Applied Adhesion Science最新文献

This paper focuses at wetting on Al-based quasicrystals and complex metallic alloys (CMAs), which comprise a significant number of crystalline compounds of changing lattice complexity, according to composition. Such compounds are thermodynamically stable and may be prepared into various sample shapes that allow easy measurement of surface physical properties in air. Surface energy (γ_S) is one of the few fundamental properties of condensed matter: it defines the equilibrium shape of a crystal, it determines the interfacial behaviour of any piece of liquid or solid against another body, etc. The paper summarizes our attempts to determine the surface energy of a large variety of CMAs, including the stable, icosahedral AlCuFe and AlPdMn quasicrystals, all equipped with their native oxide layer when placed in ambient conditions. Experimental evidence is given that the surface energy correlates to the electronic density of states underneath the oxide layer as long as its thickness remains below 10?nm. Correlation to the thickness of the oxide on the one hand and on the other to specific features of the electronic density of states will be emphasized, in line with the varying complexity of the studied CMA compounds. Potential application to low-stick cookware will be addressed with a view at finding alternatives to fluorinated surface layers.

The automotive industry is currently increasing its use of high performance structural adhesives in order to reduce vehicle weight and increase the crash resistance of automotive structures. To achieve these goals, the high performance adhesives employed in the automotive industry must not only have high mechanical strength but also large ductility, enabling them to sustain severe dynamic loads. Due to this complex behaviour, the design process necessary to engineering structures with these materials requires a complete knowledge of their mechanical properties. In this work, the mechanical properties of a structural epoxy, Sikapower^? 4720, were determined. Tensile tests were performed to determine the Young’s modulus (E) and tensile strength (σ _f). Shear tests were performed to determine the shear modulus (G) and the shear strength (τ _f). Tests were also performed to assess the toughness of the adhesive. For mode I toughness determination (G _Ic), the double-cantilever beam (DCB) test was employed. For determination of toughness under mode II (G _IIc), the end-notched flexure (ENF) test was performed. The data obtained from the DCB and ENF tests was analysed with the compliance calibration method (CCM), corrected beam theory (CBT) and compliance-based beam method (CBBM) techniques. The test results were able to fully mechanically characterize the adhesive and demonstrate that the adhesive has not only high mechanical strength but combines this with a high degree of ductility, which makes it adequate for use in the automotive industry.

The aim of this study was to determine the degree of conversion (DC) for five orthodontic resins with different viscosities, to examine a probable relationship between the viscosity factor and the degree of conversion of the materials.

Five commercially-available light-cured orthodontic bonding resins were used in this study: two medium viscosity resins [transbond XT (TR); opal bond MV (OB)]; two low viscosity resins [vertise flow (VF); opal bond flow (OF)]; and a fluoride-releasing sealant [opal seal (OS)]. The specimens were made and polymerized for 20?s. Fourier Transformed Infrared spectroscopy (FTIR) was used to assess the DC of carbon-carbondouble bonds from all samples.

The DC was significantly different among the materials: (TR, 24.6?±?0.04?%; OB, 39?±?0.02?%; VF, 44.3?±?0.01?%; OS, 52.5?±?0.01?%; OF, 53?±?0.04?%; p?<?0.05) and the lowest viscosity materials had the highest DC values.

The resins studied have different DC values, which can be explained by the unique composition of each brand of resin. There is a relationship between the viscosity of a material and its degree of conversion, which is shown in this study by the two low-viscosity orthodontic resins that had a higher DC.

The aim of present study was evaluate the effect of different percentages of an organo-functionalized silane monomer as adhesion promoter between barium borosilicate glass fillers and (co)monomer blend in experimental dental composite resin. Gamma-methacryloxypropyltrimethoxysilane (γ-MPS) was assessed in an experimental luting cement, at the concentrations of 0, 1, 3, 5, 7 and 10 (wt%). The experimental resin without fillers was used as control group. The flexural strength (FS) and elastic modulus (E) were obtained by mini-flexural test and expressed in MPa and GPa, respectively. Water sorption (WS) and solubility (SL) were determined based on ISO standard 4049:2000. Kruskal–Wallis and Student–Newman–Keuls test were used for comparisons of FS, E and WS. The comparisons of SL means were performed using one-way ANOVA and Tukey’s method (α?=?5?%). The treatment with 3?% silane revealed statistically higher FS, while the group treated with 1?% silane showed statistically higher E than 3?% silane (p?<?0.05) and E similar to control. The experimental composite without filler content showed the highest SL (p?<?0.05) while the control composite showed the highest WS (p?<?0.05). Based on present findings, flexural strength and elastic modulus can sometimes be improved with lower concentrations (1–3?%) rather than higher concentrations (5–7?%) of the silane (γ-MPS) used as coupling agent on barium borosilicate glass filler microparticles of the dental composite resin.

