Bonding of Composite Resin to Alumina and Zirconia Ceramics with Special Emphasis on Surface Conditioning and Use of Coupling Agents

Dental oxide ceramics have been inspired by their biocompability and mechanical properties which have made durable all-ceramic structures possible. Clinical longevity of the prosthetic structures is dependent on effective bonding with luting cements. As the initial shear bond strength values can be comparable with several materials and procedures, long-term durability is affected by ageing. Aims of the current study were: to measure the shear bond strength of resin composite-to-ceramics and to evaluate the longevity of the bond; to analyze factors affecting the bond, with special emphasis on: the form of silicatization of the ceramic surface; form of silanization; type of resin primer and the effect of the type of the resin composite luting cement; the effect of ageing in water was studied regarding its effect to the endurance of the bond. Ceramic substrates were alumina and yttrium stabilized zirconia. Ceramic conditioning methods included tribochemical silicatization and use of two silane couplings agents. A commercial silane primer was used as a control silane. Various combinations of conditioning methods, primers and resin cements were tested. Bond strengths were measured by shear bond strength method. The longevity of the bond was generally studied by thermocycling the materials in water. Additionally, in one of the studies thermal cycling was compared with long-term water storaging. Results were analysed statistically with ANOVA and Weibull analysis. Tribochemical treatment utilizing air pressure of 150 kPa resulted shear bond strengths of 11.2 MPa to 18.4 MPa and air pressure of 450 kPa 18.2 MPa to 30.5 MPa, respectively. Thermocycling of 8000 cycles or four years water storaging both decreased shear bond strength values to a range of 3.8 MPa to 7.2 MPa whereas initial situation varied from 16.8. Mpa to 23.0 MPa. The silane used in studies had no statistical significance. The use of primers without 10-MDP resulted spontaneous debonding during thermocycling or shear bond strengths below 5 MPa. As conclusion, the results showed superior long-term bonding with primers containing 10-MDP. Silicatization with silanizing showed improved initial shear bond strength values which considerably decreased with ageing in water. Thermal cycling and water storing for up to four years played the major role in reduction of bond strength, which could be due to thermal fatigue of the bonding interface and hydrolytic degradation of the silane coupled interface.Yhdistelmämuovin sidostaminen alumiinioksidiin ja zirkoniaan painottaen pintakäsittelyä ja sidostusaineiden käyttöä. Hammaslääketieteelliset kokokeraamiset rakenteet ovat tulleet mahdollisiksi oksidikeraamien biologisuuden ja erinomaisten mekaanisten ominaisuuksien ansiosta. Proteettisten rakenteiden kestävyys on riippuvainen onnistuneesta ja tehokkaasta sementoinnista. Vaikka useiden tuotteiden ja menetelmien takaamat sidoslujuudet ovat vertailukelpoisia alkutilanteessa, kestävyyteen ja riittävään sidoslujuuteen vaikuttaa keinotekoinen vanhentaminen. Tämän väitöskirjatyön tavoitteet olivat: mitata yhdistelmämuovin repäisysidoslujuutta keraamiin ja arvioida sen kestävyyttä; edelleen eritellä sidokseen vaikuttavia tekijöitä painottaen: silikoinnin muoto keraamisella pinnalla; silanoinnin muoto; primerin ja resiinin tyyppi; yhdistelmämuovisementin vaikutus; vedessä vanhentamisen vaikutus sidoskestävyyden arvioimiseksi. Keraamiset substraatit olivat alumiinioksidi ja yttriastabiloitu zirkonia. Keraamin esikäsittelytapoihin kuuluivat tribokemiallinen silikointi ja kaksi silaania. Kaupallista tuotetta käytettiin referenssinä. Erilaisia esikäsittelyresiini- ja yhdistelmämuovisementtikombinaatioita tutkittiin. Sidoslujuus testattiin repäisylujuusmenetelmällä. Sidoksen pitkäikäisyys tutkittiin pääasiallisesti termosyklaamalla. Lisäksi yhdessä osatutkimuksessa pitkäaikaisvesisäilytystä verrattiin termosyklaamiseen. Tulokset analysoitiin varianssianalyysillä ja Weibull analyysillä. Tribokemiallinen käsittely käyttäen 150 kPa:n ilmanpainetta tuotti 11,2 – 18,4 MPa:n sidoslujuuden ja vastaavasti 450 kPa:n ilmanpaine 18,2 – 30,5 MPa:n sidoslujuuden.. 8000 kerran termosyklaaminen tai neljän vuoden vesihaudesäilytys laskivat molemmat repäisylujuusarvot 3,8 – 7,2 MPa:iin alkutilanteen vaihdellessa 16,8. – 23,0 MPa.:n välillä. Käytetyllä silaanilla ei ollut tilastollista merkitsevyyttä.. Ilman 10-MDP:tä sisältäviä primereitä tapahtui spontaania koekappaleiden irtoamista tai repäisylujuusarvot jäivät alle 5 MPa:n. Johtopäätöksenä tulokset osoittivat parasta pitkäaikaissidosta primereillä, joissa on 10-MDP:tä. Silikointi ja silanointi osoittivat alkutilanteessa korkeita sidoslujuusarvoja, jotka pienenivät huomattavasti vesihauteessa vanhennettaessa. Termosyklaus ja vesisäilytys neljän vuoden ajan toimivat pääasiallisina tekijöinä sidoslujuuden vähenemisessä, joka voi johtua termisestä väsymisestä sidostumisalueella ja silaanin sidostumisalueen hydrolyyttisestä rappeutumisesta.Siirretty Doriast

