The effect of ambient humidity and adsorbed water can be of critical importance in the processing of fine powders in air. Adsorbed water layers can influence the adhesive properties of the powder and may lead to difficulties in processing and handling. It has been shown, in the current work, that in ambient conditions the interaction between two solid surfaces is dominated by the force arising from the presence of adsorbed water layers. In the current work an atomic force microscopy technique has been developed to determine the separation distance at which two solid surfaces, i.e. the AFM cantilever tip and the sample surface, 'jump' into contact. From the separation distance the thickness of the adsorbed water layers on the cantilever tip and sample surface can be determined based on an analytical method originally developed by Forcada (1993), which considers the interacting forces which cause the 'jump' to contact. The adsorbed layer thickness, as a function of relative humidity, has been determined for silicon wafer, using the AFM technique. This localized adsorption isotherm has been compared with those published by other investigators, who have used different measurement techniques on large sample areas. The adsorption isotherm determined using the AFM technique reports adsorbed layer thicknesses that are significantly larger than those measured by other investigators. Adsorption isotherms have been determined, using the AFM technique, for three forms of a-lactose monohydrate, which is widely used throughout the pharmaceutical industry. It was observed that each form of lactose gave a different level of water adsorption. Laboratory grown crystals exhibited the greatest levels of moisture adsorption, while commercially produced milled a-lactose displayed lower levels of water adsorption. Differences in surface roughness may possibly explain the variation. For rough samples the probe tip makes contact with surface asperities and therefore does not detect the presence of condensed water in the surface valleys. It is also possible that surface contamination and process history may have influenced the levels of water adsorption but these are complex effects to quantify. Water adsorption isotherms were measured on bulk samples of classified lactose, to attempt to validate the AFM technique, developed in the current study. It can be observed that the adsorbed layer thicknesses determined using AFM are significantly larger than those inferred from bulk measurements. The AEM method provides layer thickness values which are approximately four times larger than what are believed to be the true values. This is seen for tests on silicon, aluminium and lactose surfaces. This discrepancy is thought to arise from the presence of the probe tip on the surface causing a local spatial inhomogeneity. The associated increase in surface potential will promote nucleation of water molecules, leading ultimately to capillary condensation.

