Applied Adhesion Science最新文献

In order to simplify the technique while maintaining its effective clinical performance, as well as its adhesive properties, universal adhesive systems are constantly launched in the market. Thus, the objective of this study was to compare the presence or absence of moisture in the adhesion technique using a universal adhesive system, the Single Bond Universal (3M ESPE). There were selected forty-five human molars with indications for exodontia that were divided into three experimental groups: Single Bond Universal (3M ESPE) with and without moisture in the dentin; Scotchbond Multi-Bottles (3M ESPE) conventional technique (control). The characterization methods used were: microshear and scanning electron microscopy. Statistical analysis of variance analysis (single-factor ANOVA) and Tukey’s multiple comparison, global significance level of 5% were used. It was observed through the micro-test that there were no statistically significant differences between the groups tested. Scanning electron microscopy analysis showed that the most frequent failure mode was the adhesive type (91%), followed by the mixed type fracture (8%) and the cohesive type (1%). It was concluded through this study that, regardless of the moisture (present or absent), the Single Bond Universal adhesive system showed bond strength similar to the conventional adhesive.

The hydrofluoric acid (HF) is able to promote selective dissolution of the glassy phase in silica-based ceramic. However, the etching leaves insoluble silica-fluoride salts in the surface that affects negatively the bond, affirming the need of a post-etching cleaning.

Evaluate the shear bond strength (SBS) of composite resin to CAD/CAM lithium-disilicate ceramics after different post-etching cleaning and silane treatments.

Twenty-four 2?mm-thick slices of IPS e.max CAD?(Ivoclar Vivadent, AG, Schann,?Liechtenstein) were crystallized, embedded in acrylic resin, polished and cleaned in an ultrasonic bath. Each specimen was etched with 5% HF for 20?s, rinsed for 60?s, and treatment was completed using surface cleaning and silanization. The cleaning methods were: AW—air/water spray; UB—ultrasonic bath; PA—37% phosphoric acid; and ST—steam cleaning. The cleaned surface received: E—no silane treatment; E/S—silane application for 20?s, air drying for 20?s and hot drying (60?°C) for 20?s; E/S+—silane application for 60?s, air drying for 20?s, hot air drying (60?°C) for 20?s, rinsing with boiling water for 15?s and hot air drying for 20?s. Cylinders of composite resin (n?=?12) (Z100, 3M-ESPE, Saint Paul, MN, USA) were bonded using an adhesive resin (Optibond FL adhesive, Kerr?Corp, Orange, CA, USA). SBS testing was carried out after 24?h of storage in water. Samples for each post-etching cleaning regimen were analyzed by SEM.

According to two-way ANOVA (Bonferroni-corrected post hoc tests, p?<?0.05), the SBS was significantly influenced by the post-etching cleaning, with UB yielding the highest SBS (21?MPa for E/S); other post-etching cleaning regimens showed lower SBS values (12–17?MPa). The type of silane application was not significantly different. The SEM analysis showed a cleaner ceramic surface for UB when compared to the other groups.

Etching lithium disilicate ceramics following by ultrasonic bath cleaning and regular application of a silane is recommended.

Adhesive bonding shows a high potential to join carbon fiber reinforced plastics (CFRP), if the adhesion between adhesive and part surface is verified. Unfortunately, this adhesion is often reduced in case of the mold-based part production and its unavoidable application of release agents. Due to the resulting presence of release agent residues on the surface of the cured CFRP-parts the adhesion is lowered. To increase the bondability and correlating production efficiency, the amount of release agent transfer should be as small as possible, to reduce the effort in terms of bonding pre-treatment. To achieve this goal, a theoretical, qualitative model about the influence of the relevant processing parameters for a thermoset CFRP-production was developed focusing the (diffusion-based) transfer reduction based on an adapted processing. Indicating the time in which the diffusion is possible, as the main criteria.

