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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Carbon material and property of hole are appraised while making preface by the law of mask works

Cheng, Hao-Yu 10 August 2010 (has links)
The hitting the carbon material looks of hole of ordered structure relatively has its more apparent physics and chemical characteristic in the traditional powder sample, this research makes hitting the carbon material of hole in order to utilize the law of mask works and making and lying between the qualification of the view structure to it of preface structure. Utilize different carbon precursor containing carbon proportion, for instance: Carbon material of hole in cane sugar, phenol aldehyde tree ester and pitch come to prepare; And to the structure of hole, for instance: The hole shrinks the homogeneity, hole shrinking rate ,etc. the physical and not last comparison at chemical property. First of all, utilizing has no emulsification to get together (not add any to hand in and unite pharmaceutical) Styrene the single /last sulfic acid potassium / water prepare by polystyrene ball in system. The styrene thickness is reduced to adjust the single weight ratio to styrene of initial pharmaceutical and look on as, then the ball size of polystyrene is diminished, controlling all kinds of technology of the spheroid, can already produce the polystyrene ball under the diameter 100 nm. Use 4 second silicic acid / ammonia water / deionized water / ethanol prepare and oxidize the silicon ball two times on the other hand, experiment course make use of adjust ammonia water in not reacting ear count than may be controlled and oxidized the ball size of silicon 2 times relatively. Experiment to can produce by the twoes of the 100 nms diameter because it oxidize by silicon ball, cause accord with endure research to a the above-mentioned spheroid particle by rice grades of material size already all fully. The second part of experiment includes the carbon material of carbon proportion to prepare in order to utilize differently out and hit the carbon material of hole in order for the source, thereafter utilize SEM, X-ray and Ramam After the instrument analyzes, sum up the property difference of every carbon material and characteristic trend. The result of study reveals, in order to include carbons carbon material structure of hole prepared out of the carbon material source the lower in proportion, its diameter of average hole is smaller, the shrinking rate of hole is larger, the hole wall is thinner and slightly broken in shape. Another result reveals, the graphite intensity of the carbon material of hole relates to material source own one's share structure of carbon, contain benzene ring many line molecular structure and reticular formation facilitate, raise carbonization graphite intensity react, and molecule layer distance light; The influence containing benzene and surrounding the structure among them is superior to the reticular formation. In addition, the experimental result has revealed the material grade of hole in the average diameter of carbon material of hole has already reached for 350 nm.
2

Catalysis deactivation in staged direct coal liquefaction

McQueen, Paul January 1996 (has links)
No description available.
3

Fast Curing Phenol Formaldehyde and Isocyanate Based Hybrid Resin for Forest Products Application

Liu, Xiaomei 11 August 2017 (has links)
The objective of this study is to develop a fast curing phenolic formaldehyde (PF) and polymeric diphenyl methane isocyanate (MDI) based hybrid resin system for wood products applications. Various formulas of PF resins were synthesized with different formaldehyde to phenol ratio, sodium hydroxide to phenol and isocyanate group (-NCO) to hydroxyl group (-OH) molar ratios. The shear bonding strength property was used to evaluate and optimize the formulations by appropriate sample preparation. The optimized resins were characterized by rheometer, Fourier transform infrared spectroscopy (FTIR) and other methods. In order to eliminate the influence of hydroxyl groups from water in the PF resin, a frozen dried method was applied to remove the water while keeping PF resin in liquid state. Acetone was used to disperse the hybrid co-polymer to improve the mobility of the mixture of frozen dried PF resins and MDI. An unexpected phenomenon was observed when the two resins were mixed in acetone and a sharp reaction occurred. This led to an assumption that acetone promoted the curing of hybrid resin. The effect of acetone on the curing behavior of hybrid resin was studied by differential scanning calorimetry (DSC), confocal laser scanning microscope (CLSM) and other techniques. It was confirmed that acetone promoted the curing of the co-polymer system. The gel time of hybrid resin with acetone decreases sharply compared to that of pure phenolic resin and original hybrid resin. Acetone also helped the hybrid resin to have better penetration behavior by improving the mobility and this also resulted in less variation of the strength distribution. Finally, lap shear samples were prepared at room temperature curing commercial polyurethane (PU), phenol-resorcinolormaldehyde resin (PRF) and laboratory made hybrid resins based on PF and MDI to compare the shear strength of different resins under different application conditions. The strength reduction of frozen dried PF with acetone/MDI is the lowest in humidity, temperature and humidity-temperature conditions. With just humidity condition, its shear strength reduction is significantly lower than that of any other resins including the solid wood control.
4

