It is widely held in the field of adhesion science that the properties of the interfacial region, or interphase, between two bonded surfaces are of critical importance to the performance of an adhesive bond. This thesis describes a study in which a polyimide was modified by the addition of metal compounds in an effort to develop a graded interface between the adhesive and aluminum adherends. The results of mechanical adhesion testing and instrumental analysis of the failed surfaces indicated that the added compounds did in fact preferentially segregate toward the adhered surfaces, but that this segregation decreased the strength of bonds tested in peel. It was concluded that the collection of metal compounds at the metal surfaces did not occur in such a manner as to improve the integrity of adhesive bonds, but the possibility remains that an improved, graded interface might still be formed given a more appropriate adhesive/dopant system and improved specimen preparation and testing techniques. / Master of Science

A fracture investigation was conducted on a modified epoxy adhesive (Metlbond 1113-2). Initially various adhesive fracture strength and energy tests and the mechanisms of mechanical and chemical adhesion were discussed. A critical study was then made of the sensitivity of the strain energy release rate·to specimen preparation. The rate and time dependence of the adhesive were then investigated using the TDGB specimen. The fractured surfaces were also studied using scanning electron microscopy to determine the mechanisms of failure. / Master of Science

The most common fastening technique that is used to connect the components of wooden pallets together are helically or annularly threaded pallet nails. Pallet nails create a strong durable connection and increase manufacturing efficiency for a low cost. However, nails can also cause iron staining, wood splitting, and when exposed can cause product damage or personnel injury. Using adhesives could be a solution to these problems, but only if the adhesives' strength and durability is comparable or higher than nails. The objective of the study was to investigate the tensile and shear strength of pallet connections secured using commercially available wood adhesives and compare their performance to pallet connections secured using common pallet nails. The lowest pre-compression pressure resulted in the best tension and shear performance for a solvent based construction adhesive (SBCA). The pre-compression pressure did not have any practical effect on the performance of the two-part emulsion polymer isocyanate (EPI) adhesive. Samples made with the solvent based construction adhesive (SBCA) had greater strength and energy at failure than nailed samples. Meanwhile, the samples made with the two-part emulsion polymer isocyanate (EPI) adhesive had equal or greater strength than nailed samples, except for during the tension parallel to the grain tests in which they had equal or lower strength. / MS / The most common technique used to connect the components of wooden pallets together is nails. Pallet nails create a strong connection with high manufacturing efficiency for a low cost. However, nails can cause iron staining, wood splitting, and when exposed can cause product damage or personnel injury. Using adhesives could be a solution to these problems, but only if the adhesives’ strength and durability is comparable or higher than nails. The objective of this study was to investigate the tensile and shear strength of pallet connections when secured using commercially available wood adhesives and compare its performance to pallet connections secured by using common pallet nails. The lowest pre-compression pressure tested resulted in the best overall performance for a solvent based construction adhesive (SBCA); meanwhile, pre-compression pressure did not have any practical effect on the performance of the two-part emulsion polymer isocyanate (EPI) adhesive tested. Therefore, using a lower pre-compression pressure would provide adequate performance and could also improve the ease of manufacturing and potentially reduce overall costs. Based on the tests conducted it was found that the solvent based construction adhesive (SBCA) demonstrated the best performance of all connection methods and could be a potential replacement for nails. More tests, such as weathering and impact, should be conducted to determine the full limitations of the adhesive in use.