For detailed stress distribution analysis of bondlines, non-linear finite element analysis (FEA) is necessary. Depending on the load case in relation to shear and tension/compression adhesives show a different behaviour of the yield point [1], which is e.g. included in the Mahnken and Schlimmer [2] model. State of the art for biaxial tested adhesive material-characteristics is the use of bonded tubular butt joints under variable torsion and tension loads. Important for the quality of the determined material values is the alignment of both tubes. The quality is significantly improved, if both tubes are aligned perfectly coaxial. Also, the bondline has to be free of voids. In previous work [3], W?lper investigated the effects of coaxial and angle deviations for the results of material characteristics using FEA. A slight deviation has a strong negative impact to the results. Particularly for thin film-adhesives with elevated curing temperatures, the change of viscosity of the adhesive and the thermal expansion of the tubes must be considered. Previous investigations regarding the manufacturing of the specimens showed shortfalls in joining and curing them. Due to voids, geometric deviations or poorly-bonded tubes, no reliable results were achieved yet. Therefore, a new assembly-device is developed and tested. The results show well joined tubes without a significant angle deviation and with an average of 40?μm in coaxial deviation. The thickness of the bondline can be adjusted and is constant over the whole diameter. The new joining-device enables the testing of tubular butt joints to determine biaxial material values of thin higher-temperature-cured film-adhesives. The device is patented to DE 102017114538.9.

Composite materials are already being used in the mass production of structural components in the automotive industry, particularly at the BMW Group. Adhesive bonding is generally considered to be the best technique for joining CFRP (carbon fiber reinforced plastic) light-weight structures. The conventional NDT (nondestructive testing) methods currently being used focus on the detection of material defects, e.g. debonding. These methods give little information about the surface properties or bond quality. A new ENDT (extended nondestructive testing) method is the BonNDTinspect system, based on a patent held by the Fraunhofer IFAM. An ultrasonic atomizer nozzle creates a water-aerosol and the small water droplets are sprayed onto the surface. Depending on the surface properties (surface energy or contamination state), the aerosol will form wide or narrow drops on the surface. We determined a test for certain contaminations, including release agents, oil, and fingerprints, the detection of which is critical to ensure the performance of adhesively joined CFRP structures. The BonNDTinspect system is an inline-capable NDT technique that is suitable for distinguishing surface states for adhesive bonding of CFRP. We verify this statement with destructive tests, including the single-lap shear test. It was found by using an extension of the evaluation criteria that it is possible to detect contamination such as water-soluble release agent, CFRP dust and fingerprints. The investigated contamination with hydraulic oil allows only a clear differentiation between cleaned and contaminated. A contamination with corundum is not detectable by the BonNDTinspect system alone.

Quality assured surface pre-treatment may greatly enhance adhesive interactions and, thus, the performance and durability of material joints. This holds true as well for substrates used in coating processes as for adherents introduced into bonding processes. Wettable polymeric wetting agents—shortly called polymeric interfactants—contribute to modifying surfaces and governing the properties of interphases. This is demonstrated for amphiphilic polymers directing the adsorption of graphene oxide (GO) nano-sheets from aqueous dispersion on alumina surfaces. In this contribution, contact angle measurements as well as X-ray photoelectron spectroscopy and scanning force microscopy investigations are applied for the characterization of thin films. GO is adsorbed either from a buffered dispersion on pristine aluminum oxide surfaces or on alumina modified with a few nanometers thin layer of a polymeric interfactant. Laterally extended nanoparticles and GO nano-sheets are preferentially found on interfactant layers whereas on pristine aluminum oxide smaller adsorbates dominate. The driving forces directing the GO attachment are discussed using a phenomenological model based on polymer/substrate interactions governing the sticking probabilities of GO nano-sheets with different sizes.

Nowadays, structural adhesives are increasingly being used for new applications, replacing conventional bonding methods. Epoxy resins are the most common structural adhesives used due to their suitable mechanical, thermal and chemical properties, despite their low ductility. In the past decades, several researchers have found it crucial to reverse these properties and find new ways to increase the ductility of these adhesives. The inclusion of particles (nano or micro) is an effective method to improve ductility of structural adhesives. In the present study, natural micro particles of cork are used with the objective of increasing the ductility of a brittle epoxy adhesive. The concept is for the cork particles to act like as a crack stopper leading to more energy absorption. The influence of the cork particle size, amount and the presence of a surface treatment were studied. The maximum strain of the adhesive was assessed through tensile tests. A Taguchi design experiments was used to understand the influence of each parameter under study (amount, size and presence of surface treatment) and their interaction. Through this research it was possible to settle that cork can improve ductility and cork amount, size and the use of plasma surface treatment have influence on the mechanical properties.