Effect of Surface Treatment on Joint Performance and Fracture Morphology in Adhesively Bonded Al-Si Coated Ultra-High Strength Steel

The Corporate average fuel economy (CAFE) standard set by the National Highway Traffic Safety Administration (NHTSA) has prompted automotive manufacturers to produce increasingly fuel efficient vehicles. Lightweighting of vehicle structures to reduce carbon dioxide emissions can be enabled by advanced materials such as hot stamped ultra-high strength steel (UHSS), but requires new joining solutions for integration in future multi-material structures. Structural adhesives enable multi-material joining, and have been used to enhance the joint performance for mono-material structures to achieve improved joint strength and stiffness. However, implementation of adhesive joining for hot stamped UHSS requires an appropriate surface treatment to maximize the joint strength and to address delamination of the brittle intermetallic coating formed on the steel during processing. The present study investigated adhesive joining (3MTM Impact Resistant Structural Adhesive 7333, 3MTM Canada Company) of a hot stamped UHSS (Usibor® 1500-AS, ArcelorMittal Dofasco) using three surface preparation techniques: degrease using acetone (ACE), grit-blast (GB) treatment, and adhesion promotor (AP) treatment following grit-blasting. Three hot stamping thermal treatments were considered with three quenching die temperatures: room temperature (RT), 400°C, and 700°C, which varied the yield strength of the steel, and created some differences in the morphology of the intermetallic coating. The overall work examined the surface treatments for adhesive joining of hot stamped UHSS, intermetallic coating delamination mechanism and the adhesive failure morphology under different adhesive joint configurations. Adhesively joined adherends were evaluated using the single-lap shear (SLS) test to investigate the nine material conditions (three surface treatments, three steel thermal processing treatments). The measured joint strength of the GB and AP conditions were 60% and 56%, respectively, higher than the baseline ACE treatment (p <.001). The higher strength achieved from the GB treatment was attributed to removal of the intermetallic coating. The ACE treatment did not remove the intermetallic coating and resulted in the lowest joint strength with the largest variability of the conditions tested, attributed to intermetallic coating delamination. The intermetallic coating morphology included microcracks and Kirkendall voids, which facilitated coating delamination. The intermetallic coating delamination was associated with a measured SLS joint rotation of 2.5°-2.8° for all three thermal treatments, while the measured joint strength decreased as the thermal treatment temperature increased (22 MPa to 14 MPa). This decrease in joint strength was attributed to the lower yield strength of the adherend material enabling the critical joint rotation to be achieved at a lower applied load. Plastic deformation in the SLS adherends was observed in the GB and AP treatments for the 400°C and 700°C thermal treatments. No plastic deformation was identified for the RT thermal treatment. The fracture surfaces from four types of adhesively bonded test specimens (Mode I opening, Mode II shear, Mixed-Mode at 45° (MM45), and SLS) comprising steel adherends without any surface coating were investigated using an optical digital microscope. Analysis of the fracture surfaces revealed qualitative differences in the morphology for different modes of loading. Shear hackles were observed for Mode II loading, while Mode I demonstrated facets on the fracture surface. The fracture surfaces were quantified using the arithmetic mean roughness (Ra). Mode I demonstrated the lowest roughness (50 µm) while Mode II had the highest Ra (103 µm), attributed in part to the shear hackles. The MM45 (80 µm) and SLS (73 µm) demonstrated intermediate roughness values, corresponding to mixed mode loading. Thus, it was found that qualitative and quantitative assessment of fracture surfaces could be associated with the mode of loading, and mode mixity. Ultra-high strength boron steel provides an important design option for vehicle structural engineers, with high strength achieved through thermal processing but resulting in a brittle intermetallic coating that present challenges for adhesive joining. The present study investigated adhesive joint strength for boron steel, and the corresponding intermetallic coating failure pathways and their effect on joint strength measured using a single-lap shear test. The importance of surface treatment to remove the intermetallic coating was critical to achieve high joint strength with low variability

