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Showing 1 to 20 of 20 for “"semicrystalline polymers"”.
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Micromechanical modeling of the toughening mechanisms in particle-modified semicrystalline polymers
… appreciated that a number of sernicrystalline polymers can be effectively toughened by the addition of a well-dispersed secondary phase. In particular, when the average interparticle matrix ligament thickness, A, of the blend is reduced below a critical length parameter, Ac, dramatic jumps in …
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Investigations of the Processing-Structure-Property Relationships of Selected Semicrystalline Polymers
… (MEAUS) utilized to produce semicrystalline polymeric microporous membranes. The two semicrystalline polymers studied were selected based on a set-of-prerequisites proposed for the formation of highly porous membranes via the method in question. The prerequisites included …
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Material Extrusion based Additive Manufacturing of Semicrystalline Polymers: Correlating Rheology with Print Properties
… Current approaches towards MatEx of semicrystalline thermoplastics are in their nascent stage with fiber reinforcements being one of the most common techniques. MatEx of commodity semicrystalline thermoplastics has been investigated but most of the current methods are extremely …
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Evaluating the Time-Dependent Melting Behavior of Semicrystalline Polymers Through Strobl's 3-Phase Model
The melting behavior of polymers can provide information on their crystallization mechanism. However, the origin of the time-dependent low endotherm, or annealing peak, and the extent of melting-recrystallization-remelting during heating are still debated. The crystallization and subsequent melting …
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Design, Synthesis and Study of Thermomechanically Active Polymer Networks Based on Latent Crosslinking of Semicrystalline Polymers
… Such products are essentially composed of polymers, large molecules of high molecular weight with homogeneous or various repeating units, which researchers term “macromolecules” that engender specific structural, morphological, and physical and mechanical properties. Those polymers with the …
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Understanding of the mechanical response of semicrystalline polymers based on the block-like substructure of crystalline lamellae
We investigated the mechanical response of a range of PE and sPP samples as models of semi-crystalline polymer systems under tensile deformation. Splitting the total tensile deformation into elastic and plastic parts shows four characteristic points (A,B,C and D) from the true stress-true strain …
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Equilibrium Melting Temperature Determination of Semicrystalline Polymers through Nonlinear Hoffman-Weeks Extrapolation and Secondary Crystallization of Ethylene/Styrene Copolymers
… of the equilibrium melting temperatures of semicrystalline polymers is critically reviewed. It is shown that the linear extrapolation of observed melting temperatures cannot, in general, provide a reliable estimate of the equilibrium melting temperature. A more rigorous nonlinear HW analysis …
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UNDERSTANDING THE MOLECULAR WEIGHT DISTRIBUTION SHAPE-PROPERTY RELATIONSHIP BASED ON LINEAR UNIMODAL AND BIMODAL POLYETHYLENES MODEL SYSTEM
… is crucial in determining the properties of polymers. Previous studies on comparison of the unimodal and bimodal MWD shape without controlling dispersity, chain branching, phase separation or average molecular weight make it hard to decouple the independent contribution of MWD shape. In this …
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Rheological and Thermal Insights into Solidification Dynamics in Extrusion-Based Additive Manufacturing of Polymer Composites
… layer time) on the printing process, focusing on semicrystalline polymers as feedstock. We explore how polymer physics control process-structure-property relationships at different length- and time scales, focusing on how disparities in shear rates, rheological behavior, and heat retention affect …
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Additive Manufacturing of Commercial Polypropylene Grades of Similar Molecular Weight and Molecular Weight Distribution
… in additive manufacturing (AM). However, semicrystalline polymers, such as polypropylene (PP), have limited commercial use in MEAM processes in the past due to their rapid crystallization kinetics and the subsequent effect on the integrity of the generated structures. The rapid …
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Morphology, Crystallization and Melting Behaviors of Random Copolymers of Ethylene with 1-Butene, 1-Pentene and 1-Hexene
… behaviors of a series of ethylene/alpha-olefin copolymers were investigated as a function of comonomer content, comonomer type and processing conditions, including crystallization temperature and time. This was achieved by using a combination of techniques such as Nuclear Magnetic Resonance …
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Structure-property relationships in extruded plastics foams
Physical properties and morphology of extruded semicrystalline polymers can be significantly affected by modification and change in die design and melt viscosity of the molten polymer. Further modifications to physical properties (i.e. density and open cell fraction) of foamed material occur, …
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Crystallization Behavior of Bisphenol-A Polycarbonate: Effects of Crystallization Time, Temperature, and Molar Mass
… density of PC were investigated. Similar to many semicrystalline polymers, PC exhibits a multiple melting behavior upon heating. While for each PC sample, the coexistence of low and high temperature endothermic regions in the DSC heating traces is explained by the melting of populations of …
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Polymer structure and property studies in elongational rheology, spherulite deformation, and biaxial strain induced crystallization
… regeneration. Direct observations of polymeric semicrystalline morphologies in a copolyester by scanning electron microscopy were made possible by the development of a novel chemical etch. Spherulitic textures were consistent with classic spherulite growth mechanisms and structure theories. …
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Time Dependent Properties of Semicrystalline Poly(Arylene Ether Ether Ketone) (Peek) Above and Below the Glass Transition
Long time annealing of semicrystalline PEEK above the glass transition results in the observation of several time dependent phenomena - "physical aging", "secondary crystallization", "multiple melting" of lamellae with different thermal stability etc. Their interrelation - common origin and …
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Altering the fiber-matrix interphase in semicrystalline polymer matrix composites
When many semicrystalline polymers are used as matrix materials in composites, a morphology known as the transcrystalline region is formed on the surface of the reinforcing material. This region introduces a new crystalline structure to the system that is different from that of the bulk matrix …
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Thermoelectric Properties of Organic Polymers
… properties and the structure of organic polymers. It delves into both innovative new materials systems and established typical materials. First it introduces the background and basic experimental techniques in Chapters 1-2. Then it delves into the function of uniaxial alignment and ion …
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Characterization of the crystallinity and mechanical properties of CTFE & CTFE copolymeric films as a function of cooling rate and the implications on adhesion
… microwave circuits. Since these films are semicrystalline and, in this application, are being used as hot melt adhesives, the cooling rate is an important processing variable, affecting the crystallinity of the CTFE films which in turn affect many properties including dielectric …
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Material Characterization and Life Prediction of a Carbon Fiber/Thermoplastic Matrix Composite for Use in Non-Bonded Flexible Risers
In the effort to improve oil production riser performance, new materials are being studied. In the present case, a Polymer Matrix Composite (PMC) is being considered as a replacement for carbon steel in flexible risers manufactured by Wellstream Inc., Panama City, Florida. The Materials Response …
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Influencia de la radiación ultravioleta en el comportamiento mecánico y en la microestructura de las fibras de seda de araña
… one. Based on previous studies performed on semicrystalline polymers, to which spider silk belongs, it has been found that ultraviolet (UV) radiation modifies the bonding organization of these materials. This modification could be associated with a reduction in the molecular weight of the …