Multiple high-temperature resistant phases modified phosphate-based adhesive for engineering ceramic connection in extreme environment

The lower-strength defect of inorganic phosphate adhesive had been definitely improved by self-generating multiple high-temperature resistant phases. Compared to our previous product, the best bonding performance of this novel adhesive for mullite was increased by 270%, which was close to some popular preceramic polymer-based adhesives. The apparent shear strength at room temperature was up to 33.1?MPa after calcination at 900?°C, while the high-temperature strength researched 23.3?MPa at 900?°C and maintained above 17?MPa from 700° to 1200?°C. The reinforced effect of adhesive owed to the introduction of various Cu-based intermetallics, the premature generation of Al₄B₂O₁₈ at 900?°C, and the structure optimizing through the oxidization of Si and B₄C. Besides, the novel adhesive displayed good resistance to thermal-shock, especially for air-cooling test. After 15 thermal cycles in air, the residual strength of 1300?°C-calcined joints was still above 13?MPa (~40%).     

Effect of temperature on the joint strength of a silyl-modified polymer-based adhesive

Temperature is a very important factor that must be fully considered in the study on the adhesive joint strength. In this paper, a silyl-modified polymer-based adhesive ISR 70-08 which is widely used in engineering was studied. Dog-bone specimens were fabricated and tested at ?40°C, room temperature (RT), and 90°C. Results show a decrease in the main mechanical properties with increasing temperature. Butt joints (BJs), single-lap joints (SLJs), and Scarf joints (SJs) were fabricated and tested at different temperatures. A quadratic polynomial expression was an ideal choice to express the joint strength as a function of temperature which was obtained using the least-squares method. Temperature combinations of ?40°C, 0°C, and 90°C were obtained to study the effect of temperature on the joint strength more easily for this adhesive. A three-dimensional surface, consisting of temperature, adhesive angle, and joint strength was presented to facilitate the application of bonding structures in engineering     

Preparation of high peel strength and high anti-aging epoxy adhesive that used for bonding aluminum alloy without surface treatment

In the case of bonding of aluminum alloy, surface pretreatment have been widely adopted for adherends so as to achieve superior adhesive performance. However, the strict surface treatment of the aluminum alloy cannot be implemented without special equipment and the mechanical properties, corrosion resistance and aging resistance of the common adhesives cannot meet the demand without surface treatment. Here, acrylic oligomer modified by carboxyl terminated organosilicon and nano alumina were used to modify an epoxy formulation based on a classical DGEBA monomer to produce a high peel strength epoxy adhesive that can be used without surface pretreatment. The peel strength and the shear strength of the adhesive could reach 7.18?N/cm and 18.75?MPa, respectively, and could be well maintained under ?70?°C and 100?°C. The novel adhesive also has good heat aging resistance, water resistance and artificial seawater resistance. SEM and XPS were used to investigate mechanism of aging resistance of modified adhesives without surface treatment.     

Effect of Temperature on the Joints Strength of an Automotive Polyurethane Adhesive

In this paper, the performance of an automotive polyurethane adhesive was studied through adhesive joints tests. Butt joints and single lap joints were fabricated and tested at seven temperature measuring points (TMPs). It is shown that both the tensile strength and lap shear strength decrease with the increasing of temperature. Quadratic polynomial expression obtained by the least square method can represent the tensile and lap shear strength as a function of temperature very well. ?40°C, 0°C, and 90°C were selected as the most ideal TMPs for this adhesive through the comparison of the residual sums of squares of 35 fitting curves with different combination of TMPs. Scarf joints with adhesive angles of 60° and 30° were fabricated and tested at ?40°C, 0°C, and 90°C. It also showed a decrease in joint strength with the increasing temperature. Joint strength as a function of adhesive angle is presented. It was found to closely follow a linear behaviour. A three-dimensional surface, consisting of temperature, adhesive angle, and joint strength, is presented finally to facilitate the design of automotive bonding structures.     

