Sealant Layer Research Articles

Failure of elastomeric sealants under tension and shear: Experiments and analysis

The mechanical behaviour of two elastomeric fuel tank sealants was investigated. Laboratory tests were conducted on two sealants, an epoxy cured polythioether and a manganese cured polysulfide. Tensile, planar tension and torsion tests were performed to characterize and understand the response of the sealants under quasi-static loading. Single lap joint tests in tension were also carried out using four different sealant layer thicknesses and two types of adherend (aluminium and steel). The adherends were either primed with an epoxy primer or otherwise conventionally treated (e.g. grit blasted). Experimental results showed a decrease in joint strength with increasing sealant layer thickness. Emphasis was given to the understanding of the failure and the prediction of the strength of the single lap joints. Predicted failure loads were derived by analytical calculations and finite element simulation of the joints.

Fabrication and Evaluation of Aluminum Laminated Film for a Pouch-Type Secondary Battery.

In this study, we intend to find the laminate condition for improvement of the chemical resistance of the aluminum pouch film widely used as the coating material of the secondary battery. Here, we investigated the properties including the initial adhesive strength and electrolyte resistance between the metal film layer aluminum and the sealant layer cast polypropylene (CPP) film. As for the laminating condition, we changed the temperature and line speed and maintained the identical pressure conditions. A roll-to-roll dry laminate coating system was used in surface treatment agent coating, adhesive coating, and film laminate. As for the laminate condition of the surface treated aluminum and CPP film, the initial adhesive strength of the laminated pouch film manufactured with 110 °C temperature and 30 m/min line speed was 1300 gf/15 mm. The adhesive strength of the 85 °C electrolyte resistance measured after being immersed for 7 days was found to be 800 gf/15 mm. The initial adhesive strength of CPP film laminated to aluminum without surface treatment showed 900 gf/15 mm and decreased sharply to 150 gf/15 mm in the electrolyte at 85 °C after an hour. The initial adhesive strength and electrolyte resistance of the aluminum and CPP were measured by using the universal testing machine.

Assessing abrasion of orthodontic surface sealants using a modified ophthalmic optical coherence tomography device

Optical coherence tomography (OCT) is a clinical standard in ophthalmology. Currently, its application in dentistry is gaining increasing interest. In this study, we tested the possibility to use a modified commercially available spectral domain OCT (SD-OCT) to assess the layer thickness of orthodontic surface sealants. Reference samples of surface sealants for calibration and repeatability testing were measured using a micrometer screw. SD-OCT measurements were compared with micro-CT and light microscopic analyses. After validating the calibration of the SD-OCT, surface sealant layer thickness after aging (thermo cycling) and simulation of professional tooth cleaning (PTC) was assessed using the SD-OCT on 45 extracted teeth assigned to three test groups (n = 15 each): Light Bond™ Sealant, Pro Seal®, and Opal® Seal. SD-OCT showed excellent repeatability and accuracy for measurements of surface sealant layer thickness. Compared with micro-CT, SD-OCT showed better accordance with the reference measurements. The analysis of surface sealants after thermo cycling and PTC revealed poor resistance of Light Bond after only aging and demonstrated substantial wear of all sealants after aging and PTC. Imaging using commercially available ophthalmic SD-OCT might represent a suitable non-invasive methodology for longitudinal assessments of surface sealant layer thickness in vitro and in vivo. SD-OCT might be a suitable non-invasive method for longitudinal assessments of surface sealant durability in clinical trials.

High Frequency Guided Waves for Disbond Detection in Multi-Layered Structures

Aerospace structures often contain multi-layered metallic components where hidden defects such as localized disbonds can develop, necessitating non-destructive testing. Model structures consisting of two adhesively bonded aluminium plates and artificial defects in the bond layer were manufactured. Immersion ultrasonic C- scans were used to check the uniformity of the bond layer and the manufactured defects. Employing standard wedge transducers, high frequency guided ultrasonic waves that penetrate through the complete specimen thickness were generated. Interference occurs between the wave modes during propagation along the structure, resulting in a frequency dependent variation of the energy through the thickness with distance. Significant propagation distance with a strong, non-dispersive main wave pulse was achieved. The interaction of the high frequency guided ultrasonic waves with small disbonds in the sealant layer and lack of sealant in the multilayer structure was investigated. Guided wave pulse-echo measurements were conducted to verify the detection sensitivity and the influence of the stand-off distance predicted from the finite element simulations. The results demonstrated the potential of high frequency guided waves for hidden defect detection at critical and difficult to access locations in aerospace structures from a stand-off distance.