<p dir="ltr">Adhesives surround us on a daily basis without us even being aware. They are the unsung heroes of most commercial products we use. Whether it be the car you drive, the shoes you wear, or the furniture you sit on, glue is keeping everything together. Adhesives have been used since the cavemen utilizing tar for keeping stone tools together. Over time, adhesives have exploded in the scientific landscape through a multitude of chemical pathways. Current products are comprised of epoxies, cyanoacrylates, polyurethanes, and many others. The need for adhesives in the manufacturing of products is consistently increasing over the years in the goal of light weighting without compromising on performance of the final material. However, this comes at the cost of glues being both toxic and nonrecyclable. With this in mind an improvement was needed to address both augmenting the glue strength and improving the sustainability of the adhesive.</p><p dir="ltr">Hierarchical structures can be observed on the micro scale in natural materials. Tree limbs are able to withstand a tremendous amount of force applied from winds, human machinery, and animal life. Why they are so resistant lies in the fact there is an ordered structure of multiple length scales working in tandem upholding the integrity of the limb. The question to ask then relating this to adhesives is if there is a way to create a glue that can disperse the forces amongst the overall material without catastrophic failure. The use of fillers such as calcium carbonate and different adhesive strain rates can be used to mimic this interaction.</p><p dir="ltr">Addressing the sustainability factor of current glues, the need was set to create a more bio-based alternative using widely available materials that are cost effective and do not compromise on overall performance. Competing with or outperforming the current market adhesives was a goal in mind. Two generations of bio-based adhesives were generated through multiple formulations using epoxidized soybean oil as the common factor. Soybean oil is one of the most widely produced vegetable oils in the country. Utilizing the oil in a functionalized way through epoxide rings, the replacement of current epoxy technology was achieved.</p>

An addition polyisoimide prepolymer was modified through the incorporation of metal particles. The response of this metal/polymer composite to mechanical vibrations and the passage of electric current was measured. Model aluminum conductor bar joints containing this material were assembled and exposed to elevated temperatures for extended periods of time while the electrical properties of the composites were monitored. In the most favorable systems, no thermal degradation of the electrical properties was observed. Dynamic mechanical behavior of the metal/polymer composites indicated good adhesion between particles and the matrix and also a broadening of the glass transition region as well as a post Tg dispersion in the temperature spectrum. The adhesive properties of these metal/polymer composites to aluminum were studied and found to be influenced by the loading level of the metal in the composite. Chemical reactions occurring during the cure of a neat resin sample of the polyisoimide prepolymer were monitored using infrared spectrometry and differential scanning calorimetry. Both the crosslinking and isomerization reactions were found to be apparently first order with the isomerization having a lower activation energy than the crosslinking. Linear, high molecular weight, thermoplastic polyimides and poly(imide-siloxane) homo- and copolymers prepared by bulk and solution thermal imidization were investigated as structural adhesives for titanium. The solution thermal imidization procedure was found to result in favorable adhesive characteristics while the presence of siloxane segments in the polymer backbone improved the resistance of stressed specimens to moisture. Aluminum-sec-butoxide used as a primer was also found to improve the moisture durability of bonds prepared with these materials. / Ph. D.

The goal of this project was improve the fundamental understanding of the wood-resin interaction, by looking at the relationship between the resin wetting onto wood and the resulting penetration into wood lumens. Wetting was analyzed with the sessile drop method, which observed the initial contact angle and change in contact angle over 35s. Penetration was measured within each individual tracheid. The Lucas-Washburn equation analyzed the wetting and penetration by calculating the penetration and comparing it to the measured penetration. Wetting of four resins was compared on 3 species, to improve the understanding of adhesive wetting behavior. This study agreed with previous research, that the non-aqueous resin exhibited favorable wetting and presumably better penetration than aqueous resins, with exception of urea-formaldehyde. Wetting and penetration of pMDI was studied on 5 wood species using the Lucas-Washburn equation. The wetting behaviors exhibited grain and species effects, which had implications on the resin availability for flake/strand-based composite products. The greater surface energy of loblolly pine most likely accounted for the significantly greater penetration of loblolly pine compared to Douglas-fir. The calculated penetration, via the Lucas-Washburn equation, exceeded the measured penetration, but it was concluded that the Lucas-Washburn equation predicted penetration reasonably well. Wetting and penetration of phenol-formaldehyde and subsequent adhesives was compared on 3 wood species using the Lucas-Washburn equation. All contact angles were unfavorable due to a skin formation. The Lucas-Washburn equation did not predict any penetration; however, penetration was observed with all systems. The findings suggest that the system was too complex for the Lucas-Washburn equation to be able to predict accurately. / Master of Science / Although the wood-based composites industry has been in operation for over a century, fundamental aspects of the wood/resin interaction- what happens when the liquid resin touches wood- remain poorly understood. An important aspect of this wood/resin interaction is penetration, which is critical to the strength and durability of wood-based composites. The two types of resins used, oil-based and water-based, were observed on a variety of wood species, Douglas-fir, loblolly pine, spotted gum, European beech and yellow-poplar. When using the oil-based resin, penetration measurements were in reasonable agreement with theoretical predictions. However, when using the water-based resins, the theory predicted no penetration which contradicted measurements- a shallow penetration was clearly observed. This means that parameters modeled by theory were in error, and this is sensible because we expect water to transfer from resin into the dry wood. Consequently, controlling parameters such as resin viscosity, resin surface tension, and wood surface energy were changing. This contributes fundamental knowledge, providing a better understanding of a critical step in the manufacture of wood-based composites, the materials most North Americans use to build their homes.