Development of a protective coating system for regeneratively cooled thrust chambers Final technical report, 1 Jul. 1967 - 31 Mar. 1969

Development of protective coating system for regeneratively cooled thrust chamber

Laser and other cleaning procedures for aerospace moulds and a study of mould release agents

A selection of cleaning procedures are discussed which may be used to remove epoxide resin flash contamination bonded on metal and carbon fibre reinforced composite mould tooling that is used in the aerospace industry. Laser ablation, dry ice blasting and chemical cleaning using sodium hydride are three cleaning procedures studied in depth and have been used to treat a range of industrially sourced and model substrates, and contaminants. The effectiveness of the different cleaning regimes have been evaluated using Scanning Electron Microscopy, Atomic Force Microscopy, Auger Electron Spectroscopy, X-ray Photoelectron Spectroscopy and other analytical characterisation techniques. The necessity to clean aerospace tooling arises when moulded parts cannot be easily released from mould tooling and this is associated with mould release residues that have built up over a number of moulding cycles and eventually cause the moulding to stick. A comprehensive literature review of non-stick coatings is given and alternative mould non-silicone based release coatings are evaluated using the above analytical techniques. Coatings investigated include; fluoroalkylsilane, fluoropolymers and metal-fluoropolymer composites and the problems and merits associated with each are discussed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Investigation on the effect of low-pressure plasma treatment on the adhesion properties of different carbon-fiber-reinforced-polymer materials for structural adhesive bonding

This three-part study, developed with the collaboration of the Istituto Italiano di Tecnologia (IIT), reports a systematic and quantitative evaluation of the effects induced by various low-pressure plasma (LPP) treatments on the adhesive properties of Carbon Fiber Reinforced Polymer (CFRP) substrates. In particular, Part A of this work was focused on the surface activation of CFRP substrates, made via traditional vacuum-bag technique, which was performed using several combinations of LPP parameters. From the comparison with conventional pre-bonding preparations, it was possible to quantify the effectiveness of LPP in increasing the performance of adhesively-bonded CFRP joints. Further measurements of roughness and wettability were performed, and analyses via x-ray photoelectron spectroscopy (XPS) were also carried out, allowing identification of the morphological, physical and chemical phenomena involved in the treatments. Then, a quantitative evaluation of the aging behavior of the adhesively-bonded joints was the topic of the subsequent Part B. Four significant sets of LPP-treatment conditions were selected, and then subjected to accelerated temperature-humidity aging. To assess the durability of the CFRP-adhesive system under severe aging conditions, tensile shear strength (TSS) testing and wedge cleavage test (WT) were performed in parallel. The experimental findings showed that LPP treatment of the CFRP substrates results in increased short-term quality of the adhesive joint as well as in enhancement of its durability even under severe aging conditions. The last part of the work (Part C) was inspired by the recent developments in additive technologies for the manufacturing of structural thermoplastic-composite parts. In this context, the mechanical and failure behavior were investigated of continuous carbon-fiber (CCF) composite materials built via Fused Filament Fabrication (FFF) technology when used as substrates for bonded joints. Notably, the experiments were focused on verifying how the additively-manufactured substrates respond to adhesive bonding when the interface interactions are increased by preparing the surface with LPP treatment. This approach allowed detection of those criticalities that might limit the application of adhesive bonding to 3D-printed composite parts, with respect to that observed using traditional CFRP materials