The analysis of torsional shear strength test of sealants for solid oxide fuel cells

Abstract A torsion test recently implemented for solid oxide fuel cell sealant materials is analyzed as a method for measuring the shear strength of sealant for solid oxide fuel cells. The finite element method is used to simulate the stress distribution in the hourglass-shaped steel specimens with intermediate sealant layer with different specimen's dimensions and configurations. Also, it is analyzed how stress concentration changes if the sealant does not completely fill the gap or is squeezed out of gap. The reduction of seal thickness to outer radius ratio results in an increase in stress concentration at the outer edge of sealant. The developed specimens with a hollow halve steel plate as well as the ones with two hollow halve steel plates appear to be suitable choices for torsional shear strength test, reducing the torque for fracture and stress concentrations. Effects of lack of filling and squeezing out of gap onto the stress distribution are negligible compared to the effect of pre-existing discontinuities.

이차전지용 파우치 필름의 합지 조건에 따른 알루미늄 층과 실런트 층 간 물성조사

In this study, the intention is the determination of the optimum laminate conditions for the improvement of the chemical resistance of the aluminum-pouch films that are widely used as a packaging material for the secondary battery. Here, the properties including the initial adhesive strength and the electrolyte resistance between the metal-film layer with aluminum and the sealant layer with cast polyprophylene (CPP) film were investigated. Regarding the lamination condition, the lamination temperature, speed, and pressure conditions were changed. A roll-to-roll dry lamination-coating system was used in the surface-treatment agent coating, adhesive coating, and film lamination. For the lamination conditions of the aluminum and CPP films, the initial adhesive strength of the laminated-pouch film manufactured with a 110oC temperature and a 6.0 M/min line speed is 1200 gf/15 mm. The measured adhesive strength of the 85oC electrolyte resistance after its immersion for 7 days is 600 gf/15 mm.

Topical Application of Adipose Tissue-Derived Mesenchymal Stem Cells Ameliorates Renal Ischemia-Reperfusion Injury in Rats

Ischemia-Reperfusion Injury (IRI) was induced by clamping bilateral renal pedicles simultaneously for 60-min using bulldog clamps in Sprague-Dawley rats. They were then randomized into five groups: Group-I-3 × 106 MSCs were topically applied to the surface of each kidney with a layer of fibrin sealant, Group-II-only fibrin sealant was added, Group-III-only 3 × 106 MSCs were added, Group-IV-1 × 106 MSCs were injected directly into tail-vein and Group-V received no additional treatment (control). Serum creatinine in Group-I at Day-3 was significantly lower than the other groups. By Day-7, survival rates of animals with renal IRI were 81.3% in Group-I, 31.3% in Group-II, 37.6% in Group-III, 30.8% in Group-IV, and 25% in Group-V. At Day-3, histology of kidneys from Group-I showed less tubular necrosis and interstitial inflammation, when compared to Group-V. Reverse transcription polymerase chain reaction showed down-regulation of caspase-3 (indicator of apoptosis) and endothelin-1 (indicator of endothelial damage) and up-regulation of NQO-1 (antioxidative molecule) (p<0.05). A total of 4168 unique genes of the topical MSCs growing on the surface of ischemic kidneys were differentially regulated with reference to the MSC pellet (greater than twofold change; p<0.05). In conclusion, application of topical MSCs with fibrin sealant could improve outcomes of renal IRI ischemia in rats.

Impact of the intermediary layer on sealant retention: a randomized 24-month clinical trial

The aims of this study were to assess long-term impact of tooth eruption stages (ES) on sealant retention on occlusal surfaces previously coated with intermediary bonding layer and to determine caries prevention. Sixty-five school children were selected (aged 6-10years), with four non-carious permanent first molar in different ES (OP (operculum present), ME (marginal edge), CE (completely erupted)). Split-mouth and single-blind study design was used. The teeth (260) were randomly selected according to treatment (sealant/technique): F (Fluroshield), H (Helioseal Clear Chroma), SF (Single Bond+F), EH (Excite+H). Sealant retention, marginal integrity, discoloration, and caries prevention were assessed after 6, 12, 18, and 24months by calibrated examiner (Spearman=0.91) using visual inspection. Data were submitted to the Cox proportional hazard model (survival analysis) and Likelihood ratio χ 2 test (correlation), p≤0.05. At baseline, ES was 20% in OP, 54% in ME, and 26% in CE. There was no significant difference on sealant retention between the treatments (p=0.2774). However, significant differences were found regarding the ES on sealant retention (p=0.0041). The CE stage showed the highest retention survival rate during the 24months. The overall sealant prevention average was found to be about 99.4% and showed no difference between the groups. Eruption stages affect sealant retention irregardless of the intermediate layer and type of sealant. However, there was caries prevention on tooth occlusal surfaces after 24months, regardless of treatment. Sealing is recommended to prevent occlusal caries of newly erupted teeth in high-caries-risk patients. However, its application is critical on moisture limited control surfaces independently of sealer material and technique.

