Applied Adhesion Science最新文献

Adhesives are used in various industries to bond materials. The failure criteria of adhesive joints are based on the strength (peel) and fracture mechanisms of the materials. It is important to investigate these criteria in relation to the propagation and separation of Mode I, II, and III cracks. The purpose of this study is to use double cantilever beam (DCB) tests to measure fracture toughness in aluminum alloy (5052-H34), glass fiber-reinforced polypropylene matrix composite, and carbon fiber-reinforced epoxy matrix composite adherends bonded with a two-part acrylic-based adhesive. The fracture behaviors of the specimens are also discussed. DCB tests are carried out to measure fracture toughness under Mode I loading of adhesively bonded joints with different types of adherends. The fracture toughnesses of the aluminum alloy, glass-fiber-reinforced polypropylene matrix composite (GF/PP), and carbon fiber-reinforced epoxy matrix composite (CF/EP) specimens are 1071, 1438, and 1652 Jm^?2, respectively. The fracture surfaces of the aluminum alloy, GF/PP, and CF/EP specimens are observed to be of the interfacial, adherend, and cohesive types, respectively.

Edge-glued panels are composed by the lateral and top gluing with adhesives of solid battens. These panels use small pieces of wood, offering an optimal usage of forest resources and the development of higher value-added products. The adhesive generally used to produce the panels are the synthetic ones (PVA or EPI). The polyurethane derived from castor oil may arise an alternative to replace the adhesives derived from non-natural origin, because it has no solvent in its composition, is a biodegradable material and it comes from a renewable resource. The bonding quality of this panel was performed according to BS EN 13353, which specify the minimum resistance values for panels under different humidity and temperature conditions applied to the international market. In this context, the aim of this paper was to evaluate the lateral gluing quality of Pinus taeda panels using the polyurethane derived from castor oil, as well as assess the pressing time effect on the bonding quality. The adhesive was applied into the battens surface in weight of 180?g/m². The panels were put into a cold press machine for 1, 2, 4, 8 and 24?h, totalizing five conditions and eight together/replications. The bonding quality of this panel was performed according to BS EN 13353 and BS EN 13354, under different humidity and temperature conditions. The results were submitted to statistical analysis by outlier tests, normality test, homogeneity variance, analysis of variance and mean comparison, all with 95?% reliability. The polyurethane showed acceptable values to EN-13353 for 4?h in the press machine. The test for critical humidity and temperature conditions showed a reduction in the adhesive bond strength, but still acceptable to EN-13353. Under these circumstances, it is concluded that the polyurethane derived from castor oil may be an alternative to produce lateral glued panels for dry conditions and internal and external applications for humid conditions.

The objective of this study was to evaluate the enamel roughness and shear bond strength (SBS) of dental composite after removal of metal brackets bonded with different materials (Transbond XT, Filtek Z100, Venus Diamond and Filtek P90). Cleaning and etching were performed in vitro on 60 premolars, which were then divided into four groups (n?=?15). A metal bracket was bonded to each tooth using one of the four materials. The SBS test was performed in an Instron universal testing machine, using a chisel positioned at the junction interface with a speed of 1.0?mm/min. After testing the SBS, the teeth were analyzed using the Adhesive Remnant Index (ARI) with a stereomicroscope under 40× magnification. The remainder of the bonding material was removed with multilaminated carbide bur (FF 9642) and the surface roughness measured. The SBS and roughness data were statistically analyzed. The average SBS for the different groups in this study ranged from 6.13 to 12.72?MPa; Transbond XT (12.57?MPa) and Filtek Z100 (12.72?MPa) showed the highest values. There were differences between the bonding materials in IRA scores, but no statistically significant difference for roughness. All SBS values were adequate, since none were below the minimum acceptable level (6–8?MPa), however the enamel did not return to the conditions present prior to the bonding of the brackets.