The Influence of Certain Processing Factors on the Durability of Yttrium Stabilized Zirconia Used As Dental Biomaterial

In dentistry, yttrium partially stabilized zirconia (ZrO2) has become one of the most attractive ceramic materials for prosthetic applications. The aim of this series of studies was to evaluate whether certain treatments used in the manufacturing process, such as sintering time, color shading or heat treatment of zirconia affect the material properties. Another aim was to evaluate the load-bearing capacity and marginal fit of manually copy-milled custom-made versus prefabricated commercially available zirconia implant abutments. Mechanical properties such as flexural strength and surface microhardness were determined for green-stage milled and sintered yttrium partially stabilized zirconia after different sintering time, coloring process and heat treatments. Scanning electron microscope (SEM) was used for analyzing the possible changes in surface structure of zirconia material after reduced sintering time, coloring and heat treatments. Possible phase change from the tetragonal to the monoclinic phase was evaluated by X-ray diffraction analysis (XRD). The load-bearing capacity of different implant abutments was measured and the fit between abutment and implant replica was examined with SEM. The results of these studies showed that the shorter sintering time or the thermocycling did not affect the strength or surface microhardness of zirconia. Coloring of zirconia decreased strength compared to un-colored control zirconia, and some of the colored zirconia specimens also showed a decrease in surface microhardness. Coloring also affected the dimensions of zirconia. Significantly decreased shrinkage was found for colored zirconia specimens during sintering. Heat treatment of zirconia did not seem to affect materials’ mechanical properties but when a thin coating of wash and glaze porcelain was fired on the tensile side of the disc the flexural strength decreased significantly. Furthermore, it was found that thermocycling increased the monoclinic phase on the surface of the zirconia. Color shading or heat treatment did not seem to affect phase transformation but small monoclinic peaks were detected on the surface of the heat treated specimens with a thin coating of wash and glaze porcelain on the opposite side. Custom-made zirconia abutments showed comparable load-bearing capacity to the prefabricated commercially available zirconia abutments. However, the fit of the custom-made abutments was less satisfactory than that of the commercially available abutments. These studies suggest that zirconia is a durable material and other treatments than color shading used in the manufacturing process of zirconia bulk material does not affect the material’s strength. The decrease in strength and dimensional changes after color shading needs to be taken into account when fabricating zirconia substructures for fixed dental prostheses. Manually copy-milled custom-made abutments have acceptable load-bearing capacity but the marginal accuracy has to be evaluated carefully.Siirretty Doriast

Aerospace Environmental Technology Conference: Exectutive summary

The mandated elimination of CFC's, Halons, TCA, and other ozone depleting chemicals and specific hazardous materials has required changes and new developments in aerospace materials and processes. The aerospace industry has been involved for several years in providing product substitutions, redesigning entire production processes, and developing new materials that minimize or eliminate damage to the environment. These activities emphasize replacement cleaning solvents and their application verifications, compliant coatings including corrosion protection systems, and removal techniques, chemical propulsion effects on the environment, and the initiation of modifications to relevant processing and manufacturing specifications and standards. The papers from this conference are being published in a separate volume as NASA CP-3298

