WAXS, and SAXS). The considerable amount of β-iPP was obtained only in the gravity spun fibers. In the fibers extruded at higher velocities, the diminishing impact of the additive on the fibers structure was revealed. The changes observed in the fiber structure in connection with the impact of the additive on polypropylene crystallization was discussed. Full article
(This article belongs to the Special Issue Carbon Materials Modified Polymeric Composites)
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