Room and elevated temperature shear strength of sealants for solid oxide fuel cells

The shear strength of glass-ceramic sealants was measured in torsion to aid the developments of robust sealants that can withstand the combined complex stress situation typical for solid oxide fuel cell stacks. The specimens consisted of hour-glass-shaped samples, with the sealant layer in typical application relevant thickness between two steel plates. Partially crystallized sealant materials with either silver particles or 8YSZ fibers as filler material were tested and compared with respect to their shear strength and failure behavior at room and elevated temperatures up to 800°C. The results emphasize the importance of interfacial bonding as well the effect of creep properties of sealant and steel substrates onto the testing results. An outlook on improvements of testing procedure and specimens’ geometry is given.

Effect of BOPET film surface treatments on adhesion performance of biodegradable coatings for packaging applications

This study aims to verify the effectiveness of a biodegradable PLA coating on biaxially oriented poly ethylene terephthalate (BOPET) films substrates in order to develop a biodegradable sealant layer for improving the functional properties of polyester films. In particular, this work focuses on the evaluation of different surface treated BOPET films to understand the effect of typical polyester substrate treatments on the adhesion of the PLA coating. At this purpose the film’s surface properties and topography have been characterized respectively by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and by atomic force microscopy (AFM); while their surface tension has been analyzed by contact angle tests. Furthermore, the PLA coating adhesion to different BOPET webs has been assessed by delamination tests and dynamical mechanical analysis. In addition, to evaluate the optical properties haze and transparency measures have been performed. It was found that corona treatment proves to be more effective in increasing surface energy and roughness of substrate with respect to a chemical treatment. The coating adhesion to corona treated BOPET was higher compared to the neat and the chemical treated BOPET films. Improvement in adhesion of PLA on corona treated BOPET was interpreted on the basis of surface oxidation due to the electrical discharge as showed by AFM and ATR-FTIR analyses. Indeed the increase of both contact surface and functional groups able to form hydrogen bonds and other molecular interactions, allow to a better interface interaction between the two layers.

High frequency guided ultrasonic waves for hidden fatigue crack growth monitoring in multi-layer model aerospace structures

Especially for ageing aircraft the development of fatigue cracks at fastener holes due to stress concentration and varying loading conditions constitutes a significant maintenance problem. High frequency guided waves offer a potential compromise between the capabilities of local bulk ultrasonic measurements with proven defect detection sensitivity and the large area coverage of lower frequency guided ultrasonic waves. High frequency guided waves have energy distributed through all layers of the specimen thickness, allowing in principle hidden (2nd layer) fatigue damage monitoring. For the integration into structural health monitoring systems the sensitivity for the detection of hidden fatigue damage in inaccessible locations of the multi-layered components from a stand-off distance has to be ascertained. The multi-layered model structure investigated consists of two aluminium plate-strips with an epoxy sealant layer. During cyclic loading fatigue crack growth at a fastener hole was monitored. Specific guided wave modes (combination of fundamental A0 and S0 Lamb modes) were selectively excited above the cut-off frequencies of higher modes using a standard ultrasonic wedge transducer. Non-contact laser measurements close to the defect were performed to qualify the influence of a fatigue crack in one aluminium layer on the guided wave scattering. Fatigue crack growth monitoring using laser interferometry showed good sensitivity and repeatability for the reliable detection of small, quarter-elliptical cracks. Standard ultrasonic pulse-echo equipment was employed to monitor hidden fatigue damage from a stand-off distance without access to the damaged specimen layer. Sufficient sensitivity for the detection of fatigue cracks located in the inaccessible aluminium layer was verified, allowing in principle practical in situ ultrasonic monitoring of fatigue crack growth.

