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Showing 1 to 20 of 39 for “"Spherulites"”.
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Authigenic analcite in the Golden Valley Formation southwestern North Dakota
… top of the arkose unit. The analcite occurs as spherulites in the interstices of the arkose and as a cement in the analcimolite. Three types of spherulites are recognized: (1) spherulites with an internal radial structure; (2) spherulites with a massive center and a peripheral radial structure; …
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Structure-property relationships in extruded plastics foams
… Differential Scanning Calorimetry revealed 13-spherulites are only formed in skin layer, and beneath the thickness of 500 pm from the surface, the crystal structure of this polymer is only consist of B-spherulites. On the other hand, the chemical blowing agent (Hydrocerol CF-20), was found to …
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Polymer Crystallization: Polycarbonate and Polybutene-1
… transmission electron microscopy, revealed that spherulites grew by a nucleation and growth process; no evidence of nodular aggregation or enhanced nucleation by nodules was seen. The growth rates of the spherulites as a function of temperature, measured by a repeat replica process, were found to …
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Quantum Imaging of Biosamples
… precise, state-of-the-art engineering. Polymer spherulites, naturally occurring birefringent crystals that grow around defects in a radial pattern, are an example of this. We show through the example of ascorbic acid, commonly referred to as Vitamin C, that spherulites are capable of creating …
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Crystallization kinetics of polylactide and its blends
… the second on the growth rates of the individual spherulites. The kinetics of crystallization were found to decrease as the molecular weight of the semicrystalline component increased and as the PLA-DL content in the blend increased. In some particular cases, however, a spectacular increase of the …
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Crystallization behavior of nylon 6/6 and its blends with poly(vinyl pyrrolidone)
… striking reduction in the nucleation density of spherulites, modification of lamellar organization in spherulites (as evidenced by the occurrence of banding), and modification of interlamellar spacings.
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Polymer structure and property studies in elongational rheology, spherulite deformation, and biaxial strain induced crystallization
… studied in a model system consisting of isolated spherulites embedded in an amorphous polymer matrix. By isolating the spherulite, the mechanical influence of surrounding and often impinging spherulites found in most semicrystalline polymers on the mechanical response of an individual spherulite …
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Crystallization and structure-property investigations of semicrystalline poly(arylene ether) based polymers
… distinct populations of two kinds of spherulites were formed, with a population of coarse textured spherulites exhibiting a higher growth rate (Type II) than a population of fine textured spherulites (Type I). The morphology of these spherulites have been studied here using a variety …
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Altering the fiber-matrix interphase in semicrystalline polymer matrix composites
… dramatically reduced the nucleation density of spherulites and modified the lamellar organization in the spherulites (as evidenced by the occurrence of banding which is the twisting of lamella as they grow radially). Furthermore, in the presence of unsized fibers, the addition of small amounts …
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Deformation and Transformation Mechanisms of Polybutene and Poly(vinylidene Fluoride)
… the original crystalline lamellae comprising the spherulites with respect to the draw direction. Deformation of fresh PB thin film is accompanied by a transformation of tetragonal form to hexagonal form. Potassium permanganate etching and dark field microscopy of fresh thick and thin films reveal …
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A numerical and experimental investigation of the effects of thermal history on the structure/property relationship of PPS/carbon fiber composites
… (both amount of crystallinity and the size of spherulites) which arise during the cooling of a slab of a semicrystalline polymer reinforced with long continuous carbon fibers. This situation is commonly found during the processing of semicrystalline thermoplastic composites. Whereas published …
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Study of poly (l-lactic acid)/poly (d-lactic acid) stereocomplex as nucleating agent for poly (l- lactic acid) crystallization
… polarized microscope, the increasing number of spherulites observed at higher temperature, confirms the enhancement on PLLA nucleation brought by the stereocomplex. Yet, the irregular morphology of crystallites may indicate that the stereocomplex does not promote higher degree of crystallinity. …
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Effects of high pressure solidification on the tensile properties of polypropylene
… with increasing solidification pressure. Spherulites formed under higher pressure were smaller in size and less branched than those formed at low pressure. Yield and tensile strengths were reduced as the solidi fication pressure was increased, the reduction being about 10% when solidi …
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Effect of Laser Induced Crystallinity Modification on Degradation and Drug Release of Biodegradable Polymer
… Solvent casting produces category 1 spherulites, and annealing the spin coated films leads to category 2 spherulites. Crystal structure of the two kinds of films shows distinct features. The results advance the understanding of PLLA crystal structures, which is essential for its …
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Structure property and deformation analysis of polypropylene montmorillonite nanocomposites.
… and polarized optical microscopic examination of spherulites sizes showed changes in nucleation and growth resulting from both the maleated PP compatibilizer and the MLS. These structural changes resulted in a tough nanocomposite, a concept not reported before in the PP literature. Nonlinear creep …
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Melting point depression in biodegradable polyesters
… camera, the diameter growths of individual spherulites could be measured minute-by-minute. Using the results obtained through hot-stage microscopy, re-processing of PLA could be carried out to restore the original crystallinity at Tmax 118°C. Plots showing % crystallinity with storage time …
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The Crystallization of Polyetheretherketone (Peek) From the Glass
… was predominantly nucleated heterogeneously as spherulites when annealed at 162$\sp\circ$C or higher. Diffusion of the chains was the rate controlling process. Melt history affected only the kinetics of the crystallization and not the mechanisms. Graphite fibers had no nucleating effect on the …
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Iron minerals in sedimentary phosphorites of the southeastern United States
… gossan, and secondary ferromanganese oxide spherulites as accessory minerals in Tennessee deposits are made in this study
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Heterogeneous nucleation in polymer crystallization
… found to be related to the initial number of spherulites present in the un-nucleated polymer. The highest shift in the crystallization temperature has been obtained from partially molten polymers (self nucleation); the shift which can be obtained with the best nucleating agents is approaching …
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Crystallization and Melting Studies of Poly(ε-caprolactone) and Poly(ethylene oxide) using Flash™ Differential Scanning Calorimetry and Preparation and Characterization of Poly(δ-valerolactone) Fractions
… primary nucleation temperature range, and spherulites grow in the heterogenous primary nucleation range. Poly(δ-valerolactone) was synthesized using microwave-assisted techniques. Narrow molecular weight fractions were obtained using successive precipitation fractionation. Preliminary …
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