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Structure-property Evolution During Polymer CrystallizationArora, Deepak 01 September 2010 (has links)
The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical spectroscopy, is not caused by packing/jamming of spherulites but by the formation of a percolating network structure. The effect of strain, Weissenberg number (We) and specific mechanical work (w) on rate of crystallization (nucleation followed by growth) and on growth of anisotropy was studied for shear-induced crystallization of isotactic poly-1-butene. The samples were sheared for a finite strain at the beginning of the experiment and then crystallized without further flow (Janeschitz-Kriegl protocol). Strain requirements to attain steady state/ leveling off of the rate of crystallization were found to be much larger than the strain needed to achieve steady state of flow. The large strain and We >1 criteria were also observed for morphological transition from spherulitic growth to oriented growth. An apparatus for small angle light scattering (SALS) and light transmission measurements under shear was built and tested at the University of Massachusetts Amherst. As a new development, the polarization direction can be rotated by a liquid crystal polarization rotator (LCPR) with a short response time of 20 ms. The experiments were controlled and analyzed with a LabVIEWTM based code (LabVIEWTM 7.1) in real time. The SALS apparatus was custom built for ExxonMobil Research in Clinton NJ.
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Elastomers with O-Phenylene Cross-LinkersMiller, Kristopher Andrew 14 February 2022 (has links)
No description available.
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The influence of multi-walled carbon nanotubes on the properties of polypropylene nanocomposite. The enhancement of dispersion and alignment of multiwalled carbon nanotube in polypropylene nanocomposite and its effect on the mechanical, thermal, rheological and electrical properties.Ezat, Gulstan S. January 2012 (has links)
Carbon nanotubes are known as ideal fillers for polymer systems; the main advantage of
carbon nanotubes over other nano-reinforcing particles is the combination of superior
strength and stiffness with large aspect ratio. Carbon nanotubes may improve the
mechanical, electrical and thermal properties of polymers, but to realise their potential
in polymer systems uniform dispersion, strong interfacial adhesion and alignment of
nanotubes within the polymer matrix are necessary. These properties are not easy to
achieve and they are key challenges in producing CNT/Polymer system. This research
was carried out in an attempt to understand how the properties of CNT/Polymer
composite can be optimised by manipulation of additives, compounding and postcompounding
conditions.
Polypropylene/Multi-Walled Carbon Nanotube (PP/MCNT) composites were prepared
by conventional twin screw extrusion. Dispersants and compatibilisers were used to
establish good interaction between filler and polymer. Several different extruder screw
configurations were designed and the properties of PP/MCNT composite prepared by
each configuration investigated. The results indicated that the addition of carbon
nanotubes without additives enhanced mechanical, electrical and thermal properties of
polypropylene polymer. Incorporation of compatibilisers into PP/MCNT improved the
stiffness but decreased the strength of the nanocomposite, whilst addition of dispersants
decreased the mechanical properties of the nanocomposite. Addition of both additives at
high concentration improved electrical conductivity and induced electrical percolation
in the nanocomposite.
Extruder screw configuration was found to have significant effect on the electrical
conductivity whilst only slightly affecting mechanical properties of the nanocomposite, possibly due to the competition between dispersion and degradation of polymer chains
and possible reduction of carbon nanotube length by intensive shear during
compounding. The use of screw configuration with high mixing intensity promoted the
dispersion of nanotubes and favoured the conduction process in the nanocomposite.
Finally in an attempt to improve dispersion and alignment of carbon nanotubes,
compounded PP/MCNT composite was subjected to micromoulding, fibre spinning and
biaxial stretching processes and the resultant properties investigated. Application of
post-compounding process was found to have significant effect on mechanical and
rheological properties of the nanocomposite. Stiffness and strength of the
nanocomposites treated by post-compounding processes were found to increase by up to
160% and 300%, respectively. The reinforcement effect of carbon nanotubes in the
stretched nanocomposites was found to be the greatest. Rheological analysis suggested
that the application of post-compounding processes enhanced dispersion of carbon
nanotubes within the nanocomposite.
Overall, this finding of this research has shown that carbon nanotubes can be
incorporated into polypropylene using conventional equipment to provide significant
improvement in properties. By careful choices of additives, compounding and postcompounding
conditions, specific properties can be further enhanced. / Ministry of higher education in Kurdistan region in Iraq.
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Liquid Crystal Polymers And Dendritic Liquid Crystals: Synthesis, Morphology, Rheology And Binary MixturesDong, Shaosheng January 2005 (has links)
No description available.
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The effects of grain size on the strength of magnesite aggregates deforming by low temperature plasticity and diffusion creepMcDaniel, Caleb Alan 26 July 2018 (has links)
No description available.
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Effect of molecular mass, concentration and temperature on the rheological properties of non-newtonian aqueous polymeric solutionsBhatia, Rupesh 26 September 2011 (has links)
No description available.
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The Preparation and Characterization of Poloxamer-based Temperature-sensitive Hydrogels for Topical Drug Delivery.Gandra, Sarath Chandra Reddy 27 August 2013 (has links)
No description available.
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Rheology of a 36 wt% coal-water slurryLu, Ching-Huang January 1987 (has links)
No description available.
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Investigation of Relationships among Microstructure, Rheology, Drag Reduction and Heat transfer of Drag Reducing Surfactant SolutionsQi, Yunying January 2002 (has links)
No description available.
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In-mold coating of thermoplastic and composite parts: microfluidics and rheologyAramphongphun, Chuckaphun 13 March 2006 (has links)
No description available.
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