Lignin based adhesives for particleboard production

Özmen, Nilgül January 2000 (has links)
The purpose of this study was to utilise lignin as a partial substitute for phenol in PF resins. To achieve this, initially brown rot lignin was produced by a bioconversion technique. During the course of the study, it became clear that the production of brown rot lignin had a limited success. Since brown rot lignin could not be obtained in sufficient quantity and purity by a bioconversion method, other alternative lignin production methods, as well as commercially available lignin, were chosen; namely production of lignin from black liquor and Alcell® (organosolv) lignin. Before performing production of resin formulations, the lignin sources were characterised in terms of reactivity and physical properties of lignins. Both lignins had a similar reactivity, but organosolv lignin was found to be more pure, with a low ash content. Since isolation of lignin from black liquor in laboratory conditions is more complex and requires more time, it was decided to use organosolv lignin for subsequent production of lignin-based reSIns. The lignin was introduced to the resin in two different ways. The first method was the replacing of a certain percentage of phenol with lignin (as supplied) directly into resins. In the second method, lignin was modified prior to resin manufacture by phenolation. Different degrees of phenol substitution (from 5% to 60%) were tried for the production of lignin-based resins. Bond qualities of lignin-phenol-formaldehyde (LPF) , phenolated-ligninformaldehyde, commercial phenol-formaldehyde (PF _com) and laboratory made phenol-formaldehyde (PF _made) resins were assessed by using an Automatic Bonding Evaluation System (ABES), prior to production of particleboards, in order to eliminate some of the poor quality resins. The effect of press temperature and time on bond strength appeared to be highly significant, as the lignin substitution levels increased. Up to 30% phenol substitution was achieved without sacrificing bond strength. The bond strength values of phenolated-lignin-formaldehyde resins were similar to commercial phenol-formaldehyde and laboratory made phenolformaldehyde resins, but better than the LPF resins. It was apparent that resins containing a high level of lignin substitution gave the poorest bond strength values. From these results, some of the resins were eliminated, prior to particleboard production. In order to evaluate the quality of lignin-based resins, particleboards were produced and mechanical and physical tests performed. Effect of press platen temperature (140°C, 160°C, 180°C) and press cycle time (5 min, 8 min, IS min) on the mechanical properties of particleboard, produced by using lignin-based resins, were investigated. It was found that particleboards bonded with up to 30% lignin content resins gave similar mechanical and physical properties to commercial phenolformaldehyde resin, as long as a sufficient heating regime and time were applied.
5

Production of Phenol-formaldehyde Adhesives from Catalytic Pyrolysis Oil

Akude, Angela M. 01 May 2017 (has links)
Phenol-formaldehyde adhesives are important adhesives known to have superior water resistance capacity and high mechanical strength when utilized in wood-based applications. Due to unsustainability and environmental issues associated with the use of fossil fuels, there is an urgent need to look for alternative raw materials, which are renewable in nature. Pinyon-juniper biomass has been found to be a suitable replacement for petroleum-based phenol because it is renewable, abundant, and readily available. In this thesis, bio-oil produced from the pyrolysis of pinyon-juniper biomass using red mud alumina catalyst was used to produce wood adhesives. The characterization of pinyon-juniper bio-oil showed the presence of phenolics, aromatic hydrocarbons, aliphatic hydrocarbons, carboxylic acids, ethers, ketones, aldehydes, and aliphatic alcohols. Resol synthesis parameters such as formaldehyde-to-phenol molar ratio (1.8 and 2), catalyst loading (0.25, 0.63, and 1.25 g of NaOH), reaction time (60 minutes), and reaction temperature (95°C), were investigated in the production of pinyon-juniper adhesives. Based on the results obtained, the extent of phenol substitution with pinyon-juniper bio-oil was dependent on the amount catalyst used during the synthesis process. The maximum phenol substitution of 80% was achieved using a catalyst loading of 1.25 g of NaOH while the minimum phenol substitution of 50% was obtained at a catalyst loading of 0.25 g of NaOH. Dry shear strength (8.99 to 12.73 MPa) and wet shear strength of (5.16 to 7.36 MPa) for both pure phenol-formaldehyde resols and pinyon-juniper substituted resols were comparable and exceeded the minimum requirement of 0.66 MPa for plywood. Finally, the chemical structure of pure phenol-formaldehyde resols showed the presence of more phenolic OH groups compared to pinyon-juniper substituted resols. This observation was corroborated by the higher concentration of free phenol in pure phenol-formaldehyde adhesives compared to pinyon-juniper substituted resols.
6