Spacer Thickness‐Dependent Electron Transport Performance of Titanium Dioxide Thick Film for Dye‐Sensitized Solar Cells

A titanium dioxide (P25) film was deposited by cast coating as conductive photoelectrode and subsequently immersed in dye solution (N719) to fabricate the photoanode of dye‐sensitized solar cells (DSSCs). A plastic spacer was used as a separation and sealant layer between the photoanode and the counter electrode. The effect of the thickness of this spacer on the transfer of electrons in the liquid electrolyte of the DSSCs was studied by means of both IV curves and electrochemical impedance. Using a spacer thickness range of 20 μm to 50 μm, efficiency ranges from 3.73% to 7.22%. The highest efficiency of 7.22% was obtained with an optimal spacer thickness of 40 μm.

Effect of surface pre-treatment on the hydrophilicity and adhesive properties of multilayered laminate used for lithium battery packaging

The surface of aluminum foil was treated using silane coupling agent and chromate–phosphate conversion solution respectively, then a flexible laminate consisting of five layers was prepared using polypropylene film as inner sealant layer and epoxy resin as adhesive between polypropylene film and aluminum foil. The surface morphology and composition of the foil after treatment were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and the hydrophilicity of the foil was evaluated by contact angle measurement (CAM). The adhesive strength between the aluminum foil and polypropylene film, and the heat sealing strength of polypropylene film were measured by tensile tester, their dependences on the surface treatments were further investigated. It can be concluded that the adhesive strength and heat sealing strength depend on not only the hydrophilicity, but also the morphology of the foil surface. The rough and porous surface of the treated foil can enhance both the adhesive strength and heat sealing strength.

Improvement on the Long-Term Stability of Dye-Sensitized Solar Module by Structural Alternation

Dye-sensitized solar cell (DSC) module still lacks the long-term stability because of a volatile electrolyte. In this work, structural alternation of DSC parallel modules was proposed for high performance and stability. In the conventional module, the adhesion with the photo/counter electrodes was not stable with only one layer of sealant so that the stability was poor. On the other hand, buried grid module proposed in this work is possible to be stably sealed with only one layer of sealant. In this structure, grid electrodes are leveled with the same height of transparent conductive oxides (TCOs) because grid electrodes are inserted under furrows of etched TCOs. Consequently, the buried grid module had better long-term stability than conventional module. Additionally, the photo-current and efficiency were improved by the sonicated grid and the light scattering layer.

Improvement on the Long-Term Stability of Dye-Sensitized Solar Module by Structural Alternation

Dye-sensitized solar cell (DSC) module still lacks the long-term stability because of a volatile electrolyte. In this work, structural alternation of DSC parallel modules was proposed for high performance and stability. In the conventional module, the adhesion with the photo/counter electrodes was not stable with only one layer of sealant so that the stability was poor. On the other hand, buried grid module proposed in this work is possible to be stably sealed with only one layer of sealant. In this structure, grid electrodes are leveled with the same height of transparent conductive oxides (TCOs) because grid electrodes are inserted under furrows of etched TCOs. Consequently, the buried grid module had better long-term stability than conventional module. Additionally, the photo-current and efficiency were improved by the sonicated grid and the light scattering layer.

Correlation between thermal behavior of a sealant and heat sealing of polyolefin films

The correlation between melting behavior of a sealant and heat-sealing properties of multilayer polyolefin films was investigated. Different films with propylene-ethylene copolymers as sealant layer were produced via co-extrusion, and standard heat seal and hot tack measurements were performed. The sealing behavior was correlated with melting behavior of the sealant materials using successive self-nucleation and annealing thermal analysis (SSA-DSC). This technique enables solid-melt fractionation through different annealing temperatures, inducing crystallization of different polymer fractions at each temperature. Results demonstrated that heat seal and hot tack closely follow melting curves. A linear correlation was found between heat seal initiation temperature (HSIT taken at 4N/25.4 mm seal strength) and the temperature at which 40% of the polymer melted (using the SSA-DSC thermal fractionation method). This technique can be applied for predicting sealant properties of research materials, which are usually produced in small quantities.