Peanut meal as plywood adhesives: preparation and characterization

Bio-based adhesives have attracted much attention due to its renewable and environment-friendly properties. This study describes a route for the preparation of a new bio-based adhesive from peanut meal. For this purpose, different types of raw materials (hot-pressed peanut meal and cold-pressed peanut meal) were compared. Moreover, the crushing methods and modification agents were investigated in great details. Furthermore, response surface methodology was applied to optimize the preparation conditions of peanut meal adhesive. The apparent viscosity and the Fourier transform infrared spectroscopy (FITR) of peanut meal adhesives were also evaluated to confirm the validity of the optimal preparation conditions. These results showed that hot-pressed peanut meal is a good candidate for adhesive materials and the addition of sodium dodecyl sulfate (SDS) improves the adhesive bonding strength. In addition, the regression model for the peanut meal adhesive preparation revealed statistical significance. Modification time and material liquid ratio had a significant effect on wet strength while the variables of modification temperature and the addition amount of modifier were insignificant. The optimal preparation conditions were determined as follows: modification temperature of 60?°C, modification time of 3?h, ratio of material to liquid of 1:3 and the addition amount of modifier of 3.2%. The average value of the adhesive bonding strength of 1.05?±?0.07?MPa was obtained, which is close to the predicted value. Under these conditions, the best wet strength and adhesive performance were achieved for the plywood.     

High‐Temperature Shear Strength and Bonding Mechanism of the Mullite Ceramic/Fiber Brick Component Joined by Phosphate Adhesive

The mullite ceramic/fiber brick system was bonded by two kinds of phosphate adhesives. The specimens were treated from 200 to 1400°C. The mechanical properties were tested at room temperature and at high temperature, and the relevant bonding mechanism was also discussed. The results show that the addition of silicon can greatly improve the adhesive's mechanical properties. The room‐temperature shear strength of the component bonded by adhesive with the silicon calcined at 800°C can reach 6.58 MPa. The shear strength of the adhesive with silicon tested at 800°C can reach 0.42 MPa.     

Accelerated-curing epoxy structural film adhesive for bonding lightweight honeycomb sandwich structures

Accelerating the curing of epoxy/aromatic amine adhesives and improving their toughness are challenges in heat-resistant epoxy structural adhesives. Herein, we report an epoxy/aromatic amine adhesive accelerated curing system with an oxo-centered trinuclear (chromium III) complex, which is toughened using a thermoplastic block copolymer (TPBC). The reaction characteristics, heat resistance, microstructure, and bonding properties of the accelerated epoxy adhesives were analyzed. The reaction peak temperature of the epoxy with 3% catalyst was 113.1°C, which was 113.6°C lower than that of epoxy without catalyst, and the modified epoxy resin demonstrated a potential for rapid curing at medium temperature. The glass transition temperature of the TPBC-toughened epoxy adhesive was 125°C after curing, indicating excellent thermal stability after medium temperature curing. The introduction of the TPBC increased the single-lap shear strength of the epoxy adhesive without reducing its heat resistance. The shear strength at room temperature and 120°C of the modified epoxy adhesive with 50 phr of TPBC was 25.2 and 10.9 MPa, respectively. Moreover, the epoxy film adhesive exhibited outstanding bonding properties when used in the bonding of lightweight honeycomb sandwich structures.     

A novel B2O3/B4C-modified composite adhesive with wide operative temperature range for alumina fiber fabric bonding

A heat resistance adhesive with wide operative temperature range for bonding alumina fiber fabric was developed by organic-inorganic modification. The polyvinyl alcohol modified by B₂O₃ generated a complex cross-linked network connected by B–O–C bonds, which can enhance the bonding strength of adhesive after heat-treatment from RT to 400 °C. Moreover, the addition of B₄C can enhance the bonding strength of adhesive after heat-treatment from 400 °C to 800 °C due to the formation of molten B₂O₃ and borosilicate glass. Significantly, the appropriate addition of B₄C can make the adhesive form a denser structure without transforming the fracture mode of the bonding joints, which is conducive to enhance the strength performance of bonding joints after sintered at 800 °C. On the contrary, the excessive addition of B₄C will transform the fracture mode of the bonding joints into brittle fracture, which will degrade the strength performance of bonding joints.     

A heat-resistant preceramic polymer with broad working temperature range for silicon carbide joining

A room temperature curable heat-resistant adhesive with broad working temperature range was prepared through organic and inorganic modification. The preceramic polymethylsiloxane showed low bonding strength for silicon carbide from 400 °C to 600 °C because of the decomposition of polymer network. So the modification with epoxy resin was used to generate strong blending and copolymerization network which decomposed at higher temperature over 500 °C. The ceramization of active fillers and preceramic polymer compensated the bonding strength with rising temperature, thus eliminating the weak stage from 400 °C to 600 °C. The modification with fillers greatly improved its bonding strength at high temperature over 1000 °C. Consequently, the modified adhesive exhibited outstanding bonding strength tested at room temperature between 9.29 ± 0.56 MPa and 37.28 ± 1.33 MPa after heat-treatment from 25 °C to 1500 °C and the bonding strength directly tested at the temperature from 25 °C to 800 °C over 8.21 ± 0.40 MPa. The adhesive shows the potential to extend the application for engineering ceramic joining.     

