Papers by Keyword: Adhesive

Abstract: This investigation assessed how incorporating vanillin into a dental adhesive influences bacterial adhesion and biofilm formation. Experimental adhesives, formulated with 0.5% and 1.0% vanillin, were compared against a vanillin-free adhesive and a control using a multi-species biofilm model. No significant differences in bacterial adhesion were observed across the groups, with optical density (OD) values ranging from 0.28 to 0.40. In contrast, adhesives containing vanillin demonstrated a marked reduction in biofilm formation. After 48 hours, the strongest inhibition was recorded for the 1.0% vanillin adhesive (0.63 ± 0.07), followed by the 0.5% vanillin adhesive (0.77 ± 0.04), which were significantly lower than the vanillin-free (1.19 ± 0.08) and control (1.68 ± 0.05) groups. While biofilm accumulation increased in all groups by 72 hours, the vanillin-containing adhesives consistently maintained lower values than the controls. A concentration-dependent effect was confirmed by percent reduction analysis, which showed the 1.0% vanillin adhesive lowered biofilm by 62.5% at 48 hours and 45.0% at 72 hours. Vanillin also suppressed acidogenicity, as reflected by significantly higher culture medium pH values that remained near neutral at both 48 and 72 h, while the vanillin-free adhesive and control dropped below the critical pH 5.5 threshold. These findings suggest that vanillin effectively suppresses biofilm development without impacting bacterial adhesion, potentially serving as a natural additive to enhance the antibacterial properties of dental adhesives and minimize the risk of secondary caries.

Abstract: Thermosets play an important role in composite processing, adhesive bonding and coating. In all these applications, shrinkage my cause a significant amount of residual stress, leading to distortion, reduced load carrying capacity and cracking. The chemical curing reaction is accompanied by a reduction in volume called “chemical shrinkage”. If curing is performed at elevated temperature, cooling to ambient conditions afterwards is accompanied by “thermal shrinkage” and further shrinkage due to so-called “physical ageing”. A skillful combination of available methods makes it possible to separate chemical shrinkage in the viscous state from shrinkage in the gelled and vitrified state. Modeling of the time-and temperature-dependent properties is the prerequisite for the prediction and control of residual stresses caused by shrinkage in thermoset polymers.

Abstract: Adhesive joints are essential in modern engineering, offering lightweight, durable and efficient solutions for bonding in industries such as aerospace, automotive, and renewable energy. However, their fatigue performance under cyclic loading remains a critical challenge, shaped by a complex interplay of geometrical, material, environmental, and loading factors. This review explores the mechanisms of fatigue failure, highlighting the importance of joint design, material optimization, and surface preparation in mitigating stress concentrations and enhancing durability. Advances in toughened adhesives, surface treatments, and environmental protection methods are highlighted, along with predictive models ranging from empirical S-N curves to advanced finite element simulations and probabilistic approaches. Despite significant progress, challenges remain in integrating these techniques for real-world applications, particularly under variable loading and harsh environmental conditions. Future research must focus on hybrid methodologies, adaptive materials, and standardized protocols to bridge the gap between laboratory insights and practical implementations. This comprehensive review provides a foundation for improving the fatigue performance of adhesive joints, ensuring their reliability and effectiveness in critical engineering systems.