Fiber-reinforced composites have recently been advocated as an alternative to fixed metal framework prostheses. The aim of this study was to evaluate the effect of glass-fiber reinforcement on the flexural strength of different resin composites. The tested composites were X-tra fil, Filtek Z350 XT Flow and Filtek Z350 XT commercially available and reinforced with glass-fiber. Six groups of bars specimens (2?×?2?×?20?mm) were prepared (n?=?10). The measurement of flexural strength of the resin composites was carried out by the three-point bending test. Data were subjected to ANOVA and post hoc Tukey’s tests (α?=?0.05). The flexural strength of all composites was improved when combined with glass fiber. The bulk-fill X-tra fil composite (133.53?MPa) was the strongest fiber-reinforced material. Clinically, fiber reinforcement should be employed in extensive restorations to provide increased flexural strength.

Corrosion of oil and gas pipelines significantly reduces the service life of the pipelines, thus increasing costs, and more seriously, it can cause catastrophic environmental accidents. More recently, the exploitation of oil in ultra-deep seawater fields is facing new technological challenges in material selection owing to the extreme production conditions. Thus, the development of organic coatings as protective layers for steel pipelines is of crucial importance against highly corrosive environments. In this work, fusion bonded epoxy (FBE) coatings were deposited onto chemically functionalized carbon steel surfaces with organosilanes to investigate the potential applications in protection against corrosion and degradation in harsh marine environments. Carbon-steel API 5L X42 (American Petroleum Institute Standard grade) was chemically functionalized with two organosilanes, 3-APTES [(3-Aminopropyl)triethoxysilane], and 3-GPTMS [(3-Glycidyloxypropyl)trimethoxysilane], followed by the deposition of FBE composite coatings. The systems were extensively characterized with respect to each component as well as the steel-coating interface. The contact angle measurements and Fourier transform infrared spectroscopy (FTIR) results clearly indicated that the steel surface was effectively modified by the functional amine and glycidyl silane groups, leading to the formation of interfacial covalent bonds with increased hydrophobicity compared to bare steel surfaces. In addition, the morphological and chemical characterizations of FBE by scanning electron microscopy, atomic force microscopy, X-ray diffraction, and FTIR showed that it is composed of an epoxy-based organic matrix of bisphenol-A diglycidyl ether (DGEBA) reinforced with uniformly dispersed inorganic phases of calcium silicates and TiO₂ particles. Moreover, the chemical functionalization of the steel surfaces with amino and glycidyl silanes significantly altered the interfacial forces with the FBE coatings, resulting in higher adhesion strength for 3-APTES-modified steel compared to 3-GPTMS-steel; however, both mostly showed cohesive rupture mode in the FBE component.

This study investigated the influence of the waiting time for placing resin composite (RC) restorations after dental bleaching on the shear bond strength (SBS) to enamel. Seventy bovine incisors were obtained, of which 60 were stained in coffee solution for 1?week and then bleached with the whitening agent Lase Peroxide Sensy (DMC Equipments, Brazil), following the manufacturer directions of use. Next, all teeth were allocated into seven groups (n?=?10) according to the waiting time after bleaching for placing the RC: immediately (0?h), 24?h, 3, 7, 14 and 28?days (d). Ten teeth were not bleached to serve as control. The specimens were prepared for SBS test and also for failure mode analysis. Scanning electron microscopy images were taken in non-bleached and bleached specimens. Data was analyzed by one-way ANOVA and Tukey’s test (α?=?0.05). The SBS means (standard deviations), in MPa, were: control?=?8.5^b (5.8); 0?h?=?14.5^a (5.9); 24?h?=?18.8^a (7.4); 3 d?=?15.7^a (0.1); 7 d?=?15.6^a (7.0); 14 d?=?15.0^a (6.7); and 28 d?=?17.9^a (7.7). All bleached groups resulted in similar SBS to enamel (p?≥?0.221), but higher than the control (p?≤?0.004). Adhesive failures were predominant in all groups. Bleaching produced an acid-etching pattern (enamel prisms exposure) on enamel, differently to the non-bleached teeth, which showed an unaltered surface. In conclusion, dental bleaching did not affect resin-enamel bond strength, regardless of the waiting time to place the restoration after bleaching.