Submitted by Stella Renata Machado Silva Esteves null (stellarmse@gmail.com) on 2018-03-15T12:49:21Z No. of bitstreams: 1 tese doutorado arquivo unico.pdf: 3856356 bytes, checksum: d346b9a5b9474275d35a835574475d08 (MD5) / Approved for entry into archive by Silvana Alvarez null (silvana@ict.unesp.br) on 2018-03-16T15:51:18Z (GMT) No. of bitstreams: 1 esteves_srms_dr_sjc.pdf: 3856356 bytes, checksum: d346b9a5b9474275d35a835574475d08 (MD5) / Made available in DSpace on 2018-03-16T15:51:18Z (GMT). No. of bitstreams: 1 esteves_srms_dr_sjc.pdf: 3856356 bytes, checksum: d346b9a5b9474275d35a835574475d08 (MD5) Previous issue date: 2018-02-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo desse estudo foi avaliar um adesivo experimental com diferentes concentrações de água, bem como sua degradação morfológica, química, física e mecânica. A primeira etapa envolveu a manipulação do adesivo experimental contendo 45/55% de HEMA e BisGMA, 0.5% de canforoquinona, 0.5% EDMAB e 1% de DPIHP. Foram incorporadas diferentes concentrações de água a partir dessa formulação adesiva (0, 10 e 16%). Os modelos adesivos foram fotopolimerizados e as análises iniciais realizadas: Morfológicas (Estereomicroscopio e Micro-xct); Físicas (Rugosidade-Ru, Sorção-Sor, Solubilidade-Sol); Químicas (Grau de conversão-GC, Mapeamento do espécime com 16% de água e os monômeros liberados pela CLAE); Mecânicas (Resistência flexural-RF, Módulo de elasticidade-ME e Resistência a compressão-RC). Em seguida os espécimes foram divididos conforme a solução de envelhecimento (água, etanol e acetona). Foram realizadas novas análises após o envelhecimento por 2 e 84 dias. Os testes estatísticos ANOVA e Tukey (5%) foram realizados. Os resultados iniciais, sem o envelhecimento, mostraram que as diferentes concentrações de água influenciam as propriedades dos adesivos. Na análise morfológica notou-se a presença de bolhas no espécime com 16% de água. Para a Ru e GC os maiores valores foram encontrados para os espécimes com mais água em sua composição e os menores para 0%. Já nas análises mecânicas, para RF e ME os espécimes com 10% de água foram mais resistentes; e em RC os espécimes com 16% foram menos resistentes. Após o envelhecimento notou-se trincas nos espécimes 0% e 16% na solução de acetona. Nos testes físicos, os espécimes com 16% absorveram mais solução; o etanol mostrou menores valores de solubilidade; Para Ru a água e a acetona diferiram em todas as concentrações e períodos, o mesmo ocorrendo para as concentrações 0 e 16%. Nos testes químicos o GC não foi alterado pelo envelhecimento. O mapeamento na amostra com 16% de água mostrou que inicialmente perto do poro o GC é menor e a quantidade de HEMA é maior; longe do poro a relação é inversa. Porém, após o envelhecimento, o GC próximo ao poro se tornou similar ao distante do poro. Através da CLAE observou-se uma maior liberação de componentes do espécime com 0% de água que os espécimes com 10% e 16%. Os testes mecânicos mostraram que o envelhecimento em acetona foi mais prejudicial que em água. Para a RF e ME os espécimes com 0% de água foram mais afetados que os espécimes com 10% e 16% em 2 e 84 dias. Para a RC após 2 dias o espécime com 16% foi mais afetado que 0 e 10%, no entanto, após 84 dias o espécime com 0% foi mais afetado pelo envelhecimento. Pode-se constatar que a quantidade de água e o tipo de envelhecimento afetam as propriedades dos sistemas adesivos baseados na composição 45/55% HEMA/BisGMA. / The aim of this study was evaluated an experimental adhesive with different water content, as well the degradation morphological, physical, chemical and mechanical. Firstly the dental adhesive was manipulated with 45/55% of HEMA and BisGMA, 0.5% of CQ, 0.5% EDMAB e 1% of DPIHP. Was added different water content (0, 10 and 16%). The adhesive model was cured and the analysis was done: Morphological (Stereomicroscope and Micro-xct); Physical (Surface Roughness), Sorption, Solubility); Chemical (Degree of convertion, Map of the pore on 16% water content sample and the released monomers- HPLC); Mechanicals (Flexural strength, Modulus of elasticity and Compressive strength). After the these analyzes, the samples were divided to each evaluation into 3 groups according to solution for performed ageing (water, ethanol and acetone). Further analyzes were performed after aging for 2 and 84 days. Statistical tests of ANOVA and Tukey (5%) were performed. Initial results, without aging, showed that the different water content influence adhesive properties. In the morphological analysis, bubbles were present on the sample with 16% water. For Ru and DC all specimens differed from each other, with the highest values for the specimens with 16% and the lowest to 0%. In the mechanical analyzes, for RF and ME the specimens with 10% water were more resistant; and in RC the specimens with 16% were less resistant. After aging it is possible notice cracks on the border of specimens 0% and 16% in the acetone. In the physical tests, the specimens with 16% absorbed more solution; ethanol showed lower values of solubility; For Ru, water and an acetone are differed in all concentrations and periods, the same for the concentration 0 and 16%. In the chemical tests DC was not altered by aging. The mapping in the sample with 16% of water showed that near to the pore the DC is smaller and a quantity of HEMA is larger; far from the pore this relation is inverse. However, after aging solutions, the DC near the pore became similar to the far from pore. Through HPLC was possible observed that release more components of the sample with 0% than 10% and 16%. The mechanical tests showed that the acetone damage more samples than water. For an RF and ME the specimens 0% were more affected than 10% and 16% after 2 and 84 days. For a RC after 2 days the sample with 16% was more affected than 0 and 10%, however, after 84 days the specimen with 0% was more affected by aging. It can be seen that the amount of water and the type of aging affect the adhesive properties of the database systems based on the 45/55% HEMA / BisGMA composition.