Development of Biobased Phenolic Adhesives for Engineered Wood Products

Kalami, Somayyeh 10 August 2018 (has links)
Phenolic adhesives are widely used in the production of engineered wood products due to their exceptional moisture and thermal resistance, chemical stability, and bonding strength. The phenolic adhesive is currently produced through condensation polymerization of two fossil fuel-derived compounds: phenol and formaldehyde. However, due to fluctuations in the price of phenol and formaldehyde with the price of oil, environmental and health issues associated with using these compounds, there is a strong interest in finding alternative renewables feedstocks. Lignin is a natural polyphenolic compound with excellent potential to substitute phenol in phenolic adhesive formulations. Lignin is produced as byproducts during pulp and bioethanol processes. On the other hand, biobased aldehydes such as glyoxal have recently gained a lot of attention for replacing the toxic formaldehyde in production of environmentally friendly wood products. In this study, a wide range of lignin samples from different resources (hardwood, softwood, wheat straw, and corn stover), and isolated via various processes (kraft, organosolv, soda, sulfite, and enzymatic hydrolysis), were used to formulate 100% lignin-based phenolic adhesives. In a separate work, formaldehyderee phenolic adhesives were also developed using either glyoxal or gossypol (a dialdehyde from cotton seed) in combination with phenol. Chemical, physical, and thermal properties of lignin samples and developed phenolic resins and adhesive were measured using advanced analytical techniques and appropriate ASTM standard test methods. Based on two-way ANOVA analysis results of shear strength data, a biorefinery corn stover lignin that had the highest p-hydroxyphenyl and p-coumaric acid content was the most suitable lignin for replacing 100% of phenol in phenolic adhesive formulation. In addition, the developed lignin-based adhesive (formulated with biorefinery corn stover lignin) showed similar dry and wet adhesion strengths as that of commercially formulated phenol resorcinol formaldehyde (PRF) adhesive. On weight basis, the formaldehyde consumption in the developed lignin-based adhesive was 50% lower than the formaldehyde used in phenol formaldehyde (PF) resin. Moreover, two formaldehyderee formulated adhesives using glyoxal and gossypol (renewable feedstocks) had very similar physico-chemical properties to phenol formaldehyde adhesive.
7