In this paper, an experimental study on the effect of surface roughness of different adherend material on adhesive bond strength was carried out. The adherend material used was aluminium AA6061 and wood in the form of sheet, and the adhesive was an epoxy resin. Different surface roughness obtained by mechanical abrasion using an emery paper and sand paper for aluminium and wood adherend samples respectively. Single strap joints were tested at room temperature. Results showed that there is clear dependency observed in between the adhesive bond strength and surface roughness of both wood and aluminium adherend joints. Optimum surface roughness values were obtained in the range of R_a?=?1.68?±?0.14?μm and R_a?=?1.64?±?0.2?μm for the aluminium and wood adherend joints respectively. Surface roughness along with the adhered material parameters should be considered during design stage of adhesively bonded joints.

The aim of this study was to evaluate the influence of air-abrasion executed with Bioglass 45S5 on the bonding performance of total and self-etching techniques. Human molars were divided into four groups (n?=?5) according to the surface treatment: G1: self-etching without air-abrasion; G2: total-etching without air-abrasion; G3: self-etching with air-abrasion Bioglass 45S5 for 1?min; and G4: total-etching with air-abrasion Bioglass 45S5 for 1?min. The Single Bond Universal (3?M ESPE, St. Paul, Minnesota, USA) was used in both etching techniques. The adhesive was photo-activated by a LED with 800 mW/cm² irradiance (Ultralume 5, Ultradent Products, South Jordan, UT, USA). Composite resin blocks were made on the dentin using Filtek Z100 (3M ESPE, St. Paul, MN, USA). Then, the samples were cut to obtain sticks attached to a jig in a universal testing machine (EZ Test, Shimadzu, Kyoto, Kansai, Japan) for testing microtensile bond strength (μTBS). The values μTBS of microtensile bond strength were submitted to two-way ANOVA and means were compared by Tukey test (p?<?0.05). The results showed significant differences in μTBS between G1 and G2. No differences were found between G3 and G4. For the self-etching technique no differences were found for G1 and G3. In total-etching, G2 showed greater μTBS than G4. The application of Bioglass 45S5 on dentin did not increase the microtensile bond strength in self-etching groups and decreased the bond strength values for total-etching groups, but improved the quality of the hybrid layer.

This paper describes an experimental and theoretical analysis of strengthened damaged reinforced concrete corbel by gluing carbon fibre fabrics. The main objective of this study is to investigate the damage effect on the strengthening of reinforced concrete structures, especially on short reinforced concrete corbel and to propose an analytical model. Therefore, an experimental program was developed to evaluate the mechanical damaging effect on short corbels behaviour by using strain gauges. According to this program, five reinforced concrete corbels were tested under a three-point bending up to failure. Three of them were damaged at 45, 65 and 90?% of their ultimate load. After the specimens were repaired with carbon fibre fabrics and the loading was conducted till their failure. The fourth corbel which was not damaged. It was strengthened and tested until its collapse. The last one is the reference specimen corbel which was not reinforced. The test results with corbel specimens which were strengthened and unstrengthened are given. The significance to member performance is also explained. The measured load versus strain was too measured in the same way (with precision strain gauges) for others materials such as composite fibre fabrics, steel bar and concrete at the cross section of corbel. The study shows that the composite fibre fabrics using bonding technique could be a convenient and effective strengthening method for concrete structures. Thus, steel reinforcement and carbon fabrics played a major role in the repair of corbels. A theoretical analysis is presented describing the behaviour of strengthened damaged concrete corbel using the damage theory of reinforced concrete beams.