Though using bulk adhesive properties to predict adhesively bonded joint response has yet to be proven infallible, based upon the success of previous works, this effort attempts to shed some light on the stresses present in a typical automotive bonded joint. Adhesive material properties obtained in previous works were used in a finite element analysis of a simulated automotive joint to predict the stresses in that joint. The automotive joint analyzed was a simplified representation of a joint provided by General Motors. The specifications included the rate or stiffness of the joint and the materials to be used. The basic design of the joint is a rectangular solid section steel frame to which an SMC panel is bonded using Ashland Chemical urethane based adhesives. Due to computer time constraints and problem complexity, a complete analysis including a time dependent, viscoelastic analysis was not possible. The linear elastic case analyzed gave important insight into the magnitudes of stresses to be expected in a typical joint. It was found that for an applied load to produce a 1 degree deflection in the steel frame, the stresses in the adhesive were below 20% of the ultimate tensile strength of the adhesive. This low stress state is significant because the adhesive behaves as a linear viscoelastic material in that range, making further analysis less complicated and time consuming. / Master of Science

The analysis of peeling tape or a bandage from skin is a challenging problem. Skin is a very complex material made of many layers with anisotropic material properties. Adhesives that bond tapes or patches to skin must attach to skin through moisture and skin movement, but then be removed with little skin trauma. A computer model of peeling from skin apparently has not been developed previously. With experiments and the application of mechanics, research was conducted to analyze adhesion to skin. Numerous peeling experiments were performed on human subject arms using 2.54-cm-wide pressure sensitive tape Durapore™ by 3M. Various rates, angles, and dwell times were tested. Testing machines recorded peel force and the displacement of the end of the tape. A range of maximum and average peeling force values were noted for human subjects, along with the influence of angle, rate, order of testing, dwell time, and subject. Also, rigid substrates were tested for comparison with human skin. Computer models were also developed to simulate peeling and skin behavior. Initial models dealt with peeling from a rigid surface, and intermediate models concerned plucking skin. The final model involved peeling a piece of tape from skin, the overall goal of this research. The skin and tape were modeled as they behave during peeling. With the final model, the peel angle, debonding moment, normal force on the skin, and net shear force tangential to the skin were analyzed. Results from the experiments and computer models of this research will increase knowledge of skin behavior and could contribute to improvements in the design of adhesives that contact the skin. / Master of Science