Preparation and performance of a heat-resistant organic adhesive obtained via a liquid SiC precursor

A heat-resistant organic adhesive rich in active SiH bonds and CHCH₂ bonds has been synthesized by modifying polymethylsilane with D4Vi. The structure and properties of the adhesive have been investigated by FTIR, GPC, TGA, XRD, bonding strength tests, and SEM. The results show that the obtained adhesive exhibits outstanding thermal stability and bonding properties. The ceramic yields of the adhesive treated in Ar or in air at up to 1200 °C were measured as 81% and 90.6%, respectively. The adhesive can maintain an amorphous state even when heat-treated at 1200 °C for 2 h in air. The room temperature shear strength of the adhesive was measured as 14.9 MPa, and this increased to a maximum value of 31.7 MPa after heat-treatment at 1000 °C for 2 h.     

Epoxy–imide resins from N‐(4‐ and 3‐carboxyphenyl)trimellitimides. I. Adhesive and thermal properties

Epoxy–imide resins were obtained by curing Araldite GY 250 (diglycidyl ether of bisphenol‐A and epichlorohydrin; difunctional) and Araldite EPN 1138 (Novolac–epoxy resin; polyfunctional) with N‐(4‐ and 3‐carboxyphenyl)trimellitimides derived from 4‐ and 3‐aminobenzoic acids and trimellitic anhydride. The adhesive lap shear strength of epoxy–imide systems at room temperature and at 100, 125, and 150°C was determined on stainless‐steel substrates. Araldite GY 250‐based systems give a room‐temperature adhesive lap shear strength of about 23 MPa and 49–56% of the room‐temperature adhesive strength is retained at 150°C. Araldite EPN 1138‐based systems give a room‐temperature adhesive lap shear strength of 16–19 MPa and 100% retention of room‐temperature adhesive strength is observed at 150°C. Glass transition temperatures of the Araldite GY 250‐based systems are in the range of 132–139°C and those of the Araldite EPN 1138‐based systems are in the range of 158–170°C. All these systems are thermally stable up to 360°C. The char residues of Araldite GY 250‐ and Araldite EPN 1138‐based systems are in the range of 22–26% and 41–42% at 900°C, respectively. Araldite EPN 1138‐based systems show a higher retention of adhesive strength at 150°C and have higher thermal stability and T_g when compared to Araldite GY 250‐based systems. This has been attributed to the high crosslinking possible with Araldite EPN 1138‐based systems arising due to the polyfunctional nature of Araldite EPN 1138. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1729–1736, 2000     

A Study on the Bonding Technology in Sliced Bamboo Veneer Manufacturing

This paper deals with the gluing of small sized bamboo strips into laminated bamboo timbers, and is aimed at utilizing bamboo resources to produce sliced bamboo veneer to replace the current more expensive sliced wood veneer. These laminated bamboo planks glued with MUF (melamine-urea-formaldehyde) resin retained their adhesion even after treatment in water at 60°C for 3 h under a pressure of 0.4 MPa. The bamboo laminated timbers produced from gluing laminated bamboo planks (the ratio of the matrix to the curing agent was 100:25 by weight) can satisfy the requirement of adhesion sustainability after treatment in water at 50°C for 8 h. The results showed that mixture of UF (urea-formaldehyde) resin and PVA (polyvinyl acetate) adhesive with a weight ratio of 1:1 can be used to overlay non-woven cloth on the back of sliced bamboo veneer. The surface bonding strength of MDF (medium-density fibreboard) overlaid by sliced bamboo veneer, backed with non-woven cloth, satisfies the requirement of the Chinese standard GB/T15104.     

Preparation of a modified phosphate-based adhesive and its hot bonding performance on 316L stainless steel

In this study, a novel phosphate-based adhesive was prepared by using homemade aluminum phosphate as a matrix and by adding different fillers simultaneously. The effects of calcination temperature and filler composition on the bonding mechanism and high-temperature bonding strength of the adhesive for high-temperature alloys were studied. The results indicated that the crystalline transformation of AlPO₄ occurred at 500 °C. AlPO₄ has two crystalline forms at 500 °C: orthorhombic and hexagonal. The addition of CuO to the fillers resulted in the exchange of Fe and Cu at the substrate interface and enhanced the high-temperature bonding strength of the specimens. The maximum tensile strength of the specimens reached 3.9 MPa at 500 °C. These composites have potential applications in aviation, aerospace, and other fields.     

