Thesis (M. Phil.)--University of Hong Kong, 1995. / Includes bibliographical references (leave 207-219).

Thesis (M.S.)--Catholic University of America. / Includes bibliographical references.

No description available.

This thesis outlines a methodology for formatting and applying stress models, collecting visco-elastic material properties, and presenting the material data for use in adhesive joint designs. There are a number of models/theories that can be applied to the design of Pressure Sensitive Adhesive (PSA) joints. Unfortunately, few design engineers are familiar with these models and the models are not formatted in a manner that can easily be applied to joint designs. By developing a format that is based on the existing knowledge of the designer and presenting them in a familiar manner the theories/models can easily be used in joint designs. This technique was demonstrated with Beam-on-Elastic Foundation, Shear Lag, and Shape Factors. Design examples successfully demonstrated the application of all of these models in the analysis and design of simple adhesive joints. The material properties of PSAs are a function of loading/displacement rate, temperature, relative humidity, and stress state. The Arcan_m fixture was used to test VHB™ 4950 over a range loading and stress states including fixed load and displacement rates. Several bond widths were tested to determine the extent of the shape factor effect. A second fixture was used to determine the impact of gradient-tensile stresses on the failure strength. All of the collected data was used to generate design plots. The strength data was presented as allowable strength envelopes with respect to rate. The moduli were calculated from the load-displacement data and plotted with respect to the displacement rate. The failure strength from the fixed load and displacement data were used to transform from one loading case to the other and a plot was generated. These three plots were used in the design and analysis of several adhesive joints. The methods demonstrated in this thesis show a great deal of promises as a design tool, but there is still a large amount of work to be done. The design space for this material is much larger than what was covered by this work. Additional strength testing needs to be conducted to fully characterize the material for all key applications. The principle of time-temperature superposition, beam-on-elastic foundation, shear lag, and shape factors all need to be validated for this material. / Master of Science

After cellulose, lignin is the second most abundant natural polymer in the world. It has multiple functional groups, providing great potential for polymer production. In this project, we explored the use of this renewable and valuable resource in two different adhesive applications to displace petroleum-based additives, thereby providing a more sustainable and “green” product. In this regard, two types of lignin, water-soluble (Amalin LPH) and non-water-soluble lignin (Amalin HPH) provided by the British Columbia Research Institute (BCRI) were used. In the first case, lignin was added to a pressure-sensitive adhesive (PSA) formulation via in-situ seeded semi-batch emulsion polymerization. It was seen that lignin does not readily take part in the polymerization reaction; rather, its presence results in reaction inhibition. Therefore, Amalin LPH lignin was modified via acrylation to overcome this issue. In another modification approach, maleic anhydride was used to produce maleated Amalin HPH lignin. Both the acrylated and maleated lignins were used in butyl acrylate/methyl methacrylate emulsion copolymerizations to produce PSA films. A series of controlled experiments with different lignin loadings was conducted. Adhesive properties of the PSA films were measured and compared with the corresponding acrylic base case formulation. The incorporation of lignin in the PSA formulation was a “green” solution to conventional PSA production and led to a simultaneous increase in tack and shear strength. Further characterization of the latex films via transmission electron microscopy (TEM) showed that lignin was successfully incorporated into the polymer particles. It also showed that the use of maleated lignin at a higher concentration led to a core-shell morphology. In the second application, unmodified Amalin LPH lignin was used to create a starch-based adhesive through the Stein-Hall process, a two-step process involving a “carrier” portion and a “slurry” portion. Several formulations with lignin loadings up to 35 wt% distributed in varying ratios in the carrier and slurry portions were prepared. It was shown that the addition of lignin to the starch-based adhesive formulation increases the water-resistance of the adhesive. Therefore, lignin addition is a solution for a common issue in starch-based adhesives, their lack of water-resistance due to the high affinity of starch toward water. Lignin incorporation solely in the slurry portion significantly increased the strength of the glued joints in a paper board adhesive test. The use of lignin as a renewable replacement of petroleum-based components in two different adhesive formulations was demonstrated successfully. This research strongly suggests that lignin can be used as a high value-added property modifier in adhesive applications.

No description available.

