Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 33 for “"amorphous polymer"”.
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Concentration profiles at amorphous polymer-polymer interfaces
… and the asymmetric interfaces of two different polymers. The profiles obtained are used to study the properties of corresponding interface. Specular reflectivity of neutrons (SRN) and secondary ion mass microscope (SIMS) are used to examine the profiles and the properties.
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Applications of Monte Carlo techniques to the study of amorphous polymer deformation
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998.
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The Pressure Dependence of the Low Temperature Thermal Properties of an Amorphous Polymer
… thermal properties of Scotchcast-8 epoxy, an amorphous polymer, were used to probe glassy behavior as a function of pressure. The thermal measurements were performed over the range 0.3 K-10 K at pressures up to roughly 4 kbar. The low-temperature specific heat was observed to drop with …
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The pressure dependence of the low-temperature thermal properties of an amorphous polymer
… thermal properties of Scotchcast-8 epoxy, an amorphous polymer, were used to probe glassy behavior as a function of pressure. The thermal measurements were performed over the range 0.3 K- 10 Kat pressures up to roughly 4 kbar. The low-temperature specific heat was observed to drop with …
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Binding affinity of a small molecule to an amorphous polymer in a solvent
… to a surface and nucleation enhancement. Amorphous polymers have been used in controlling crystallization. However, to our knowledge no attempt has been made to investigate the possibility of using binding affinity to help guide the selection of polymers promoting heterogeneous nucleation. …
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The role of molecular length scale on the viscoplastic response of amorphous polymer nanofibers in the glassy state
Polymeric nanostructures are quite distinct because of the large ratio of surface-to-volume macromolecules which result in very different physical and mechanical behavior compared to bulk. Of special interest are nanostructures in which the constituent polymer is in its glassy state to provide …
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Using narrowband pulse-shaping to characterize polymer structure and dynamics : Deathstar GHz spectroscopy
… The validation of this technique for probing amorphous polymer structure and dynamics lays the ground for further study of heterogeneous materials, such as nanocomposites and block copolymers.
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Reductive conversion of lignin to aromatic chemicals with earth abundant catalysts
… which comprises 15-30 wt% of biomass, is an amorphous polymer composed of multiple phenolic monomers. Lignin polymerization occurs through an uncontrolled radical coupling of monomers leading to an array of C-O and C-C bonds in the polymer. As such, lignin is highly recalcitrant and is …
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Critical thickness in silicone resin
… at which a toughness transition occurs in a polymer was determined for the Dow Corning 4-3136 silicone resin. 4-3136 is macroscopically brittle, but becomes up to ten times more ductile when it is processed in the form of a sufficiently thin film. Thickness was controlled for the thin films …
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Toughening mechanisms in composites of miscible polymer blends with rigid filler particles
Fillers are often added to polymers improve stiffness at the cost of reduced toughness, but this tradeoff is not universal. Well-dispersed microscopic particles have been shown to improve toughness and stiffness simultaneously in some cases. The effect depends on interparticle distance as well as …
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Thermomechanical properties of polyhedral oligomeric silsequioxane- poly(methyl methacrylate) nanocomposites
… properties of this commercially important amorphous polymer. The effect of POSS on the rheological properties varied depending on the type of POSS cage and whether the POSS was covalently tethered to the PMMA backbone. A highly miscible acrylic-POSS species plasticizes PMMA, decreasing the …
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Surface properties of poly(bisphenol-A-carbonate)
… a technique to measure surface free energies of amorphous polymers <br></br>(b) an investigation of chemical polishing and <br></br>c) the problems of injection moulded polycarbonate. <br></br><br></br>Grooves inscribed in an amorphous polymer surface change in dimensions on thermal annealing, …
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Oriented polymer crystal growth from flowing solutions
… flow geometry have been quantified for several polymer systems using digital image processing to observe and monitor the birefringence of the crystallizing fiber. Three molecular weights of polyethylene were studied in 0.01 wt% xylene solutions as well as solutions of polypropylene in decalin …
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Multiscale chemomechanics of polymer deformation under contact : predicting structure-property correlations from the bulk to the interphase
The development of nanoscale polymeric materials for mechanical applications necessitates advances in small-volume experimental techniques and analyses that reflect the viscoelastoplastic behavior of such materials. In this thesis, the time-dependence and response of homogeneous engineering …
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Modeling of nano-scale fracture mechanisms in a graphene sheet using the atomistic j-integral
… a few weight percent of nanoscale particles in polymer matrices to mitigate the brittleness and microcracking of polymer matrices without incurring weight penalty and improve their strain to failure and fracture toughness. This thesis aims at studying these length scale effects in nano-fillers, …
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The Studies of Polymer Adhesion Using Segmental Dynamics Model
Polymer adhesives play a very important role in many applications. However, because it is very hard to observe an amorphous polymer at the molecular level, there are many questions about adhesion and failure mechanisms. Several computer simulation techniques have been of great success in describing …
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Layer bonding of solvent-cast thin films for pharmaceutical solid dosage forms
… films was interpreted as an interdiffusion of amorphous polymer chain end segments. In this context, relative contact area, polymer mobility, which is measured by glass transition temperature, and dwell time were proposed as critical factors in determining bonding threshold pressure. The …
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Determining the role of charges in ionic polymer blend systems
… about the effect of charge in ionic multi-polymeric systems. Theory has shown that many charged systems have unusual phase diagrams that are asymmetric. Such a phenomenon would be ideal for tuning domain sizes or obtaining nontraditional structures in materials. One of the two studies …
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The synthesis of novel biodegradable polyesters and copolyesters from anhydrosulfites
… with the synthesis and the ring-opening polymerisation of anhydrosulfites (1,3,2-dioxa-thiolan-4-one-2-oxides), and secondly with the copolymerisation of anhydrosulfites with -caprolactone. The polyesters and copolyesters synthesised are of considerable interest in medical applications …
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The Dynamics of Phase Separation and Structure Formation in Phase Inversion
… are presented, the process by which a cast polymer solution is converted into a porous, polymer gel by either thermal or nonsolvent quenching. In all three of the studies presented in this thesis, in-situ optical techniques have been used to study the dynamics of phase separation and …
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