“Refractory Metal,RM – Wrap”: A tailorable,pressure-less joining technology

The RM-wrap (RM = Refractory Metal) is a pressure-less, versatile and tailorable joining process: it consists of wrapping Si foils inside a refractory metal wrap (i.e., Mo, Nb, Ta) in order to prevent molten silicon from leaking outside the joined region and infiltrating the facing materials during the joining process.RM-wrap (RM = Mo, Nb, Ta) has been successfully applied to join C/SiC composites in this work: optimized joining treatment consisted of heating to 1450?°C with a heating rate of 1000?°C/h followed by a dwell time of 5?min in a non-reactive environment of Argon flow.The joints were characterized by morphological analysis and lap shear tests at room temperature and 1000?°C.Microscopical analysis revealed an in-situ formed composite joint consisting of a silicon matrix reinforced with silicides of the refractory metals. Joining material exhibited continuous and cracked free bonding with C/SiC irrespective of composite fibre orientation.Joints lap shear strength values at 1000?°C were higher than at room temperature, probably due to the brittle to ductile transition (BTDT) of silicon and silicides.Vickers microhardness on refractory metal disilicides measured inside the joints showed a trend similar to their mechanical strength, with higher lap shear strength and hardness for Mo-Wrap and lower for Ta-wrap joints.     

Influence of the preheating of bonding agents on the degree of conversion and bond durability in tridimensional dentin cavities

Objectives: The aim of this study was to evaluate the degree of conversion (DC) of dental bonding agents at different temperatures and the bond durability of restorations bonded with preheated dental bonding agents. Materials and methods: Three multistep adhesive systems, including one 3-step etch-and-rinse (Adper Scotchbond Multipurpose Plus) and two 2-step self-etching systems (Clearfil SE Bond; Filtek Low-Shrinkage Adhesive System), were evaluated. Dental bonding agents were preheated at 25, 37, and 60?°C. Bar-shaped specimens (n?=?5) were prepared for DC analysis. Fourier Transform Infrared/Attenuated Total Fluorescence spectra were obtained, and the DC was calculated by comparing the aliphatic bonds/reference peaks of nonpolymerized and polymerized materials. For bond durability analysis, tridimensional dentin cavities were prepared in 180 bovine incisors, which were then restored. Samples were stored in water for 24?h, and half of them were subjected to additional degradation with 10% NaOCl for 5?h. The push-out bond strength test was performed in a universal testing machine until failure. Failure modes were analyzed by scanning electron microscopy. Data were analyzed by analysis of variance (ANOVA) and Tukey’s tests (p?<?0.05). Results: Dental bonding agents preheated at 60?°C showed higher DC values than those preheated at 25 and 37?°C. The temperature of the dental bonding agent did not influence the bond durability, although fewer adhesive failures were observed in restorations bonded with dental bonding agents at 60?°C. Conclusion: Although the preheating of dental bonding agents can increase the DC, it may not improve the bond durability of dentin restorations.     

Atmospheric pressure plasma activation as a surface pre-treatment for the adhesive bonding of aluminum 2024

A low-temperature, atmospheric pressure helium and oxygen plasma has been used for the surface preparation of aluminum 2024 prior to adhesive bonding. The plasma converted the aluminum from a water contact angle (WCA) of 79° to down to 38° within 5 s of exposure, while sanding reduced the WCA to only 51°. Characterization of the aluminum surface by X-ray photoelectron spectroscopy revealed a decrease in carbon contamination from 70 to 36% and an increase in the oxygen content from 22 to 50% following plasma treatment. Similar trends were observed for sanded surfaces. Lap shear results demonstrated bond strengths of 30?±?2?MPa for the sanded aluminum vs. 33?±?1?MPa for plasma-treated aluminum, where sol–gel and primer coatings were added to the surface preparation. Following seven days of aging, wedge crack extension tests revealed cohesive failure percentages of 86, 92, and 96% for sanded, plasma-treated, and sanded/plasma-treated aluminum, respectively. These results indicate that atmospheric pressure plasmas are an attractive alternative to acid treatment or abrasion techniques for surface preparation prior to bonding.     

Adhesive properties of water-washed cottonseed meal on four types of wood

The interest in natural product-based wood adhesives has been steadily increasing due to the environmental and sustainable concerns of petroleum-based adhesives. In this work, we reported our research on the utilization of water-washed cottonseed meal (WCM) as wood adhesives. The adhesive strength and water resistance of WCM adhesive preparations on poplar, Douglas fir, walnut, and white oak wood veneers were tested with press temperatures of 80, 100, and 130 °C. Our data indicated that raising the hot press temperature from 80 to 100–130 °C greatly increased the bonding strength and water resistance of the WCM adhesives. The general trend of the adhesive strength of WCM on the four wood species was Douglas fir > poplar ≈ white oak > walnut. The rough surface of Douglas fir with tipping features could enhance the mechanical interlocking between the wood fibers and adhesive slurry, contributing to the high adhesive strength. The dimensional swelling of the bonded wood pairs due to water soaking was in the order: thickness > width (i.e. perpendicular to the wood grain) > length (i.e. parallel to the wood grain). The greatest dimensional changes were observed in Douglas fir specimens. However, the highest decrease in adhesive strength by water soaking was with poplar wood specimens. These observations suggested that the wood dimensional changes were not dominant factors on water weakening the bonding strength of these wood pairs.     