Rheology And Organic Filler Interactions in Phenolic Resin Formulations

Gray, Ryan A. 14 December 2023 (has links)
Phenol formaldehyde (PF) is the oldest known synthetic polymer. This polymer has seen many applications throughout history, including jewelry, electric wire insulation, and resins used to make adhesives. Today, PF resins are still crucial components used in the wood products industry. These PF resins are formulated into adhesives used to make plywood and various other wood composite products. For example, in the United States, 90 % of the homes are still frame homes that use plywood for construction. The PF adhesives used to make these composites are formulated using agricultural waste products like walnut shells and corn-cob residue. These organic waste products act as fillers that reduce the cost, increase the viscosity, and affect the rheology of the fillers. Wheat flour is added as an extender to reduce cost and affect the tack of the adhesive. These organic fillers are lignocellulosic materials that are made of lignin, cellulose, and hemicellulose. Not much is known about the interactions of these organic fillers and the polymer resin. Rheological studies in our lab have shown that not all of the additions to the adhesive formulation are inert components in the adhesive. The steady-state flow curve analysis of PF adhesives revealed that there is a liquid structure change that occurs at high shear rate. This structure change is observed as a viscosity increase that occurs after applying a maximum shear rate of 4000 1/s. A rheological analysis was conducted to determine the source of this change, with individual components added to the resin. The PF base resin (with nothing added) has a Newtonian rheological behavior. When wheat flour is added to the resin, the overall viscosity increases, and shear thinning occurs at highe shear rates. There is no final viscosity change observed on with the addition of wheat flour. Adding corn-cob residue to the resin increased viscosity, led to some shear thinning at higher shear rates, and allowed the viscosity changes observed in the fully formulated adhesives. These experiments showed that the liquid structural changes that occur in the adhesives are attributed to the organic fillers. All organic fillers used in our studies, including corn-cob residue, walnut shell, almond shell, and Alder bark produce different levels of viscosity change in the PF adhesive formulations. These biomass materials have varying amounts of lignocellulosic content, particle size distributions, and particle shape. Among the fillers, corn-cob residue was shown to cause the most viscosity change compared to any of the fillers. Corn-cob residue is unique compared to the others because it has undergone acid digestion to convert its xylans to furfural. During the viscoelastic oscillation studies, the corn-cob residue filled adhesives showed that they developed network structures in response to a high shear rate that were not observed using the other fillers. With the discovery of these network structures, the next goal of this research was to correlate the effects observed on the rheometer to relevant adhesive application technology like high shear spraying. The corn-cob residue adhesive was sprayed at approximately 70,000 1/s compared to the 4000 1/s of rotational shear on the rheometer. The viscoelastic oscillation studies revealed that there was no network structure formation after high-shear spraying. Further, there was no change observed in the flow curve analysis after spraying the adhesive. This study showed that there are limitations when trying to correlate changes that happen in adhesives during spraying, where extensional forces dominate compared to shear forces. In future research, there is the opportunity to explore the effects of extensional deformation that occurs during the atomization of the adhesive, which will be more reflective of the changes that occur during spraying. / Doctor of Philosophy / Phenol-formaldehyde adhesives are crucial products in the home construction industry. These adhesives are used to make plywood that is used to build frame homes, which represent approximately 90 % of the homes in the United States. These phenol-formaldehyde adhesives are made using organic materials repurposed from agricultural waste products like corn cobs, walnut shells, almond shells, and tree bark. These products help to enhance the properties of the adhesive, reduce the cost, and reduce the amount of resin used. The goal of this research is to understand better the interactions between the adhesive and the organic fillers using rheology. Rheology is a field that studies how materials change and flow with applied external forces. This is an important field because it provides information on viscosity and viscoelastic behavior. Our research has shown that in response to high shear rates, the viscosity of these phenol-formaldehyde adhesives increases. Studying these changes can lead to a better understanding of how these materials change during industrial spraying. This understanding could lead to improved building adhesive materials in the home construction industry.
8

Filler effects in resole adhesive formulations

Wang, Xuyang 20 September 2016 (has links)
This was a university/industry research cooperation with focus on how organic fillers affect the properties of phenol-formaldehyde resole (PF) resins that are formulated for veneer applications like plywood and laminated veneer lumber. The PF formulations studied in this work used fillers that were derived from walnut shell (Juglans regia), alder bark (Alnus rubra), almond shell (Prunus dulcis), and corn cob (furfural production) residue. The chemical composition of all fillers was measured and compared to published data. The basic rheological behavior of the formulations was determined and used to develop an adhesive tack measurement based upon lubrication theory. In this work, the probe-tack test was adapted to a typical stress-controlled rheometer by using the normal force and displacement system to compress the adhesive between parallel plates. By employing a simple power law to describe the complex rheology of adhesives and a lubrication approximation for the viscous force, squeeze flow of adhesives between two flat, impermeable steels and between steel and porous wood can be successfully modeled. However, deviations from theory were encountered as related to the method of adhesive application. Both meniscus force in consequence of the surface tension of adhesive pull around the edge of plate and viscous force due to the viscosity of adhesive operate inside the meniscus when adhesive was spread on the entire surface by a hard roller. manufacture where viscosity and surface tension effects were both involved. Last but not Such is probably the case when wood veneer is cold-pressed (pre-pressed) in plywood least, rheological behavior and alkali modification of wheat flour was determined by rheological and infrared studies, respectively. / Master of Science
9