This thesis has identified the failure and damage processes in a particle filled epoxy which is typical of adhesives used industrially. Micromechanical analyses have been carried out to predict the material properties of damaged adhesive, and to investigate the applicability of different failure criteria. The general body of evidence suggests that there is no direct method of predicting the failure load of adhesive joints from the strength and toughness of the adhesive used. Therefore, a favoured approach has been to postulate a failure criterion, and to implement it in the constitutive equation for the adhesive. In contrast, this work has begun from the microstructural modelling of damage, and derived credible failure criteria from this model. The experimental program quantified the adhesive morphology and identified the damage processes that occur in the adhesive prior to failure. Bulk and joint specimens were tested both in-situ in a scanning electron microscope, and on a conventional tensile testing machine. The tests showed that the mechanisms for damage and failure in both joint and bulk form are particle debonding followed by cracking in the matrix. The concept of a representative unit cell of material was used to determine the effects of particle cracking and debonding. In a regular' array of cracked particles, the stiffness remained relatively unchanged in the plane of the cracks, but perpendicular to it, a significant reduction was found. Modelling debonded particles is more complex, because partial contact must be considered in addition to the fully bonded and fully debonded conditions. The unit cell was used to define the elasticity matrix for adhesive containing debonded particles as a function of strain state. The unit cell concept was extended further by including material that obeyed a modified (i.e. hydrostatically sensitive) Von Mises yield criterion. Particle debonding was found to contribute significantly to the hydrostatic sensitivity and to the softening of the adhesive. The unit cell concept was used to implement a strain at a distance failure criteria, using both elastic and plastic material properties. New types of failure criteria also based on the unit cell have been proposed. The criteria relate the strain state in an adhesive joint to the likelihood of shear banding or tensile plastic flow. The regions in a joint that experience one or the other of the mechanisms were identified. Hence the nature and extent of the adhesive failure in joints with varying joint geometry and loading may be predicted.

A growing market of environmentally-conscious consumers combined with a progression toward ‘greener’ products has caused the wood industry to investigate adhesives containing little to no formaldehyde. This study examines cottonseed proteins’ ability to bind southern yellow pine for plywood applications. Three-ply plywood panels were constructed with varying blends of cottonseed protein isolate (CSPI), soy protein, and phenol: formaldehyde adhesive. Wet and dry shear testing revealed that while the novel adhesives did not perform as well as a commercial control, the CSPI and soy adhesives generated similar shear strengths. Another set of boards were created, varying the CSPI amount added and the ratio of water. The powdered adhesive was spread at 15, 25, 35 and 45 lbs./1000 ft2 and the ratios of protein to water (w/w) were 0.5, 1.0, 1.5 and 2. The resulting boards were tested for internal bond strength (IB) using ASTM D1037 and the treatments were found to not be statistically different. Furthering the study into optimizing the temperature and time, the lowest amount and water ratio were used. The highest mean IB strength was obtained by pressing at 284°F (140 ℃). The highest mean IB strength for time was 10 minutes and produced IB strengths significantly different from all other pressing times. Temperature and time were not found to interact and therefore each affected the mean IB strength individually (p = 0.0553). Using the optimized time and temperature CSPI adhesive, commercial cottonseed meal (CM), water washed cottonseed meal (WW) and defatted cottonseed flour (DF) were used to decide if purity of the protein mattered and if the amount had changed. Using ASTMD1037, it was discovered that WW at 45 lbs./1000 ft2 had the highest mean internal bond strength. Boards made with CSPI adhesive alone and CSPI with guayule were tested for termite resistance, first by using hardwood veneer and later softwood, against the native subterranean termite Reticulitermes spp. Both tests were completed by AWPA E1-16 standard trials. Each was found that CSPI had a performance against termites that was not significantly different from guayule (a known antifeedant). CSPI’s ability to deter termites is a place for future exploration and is not looked at in depth in this study.