Advanced high-temperature (RT-1100°C) resistant adhesion technique for joining dissimilar ZrO2 ceramic and TC4 superalloys based on an inorganic/organic hybrid adhesive

To meet the high demand for ceramic/superalloy composite structural components in various fields, an advanced high-temperature adhesion technique was firstly developed by preparing a novel inorganic/organic hybrid adhesive suitable for ZrO₂ and TC4. Chemical bonding started to work at ～600°C, and became the crucial bonding mechanism at elevated temperatures. The formation of ZrSiO₄ and Ti₅Si₃ at the interfaces of two substrates not only increased the interfacial connection strength, but also formed two gradient layers with a size of ～2 μm to effectively alleviate the difference of composition and performance between the adhesive and substrates. In the temperature range of 500–900°C, the matching degree of CTE among ZrO₂, adhesive and TC4 is higher, and the maximum difference does not exceed 3×10^-6 K^-1. Meanwhile, the formation of a composite structure containing various ceramics (ZrO₂, SiC and ZrB₂) and intermetallics (Ni–Si, Al–Ni), and the improvement of structural compactness of adhesive from 500 to 900°C greatly improved the bonding strength to the maximum value of 31.4 MPa at 900°C. Also, the adhesive pretreated at 900°C showed good thermal cycling resistance, and the strength was still higher than 15 MPa after 50 cycles. For cured adhesive, when used directly in an extreme environment, it can provide bonding strength not less than 5 MPa in the whole temperature range, indicating that the adhesive possessed potential emergency repair convenience. This work significantly broadened the application of high-temperature-resistant adhesion technology in the connection of dissimilar ceramics and alloys.     

Experimental investigation into the effect of adhesion properties of PEEK modified by atmospheric pressure plasma and low pressure plasma

High performance polymer, Polyether Ether Ketone (PEEK) (service temperature ?250°C to +300°C, tensile strength: 120 MPa) is gaining significant interest in aerospace and automotive industries. In this investigation, attention is given to understand adhesion properties of PEEK, when surface of the PEEK is modified by two different plasma processes (i) atmospheric pressure plasma and (ii) low pressure plasma under DC Glow Discharge. The PEEK sheets are fabricated by ultra high temperature resistant epoxy adhesive (DURALCO 4703, service temperature ?260°C to +350°C). The surface of the PEEK is modified through atmospheric pressure plasma with 30 and 60 s of exposure and low pressure plasma with 30, 60, 120, 240, and 480 s of exposure. It is observed that polar component of surface energy leading to total surface energy of the polymer increases significantly when exposed to atmospheric pressure plasma. In the case of low pressure plasma, polar component of surface energy leading to total surface energy of the polymer increases with time of exposure up to 120 s and thereafter, it deteriorates with increasing time of exposure. The fractured surface of the adhesively bonded PEEK is examined under SEM. It is observed that unmodified PEEK fails essentially from the adhesive to PEEK interface resulting in low adhesive bond strength. In the case of surface modified PEEK under atmospheric pressure plasma, the failure is entirely from the PEEK and essentially tensile failure at the end of the overlap resulting in significant increase in adhesive bond strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Lowering curing temperature in adhesive bonding of aluminum AA6061-T4

ABSTRACT

To minimize the part distortion and investment in the E-coat oven in adhesive bonding of metals for automotive applications, lowering the curing temperature of adhesive without apparent loss of the joint strength is desirable. The key to lower the curing temperature of adhesive bonding of lightweight materials is to accelerate the curing process of structural adhesives. In this study, curing agent (i.e., aliphatic polyamine) and curing accelerator (i.e., acetylacetone salt) were added into commercial Henkel 5089 adhesive and the effect of these curing additives on the curing temperature of Henkel 5089 in adhesive bonding of aluminum AA6061-T4 was studied. The test results showed that the addition of a curing agent and accelerator in Henkel 5089 lowered the curing temperature from 177°C to 130°C without sacrificing the strength of the adhesive-bonded aluminum AA6061-T4.