A combination of surface analytical techniques, colloid probe Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) was used to optimise the grafting density of covalently attached 5, 20 and 40 kDa methoxy-terminated PEO layers (under marginal solvation (cloud point) conditions for the PEO molecules). The combination of these techniques allowed us to relate the PEO layer density and molecular conformations to the range, magnitude and types of forces generated by coatings of various grafting densities. The key optimisation parameter was the grafting time with the concentration of PEO in solution having a weaker effect. Oxidation of the substrate occurred, but did not significantly limit the surface density of the functional groups used to chemically attach the PEO molecules. Interactions between the substrate and silica were electrostatic in origin and did not contribute to the interaction between silica and the PEO surfaces due to salt screening effects Surfaces with dense, highly stretched PEO layers (brushes) generated purely repulsive forces at all separation distances, arising from compression by the silica spherical probe used. The force profiles for lower density surfaces comprised long-ranged attractive and short-ranged repulsive forces. The attractive forces were most likely due to attractive bridging interactions between the PEO chains and the SiO2 surface. For low grafting densities, i.e. inter-chain grafting distances, s &gt ??RF, the PEO layers were not strongly stretched and free to adsorb onto the opposing silica surface. XPS analysis demonstrated that HSA and Fibrinogen adsorbed onto low density 20 kDa PEO coatings (s &gt ??RF), most likely via diffusion through the PEO layer. No protein adsorption was found (detection limit &gt 10 ng/cm2) on high density, ???strongly stretched brush??? coatings (s &lt ?? RF). Analysis of data from the more sensitive Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) techniques indicated that low amounts of adsorbed HSA, lactoferrin, lysozyme, and IgG were present on high density 20 and 40 kDa surfaces; the most likely explanation being attractive interactions between the proteins and the PEO layers during the protein adsorption experiments. ToF-SIMS data obtained for the strongly stretched (s &lt ?? RF) 5 kDa PEO surfaces suggested that no protein was adsorbed, in line with the XPS data for the same surfaces.

Linear Low Density Polyethylene (LLDPE) is a relatively new plastic that is becoming widely used in many applications. In fact the production rate of LLDPE is vital in determining the process characteristics and subsequent properties of the end products. In this work we have examined, specifically, the influence of surfaces and structure on the rheology and processing properties of LLDPE. A review of the effect of surfaces on the rheology and processing of polymers is given, with particular emphasis on the interaction between metals and polymers. The influence of oxidative degradation and radiation on the structural modification of polymers is also reviewed. Standard rheological characterisation tests determined there was no effect of various metal and teflon surfaces on the rheology of LLDPE. There was also no evidence of wall slip on metal or teflon surfaces. The generalised Maxwell model (with Wagner's damping function) predicted dynamic and steady shear properties at standard characterisation rates well. The effects of degradation of LLDPE were quantified, and an increase in elasticity due to increased crosslinking of long polymer chains was noted during degradation tests. This effect increased with time (after a degradation time) and temperature. There was no effect of metals on the degradation properties of LLDPE, however, there was evidence of increased carbon-oxygen species (or increased oxidation) at the metal/LLDPE interface for metals containing copper at the interface (copper and brass). The migration of copper was facilitated by the low heat of formation of the oxides on the copper-containing metals. Increasing gamma and ion beam radiation dose decreased melting temperatures, heats of melting and crystallinity due to increased crosslinking at the crystallite surfaces and the reduction in crystal sizes. Gel fraction and tightness of gel increased with radiation dose due to increased crosslinking. Increased radiation dose also increased the elasticity and flow resistance of the samples as shown by rheological tests. The extension of a power law representation of the relaxation modulus of irradiated samples was extended to predict stress build-up and relaxation properties in steady shear tests. There was little effect of type of radiation (gamma or ion beam) on physical and rheological properties. However, there was a marked increase in the effects of irradiation in the melt (150degC) on the physical and rheological properties of LLDPE, which was due to the increased effective amorphous nature of the sample in the melt. The equivalence of the effects of degradation and irradiation are discussed. Viscosity was well predicted by the generalised Maxwell model (with Wagner's damping function) at processing rates. The normal stress differences calculated by Boger and Denn's model correlated well with this generalised Maxwell model, which was due to the inclusion of a flow rearrangement term. There was a marked increase in exit pressures, exit losses, flow rearrangement length, flow singularity, and exit stresses for flow over brass inserts at the die exit. These effects coincided with the production of a porous, copper-rich brass surface and it was postulated that this was the results of surface dezincification which caused increased adhesion between the LLDPE and the brass via physical interlocking at the porous surface. Extension of these results to melt fracture are discussed.

Dissertation (Ph.D.)--University of Toledo, 2007. / Typescript. "Submitted as partial fulfillment of the requirements for The Doctor of Philosophy Degree in Engineering." Bibliography: leaves 200-205.

Thesis (Ph.D.) -- McMaster University, 2003. / Includes bibliographical references (p. 154-172). Also available via World Wide Web.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: L. L. Brash and H. Sheardown. Includes bibliographical references.

Thesis (Ph.D.) -- McMaster University, 2003. / Includes bibliographical references (p. 154-172). Also available via World Wide Web.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: L. L. Brash and H. Sheardown. Includes bibliographical references.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: Michael A. Brook. Includes bibliographical references. Also available online.

Techn. Univ., Diss., 2006--Darmstadt

Thesis (M.S.)--Ohio University, June, 2000. / Title from PDF t.p.