To clarify the optimal amount of air-drying time, this study measured the time taken to remove residual excess solvent from self-etching primer under observation with a 3D video microscope. One hundred teeth were restored with direct resin composite restorations (16 upper anterior teeth, three lower anterior teeth, 14 upper premolars, 13 lower premolars, 16 upper molars, and 38 lower molars) under observation with a 3D video microscope. In all restorations, Clearfil SE Protect was used for bonding of the resin composite under controlled environmental conditions (intra-oral temperature and humidity) using an intra-oral vacuum device. The duration of air-drying needed to evaporate the residual solvent from the self-etching primer solution was simultaneously measured. The data obtained were statistically evaluated by one-way ANOVA and Tukey’s HSD multiple comparisons (p?<?0.05). The duration for complete air-drying of the 100 cases was 40.9?±?18.7?s. The air-drying durations in lower molar and upper anterior restorations were 48.1?±?21.7 and 27.3?±?14.6?s, respectively, with a statistically significant difference (p?=?0.002). This study revealed that a greater air-drying duration was needed to evaporate solvent from the self-etching primer than routine air-drying in the clinical situation. It also indicated that a greater air-drying duration was required for posterior cavities than for anterior cavities.

Magnesium and its alloys are the lightest metallic materials used for structural applications. Tuning the surface functionalization of magnesium alloys may contribute to increasing their durability. Dry or wet processes may be effective for the modification of magnesium alloy surfaces. The resulting layers may cover surface inhomogeneities and separate the substrate surface from molecular films. This work demonstrates the feasibility and effectiveness of the concepts and techniques comprising laser or plasma based pretreatment processes or dipping procedures that involve synthetic amphiphilic polymers or biopolymers. In detail, the effects of barrier layers that have been applied by the deposition of siliceous polymer coatings in low pressure plasma processes, by laser surface treatments in controlled gas atmospheres or by dipping in liquid formulations containing a recently developed polymeric inhibitor or a mixture of the enzyme laccase and the polysaccharide maltodextrin are monitored. In this respect, a time-resolved hydrogen bubble formation test is performed, revealing interactions between water films and the modified surfaces. The surface modification is shown with X-ray photoelectron spectroscopy investigations and, in addition, the alloy surface and grain structure is characterized using energy dispersive X-ray analysis, scanning electron microscopy and scanning force microscopy. These investigations reveal that the thus established layer/substrate and layer/environment interphases differ in their composition as a result of the non-centrosymmetric layer concepts for surface functionalization applied here.

The use of adhesive bonding for designing lightweight load-bearing components has increased in recent decades. In this paper the influence of plasticity on the lifetime prediction of bonded joints using the stress-life approach was investigated. The adhesive was a toughened epoxy for structural applications. Stress calculations were performed using finite element analysis. Three material models were employed, a linear-elastic model and two elastoplastic models: Von Mises (pressure independent) and Drucker–Prager (pressure dependent). Effective stress was calculated using the theory of critical distances. Lifetime predictions were based on SN curves from literature for scarf and single-lap joints at four different temperatures (?35, ?10?°C, RT, +50?°C). The material properties were acquired from uniaxial tensile quasi-static experiments on bulk adhesive specimens. These experiments showed a reduction in the values of Young’s modulus and yield stress with increasing temperature. A model was proposed based on an Arrhenius-type equation in order to fit the yield stress as a function of temperature. The model showed good agreement to the experimental findings. Regarding lifetime predictions (a) the influence of critical distance was higher for single-lap joints than scarf joints and (b) the prediction errors were lower for elastoplastic modelling than linear-elastic modelling, especially for single-lap joints.