Abstract: Adhesive bonding is often found for engineering construction technology applications in industries such as aeronautics, automotive, electronics, and aerospace. Single lap joint type connections can be applied to dissimilar materials so that they can reduce the weight of construction. The objective of this study to determine the effects of adding natural latex adhesive to aluminum-cocofiber composites single lap joints. The research material uses two types of adherend, namely aluminum and cocofiber-reinforced composite with an Unsaturated Polyester matrix (UPRs) type Yukalac BQTN with a MEXPO catalyst. Adhesive bonding material uses epoxy resin and the addition of natural latex. The connection is carried out using a single lap joint adhesive bonding method between two different adherend materials. The adhesive material in the single lap joint is 0.2 mm thick using variations in the addition of natural latex adhesive to epoxy with variations of 5%NK: 95%EP, 15%NK: 85%EP, 25%NK: 75%EP, and 35%NK: 65%E.P. The adherend surface treatment was given by roughing the surface with sandpapering grid #150. The single lap joints shear test refers to ASTM D-1002. The test results indicated that the shear strength increases with the addition of 5% natural latex to the epoxy. The roughness treatment applied to the surface provides an irregular effect, thus increasing the bond between the adhesive and the adherend. In addition, it also improves the mechanical interlocking of the single lap joint. The failure modes after the shear stregth test that occur based on macro observations are cohesive, stock-break, thin layer cohesive, and fiber pull-out.

Abstract: Chitin is a biopolymer that can be used as a candidate material for a strong and environmentally friendly glass adhesive. In the form of nanoparticles with needle-like morphology and attractive functional groups in the form of amide and hydroxyl, Chitin Nanoparticle (ChNP) shows a strong Van der Walls adhesive force against glass. In the study, ChNP was successfully isolated from crab shells from the sea of Lombok. The isolated ChNP has a characteristic size around 351 nm with -chitin conformation and needle-shaped morphology. Based on the results of shear strength testing, 0.42 mg of ChNP can withstand a load of 21 kg and the addition of Gum Arabic (GA) and Hen Egg White lysozyme (HEWL) in a ratio of 1: 1 to ChNP succeeded in increasing adhesion by 72%.

Abstract: The thickness of the adhesive has a major influence on the shear strength of bonded assemblies. This work is based on a study of the fatigue behavior of two cracked aluminum (2024 T351) plates repaired by patch (graphite/epoxy) under cyclic loading. For this we used a computer code to study the propagation of fatigue cracks to predict the life of the plates repaired named AFGROW. The first plate was repaired using an adhesive made from date palm waste whereas the second plate was repaired using FM-73 adhesive. The results obtained from this study show that, despite the low shear modulus of the adhesive made from date palm waste and the very low film thickness, the joint bonded with the latter gives good joint strength and a lifetime (number of cycles) similar to the joint bonded with the FM-73 adhesive when the thickness of the joint of the adhesive is greater than that of the adhesive made by the waste of the date palm. This shows that the strength of the bonded joint increases rapidly from very low thicknesses (less than a few hundredths of a millimeter). Finally, we recommend using the adhesive made from date palm waste for patch repair as well as for applications such as lightweight construction, electric vehicles or solar panels.

Abstract: Bonding metallic structures with composite materials is widely considered to be the most optimal method for joining damaged and fractured structures. This method offers important advantages, such as reducing the stress intensity factor (SIF) and increasing the lifetime of the joined structure. However, hygrothermal aging is a phenomenon that can reduce the lifetime of reinforced structures made of glass fiber-reinforced polymer (GFRP). This study used numerical modeling to investigate a cracked stainless steel pipe operating in a hygrothermal environment and repaired with three patches. The main objective of this work is to determine the effect of adhesive aging due to hygrothermal damage on the repair efficiency of a cracked SA312 type 304 stainless steel pipe. The Finite Element Method (FEM) is used to evaluate the SIF as a function of applied load for different immersion times and at two different temperatures. First, the developed model was validated against literature results. A parametric study was then carried out. The obtained results showed that the adhesive maintains its stiffness for 7.5 months of immersion and that the mechanical properties of the adhesive are acceptable even at temperatures of 90°C or lower and internal pressures less than or equal to 50 bar. However, when the pressure load exceeds 50 bar (p_int > 50 bar), the degradation of the adhesive becomes more significant, and the hygrothermal aging leads to variations in the mechanical properties of the joined structure. It is important to note that these results can contribute to the improvement of the existing composite repair design standard and can provide reliability for the application of GFRP in different humid environments.