Dopamine is an interesting biomolecule that functions as a neurotransmitter in the brain. It has been found able to stick to almost all surfaces due to its unique catecholamine structure. Under alkaline conditions, the catechol functional group oxidizes to quinone allowing dopamine to self-polymerize and form thin films on support surfaces. The facts that dopamine can be coated to virtually any materials and the amine and catechol functional groups support a variety of reactions with organic species make polydopamine an attractive multifunctional bioadhesive/coating. To date, most of research on polydopamine has been focusing on its applications as thin films and little attention has been paid to the adhesion aspect of the material. In the study, we evaluated the properties of self-polymerized dopamine thin films as a bioadhesive. The thesis consists of three consecutive studies: (i) characterization of the adhesion properties of polydopamine thin films; (ii) investigation of the mechanical properties of polydopamine thin films; and (iii) exploration of the potential of polydopamine thin films as a wet adhesive. Fundamental insights on the wettability, adhesion behaviours, and mechanical properties of polydopamine thin films for both wet and dry conditions were derived through sets of well-designed contact angle, contact adhesion, and contact deformation experiments. It was found that dopamine is able to coat plastic, ceramic and metal surfaces, and join or bond rigid substrates but might not be suitable for joining soft or flexible parts as polydopamine is fairly rigid and the bonding might be too slow and too rigid for practical applications if polydopamine is directly used as an adhesive. Based on the understanding, a new strategy for fabricating underwater adhesive was proposed and tested. In the strategy, polydopamine with ferric ion as the oxidant was utilized as a cross-linker to alginate solution, effectively turning the solution into a wet adhesive, which demonstrated better practical performances than other studies; the adhesive was able to produce a permanent tensile adhesive strength of 80 kPa joining aluminum and glass with macroscopic roughness at the interface within 2 hours of curing time. Inspired by the results from the contact deformation experiments, we were able to extend the JKR theory with the well-known plate theory to accommodate the deformation of nanometer thin films, obtaining their elasticity. We termed this extended theory the “thin film contact mechanics” and validated the theory against gold thin films and found it predicted the mechanical behaviours of the thin films fairly well.

No description available.

Dopamine is an interesting biomolecule that functions as a neurotransmitter in the brain. It has been found able to stick to almost all surfaces due to its unique catecholamine structure. Under alkaline conditions, the catechol functional group oxidizes to quinone allowing dopamine to self-polymerize and form thin films on support surfaces. The facts that dopamine can be coated to virtually any materials and the amine and catechol functional groups support a variety of reactions with organic species make polydopamine an attractive multifunctional bioadhesive/coating. To date, most of research on polydopamine has been focusing on its applications as thin films and little attention has been paid to the adhesion aspect of the material. In the study, we evaluated the properties of self-polymerized dopamine thin films as a bioadhesive. The thesis consists of three consecutive studies: (i) characterization of the adhesion properties of polydopamine thin films; (ii) investigation of the mechanical properties of polydopamine thin films; and (iii) exploration of the potential of polydopamine thin films as a wet adhesive. Fundamental insights on the wettability, adhesion behaviours, and mechanical properties of polydopamine thin films for both wet and dry conditions were derived through sets of well-designed contact angle, contact adhesion, and contact deformation experiments. It was found that dopamine is able to coat plastic, ceramic and metal surfaces, and join or bond rigid substrates but might not be suitable for joining soft or flexible parts as polydopamine is fairly rigid and the bonding might be too slow and too rigid for practical applications if polydopamine is directly used as an adhesive. Based on the understanding, a new strategy for fabricating underwater adhesive was proposed and tested. In the strategy, polydopamine with ferric ion as the oxidant was utilized as a cross-linker to alginate solution, effectively turning the solution into a wet adhesive, which demonstrated better practical performances than other studies; the adhesive was able to produce a permanent tensile adhesive strength of 80 kPa joining aluminum and glass with macroscopic roughness at the interface within 2 hours of curing time. Inspired by the results from the contact deformation experiments, we were able to extend the JKR theory with the well-known plate theory to accommodate the deformation of nanometer thin films, obtaining their elasticity. We termed this extended theory the “thin film contact mechanics” and validated the theory against gold thin films and found it predicted the mechanical behaviours of the thin films fairly well.

No description available.