Induction of a geochemical barrier for As, Fe and S immobilization in a sulfide substrate

Acid mine drainage (AMD) is an environmental concern due to the risk of element mobilization, including toxic elements, and inclusion in the food chain. In this study, three cover layers were tested to minimize As, Fe and S mobilization from a substrate from former gold mining, containing pyrite and arsenopyrite. For this purpose, different layers (capillary break, sealant and cover layer) above the substrate and the induction of a geochemical barrier (GB) were used to provide suitable conditions for adsorption and co-precipitation of the mobilized As. Thirteen treatments were established to evaluate the leaching of As, Fe and S from a substrate in lysimeters. The pH, As, Fe, S, Na, and K concentrations and total volume of the leachates were determined. Mineralogical analyses were realized in the substrate at the end of the experimental period. Lowest amounts of As, Fe and S (average values of 5.47, 48.59 and 132.89 g/lysimeter) were leached in the treatments that received Na and K to induce GB formation. Mineralogical analyses indicated jarosite formation in the control treatment and in treatments that received Na and K salts. However, the jarosite amounts in these treatments were higher than in the control, suggesting that these salts accelerated the GB formation. High amounts of As, Fe and S (average values of 11.7, 103.94 and 201.13 g/lysimeter) were observed in the leachate from treatments without capillary break layer. The formation of geochemical barrier and the use of different layers over the sulfide substrate proved to be efficient techniques to decrease As, Fe and S mobilization and mitigate the impact of acid mine drainage.

Formation of magnetic aluminium oxyhydroxide nanorods and use for hyperthermaleffects

In the present work, we show that a porous alumina template can easily be filled withmagnetic nanoparticles and then be sealed by a hot water treatment (by forming analuminium oxyhydroxide (AlOOH) sealant layer). The porous layer then can be separatedfrom the substrate by an etch to form free magnetic AlOOH nano-capsules. The processallows for a straightforward and highly defined size control of the magnetic units and caneasily be scaled up. Furthermore, as AlOOH is biocompatible and has been used as a drugadjuvant for human use, the nanorod shaped capsules are highly promising for biomedicalapplications such as hyperthermal effects (heating in alternating magnetic fields).

Structural control of polyvinyl chloride sealant layer for electrochromic switchable mirror glass based on Mg-Ni thin film

We have been engaged in research and development of an electrochromic switchable mirror with a multilayer structure of Mg4Ni/Pd/Al/Ta2O5/HXWO3/indium tin oxide (ITO) on a glass substrate. In our recent work, an as-prepared device was found to be easily degraded by environmental factors such as temperature and humidity, as shown by a degraded surface of the device. In this work, a polyvinyl chloride (PVC) layer was fabricated as a sealant layer for improving the environmental durability of the device. The structure of the layer could be controlled by adjusting the fabrication conditions such as the concentration of materials and rotational speed used in spin coating. The optical switching properties of the device with the sealant layer were also investigated. The sealant layer was fabricated using 1.25 wt % PVC solution in tetrahydrofuran at a rotational speed of 500 rpm. Although the device with the sealant layer had a thicker film, it showed superior optical switching properties even with a change in reflectance range due to multilayer interference. Furthermore, the device without the sealant layer easily degraded in an accelerated degradation test at a constant temperature of 40°C and a constant relative humidity of 80% after only 2 days. On the other hand, the surface of the device with the sealant layer showed no change in the same test. This result suggests that the PVC sealant layer has some advantages for preventing the environmental effects on the properties of the device.

Does the amount of filler content in sealants used to prevent decalcification on smooth enamel surfaces really matter?

To determine how filler content and an acidic environment affect the retention of sealants placed on smooth enamel surfaces. A sample of 120 teeth was randomly divided into six subsamples. Three experimental sealants with identical formulas, with the exception of the amount of filler content (18%, 30%, 50%), were applied according to manufacturers' recommendations. Half of the subsamples were exposed to an acid environment (pH of 2.5) for 96 hours. With the use of a tooth-brushing simulator, each tooth was exposed to 15,000 brushing strokes, while a slurry of 1 : 3 toothpaste/neutral sodium bicarbonate cycled through the machine. Initial and final photographs were analyzed subjectively and objectively. Scanning electron microscope photomicrographs were used to evaluate the tooth surface. Subjective analyses showed significant (P < .05) filler effects, with the 18% filled sealant showing the least change, followed by the 30% sealant, then the 50% filled sealant, which showed the greatest loss. Objective analyses showed the same pattern of loss, but the differences between sealants were not statistically significant. Exposure to an acidic environment had no significant effect on sealant retention. SEMS showed a layer of sealant remaining on all of the sealed teeth evaluated. Filler content of resin sealant material affects the retention of sealants on smooth enamel surfaces; exposure to an acid environment has no effect on sealant retention. Within the limits of this study, highly filled resin sealants once saturated have the ability to endure the oral environment and remain on a smooth enamel surface, regardless of the amount of filler content.