The Feasibility of Bio-Lubricants as Automotive Engine Oils

The use of and demand for bio-lubricants is slowly increasing, primarily as a result of newly introduced legislation. Mineral oil based lubricants are now prohibited in certain areas, such as in lakes and forests, by several countries, including Belgium, Germany, Austria and Switzerland. The European Union’s Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) is thought to be the most important legislation to aid the development of bio-lubricants. REACH has been implemented in an attempt to clean up the chemical industry and reduce the use of toxic substances. Additionally to the environmental reasons, the increase in cost of crude oil, along with concerns around the security of supply, gives a long term financial incentive to switch to bio-lubricants. It is critical therefore, that the performance of bio-lubricants can match mineral based lubricants. The aim of this research was to assess the feasibility of using bio-lubricants with materials found in a typical oil circuit in four stroke internal combustion engine. This was done by assessing the tribological properties of bio-lubricants through the use of various experimental and analytical methods, including reciprocating wear, elastomer relaxation, advanced microscopy, and chemical analysis. Current and novel automotive surface treatments were used in multi-layers. This was done to analyse the interaction of the bio-lubricants with these treatments and assess if any performance gains could be made if they were used in automotive contacts. The treatments used were: diamond like carbon (DLC), a calcium based chemical dip, shot blasting using a molybdenum disulphate doping media and nano fullerene. The surface treatments used did not give any performance advantages in comparison to a super finished steel surface. A reduction in wear and coefficient of friction was found when bio-lubricants were used with DLC coatings, compared with mineral based lubricants. The calcium based chemical dip proved to be as effective, in terms of wear protection, as DLC and works well with bio-lubricants. There was no apparent tribological benefit to using multiple layers of surface treatments. Wear and friction data was acquired to assess tribological performance. Potential bio-lubricant base stock candidates jojoba, soybean and palm kernel oil were used, with a mineral base stock for comparison. An assessment of lubricant performance was also made through calculations of spreading parameter and Hanson Solubility Parameters. Stress relaxation tests with EPDM, nitrile rubber and fluorocarbon rubber, with the bio-base stock candidates revealed that soybean and palm kernel oil are compatible with EPDM, which is in disagreement with industry chemical resistance data that presents a cautious overview of compatibility. Jojoba and mineral oil cause relatively high levels of swell with EPDM. Tests with nitrile rubber found no difference in the compatibility of bio-base stocks compared with mineral base stock. All base stock candidates were found to be compatible with fluorocarbon rubber. The use of Hanson Solubility Parameters to predict material compatibility was found to work for EPDM. Overall, this work has shown that there may be some performance benefits to using bio-lubricants over conventional mineral based lubricants, in internal combustion engines. Bio-lubricants can offer lower wear rates and coefficient of friction, particularly with the novel multi-layer surface treatments used in this work. Bio-lubricants are at least as compatible with elastomers as mineral based lubricants

Bond strength of concrete patch repairs: an evaluation of test methods and the influence of workmanship and environment

Experiments were carried out to study the effect of workmanship and environmental conditions on bond strength for concrete patch repairs. Four repair materials, sand/cement mortar, acrylic modified cementitious mortar, SBR modified cementitious mortar, and flowing concrete, were tested with mainly three test methods (core pull-off test, patch compressive test, and patch flexural test). At the beginning of this project, slant shear tests were also carried out. In the study of the effect of workmanship, the following parameters were included: surface roughness, surface cleanliness, surface soundness, moisture condition, application method, bond coat mistiming, repair material mistiming, and curing methods. In the study of the effect of environmental conditions, four parameters were considered: high temperature curing followed by drying shrinkage, high temperature curing followed by thermal cycling, low temperature curing, and low temperature curing followed by freeze/thaw cycling. A rougher surface produces a higher bond strength, but the increase depends on individual repair material. Sand/cement mortar favours a rough surface, but polymer modified mortars are not very sensitive to surface roughness. Environmental conditions affect the bond strength development, but the effect varies with each repair material. Test results suggest that low temperature curing should be avoided for polymer modified cementitious mortars. In addition to the experimental study, theoretical analyses were carried out to evaluate the available bond test methods. The evaluation was concentrated on answering the following questions: (1) What kind of factors will influence conductinga bond test? (2) What are the response of each factor involved to a specific test method? (3) What kind of influences are crucial in ensuring the full development of the bond strength? (4) Which factors are important to achieve a durable repair? and (5) What kind of a test can be used to monitor the quality of these crucial factors? In total, about 800 tests were conducted (500 core pull-off tests, 90 patch compressive tests, 100 patch flexural tests, and 80 slant shear tests)