Organic Fillers in Phenol-Formaldehyde Wood Adhesives

Yang, Xing 10 October 2014 (has links)
Veneer-based structural wood composites are typically manufactured using phenol-formaldehyde resols (PF) that are formulated with wheat flour extender and organic filler. Considering that this technology is several decades old, it is surprising to learn that many aspects of the formulation have not been the subject of detailed analysis and scientific publication. The effort described here is part of a university/industry research cooperation with a focus on how the organic fillers impact the properties of the formulated adhesives and adhesive bond performance. The fillers studied in this work are derived from walnut shell (Juglans regia), alder bark (Alnus rubra), and corn cob (furfural production) residue. Alder bark and walnut shell exhibited chemical compositions that are typical for lignocellulosic materials, whereas corn cob residue was distinctly different owing to the high pressure steam digestion used in its preparation. Also, all fillers had low surface energies with dominant dispersive effects. Surface energy of corn cob residue was a little higher than alder bark and walnut shell, which were very similar. All fillers reduced PF surface tension with effects greatest in alder bark and walnut shell. Surface tension reductions roughly correlated to the chemical compositions of the fillers, and probably resulted from the release of surface active compounds extracted from the fillers in the alkaline PF medium. It was shown that viscoelastic network structures formed within the adhesive formulations as a function of shear history, filler type, and filler particle size. Relative to alder bark and walnut shell, the unique behavior of corn cob residue was discussed with respect to chemical composition. Alder bark and walnut shell exhibited similar effects with a decrease of adhesive activation energy. However, corn cob reside caused much higher adhesive activation energy. Alder bark exhibited significant particle size effects on fracture energy and bondline thickness, but no clear size effects on penetration. Regarding corn cob residue and walnut shell, particle size effects on fracture energy were statistically significant, but magnitude of the difference was rather small. Classified corn cob residue fillers all resulted in a similar bondline thickness (statistically no difference) that was different walnut shell. / Ph. D.
10

The evaluation of an organophosphate thermosetting resin for use in a high temperature resistant composite and a study of chemistry of ionomer cements

Reader, A. L. January 1974 (has links)
Two different research projects were investigated for this thesis, which has consequently been presented in two parts. PART 1 An attempt has been made to improve the high temperature performance of phenol-formaldehyde thermosets by modification of their structure with inorganic phosphate groups. Transesterification of tri-phenyl phosphate with resorcinol has given a resorcinol phosphate resin, which cured with hexamethylenetetramine. A pilot scale batch of this resin has been made and used in high temperature stability studies. Post-cured resorcinol phosphate resin-chrysotile asbestos (30: 70) moulded bars retained 59.5% of their flexural strength after ageing at 523K for 1000 hr in air. Similar phenol-formaldehyde composite bars aged under identical conditions retained only 5.3% of their initial flexural strength. The utility of the resorcinol phosphate resin composite as a commercial product is limited, since the bars had a much lower initial flexural strength (30.85 MNm-2) than the phenol-formaldehyde resin composite bars (108.5 MNm-2). Thermogravimetry and isothermal heating studies have indicated that the degradation of resorcinol phosphate resin was greatly accelerated by chrysotile asbestos, which may catalyse a bond re-organisation process that has been tentatively proposed as a mechanism for the fragmentation of the resin. PART 2 Recently an ionomer dental cement (ASPA), prepared from aqueous poly(acrylic acid) and an ion-leachable aluminosilicate glass, has been developed. The system has been extended by studying other aqueous polymers. The factors influencing the gelation and the properties of the set cements have been examined. Poly(carboxylic acids) with hydrophobic, or no pendant substituents were found to be the most satisfactory polymers for preparing water stable cements. To study the influence of the nature of the cation and polymer structure on the gelation and water stability of ionomer cements, a wide range of metal oxide-polyacid products have been studied. The formation of water stable cements depended markedly on the type of oxide and polyacid employed and appeared to involve factors such as the co-ordination geometry and radius of the cation and the nature of the cation-polyanion bonding in the matrix. A comparison between the water stabilities of ASPA cement and poly(acrylic acid)-CaO, Al2O3, or Al(OH)3 cements has shown that the chemistry of ASPA cement is more complex than has been hitherto reported. Stability constants have been determined for Ca 2+ and Cd 2+ with poly(acrylic acid) and ethyl ethylene-maleic acid copolymer by a potentiometric titration method developed by Gregor and modified by Mandel and Leyte. The stability constants obtained in 1.0M NaNO3 at 298.2 ± 0.2K were: for poly(acrylic acid), with Cat2+, log b1 Ca2+ PAA ~ -3.35 with Cd2+, log Bav Cd2+ PAA = -2.30 for ethylene-maleic acid copolymer, with Cat2+, log b1 CA2+ EMA ~ -4.05 with Cd2+, log Bav Cd2+ EMA = -1.95 The log b1 values probably had little precise meaning, although to a first approximation, log b1 Ca2+ PAA > log b1 Ca2+ EMA The determined stability constants have been used with limited success in predicting the water stabilities of the corresponding metal oxide-polyacid cements.

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