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Experiments were performed to characterize the pH, gelation time, diffusion processes, material properties, adhesive properties, and the drying variables on the material and adhesive properties of Gelatin Resorcinol Dialdehyde (GR-DIAL) tissue adhesives by varying formulation. Three adhesive formulations with altered weight content of water and glyoxal (a dialdehyde) were utilized. The adhesive formulations were characterized by pH and gelation time in situ, and absorption/desorption of water in the formed resin. Thermal analysis, mechanical testing, and lap shear adhesive bond testing were utilized to characterize fresh GR-DIAL adhesive formulations and formulations dried at 370C. From the results, the diffusion processes, material and adhesive properties of the adhesive formulations were primarily affected by hydrogen bonding, chemical cross-linking, and the existence of bound water within the bulk adhesive. Formulations with increased glyoxal content had both a higher degree of cross-linking and proportion of bound water within the bulk adhesive. The increased number of chemical cross-links greatly increased the swelling resistance of the adhesives, while, the existence of bound water within the adhesive increased the resistance to drying, and plasticized the resin by depressing the resin glass transition temperature, and increased the adhesive ductility. Hydrogen bonding increased with increased gelatin content or decreased water content, resulting in increased strength and modulus of the adhesives as well as increased adhesive strength. / Master of Science

Doctor of Philosophy / Department of Grain Science and Industry / Xiuzhi Susan Sun / Soy protein is one of the most promising bio-degradable adhesives as an alternative to synthetic petroleum-based adhesives for wood composite industries. In this study, soy protein was modified to improve adhesion properties and water resistance, which could facilitate the industrialization of soy protein-based adhesives. Furthermore, we attempted to identify a reliable indicator to predict the adhesion properties of soy protein by establishing the correlation of physical and mechanical properties with adhesion properties of soy protein. One of the objectives in this work was to investigate if inorganic calcium silicate hydrate (CSH) hybrids could improve adhesion properties of soy protein-based adhesives. 3-aminopropyltriethoxysilane (APTES) was used as a crosslinking agent between organic soy protein and inorganic CSH phases. APTES helped to form a crosslinked interface between soy protein and CSH, which was confirmed by changes in thermal, rheological, spectroscopic, and morphological properties with aging effect. More entangled structure and reduction of water-sensitive functional groups could lead to improvements in adhesion strength compared to unmodified soy protein-based adhesives. The second objective was to identify reliable indicators to predict shear adhesion properties by building the correlation between physical properties and adhesion properties of enzymatically modified soy protein-based adhesives (ESP). ESP was prepared with three independent variables (X1: trypsin concentration, X2: incubation time, and X3: glutaraldehyde (GA) concentration as a crosslinker) using a response surface methodology (RSM) called a central composite design (CCD). The important physical properties of viscosity (Y1), tacky force (Y2), and water resistance (Y3) were measured and investigated their relationship with adhesion strength. Viscosity, tacky force and water resistance showed solid correlation with adhesion strength of ESP and they were used to predict adhesion performance of soy protein modification system in this work. In addition, we studied the correlation between film strength and adhesion strength of another soy protein system. Because cohesion among protein molecules plays an important role in film and bonding mechanisms, we assumed that the film strength may be a reliable indicator to predict the adhesion strength of soy protein. The mechanical properties of the film and adhesion properties of soy protein on cherry wood were measured in terms of different concentrations of plasticizer (poly (propylene glycol) bis (2-aminopropyl ether) (H2N–PPG–NH2)). The results found out the low correlation between film and adhesion strength of soy protein in the presence of the plasticizer. We believe this might be caused by different curing conditions for film and adhesive applications of soy protein. Curing conditions greatly affect the thermal and curing behavior as well as mechanical properties of final materials. Thus, similar or comparable curing conditions should be required to obtain the information on the relationship between film and adhesion strength of soy protein.

No description available.

No description available.