A tendência atual de simplificação de sistemas adesivos transformou-os em polímeros altamente hidrofílicos e prontamente susceptíveis à permeação de água através de sua estrutura. Estudos recentes têm demonstrado que os sistemas adesivos simplificados se comportam como membranas semipermeáveis, permitindo o movimento de fluidos através da sua estrutura. Soluções a base de oxalato de potássio são efetivos agentes de redução da condutividade hidráulica dentinária. Quando são aplicados na dentina após o condicionamento ácido, podem ser utilizados em associação com os sistemas adesivos sem o comprometimento da adesão. Este trabalho objetivou avaliar os efeitos dos sistemas adesivos AdheSE, One Up Bond F e Single Bond, associados ou não a uma solução a base de oxalato de potássio, na condutividade hidráulica da dentina. Foram realizados preparos de coroas totais em terceiros molares humanos que tiveram suas raízes secionadas e a polpa coronária removida. Os segmentos coronários obtidos foram conectados ao ?Medidor de Fluxo? (Flodec?System, De marco Engineering, Switzerland). A condutividade hidráulica dos espécimes foi mensurada antes e após a aplicação dos sistemas adesivos Single Bond -3M ESPE, One UP Bond F -Tokuyama Inc, AdheSe- Ivoclar- Vivadent. Os adesivos foram aplicados seguindo as recomendações do fabricante (grupos SBF, ADF e OBF), de forma experimental (grupos ADE e OBE), e em combinação com uma solução a base de oxalato de potássio (grupos SBO, ADO e OBO). Cada espécime teve seu valor de permeabilidade original ( smear layer) e máxima (após condicionamento ácido) medidos anteriormente, os quais serviram como parâmetros para o cálculo das respectivas alterações frente aos tratamentos, expressas em porcentagem. Após a determinação da condutividade hidráulica, os preparos foram moldados para obtenção de réplicas em resina, as quais foram examinadas em MEV (JEOL 2800, Japão) para qualificar a permeação de fluido através do adesivo. A Análise de variância a 2 critérios mostrou que apesar dos procedimentos adesivos causarem uma redução significante (p< 0.05) na condutividade hidráulica da dentina condicionada, nenhum foi capaz de eliminar completamente a passagem de fluidos através do adesivo polimerizado. Para os três adesivos testados, o tratamento com o oxalato de potássio foi o tratamento mais eficaz na redução da permeabilidade dentinária e esta diferença foi estatisticamente significante quando comparada aos outros tratamentos (p<0,05). Não houve diferença entre os três sistemas adesivos estudados com relação à redução da permeabilidade dentinária (p> 0,05). A análise das réplicas em MEV mostrou que mesmo após a polimerização do adesivo, a transudação de fluidos pôde ser identificada na superfície de todas réplicas examinadas. Nenhum dos sistemas adesivos testados foi capaz de eliminar a permeação de fluidos através da dentina, contudo a associação destes adesivos com uma solução a base de oxalato de potássio reduziu de forma significante a permeabilidade dentinária. / There is an ongoing trend to move away from classical multi-component bonding systems toward simplified adhesives. An immediate consequence of adhesive simplification is the intrinsic permeability to water that result from their increase in hydrophilicity. Current studies have demonstrated that single-step adhesives may act as semi-permeable membranes that allow water diffusion through its structure. Oxalate desensitizers are effective in reducing the hydraulic conductance of dentin. When oxalates are used after acid- etching they do not interfere with subsequent resin bonding. The objective of this study was to test the effects of adhesives systems with or without the application of an oxalate desensitizer on dentin permeability. Crown preparations were made from human extracted teeth. After the roots were sectioned and the coronal pulp removed, the crown segments were connected to an automatic flow-recording device (Flodec-System, De Marco Engineering, Switzerland). Fluid conductance was measured before and after the bonding procedures with the adhesives Single Bond -3M ESPE, One UP Bond F -Tokuyama Inc and AdheSe- Ivoclar Vivadent. Specimens were prepared and tested after the surface had been bonded according to manufacturer?s instructions (SBF,ADF and OBF groups) , in a experimental way (ADE and OBE groups) or integrating with a oxalate desensitizer gel (SBO, ADO and OBO groups). For each specimen, fluid flow across the smear-layer and bonded dentin was expressed as a percentage of acidetched dentin, which was assigned a value of 100% flow rate. After the hydraulic conductance measures, impressions were taken from the crown segments and epoxy resin replicas were produced for SEM examination. Two-Way ANOVA reveled that the adhesive systems reduced dentin permeability significantly (p< 0.05) compared to acid etched dentin, but no bonding system was able to eliminate the fluid flow though dentin. For the three bonding systems tested, treating the acid-etched dentin with potassium oxalate prior to the application of the adhesive was the most effective in reducing the hydraulic conductance of the specimens, and this difference was significant (p< 0.05) when comparing to the other treatments. There were no significant differences among the adhesives in their ability to reduce dentin permeability (p> 0.05). SEM micrographs of resin replicas showed that transudation of dentinal fluid droplets could be identified on the surfaces of all replicas examined.

Thesis (M. Sc.)--University of Manitoba, 1996. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.