Abstract: Dental caries, or tooth decay, is one of the most widespread chronic and multifactorial diseases affecting people worldwide. It is described as the localized destruction of tooth structure by acids produced from bacteria fermentation of edible carbohydrates. The disease process begins within the bacterial biofilm on the surfaces of the teeth. Streptococcus sanguinis, Sreptococcus gordonii, and Streptococcus mutans are the main organisms in the biofilm associated with health or disease conditions in the oral cavity. Streptococcus mutans is believed to be the primary cause of enamel demineralization and the development of dental caries. S. gordonii and S. sanguinis belong to a group of streptococci considered health-related commensal oral bacteria, crucial for forming a biofilm on oral hard tissues. Several types of materials with multipurpose characteristics have been incorporated into dental adhesives. Recently, the calcium salt of an acidic monomer (calcium salt of 4-methacryloxyethyl trimellitic acid, or CMET) has been included in dental adhesive and demonstrated to suppress cariogenic biofilm formation of S. mutans. However, using a single-species model may not mimic the intricate antagonistic and synergistic relations that occur in oral biofilms. Therefore, the effect on cariogenic multi-species biofilm was assessed in this study. Dental adhesive consisting of CMET and 10-methacryloyloxydecyl dihydrogen calcium phosphate (MDCP) (Bio-Coat CA) was spread over the flat-bottom surface of the 96-well plate and LED light-cured. Then it was coated with sterile saliva at 37 °C for 45 min to form an acquired pellicle for microbial attachment. The multi-species bacterial suspension containing Streptococcus mutans ATCC 25715, Streptococcus sanguinis ATCC 10556, and Streptococcus gordonii ATCC 10558 was prepared and added to the saliva-coated well. Then, the plate was incubated at 37°C in a 5% CO2 atmosphere for 24 h, 48 h, and 72 h to support the biofilm formation. The number of vital bacteria in the biofilm was determined with the WST-8 Microbial Cell Counting Kit (Dojindo Molecular Technologies, USA). All tests were done in triplicate and repeated three times. For statistical analysis, Kruskal-Wallis and Dunn’s tests were employed. The results showed that at 24 h, 48 h, and 72 h, dental adhesive with CMET could inhibit the biofilm formation of multi-species bacteria significantly compared with controls. The percentages of biofilm inhibition were 29.1%, 34.7%, and 33.2% at 24 h, 48 h, and 72 h, respectively. Dental adhesive containing CMET displayed favorable multi-species biofilm-inhibiting effects up to 72 h of biofilm growth. It is a promising adhesive for use to prevent secondary caries at the sites of restorations.

Abstract: Non-isothermal DSC has been used to investigate the curing kinetics of epoxy adhesives (DGEBA-cycloaliphatic amine). The epoxy samples were scanned on DSC with five heating rates (5°C/min, 7.5°C/min, 10°C/min, 12.5°C/min, and 15°C/min). The curing kinetics were obtained through ASTM standards E2890 and E698 (the Ozawa and Kissinger methods). The kinetic parameters obtained include Ea (activation energy), A (pre-exponential factor), and n (reaction order). The activation energy calculated from the Kissinger and Ozawa method was slightly different but insignificant. The reaction rate (dα/dt) and degree of curing/conversion (α) relationship towards temperature (T), and time (t) was also investigated. The curing process's reaction rate (dα/dt) has maximum value; it can no longer increase after a specific conversion rate (α).

Abstract: This paper deals with the problematics of polymer repair and adhesive mortars. In this study, the vinyl ester and epoxy resins filled with siliceous filler are used. This paper studies physical-mechanical properties and chemical resistance of developed mortars. The compressive strength, flexural strength and visual evaluation of reaction and degradation of polymer mortars in presence of common acids, alkalis and other compounds are compared. The results show, the amine-based epoxy mortar can withstand against a large variety of solutions, but the overall chemical resistance of vinyl ester mortar is higher.