The present work describes pretreatment processes of thermoplastic polyurethane elastomer (TPU) material, used as an adhesive in powder form, that results in the increased peeling resistance of joints. The TPU in powder form is an environmentally-friendly adhesive and provides safer bonding conditions in the shoe manufacturing industry. TPU particles are soft and require an anti-blocking agent to prevent agglomeration. However, particles covered by such an anti-blocking agent may account for a low peeling resistance in the resulting joints. To overcome this disadvantage, two pretreatment processes for the TPU adhesive were evaluated. The results of a two-step wet washing process, representing a conventional solvent-based procedure that involves both the application of a solvent and a powder separation step, are compared to the performance of a one-step dry plasma treatment process. The process type did not affect the size and agglomeration behavior of the particles, and both processes were effective in improving joint strength according to peeling test results. Spectroscopic investigation of the particle surface after washing or plasma treatment indicated some zinc concentration, which is interpreted to result from the anti-blocking agent. The crystallinity of the TPU, investigated by thermal analysis, was higher after pretreatment. The obtained results indicate that TPU in powder form is a versatile adhesive for the shoe industry with a safer application compared to solvent based adhesive systems.

Bonded indirect restorations require two appointments: one for provisional treatment and one for luting with resin cement and dentin bonding agents (DBA). The DBA layer may be accomplished during a delayed dentin sealing (DDS) step following the provisional phase or an immediate dentin sealing (IDS) step after tooth preparation and during final luting procedures. The purpose of this study was to compare the effect of resin-based provisional material (RBPM) on the tensile bond strength to human dentin developed using DDS and IDS procedures. Flat dentin surfaces were prepared on 48 molars for microtensile testing. The specimens were restored using a 3-step etch-and-rinse DBA and composite resin (CR). A set of control specimens (G1) was directly restored using DBA and CR, while the remaining samples were treated using a provisional restoration procedure for 2?weeks: DDS?+?acrylic resin (AR)?+?calcium hydroxide cement (CHC) (group G2), DDS?+?AR?+?eugenol-free cement (G3), DDS?+?RBPM (G4), IDS?+?glycerin?+?RBPM (G5), or IDS?+?RBPM (G6). After storage of the final restoration in water for 24?h, the specimens were serially sectioned to obtain bonded sticks 0.8?mm² in area. The tensile strength was tested at a crosshead speed of 0.5?mm/min. The results were analyzed using ANOVA and Tukey’s post hoc tests (α?=?0.05). The mean (standard-deviation) bond strengths for groups G1–G6 were 42.18 (±2.63); 40.14 (±3.46); 37.77 (±0.93); 37.16 (±2.61); 34.11 (±1.08) and 23.79 (±0.49) MPa. The mean bond strength of group G6 was significantly lower (p?<?0.05), suggesting that adhesion to dentin is influenced by use of RBPM with IDS prior to placement of a definitive restoration.

The formation of nano-scale biofilms on hydrophilic silica surfaces from aqueous polypeptide/polysaccharide mixtures containing laccase and maltodextrin was investigated in situ with quartz crystal microbalance with dissipation monitoring (QCM-D). Surface analysis techniques such as X-ray photoelectron spectroscopy (XPS), optically stimulated electron emission (OSEE) and atomic force microscopy (AFM) were applied for characterizing the resulting layers obtained after periods varying from a few seconds to several hours of contact between the substrate and the biopolymers formulation. The biofilm formation in contact with the aqueous laccase/maltodextrin suspension was studied at pH level 4.75, under conditions close to the isoelectric point of the enzyme. The few nanometers rough biofilms obtained were composed of a laccase/maltodextrin mixture, and their thickness was observed to steadily increase during 4?h of contact with the aqueous mixture of biopolymers. Remarkably, the still adhesive films obtained after 1?h of contact with aqueous polypeptide/polysaccharide mixture resisted a 30?min rinsing with acetate buffer. The biofilms growing process was monitored using OSEE, due to the effected attenuation of the UV-induced electron emission from the SiO₂/Si substrate, which was found to be more pronounced than the attenuation of the photoelectrons from the substrate which contribute to the XPS signals. Layers as thin as 1?nm were detected by the OSEE.